fe-connect.c

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/*-------------------------------------------------------------------------
 *
 * fe-connect.c
 *    functions related to setting up a connection to the backend
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/interfaces/libpq/fe-connect.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres_fe.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>
#include <time.h>
#include <unistd.h>

#include "libpq-fe.h"
#include "libpq-int.h"
#include "fe-auth.h"
#include "pg_config_paths.h"

#ifdef WIN32
#include "win32.h"
#ifdef _WIN32_IE
#undef _WIN32_IE
#endif
#define _WIN32_IE 0x0500
#ifdef near
#undef near
#endif
#define near
#include <shlobj.h>
#ifdef WIN32_ONLY_COMPILER      /* mstcpip.h is missing on mingw */
#include <mstcpip.h>
#endif
#else
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#ifdef HAVE_NETINET_TCP_H
#include <netinet/tcp.h>
#endif
#include <arpa/inet.h>
#endif

#ifdef ENABLE_THREAD_SAFETY
#ifdef WIN32
#include "pthread-win32.h"
#else
#include <pthread.h>
#endif
#endif

#ifdef USE_LDAP
#ifdef WIN32
#include <winldap.h>
#else
/* OpenLDAP deprecates RFC 1823, but we want standard conformance */
#define LDAP_DEPRECATED 1
#include <ldap.h>
typedef struct timeval LDAP_TIMEVAL;
#endif
static int ldapServiceLookup(const char *purl, PQconninfoOption *options,
                  PQExpBuffer errorMessage);
#endif

#include "libpq/ip.h"
#include "mb/pg_wchar.h"

#ifndef FD_CLOEXEC
#define FD_CLOEXEC 1
#endif


#ifndef WIN32
#define PGPASSFILE ".pgpass"
#else
#define PGPASSFILE "pgpass.conf"
#endif

/*
 * Pre-9.0 servers will return this SQLSTATE if asked to set
 * application_name in a startup packet.  We hard-wire the value rather
 * than looking into errcodes.h since it reflects historical behavior
 * rather than that of the current code.
 */
#define ERRCODE_APPNAME_UNKNOWN "42704"

/* This is part of the protocol so just define it */
#define ERRCODE_INVALID_PASSWORD "28P01"
/* This too */
#define ERRCODE_CANNOT_CONNECT_NOW "57P03"

/*
 * fall back options if they are not specified by arguments or defined
 * by environment variables
 */
#define DefaultHost     "localhost"
#define DefaultTty      ""
#define DefaultOption   ""
#define DefaultAuthtype       ""
#define DefaultPassword       ""
#ifdef USE_SSL
#define DefaultSSLMode "prefer"
#else
#define DefaultSSLMode  "disable"
#endif

/* ----------
 * Definition of the conninfo parameters and their fallback resources.
 *
 * If Environment-Var and Compiled-in are specified as NULL, no
 * fallback is available. If after all no value can be determined
 * for an option, an error is returned.
 *
 * The value for the username is treated specially in conninfo_add_defaults.
 * If the value is not obtained any other way, the username is determined
 * by pg_fe_getauthname().
 *
 * The Label and Disp-Char entries are provided for applications that
 * want to use PQconndefaults() to create a generic database connection
 * dialog. Disp-Char is defined as follows:
 *      ""      Normal input field
 *      "*"     Password field - hide value
 *      "D"     Debug option - don't show by default
 *
 * PQconninfoOptions[] is a constant static array that we use to initialize
 * a dynamically allocated working copy.  All the "val" fields in
 * PQconninfoOptions[] *must* be NULL.  In a working copy, non-null "val"
 * fields point to malloc'd strings that should be freed when the working
 * array is freed (see PQconninfoFree).
 *
 * The first part of each struct is identical to the one in libpq-fe.h,
 * which is required since we memcpy() data between the two!
 * ----------
 */
typedef struct _internalPQconninfoOption
{
    char       *keyword;        /* The keyword of the option            */
    char       *envvar;         /* Fallback environment variable name   */
    char       *compiled;       /* Fallback compiled in default value   */
    char       *val;            /* Option's current value, or NULL       */
    char       *label;          /* Label for field in connect dialog    */
    char       *dispchar;       /* Indicates how to display this field in a
                                 * connect dialog. Values are: "" Display
                                 * entered value as is "*" Password field -
                                 * hide value "D"  Debug option - don't show
                                 * by default */
    int         dispsize;       /* Field size in characters for dialog  */
    /* ---
     * Anything above this comment must be synchronized with
     * PQconninfoOption in libpq-fe.h, since we memcpy() data
     * between them!
     * ---
     */
    off_t       connofs;        /* Offset into PGconn struct, -1 if not there */
}   internalPQconninfoOption;

static const internalPQconninfoOption PQconninfoOptions[] = {
    /*
     * "authtype" is no longer used, so mark it "don't show".  We keep it in
     * the array so as not to reject conninfo strings from old apps that might
     * still try to set it.
     */
    {"authtype", "PGAUTHTYPE", DefaultAuthtype, NULL,
    "Database-Authtype", "D", 20, -1},

    {"service", "PGSERVICE", NULL, NULL,
    "Database-Service", "", 20, -1},

    {"user", "PGUSER", NULL, NULL,
        "Database-User", "", 20,
    offsetof(struct pg_conn, pguser)},

    {"password", "PGPASSWORD", NULL, NULL,
        "Database-Password", "*", 20,
    offsetof(struct pg_conn, pgpass)},

    {"connect_timeout", "PGCONNECT_TIMEOUT", NULL, NULL,
        "Connect-timeout", "", 10,      /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, connect_timeout)},

    {"dbname", "PGDATABASE", NULL, NULL,
        "Database-Name", "", 20,
    offsetof(struct pg_conn, dbName)},

    {"host", "PGHOST", NULL, NULL,
        "Database-Host", "", 40,
    offsetof(struct pg_conn, pghost)},

    {"hostaddr", "PGHOSTADDR", NULL, NULL,
        "Database-Host-IP-Address", "", 45,
    offsetof(struct pg_conn, pghostaddr)},

    {"port", "PGPORT", DEF_PGPORT_STR, NULL,
        "Database-Port", "", 6,
    offsetof(struct pg_conn, pgport)},

    {"client_encoding", "PGCLIENTENCODING", NULL, NULL,
        "Client-Encoding", "", 10,
    offsetof(struct pg_conn, client_encoding_initial)},

    /*
     * "tty" is no longer used either, but keep it present for backwards
     * compatibility.
     */
    {"tty", "PGTTY", DefaultTty, NULL,
        "Backend-Debug-TTY", "D", 40,
    offsetof(struct pg_conn, pgtty)},

    {"options", "PGOPTIONS", DefaultOption, NULL,
        "Backend-Debug-Options", "D", 40,
    offsetof(struct pg_conn, pgoptions)},

    {"application_name", "PGAPPNAME", NULL, NULL,
        "Application-Name", "", 64,
    offsetof(struct pg_conn, appname)},

    {"fallback_application_name", NULL, NULL, NULL,
        "Fallback-Application-Name", "", 64,
    offsetof(struct pg_conn, fbappname)},

    {"keepalives", NULL, NULL, NULL,
        "TCP-Keepalives", "", 1,    /* should be just '0' or '1' */
    offsetof(struct pg_conn, keepalives)},

    {"keepalives_idle", NULL, NULL, NULL,
        "TCP-Keepalives-Idle", "", 10,  /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, keepalives_idle)},

    {"keepalives_interval", NULL, NULL, NULL,
        "TCP-Keepalives-Interval", "", 10,      /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, keepalives_interval)},

    {"keepalives_count", NULL, NULL, NULL,
        "TCP-Keepalives-Count", "", 10, /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, keepalives_count)},

    /*
     * ssl options are allowed even without client SSL support because the
     * client can still handle SSL modes "disable" and "allow". Other
     * parameters have no effect on non-SSL connections, so there is no reason
     * to exclude them since none of them are mandatory.
     */
    {"sslmode", "PGSSLMODE", DefaultSSLMode, NULL,
        "SSL-Mode", "", 8,      /* sizeof("disable") == 8 */
    offsetof(struct pg_conn, sslmode)},

    {"sslcompression", "PGSSLCOMPRESSION", "1", NULL,
        "SSL-Compression", "", 1,
    offsetof(struct pg_conn, sslcompression)},

    {"sslcert", "PGSSLCERT", NULL, NULL,
        "SSL-Client-Cert", "", 64,
    offsetof(struct pg_conn, sslcert)},

    {"sslkey", "PGSSLKEY", NULL, NULL,
        "SSL-Client-Key", "", 64,
    offsetof(struct pg_conn, sslkey)},

    {"sslrootcert", "PGSSLROOTCERT", NULL, NULL,
        "SSL-Root-Certificate", "", 64,
    offsetof(struct pg_conn, sslrootcert)},

    {"sslcrl", "PGSSLCRL", NULL, NULL,
        "SSL-Revocation-List", "", 64,
    offsetof(struct pg_conn, sslcrl)},

    {"requirepeer", "PGREQUIREPEER", NULL, NULL,
        "Require-Peer", "", 10,
    offsetof(struct pg_conn, requirepeer)},

#if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
    /* Kerberos and GSSAPI authentication support specifying the service name */
    {"krbsrvname", "PGKRBSRVNAME", PG_KRB_SRVNAM, NULL,
        "Kerberos-service-name", "", 20,
    offsetof(struct pg_conn, krbsrvname)},
#endif

#if defined(ENABLE_GSS) && defined(ENABLE_SSPI)

    /*
     * GSSAPI and SSPI both enabled, give a way to override which is used by
     * default
     */
    {"gsslib", "PGGSSLIB", NULL, NULL,
        "GSS-library", "", 7,   /* sizeof("gssapi") = 7 */
    offsetof(struct pg_conn, gsslib)},
#endif

    {"replication", NULL, NULL, NULL,
        "Replication", "D", 5,
    offsetof(struct pg_conn, replication)},

    /* Terminating entry --- MUST BE LAST */
    {NULL, NULL, NULL, NULL,
    NULL, NULL, 0}
};

static const PQEnvironmentOption EnvironmentOptions[] =
{
    /* common user-interface settings */
    {
        "PGDATESTYLE", "datestyle"
    },
    {
        "PGTZ", "timezone"
    },
    /* internal performance-related settings */
    {
        "PGGEQO", "geqo"
    },
    {
        NULL, NULL
    }
};

/* The connection URI must start with either of the following designators: */
static const char uri_designator[] = "postgresql://";
static const char short_uri_designator[] = "postgres://";

static bool connectOptions1(PGconn *conn, const char *conninfo);
static bool connectOptions2(PGconn *conn);
static int  connectDBStart(PGconn *conn);
static int  connectDBComplete(PGconn *conn);
static PGPing internal_ping(PGconn *conn);
static PGconn *makeEmptyPGconn(void);
static void fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
static void freePGconn(PGconn *conn);
static void closePGconn(PGconn *conn);
static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
static PQconninfoOption *parse_connection_string(const char *conninfo,
                        PQExpBuffer errorMessage, bool use_defaults);
static int  uri_prefix_length(const char *connstr);
static bool recognized_connection_string(const char *connstr);
static PQconninfoOption *conninfo_parse(const char *conninfo,
               PQExpBuffer errorMessage, bool use_defaults);
static PQconninfoOption *conninfo_array_parse(const char *const * keywords,
                     const char *const * values, PQExpBuffer errorMessage,
                     bool use_defaults, int expand_dbname);
static bool conninfo_add_defaults(PQconninfoOption *options,
                      PQExpBuffer errorMessage);
static PQconninfoOption *conninfo_uri_parse(const char *uri,
                   PQExpBuffer errorMessage, bool use_defaults);
static bool conninfo_uri_parse_options(PQconninfoOption *options,
                           const char *uri, PQExpBuffer errorMessage);
static bool conninfo_uri_parse_params(char *params,
                          PQconninfoOption *connOptions,
                          PQExpBuffer errorMessage);
static char *conninfo_uri_decode(const char *str, PQExpBuffer errorMessage);
static bool get_hexdigit(char digit, int *value);
static const char *conninfo_getval(PQconninfoOption *connOptions,
                const char *keyword);
static PQconninfoOption *conninfo_storeval(PQconninfoOption *connOptions,
                  const char *keyword, const char *value,
              PQExpBuffer errorMessage, bool ignoreMissing, bool uri_decode);
static PQconninfoOption *conninfo_find(PQconninfoOption *connOptions,
              const char *keyword);
static void defaultNoticeReceiver(void *arg, const PGresult *res);
static void defaultNoticeProcessor(void *arg, const char *message);
static int parseServiceInfo(PQconninfoOption *options,
                 PQExpBuffer errorMessage);
static int parseServiceFile(const char *serviceFile,
                 const char *service,
                 PQconninfoOption *options,
                 PQExpBuffer errorMessage,
                 bool *group_found);
static char *pwdfMatchesString(char *buf, char *token);
static char *PasswordFromFile(char *hostname, char *port, char *dbname,
                 char *username);
static bool getPgPassFilename(char *pgpassfile);
static void dot_pg_pass_warning(PGconn *conn);
static void default_threadlock(int acquire);


/* global variable because fe-auth.c needs to access it */
pgthreadlock_t pg_g_threadlock = default_threadlock;


/*
 *      pqDropConnection
 *
 * Close any physical connection to the server, and reset associated
 * state inside the connection object.  We don't release state that
 * would be needed to reconnect, though.
 */
void
pqDropConnection(PGconn *conn)
{
    /* Drop any SSL state */
    pqsecure_close(conn);
    /* Close the socket itself */
    if (conn->sock >= 0)
        closesocket(conn->sock);
    conn->sock = -1;
    /* Discard any unread/unsent data */
    conn->inStart = conn->inCursor = conn->inEnd = 0;
    conn->outCount = 0;
}


/*
 *      Connecting to a Database
 *
 * There are now six different ways a user of this API can connect to the
 * database.  Two are not recommended for use in new code, because of their
 * lack of extensibility with respect to the passing of options to the
 * backend.  These are PQsetdb and PQsetdbLogin (the former now being a macro
 * to the latter).
 *
 * If it is desired to connect in a synchronous (blocking) manner, use the
 * function PQconnectdb or PQconnectdbParams. The former accepts a string of
 * option = value pairs (or a URI) which must be parsed; the latter takes two
 * NULL terminated arrays instead.
 *
 * To connect in an asynchronous (non-blocking) manner, use the functions
 * PQconnectStart or PQconnectStartParams (which differ in the same way as
 * PQconnectdb and PQconnectdbParams) and PQconnectPoll.
 *
 * Internally, the static functions connectDBStart, connectDBComplete
 * are part of the connection procedure.
 */

/*
 *      PQconnectdbParams
 *
 * establishes a connection to a postgres backend through the postmaster
 * using connection information in two arrays.
 *
 * The keywords array is defined as
 *
 *     const char *params[] = {"option1", "option2", NULL}
 *
 * The values array is defined as
 *
 *     const char *values[] = {"value1", "value2", NULL}
 *
 * Returns a PGconn* which is needed for all subsequent libpq calls, or NULL
 * if a memory allocation failed.
 * If the status field of the connection returned is CONNECTION_BAD,
 * then some fields may be null'ed out instead of having valid values.
 *
 * You should call PQfinish (if conn is not NULL) regardless of whether this
 * call succeeded.
 */
PGconn *
PQconnectdbParams(const char *const * keywords,
                  const char *const * values,
                  int expand_dbname)
{
    PGconn     *conn = PQconnectStartParams(keywords, values, expand_dbname);

    if (conn && conn->status != CONNECTION_BAD)
        (void) connectDBComplete(conn);

    return conn;

}

/*
 *      PQpingParams
 *
 * check server status, accepting parameters identical to PQconnectdbParams
 */
PGPing
PQpingParams(const char *const * keywords,
             const char *const * values,
             int expand_dbname)
{
    PGconn     *conn = PQconnectStartParams(keywords, values, expand_dbname);
    PGPing      ret;

    ret = internal_ping(conn);
    PQfinish(conn);

    return ret;
}

/*
 *      PQconnectdb
 *
 * establishes a connection to a postgres backend through the postmaster
 * using connection information in a string.
 *
 * The conninfo string is either a whitespace-separated list of
 *
 *     option = value
 *
 * definitions or a URI (refer to the documentation for details.) Value
 * might be a single value containing no whitespaces or a single quoted
 * string. If a single quote should appear anywhere in the value, it must be
 * escaped with a backslash like \'
 *
 * Returns a PGconn* which is needed for all subsequent libpq calls, or NULL
 * if a memory allocation failed.
 * If the status field of the connection returned is CONNECTION_BAD,
 * then some fields may be null'ed out instead of having valid values.
 *
 * You should call PQfinish (if conn is not NULL) regardless of whether this
 * call succeeded.
 */
PGconn *
PQconnectdb(const char *conninfo)
{
    PGconn     *conn = PQconnectStart(conninfo);

    if (conn && conn->status != CONNECTION_BAD)
        (void) connectDBComplete(conn);

    return conn;
}

/*
 *      PQping
 *
 * check server status, accepting parameters identical to PQconnectdb
 */
PGPing
PQping(const char *conninfo)
{
    PGconn     *conn = PQconnectStart(conninfo);
    PGPing      ret;

    ret = internal_ping(conn);
    PQfinish(conn);

    return ret;
}

/*
 *      PQconnectStartParams
 *
 * Begins the establishment of a connection to a postgres backend through the
 * postmaster using connection information in a struct.
 *
 * See comment for PQconnectdbParams for the definition of the string format.
 *
 * Returns a PGconn*.  If NULL is returned, a malloc error has occurred, and
 * you should not attempt to proceed with this connection.  If the status
 * field of the connection returned is CONNECTION_BAD, an error has
 * occurred. In this case you should call PQfinish on the result, (perhaps
 * inspecting the error message first).  Other fields of the structure may not
 * be valid if that occurs.  If the status field is not CONNECTION_BAD, then
 * this stage has succeeded - call PQconnectPoll, using select(2) to see when
 * this is necessary.
 *
 * See PQconnectPoll for more info.
 */
PGconn *
PQconnectStartParams(const char *const * keywords,
                     const char *const * values,
                     int expand_dbname)
{
    PGconn     *conn;
    PQconninfoOption *connOptions;

    /*
     * Allocate memory for the conn structure
     */
    conn = makeEmptyPGconn();
    if (conn == NULL)
        return NULL;

    /*
     * Parse the conninfo arrays
     */
    connOptions = conninfo_array_parse(keywords, values,
                                       &conn->errorMessage,
                                       true, expand_dbname);
    if (connOptions == NULL)
    {
        conn->status = CONNECTION_BAD;
        /* errorMessage is already set */
        return conn;
    }

    /*
     * Move option values into conn structure
     */
    fillPGconn(conn, connOptions);

    /*
     * Free the option info - all is in conn now
     */
    PQconninfoFree(connOptions);

    /*
     * Compute derived options
     */
    if (!connectOptions2(conn))
        return conn;

    /*
     * Connect to the database
     */
    if (!connectDBStart(conn))
    {
        /* Just in case we failed to set it in connectDBStart */
        conn->status = CONNECTION_BAD;
    }

    return conn;
}

/*
 *      PQconnectStart
 *
 * Begins the establishment of a connection to a postgres backend through the
 * postmaster using connection information in a string.
 *
 * See comment for PQconnectdb for the definition of the string format.
 *
 * Returns a PGconn*.  If NULL is returned, a malloc error has occurred, and
 * you should not attempt to proceed with this connection.  If the status
 * field of the connection returned is CONNECTION_BAD, an error has
 * occurred. In this case you should call PQfinish on the result, (perhaps
 * inspecting the error message first).  Other fields of the structure may not
 * be valid if that occurs.  If the status field is not CONNECTION_BAD, then
 * this stage has succeeded - call PQconnectPoll, using select(2) to see when
 * this is necessary.
 *
 * See PQconnectPoll for more info.
 */
PGconn *
PQconnectStart(const char *conninfo)
{
    PGconn     *conn;

    /*
     * Allocate memory for the conn structure
     */
    conn = makeEmptyPGconn();
    if (conn == NULL)
        return NULL;

    /*
     * Parse the conninfo string
     */
    if (!connectOptions1(conn, conninfo))
        return conn;

    /*
     * Compute derived options
     */
    if (!connectOptions2(conn))
        return conn;

    /*
     * Connect to the database
     */
    if (!connectDBStart(conn))
    {
        /* Just in case we failed to set it in connectDBStart */
        conn->status = CONNECTION_BAD;
    }

    return conn;
}

static void
fillPGconn(PGconn *conn, PQconninfoOption *connOptions)
{
    const internalPQconninfoOption *option;

    /*
     * Move option values into conn structure
     *
     * Don't put anything cute here --- intelligence should be in
     * connectOptions2 ...
     *
     * XXX: probably worth checking strdup() return value here...
     */
    for (option = PQconninfoOptions; option->keyword; option++)
    {
        const char *tmp = conninfo_getval(connOptions, option->keyword);

        if (tmp && option->connofs >= 0)
        {
            char      **connmember = (char **) ((char *) conn + option->connofs);

            if (*connmember)
                free(*connmember);
            *connmember = tmp ? strdup(tmp) : NULL;
        }
    }
}

/*
 *      connectOptions1
 *
 * Internal subroutine to set up connection parameters given an already-
 * created PGconn and a conninfo string.  Derived settings should be
 * processed by calling connectOptions2 next.  (We split them because
 * PQsetdbLogin overrides defaults in between.)
 *
 * Returns true if OK, false if trouble (in which case errorMessage is set
 * and so is conn->status).
 */
static bool
connectOptions1(PGconn *conn, const char *conninfo)
{
    PQconninfoOption *connOptions;

    /*
     * Parse the conninfo string
     */
    connOptions = parse_connection_string(conninfo, &conn->errorMessage, true);
    if (connOptions == NULL)
    {
        conn->status = CONNECTION_BAD;
        /* errorMessage is already set */
        return false;
    }

    /*
     * Move option values into conn structure
     */
    fillPGconn(conn, connOptions);

    /*
     * Free the option info - all is in conn now
     */
    PQconninfoFree(connOptions);

    return true;
}

/*
 *      connectOptions2
 *
 * Compute derived connection options after absorbing all user-supplied info.
 *
 * Returns true if OK, false if trouble (in which case errorMessage is set
 * and so is conn->status).
 */
static bool
connectOptions2(PGconn *conn)
{
    /*
     * If database name was not given, default it to equal user name
     */
    if ((conn->dbName == NULL || conn->dbName[0] == '\0')
        && conn->pguser != NULL)
    {
        if (conn->dbName)
            free(conn->dbName);
        conn->dbName = strdup(conn->pguser);
    }

    /*
     * Supply default password if none given
     */
    if (conn->pgpass == NULL || conn->pgpass[0] == '\0')
    {
        if (conn->pgpass)
            free(conn->pgpass);
        conn->pgpass = PasswordFromFile(conn->pghost, conn->pgport,
                                        conn->dbName, conn->pguser);
        if (conn->pgpass == NULL)
            conn->pgpass = strdup(DefaultPassword);
        else
            conn->dot_pgpass_used = true;
    }

    /*
     * Allow unix socket specification in the host name
     */
    if (conn->pghost && is_absolute_path(conn->pghost))
    {
        if (conn->pgunixsocket)
            free(conn->pgunixsocket);
        conn->pgunixsocket = conn->pghost;
        conn->pghost = NULL;
    }

    /*
     * validate sslmode option
     */
    if (conn->sslmode)
    {
        if (strcmp(conn->sslmode, "disable") != 0
            && strcmp(conn->sslmode, "allow") != 0
            && strcmp(conn->sslmode, "prefer") != 0
            && strcmp(conn->sslmode, "require") != 0
            && strcmp(conn->sslmode, "verify-ca") != 0
            && strcmp(conn->sslmode, "verify-full") != 0)
        {
            conn->status = CONNECTION_BAD;
            printfPQExpBuffer(&conn->errorMessage,
                            libpq_gettext("invalid sslmode value: \"%s\"\n"),
                              conn->sslmode);
            return false;
        }

#ifndef USE_SSL
        switch (conn->sslmode[0])
        {
            case 'a':           /* "allow" */
            case 'p':           /* "prefer" */

                /*
                 * warn user that an SSL connection will never be negotiated
                 * since SSL was not compiled in?
                 */
                break;

            case 'r':           /* "require" */
            case 'v':           /* "verify-ca" or "verify-full" */
                conn->status = CONNECTION_BAD;
                printfPQExpBuffer(&conn->errorMessage,
                                  libpq_gettext("sslmode value \"%s\" invalid when SSL support is not compiled in\n"),
                                  conn->sslmode);
                return false;
        }
#endif
    }
    else
        conn->sslmode = strdup(DefaultSSLMode);

    /*
     * Resolve special "auto" client_encoding from the locale
     */
    if (conn->client_encoding_initial &&
        strcmp(conn->client_encoding_initial, "auto") == 0)
    {
        free(conn->client_encoding_initial);
        conn->client_encoding_initial = strdup(pg_encoding_to_char(pg_get_encoding_from_locale(NULL, true)));
    }

    /*
     * Only if we get this far is it appropriate to try to connect. (We need a
     * state flag, rather than just the boolean result of this function, in
     * case someone tries to PQreset() the PGconn.)
     */
    conn->options_valid = true;

    return true;
}

/*
 *      PQconndefaults
 *
 * Construct a default connection options array, which identifies all the
 * available options and shows any default values that are available from the
 * environment etc.  On error (eg out of memory), NULL is returned.
 *
 * Using this function, an application may determine all possible options
 * and their current default values.
 *
 * NOTE: as of PostgreSQL 7.0, the returned array is dynamically allocated
 * and should be freed when no longer needed via PQconninfoFree().  (In prior
 * versions, the returned array was static, but that's not thread-safe.)
 * Pre-7.0 applications that use this function will see a small memory leak
 * until they are updated to call PQconninfoFree.
 */
PQconninfoOption *
PQconndefaults(void)
{
    PQExpBufferData errorBuf;
    PQconninfoOption *connOptions;

    /* We don't actually report any errors here, but callees want a buffer */
    initPQExpBuffer(&errorBuf);
    if (PQExpBufferDataBroken(errorBuf))
        return NULL;            /* out of memory already :-( */

    connOptions = conninfo_init(&errorBuf);
    if (connOptions != NULL)
    {
        if (!conninfo_add_defaults(connOptions, &errorBuf))
        {
            PQconninfoFree(connOptions);
            connOptions = NULL;
        }
    }

    termPQExpBuffer(&errorBuf);
    return connOptions;
}

/* ----------------
 *      PQsetdbLogin
 *
 * establishes a connection to a postgres backend through the postmaster
 * at the specified host and port.
 *
 * returns a PGconn* which is needed for all subsequent libpq calls
 *
 * if the status field of the connection returned is CONNECTION_BAD,
 * then only the errorMessage is likely to be useful.
 * ----------------
 */
PGconn *
PQsetdbLogin(const char *pghost, const char *pgport, const char *pgoptions,
             const char *pgtty, const char *dbName, const char *login,
             const char *pwd)
{
    PGconn     *conn;

    /*
     * Allocate memory for the conn structure
     */
    conn = makeEmptyPGconn();
    if (conn == NULL)
        return NULL;

    /*
     * If the dbName parameter contains what looks like a connection string,
     * parse it into conn struct using connectOptions1.
     */
    if (dbName && recognized_connection_string(dbName))
    {
        if (!connectOptions1(conn, dbName))
            return conn;
    }
    else
    {
        /*
         * Old-style path: first, parse an empty conninfo string in order to
         * set up the same defaults that PQconnectdb() would use.
         */
        if (!connectOptions1(conn, ""))
            return conn;

        /* Insert dbName parameter value into struct */
        if (dbName && dbName[0] != '\0')
        {
            if (conn->dbName)
                free(conn->dbName);
            conn->dbName = strdup(dbName);
        }
    }

    /*
     * Insert remaining parameters into struct, overriding defaults (as well
     * as any conflicting data from dbName taken as a conninfo).
     */
    if (pghost && pghost[0] != '\0')
    {
        if (conn->pghost)
            free(conn->pghost);
        conn->pghost = strdup(pghost);
    }

    if (pgport && pgport[0] != '\0')
    {
        if (conn->pgport)
            free(conn->pgport);
        conn->pgport = strdup(pgport);
    }

    if (pgoptions && pgoptions[0] != '\0')
    {
        if (conn->pgoptions)
            free(conn->pgoptions);
        conn->pgoptions = strdup(pgoptions);
    }

    if (pgtty && pgtty[0] != '\0')
    {
        if (conn->pgtty)
            free(conn->pgtty);
        conn->pgtty = strdup(pgtty);
    }

    if (login && login[0] != '\0')
    {
        if (conn->pguser)
            free(conn->pguser);
        conn->pguser = strdup(login);
    }

    if (pwd && pwd[0] != '\0')
    {
        if (conn->pgpass)
            free(conn->pgpass);
        conn->pgpass = strdup(pwd);
    }

    /*
     * Compute derived options
     */
    if (!connectOptions2(conn))
        return conn;

    /*
     * Connect to the database
     */
    if (connectDBStart(conn))
        (void) connectDBComplete(conn);

    return conn;
}


/* ----------
 * connectNoDelay -
 * Sets the TCP_NODELAY socket option.
 * Returns 1 if successful, 0 if not.
 * ----------
 */
static int
connectNoDelay(PGconn *conn)
{
#ifdef  TCP_NODELAY
    int         on = 1;

    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_NODELAY,
                   (char *) &on,
                   sizeof(on)) < 0)
    {
        char        sebuf[256];

        appendPQExpBuffer(&conn->errorMessage,
            libpq_gettext("could not set socket to TCP no delay mode: %s\n"),
                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif

    return 1;
}


/* ----------
 * connectFailureMessage -
 * create a friendly error message on connection failure.
 * ----------
 */
static void
connectFailureMessage(PGconn *conn, int errorno)
{
    char        sebuf[256];

#ifdef HAVE_UNIX_SOCKETS
    if (IS_AF_UNIX(conn->raddr.addr.ss_family))
    {
        char        service[NI_MAXHOST];

        pg_getnameinfo_all(&conn->raddr.addr, conn->raddr.salen,
                           NULL, 0,
                           service, sizeof(service),
                           NI_NUMERICSERV);
        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("could not connect to server: %s\n"
                            "\tIs the server running locally and accepting\n"
                            "\tconnections on Unix domain socket \"%s\"?\n"),
                          SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)),
                          service);
    }
    else
#endif   /* HAVE_UNIX_SOCKETS */
    {
        char        host_addr[NI_MAXHOST];
        const char *displayed_host;
        struct sockaddr_storage *addr = &conn->raddr.addr;

        /*
         * Optionally display the network address with the hostname. This is
         * useful to distinguish between IPv4 and IPv6 connections.
         */
        if (conn->pghostaddr != NULL)
            strlcpy(host_addr, conn->pghostaddr, NI_MAXHOST);
        else if (addr->ss_family == AF_INET)
        {
            if (inet_net_ntop(AF_INET,
                              &((struct sockaddr_in *) addr)->sin_addr.s_addr,
                              32,
                              host_addr, sizeof(host_addr)) == NULL)
                strcpy(host_addr, "???");
        }
#ifdef HAVE_IPV6
        else if (addr->ss_family == AF_INET6)
        {
            if (inet_net_ntop(AF_INET6,
                          &((struct sockaddr_in6 *) addr)->sin6_addr.s6_addr,
                              128,
                              host_addr, sizeof(host_addr)) == NULL)
                strcpy(host_addr, "???");
        }
#endif
        else
            strcpy(host_addr, "???");

        if (conn->pghostaddr && conn->pghostaddr[0] != '\0')
            displayed_host = conn->pghostaddr;
        else if (conn->pghost && conn->pghost[0] != '\0')
            displayed_host = conn->pghost;
        else
            displayed_host = DefaultHost;

        /*
         * If the user did not supply an IP address using 'hostaddr', and
         * 'host' was missing or does not match our lookup, display the
         * looked-up IP address.
         */
        if ((conn->pghostaddr == NULL) &&
            (conn->pghost == NULL || strcmp(conn->pghost, host_addr) != 0))
            appendPQExpBuffer(&conn->errorMessage,
                            libpq_gettext("could not connect to server: %s\n"
                "\tIs the server running on host \"%s\" (%s) and accepting\n"
                                       "\tTCP/IP connections on port %s?\n"),
                              SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)),
                              displayed_host,
                              host_addr,
                              conn->pgport);
        else
            appendPQExpBuffer(&conn->errorMessage,
                            libpq_gettext("could not connect to server: %s\n"
                     "\tIs the server running on host \"%s\" and accepting\n"
                                       "\tTCP/IP connections on port %s?\n"),
                              SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)),
                              displayed_host,
                              conn->pgport);
    }
}

/*
 * Should we use keepalives?  Returns 1 if yes, 0 if no, and -1 if
 * conn->keepalives is set to a value which is not parseable as an
 * integer.
 */
static int
useKeepalives(PGconn *conn)
{
    char       *ep;
    int         val;

    if (conn->keepalives == NULL)
        return 1;
    val = strtol(conn->keepalives, &ep, 10);
    if (*ep)
        return -1;
    return val != 0 ? 1 : 0;
}

#ifndef WIN32
/*
 * Set the keepalive idle timer.
 */
static int
setKeepalivesIdle(PGconn *conn)
{
    int         idle;

    if (conn->keepalives_idle == NULL)
        return 1;

    idle = atoi(conn->keepalives_idle);
    if (idle < 0)
        idle = 0;

#ifdef TCP_KEEPIDLE
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_KEEPIDLE,
                   (char *) &idle, sizeof(idle)) < 0)
    {
        char        sebuf[256];

        appendPQExpBuffer(&conn->errorMessage,
                      libpq_gettext("setsockopt(TCP_KEEPIDLE) failed: %s\n"),
                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#else
#ifdef TCP_KEEPALIVE
    /* Darwin uses TCP_KEEPALIVE rather than TCP_KEEPIDLE */
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_KEEPALIVE,
                   (char *) &idle, sizeof(idle)) < 0)
    {
        char        sebuf[256];

        appendPQExpBuffer(&conn->errorMessage,
                     libpq_gettext("setsockopt(TCP_KEEPALIVE) failed: %s\n"),
                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif
#endif

    return 1;
}

/*
 * Set the keepalive interval.
 */
static int
setKeepalivesInterval(PGconn *conn)
{
    int         interval;

    if (conn->keepalives_interval == NULL)
        return 1;

    interval = atoi(conn->keepalives_interval);
    if (interval < 0)
        interval = 0;

#ifdef TCP_KEEPINTVL
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_KEEPINTVL,
                   (char *) &interval, sizeof(interval)) < 0)
    {
        char        sebuf[256];

        appendPQExpBuffer(&conn->errorMessage,
                     libpq_gettext("setsockopt(TCP_KEEPINTVL) failed: %s\n"),
                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif

    return 1;
}

/*
 * Set the count of lost keepalive packets that will trigger a connection
 * break.
 */
static int
setKeepalivesCount(PGconn *conn)
{
    int         count;

    if (conn->keepalives_count == NULL)
        return 1;

    count = atoi(conn->keepalives_count);
    if (count < 0)
        count = 0;

#ifdef TCP_KEEPCNT
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_KEEPCNT,
                   (char *) &count, sizeof(count)) < 0)
    {
        char        sebuf[256];

        appendPQExpBuffer(&conn->errorMessage,
                       libpq_gettext("setsockopt(TCP_KEEPCNT) failed: %s\n"),
                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif

    return 1;
}
#else                           /* Win32 */
#ifdef SIO_KEEPALIVE_VALS
/*
 * Enable keepalives and set the keepalive values on Win32,
 * where they are always set in one batch.
 */
static int
setKeepalivesWin32(PGconn *conn)
{
    struct tcp_keepalive ka;
    DWORD       retsize;
    int         idle = 0;
    int         interval = 0;

    if (conn->keepalives_idle)
        idle = atoi(conn->keepalives_idle);
    if (idle <= 0)
        idle = 2 * 60 * 60;     /* 2 hours = default */

    if (conn->keepalives_interval)
        interval = atoi(conn->keepalives_interval);
    if (interval <= 0)
        interval = 1;           /* 1 second = default */

    ka.onoff = 1;
    ka.keepalivetime = idle * 1000;
    ka.keepaliveinterval = interval * 1000;

    if (WSAIoctl(conn->sock,
                 SIO_KEEPALIVE_VALS,
                 (LPVOID) &ka,
                 sizeof(ka),
                 NULL,
                 0,
                 &retsize,
                 NULL,
                 NULL)
        != 0)
    {
        appendPQExpBuffer(&conn->errorMessage,
                 libpq_gettext("WSAIoctl(SIO_KEEPALIVE_VALS) failed: %ui\n"),
                          WSAGetLastError());
        return 0;
    }
    return 1;
}
#endif   /* SIO_KEEPALIVE_VALS */
#endif   /* WIN32 */

/* ----------
 * connectDBStart -
 *      Begin the process of making a connection to the backend.
 *
 * Returns 1 if successful, 0 if not.
 * ----------
 */
static int
connectDBStart(PGconn *conn)
{
    int         portnum;
    char        portstr[MAXPGPATH];
    struct addrinfo *addrs = NULL;
    struct addrinfo hint;
    const char *node;
    int         ret;

    if (!conn)
        return 0;

    if (!conn->options_valid)
        goto connect_errReturn;

    /* Ensure our buffers are empty */
    conn->inStart = conn->inCursor = conn->inEnd = 0;
    conn->outCount = 0;

    /*
     * Determine the parameters to pass to pg_getaddrinfo_all.
     */

    /* Initialize hint structure */
    MemSet(&hint, 0, sizeof(hint));
    hint.ai_socktype = SOCK_STREAM;
    hint.ai_family = AF_UNSPEC;

    /* Set up port number as a string */
    if (conn->pgport != NULL && conn->pgport[0] != '\0')
    {
        portnum = atoi(conn->pgport);
        if (portnum < 1 || portnum > 65535)
        {
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("invalid port number: \"%s\"\n"),
                              conn->pgport);
            conn->options_valid = false;
            goto connect_errReturn;
        }
    }
    else
        portnum = DEF_PGPORT;
    snprintf(portstr, sizeof(portstr), "%d", portnum);

    if (conn->pghostaddr != NULL && conn->pghostaddr[0] != '\0')
    {
        /* Using pghostaddr avoids a hostname lookup */
        node = conn->pghostaddr;
        hint.ai_family = AF_UNSPEC;
        hint.ai_flags = AI_NUMERICHOST;
    }
    else if (conn->pghost != NULL && conn->pghost[0] != '\0')
    {
        /* Using pghost, so we have to look-up the hostname */
        node = conn->pghost;
        hint.ai_family = AF_UNSPEC;
    }
    else
    {
#ifdef HAVE_UNIX_SOCKETS
        /* pghostaddr and pghost are NULL, so use Unix domain socket */
        node = NULL;
        hint.ai_family = AF_UNIX;
        UNIXSOCK_PATH(portstr, portnum, conn->pgunixsocket);
        if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
        {
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("Unix-domain socket path \"%s\" is too long (maximum %d bytes)\n"),
                                            portstr,
                                            (int) (UNIXSOCK_PATH_BUFLEN - 1));
            conn->options_valid = false;
            goto connect_errReturn;
        }
#else
        /* Without Unix sockets, default to localhost instead */
        node = DefaultHost;
        hint.ai_family = AF_UNSPEC;
#endif   /* HAVE_UNIX_SOCKETS */
    }

    /* Use pg_getaddrinfo_all() to resolve the address */
    ret = pg_getaddrinfo_all(node, portstr, &hint, &addrs);
    if (ret || !addrs)
    {
        if (node)
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("could not translate host name \"%s\" to address: %s\n"),
                              node, gai_strerror(ret));
        else
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("could not translate Unix-domain socket path \"%s\" to address: %s\n"),
                              portstr, gai_strerror(ret));
        if (addrs)
            pg_freeaddrinfo_all(hint.ai_family, addrs);
        conn->options_valid = false;
        goto connect_errReturn;
    }

#ifdef USE_SSL
    /* setup values based on SSL mode */
    if (conn->sslmode[0] == 'd')    /* "disable" */
        conn->allow_ssl_try = false;
    else if (conn->sslmode[0] == 'a')   /* "allow" */
        conn->wait_ssl_try = true;
#endif

    /*
     * Set up to try to connect, with protocol 3.0 as the first attempt.
     */
    conn->addrlist = addrs;
    conn->addr_cur = addrs;
    conn->addrlist_family = hint.ai_family;
    conn->pversion = PG_PROTOCOL(3, 0);
    conn->send_appname = true;
    conn->status = CONNECTION_NEEDED;

    /*
     * The code for processing CONNECTION_NEEDED state is in PQconnectPoll(),
     * so that it can easily be re-executed if needed again during the
     * asynchronous startup process.  However, we must run it once here,
     * because callers expect a success return from this routine to mean that
     * we are in PGRES_POLLING_WRITING connection state.
     */
    if (PQconnectPoll(conn) == PGRES_POLLING_WRITING)
        return 1;

connect_errReturn:
    pqDropConnection(conn);
    conn->status = CONNECTION_BAD;
    return 0;
}


/*
 *      connectDBComplete
 *
 * Block and complete a connection.
 *
 * Returns 1 on success, 0 on failure.
 */
static int
connectDBComplete(PGconn *conn)
{
    PostgresPollingStatusType flag = PGRES_POLLING_WRITING;
    time_t      finish_time = ((time_t) -1);

    if (conn == NULL || conn->status == CONNECTION_BAD)
        return 0;

    /*
     * Set up a time limit, if connect_timeout isn't zero.
     */
    if (conn->connect_timeout != NULL)
    {
        int         timeout = atoi(conn->connect_timeout);

        if (timeout > 0)
        {
            /*
             * Rounding could cause connection to fail; need at least 2 secs
             */
            if (timeout < 2)
                timeout = 2;
            /* calculate the finish time based on start + timeout */
            finish_time = time(NULL) + timeout;
        }
    }

    for (;;)
    {
        /*
         * Wait, if necessary.  Note that the initial state (just after
         * PQconnectStart) is to wait for the socket to select for writing.
         */
        switch (flag)
        {
            case PGRES_POLLING_OK:

                /*
                 * Reset stored error messages since we now have a working
                 * connection
                 */
                resetPQExpBuffer(&conn->errorMessage);
                return 1;       /* success! */

            case PGRES_POLLING_READING:
                if (pqWaitTimed(1, 0, conn, finish_time))
                {
                    conn->status = CONNECTION_BAD;
                    return 0;
                }
                break;

            case PGRES_POLLING_WRITING:
                if (pqWaitTimed(0, 1, conn, finish_time))
                {
                    conn->status = CONNECTION_BAD;
                    return 0;
                }
                break;

            default:
                /* Just in case we failed to set it in PQconnectPoll */
                conn->status = CONNECTION_BAD;
                return 0;
        }

        /*
         * Now try to advance the state machine.
         */
        flag = PQconnectPoll(conn);
    }
}

/* ----------------
 *      PQconnectPoll
 *
 * Poll an asynchronous connection.
 *
 * Returns a PostgresPollingStatusType.
 * Before calling this function, use select(2) to determine when data
 * has arrived..
 *
 * You must call PQfinish whether or not this fails.
 *
 * This function and PQconnectStart are intended to allow connections to be
 * made without blocking the execution of your program on remote I/O. However,
 * there are a number of caveats:
 *
 *   o  If you call PQtrace, ensure that the stream object into which you trace
 *      will not block.
 *   o  If you do not supply an IP address for the remote host (i.e. you
 *      supply a host name instead) then PQconnectStart will block on
 *      gethostbyname.  You will be fine if using Unix sockets (i.e. by
 *      supplying neither a host name nor a host address).
 *   o  If your backend wants to use Kerberos authentication then you must
 *      supply both a host name and a host address, otherwise this function
 *      may block on gethostname.
 *
 * ----------------
 */
PostgresPollingStatusType
PQconnectPoll(PGconn *conn)
{
    PGresult   *res;
    char        sebuf[256];
    int         optval;

    if (conn == NULL)
        return PGRES_POLLING_FAILED;

    /* Get the new data */
    switch (conn->status)
    {
            /*
             * We really shouldn't have been polled in these two cases, but we
             * can handle it.
             */
        case CONNECTION_BAD:
            return PGRES_POLLING_FAILED;
        case CONNECTION_OK:
            return PGRES_POLLING_OK;

            /* These are reading states */
        case CONNECTION_AWAITING_RESPONSE:
        case CONNECTION_AUTH_OK:
            {
                /* Load waiting data */
                int         n = pqReadData(conn);

                if (n < 0)
                    goto error_return;
                if (n == 0)
                    return PGRES_POLLING_READING;

                break;
            }

            /* These are writing states, so we just proceed. */
        case CONNECTION_STARTED:
        case CONNECTION_MADE:
            break;

            /* We allow pqSetenvPoll to decide whether to proceed. */
        case CONNECTION_SETENV:
            break;

            /* Special cases: proceed without waiting. */
        case CONNECTION_SSL_STARTUP:
        case CONNECTION_NEEDED:
            break;

        default:
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext(
                                            "invalid connection state, "
                                 "probably indicative of memory corruption\n"
                                            ));
            goto error_return;
    }


keep_going:                     /* We will come back to here until there is
                                 * nothing left to do. */
    switch (conn->status)
    {
        case CONNECTION_NEEDED:
            {
                /*
                 * Try to initiate a connection to one of the addresses
                 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
                 * next one to try. We fail when we run out of addresses.
                 */
                while (conn->addr_cur != NULL)
                {
                    struct addrinfo *addr_cur = conn->addr_cur;

                    /* Remember current address for possible error msg */
                    memcpy(&conn->raddr.addr, addr_cur->ai_addr,
                           addr_cur->ai_addrlen);
                    conn->raddr.salen = addr_cur->ai_addrlen;

                    /* Open a socket */
                    conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
                    if (conn->sock < 0)
                    {
                        /*
                         * ignore socket() failure if we have more addresses
                         * to try
                         */
                        if (addr_cur->ai_next != NULL)
                        {
                            conn->addr_cur = addr_cur->ai_next;
                            continue;
                        }
                        appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("could not create socket: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        break;
                    }

                    /*
                     * Select socket options: no delay of outgoing data for
                     * TCP sockets, nonblock mode, close-on-exec. Fail if any
                     * of this fails.
                     */
                    if (!IS_AF_UNIX(addr_cur->ai_family))
                    {
                        if (!connectNoDelay(conn))
                        {
                            pqDropConnection(conn);
                            conn->addr_cur = addr_cur->ai_next;
                            continue;
                        }
                    }
                    if (!pg_set_noblock(conn->sock))
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not set socket to nonblocking mode: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        pqDropConnection(conn);
                        conn->addr_cur = addr_cur->ai_next;
                        continue;
                    }

#ifdef F_SETFD
                    if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not set socket to close-on-exec mode: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        pqDropConnection(conn);
                        conn->addr_cur = addr_cur->ai_next;
                        continue;
                    }
#endif   /* F_SETFD */

                    if (!IS_AF_UNIX(addr_cur->ai_family))
                    {
#ifndef WIN32
                        int         on = 1;
#endif
                        int         usekeepalives = useKeepalives(conn);
                        int         err = 0;

                        if (usekeepalives < 0)
                        {
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("keepalives parameter must be an integer\n"));
                            err = 1;
                        }
                        else if (usekeepalives == 0)
                        {
                            /* Do nothing */
                        }
#ifndef WIN32
                        else if (setsockopt(conn->sock,
                                            SOL_SOCKET, SO_KEEPALIVE,
                                            (char *) &on, sizeof(on)) < 0)
                        {
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("setsockopt(SO_KEEPALIVE) failed: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                            err = 1;
                        }
                        else if (!setKeepalivesIdle(conn)
                                 || !setKeepalivesInterval(conn)
                                 || !setKeepalivesCount(conn))
                            err = 1;
#else                           /* WIN32 */
#ifdef SIO_KEEPALIVE_VALS
                        else if (!setKeepalivesWin32(conn))
                            err = 1;
#endif   /* SIO_KEEPALIVE_VALS */
#endif   /* WIN32 */

                        if (err)
                        {
                            pqDropConnection(conn);
                            conn->addr_cur = addr_cur->ai_next;
                            continue;
                        }
                    }

                    /*----------
                     * We have three methods of blocking SIGPIPE during
                     * send() calls to this socket:
                     *
                     *  - setsockopt(sock, SO_NOSIGPIPE)
                     *  - send(sock, ..., MSG_NOSIGNAL)
                     *  - setting the signal mask to SIG_IGN during send()
                     *
                     * The third method requires three syscalls per send,
                     * so we prefer either of the first two, but they are
                     * less portable.  The state is tracked in the following
                     * members of PGconn:
                     *
                     * conn->sigpipe_so     - we have set up SO_NOSIGPIPE
                     * conn->sigpipe_flag   - we're specifying MSG_NOSIGNAL
                     *
                     * If we can use SO_NOSIGPIPE, then set sigpipe_so here
                     * and we're done.  Otherwise, set sigpipe_flag so that
                     * we will try MSG_NOSIGNAL on sends.  If we get an error
                     * with MSG_NOSIGNAL, we'll clear that flag and revert to
                     * signal masking.
                     *----------
                     */
                    conn->sigpipe_so = false;
#ifdef MSG_NOSIGNAL
                    conn->sigpipe_flag = true;
#else
                    conn->sigpipe_flag = false;
#endif   /* MSG_NOSIGNAL */

#ifdef SO_NOSIGPIPE
                    optval = 1;
                    if (setsockopt(conn->sock, SOL_SOCKET, SO_NOSIGPIPE,
                                   (char *) &optval, sizeof(optval)) == 0)
                    {
                        conn->sigpipe_so = true;
                        conn->sigpipe_flag = false;
                    }
#endif   /* SO_NOSIGPIPE */

                    /*
                     * Start/make connection.  This should not block, since we
                     * are in nonblock mode.  If it does, well, too bad.
                     */
                    if (connect(conn->sock, addr_cur->ai_addr,
                                addr_cur->ai_addrlen) < 0)
                    {
                        if (SOCK_ERRNO == EINPROGRESS ||
                            SOCK_ERRNO == EWOULDBLOCK ||
                            SOCK_ERRNO == EINTR ||
                            SOCK_ERRNO == 0)
                        {
                            /*
                             * This is fine - we're in non-blocking mode, and
                             * the connection is in progress.  Tell caller to
                             * wait for write-ready on socket.
                             */
                            conn->status = CONNECTION_STARTED;
                            return PGRES_POLLING_WRITING;
                        }
                        /* otherwise, trouble */
                    }
                    else
                    {
                        /*
                         * Hm, we're connected already --- seems the "nonblock
                         * connection" wasn't.  Advance the state machine and
                         * go do the next stuff.
                         */
                        conn->status = CONNECTION_STARTED;
                        goto keep_going;
                    }

                    /*
                     * This connection failed --- set up error report, then
                     * close socket (do it this way in case close() affects
                     * the value of errno...).  We will ignore the connect()
                     * failure and keep going if there are more addresses.
                     */
                    connectFailureMessage(conn, SOCK_ERRNO);
                    pqDropConnection(conn);

                    /*
                     * Try the next address, if any.
                     */
                    conn->addr_cur = addr_cur->ai_next;
                }               /* loop over addresses */

                /*
                 * Ooops, no more addresses.  An appropriate error message is
                 * already set up, so just set the right status.
                 */
                goto error_return;
            }

        case CONNECTION_STARTED:
            {
                ACCEPT_TYPE_ARG3 optlen = sizeof(optval);

                /*
                 * Write ready, since we've made it here, so the connection
                 * has been made ... or has failed.
                 */

                /*
                 * Now check (using getsockopt) that there is not an error
                 * state waiting for us on the socket.
                 */

                if (getsockopt(conn->sock, SOL_SOCKET, SO_ERROR,
                               (char *) &optval, &optlen) == -1)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                    libpq_gettext("could not get socket error status: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                    goto error_return;
                }
                else if (optval != 0)
                {
                    /*
                     * When using a nonblocking connect, we will typically see
                     * connect failures at this point, so provide a friendly
                     * error message.
                     */
                    connectFailureMessage(conn, optval);
                    pqDropConnection(conn);

                    /*
                     * If more addresses remain, keep trying, just as in the
                     * case where connect() returned failure immediately.
                     */
                    if (conn->addr_cur->ai_next != NULL)
                    {
                        conn->addr_cur = conn->addr_cur->ai_next;
                        conn->status = CONNECTION_NEEDED;
                        goto keep_going;
                    }
                    goto error_return;
                }

                /* Fill in the client address */
                conn->laddr.salen = sizeof(conn->laddr.addr);
                if (getsockname(conn->sock,
                                (struct sockaddr *) & conn->laddr.addr,
                                &conn->laddr.salen) < 0)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("could not get client address from socket: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                    goto error_return;
                }

                /*
                 * Make sure we can write before advancing to next step.
                 */
                conn->status = CONNECTION_MADE;
                return PGRES_POLLING_WRITING;
            }

        case CONNECTION_MADE:
            {
                char       *startpacket;
                int         packetlen;

#ifdef HAVE_UNIX_SOCKETS

                /*
                 * Implement requirepeer check, if requested and it's a
                 * Unix-domain socket.
                 */
                if (conn->requirepeer && conn->requirepeer[0] &&
                    IS_AF_UNIX(conn->raddr.addr.ss_family))
                {
                    char        pwdbuf[BUFSIZ];
                    struct passwd pass_buf;
                    struct passwd *pass;
                    uid_t       uid;
                    gid_t       gid;

                    errno = 0;
                    if (getpeereid(conn->sock, &uid, &gid) != 0)
                    {
                        /*
                         * Provide special error message if getpeereid is a
                         * stub
                         */
                        if (errno == ENOSYS)
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("requirepeer parameter is not supported on this platform\n"));
                        else
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("could not get peer credentials: %s\n"),
                                    pqStrerror(errno, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }

                    pqGetpwuid(uid, &pass_buf, pwdbuf, sizeof(pwdbuf), &pass);

                    if (pass == NULL)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("local user with ID %d does not exist\n"),
                                          (int) uid);
                        goto error_return;
                    }

                    if (strcmp(pass->pw_name, conn->requirepeer) != 0)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("requirepeer specifies \"%s\", but actual peer user name is \"%s\"\n"),
                                          conn->requirepeer, pass->pw_name);
                        goto error_return;
                    }
                }
#endif   /* HAVE_UNIX_SOCKETS */

#ifdef USE_SSL

                /*
                 * If SSL is enabled and we haven't already got it running,
                 * request it instead of sending the startup message.
                 */
                if (IS_AF_UNIX(conn->raddr.addr.ss_family))
                {
                    /* Don't bother requesting SSL over a Unix socket */
                    conn->allow_ssl_try = false;
                }
                if (conn->allow_ssl_try && !conn->wait_ssl_try &&
                    conn->ssl == NULL)
                {
                    ProtocolVersion pv;

                    /*
                     * Send the SSL request packet.
                     *
                     * Theoretically, this could block, but it really
                     * shouldn't since we only got here if the socket is
                     * write-ready.
                     */
                    pv = htonl(NEGOTIATE_SSL_CODE);
                    if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not send SSL negotiation packet: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }
                    /* Ok, wait for response */
                    conn->status = CONNECTION_SSL_STARTUP;
                    return PGRES_POLLING_READING;
                }
#endif   /* USE_SSL */

                /*
                 * Build the startup packet.
                 */
                if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                    startpacket = pqBuildStartupPacket3(conn, &packetlen,
                                                        EnvironmentOptions);
                else
                    startpacket = pqBuildStartupPacket2(conn, &packetlen,
                                                        EnvironmentOptions);
                if (!startpacket)
                {
                    /*
                     * will not appendbuffer here, since it's likely to also
                     * run out of memory
                     */
                    printfPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("out of memory\n"));
                    goto error_return;
                }

                /*
                 * Send the startup packet.
                 *
                 * Theoretically, this could block, but it really shouldn't
                 * since we only got here if the socket is write-ready.
                 */
                if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                        libpq_gettext("could not send startup packet: %s\n"),
                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                    free(startpacket);
                    goto error_return;
                }

                free(startpacket);

                conn->status = CONNECTION_AWAITING_RESPONSE;
                return PGRES_POLLING_READING;
            }

            /*
             * Handle SSL negotiation: wait for postmaster messages and
             * respond as necessary.
             */
        case CONNECTION_SSL_STARTUP:
            {
#ifdef USE_SSL
                PostgresPollingStatusType pollres;

                /*
                 * On first time through, get the postmaster's response to our
                 * SSL negotiation packet.
                 */
                if (conn->ssl == NULL)
                {
                    /*
                     * We use pqReadData here since it has the logic to
                     * distinguish no-data-yet from connection closure. Since
                     * conn->ssl isn't set, a plain recv() will occur.
                     */
                    char        SSLok;
                    int         rdresult;

                    rdresult = pqReadData(conn);
                    if (rdresult < 0)
                    {
                        /* errorMessage is already filled in */
                        goto error_return;
                    }
                    if (rdresult == 0)
                    {
                        /* caller failed to wait for data */
                        return PGRES_POLLING_READING;
                    }
                    if (pqGetc(&SSLok, conn) < 0)
                    {
                        /* should not happen really */
                        return PGRES_POLLING_READING;
                    }
                    if (SSLok == 'S')
                    {
                        /* mark byte consumed */
                        conn->inStart = conn->inCursor;
                        /* Set up global SSL state if required */
                        if (pqsecure_initialize(conn) != 0)
                            goto error_return;
                    }
                    else if (SSLok == 'N')
                    {
                        /* mark byte consumed */
                        conn->inStart = conn->inCursor;
                        /* OK to do without SSL? */
                        if (conn->sslmode[0] == 'r' ||  /* "require" */
                            conn->sslmode[0] == 'v')    /* "verify-ca" or
                                                         * "verify-full" */
                        {
                            /* Require SSL, but server does not want it */
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("server does not support SSL, but SSL was required\n"));
                            goto error_return;
                        }
                        /* Otherwise, proceed with normal startup */
                        conn->allow_ssl_try = false;
                        conn->status = CONNECTION_MADE;
                        return PGRES_POLLING_WRITING;
                    }
                    else if (SSLok == 'E')
                    {
                        /*
                         * Server failure of some sort, such as failure to
                         * fork a backend process.  We need to process and
                         * report the error message, which might be formatted
                         * according to either protocol 2 or protocol 3.
                         * Rather than duplicate the code for that, we flip
                         * into AWAITING_RESPONSE state and let the code there
                         * deal with it.  Note we have *not* consumed the "E"
                         * byte here.
                         */
                        conn->status = CONNECTION_AWAITING_RESPONSE;
                        goto keep_going;
                    }
                    else
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("received invalid response to SSL negotiation: %c\n"),
                                          SSLok);
                        goto error_return;
                    }
                }

                /*
                 * Begin or continue the SSL negotiation process.
                 */
                pollres = pqsecure_open_client(conn);
                if (pollres == PGRES_POLLING_OK)
                {
                    /* SSL handshake done, ready to send startup packet */
                    conn->status = CONNECTION_MADE;
                    return PGRES_POLLING_WRITING;
                }
                if (pollres == PGRES_POLLING_FAILED)
                {
                    /*
                     * Failed ... if sslmode is "prefer" then do a non-SSL
                     * retry
                     */
                    if (conn->sslmode[0] == 'p' /* "prefer" */
                        && conn->allow_ssl_try  /* redundant? */
                        && !conn->wait_ssl_try) /* redundant? */
                    {
                        /* only retry once */
                        conn->allow_ssl_try = false;
                        /* Must drop the old connection */
                        pqDropConnection(conn);
                        conn->status = CONNECTION_NEEDED;
                        goto keep_going;
                    }
                }
                return pollres;
#else                           /* !USE_SSL */
                /* can't get here */
                goto error_return;
#endif   /* USE_SSL */
            }

            /*
             * Handle authentication exchange: wait for postmaster messages
             * and respond as necessary.
             */
        case CONNECTION_AWAITING_RESPONSE:
            {
                char        beresp;
                int         msgLength;
                int         avail;
                AuthRequest areq;

                /*
                 * Scan the message from current point (note that if we find
                 * the message is incomplete, we will return without advancing
                 * inStart, and resume here next time).
                 */
                conn->inCursor = conn->inStart;

                /* Read type byte */
                if (pqGetc(&beresp, conn))
                {
                    /* We'll come back when there is more data */
                    return PGRES_POLLING_READING;
                }

                /*
                 * Validate message type: we expect only an authentication
                 * request or an error here.  Anything else probably means
                 * it's not Postgres on the other end at all.
                 */
                if (!(beresp == 'R' || beresp == 'E'))
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext(
                                      "expected authentication request from "
                                                "server, but received %c\n"),
                                      beresp);
                    goto error_return;
                }

                if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                {
                    /* Read message length word */
                    if (pqGetInt(&msgLength, 4, conn))
                    {
                        /* We'll come back when there is more data */
                        return PGRES_POLLING_READING;
                    }
                }
                else
                {
                    /* Set phony message length to disable checks below */
                    msgLength = 8;
                }

                /*
                 * Try to validate message length before using it.
                 * Authentication requests can't be very large, although GSS
                 * auth requests may not be that small.  Errors can be a
                 * little larger, but not huge.  If we see a large apparent
                 * length in an error, it means we're really talking to a
                 * pre-3.0-protocol server; cope.
                 */
                if (beresp == 'R' && (msgLength < 8 || msgLength > 2000))
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext(
                                      "expected authentication request from "
                                                "server, but received %c\n"),
                                      beresp);
                    goto error_return;
                }

                if (beresp == 'E' && (msgLength < 8 || msgLength > 30000))
                {
                    /* Handle error from a pre-3.0 server */
                    conn->inCursor = conn->inStart + 1; /* reread data */
                    if (pqGets_append(&conn->errorMessage, conn))
                    {
                        /* We'll come back when there is more data */
                        return PGRES_POLLING_READING;
                    }
                    /* OK, we read the message; mark data consumed */
                    conn->inStart = conn->inCursor;

                    /*
                     * The postmaster typically won't end its message with a
                     * newline, so add one to conform to libpq conventions.
                     */
                    appendPQExpBufferChar(&conn->errorMessage, '\n');

                    /*
                     * If we tried to open the connection in 3.0 protocol,
                     * fall back to 2.0 protocol.
                     */
                    if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                    {
                        conn->pversion = PG_PROTOCOL(2, 0);
                        /* Must drop the old connection */
                        pqDropConnection(conn);
                        conn->status = CONNECTION_NEEDED;
                        goto keep_going;
                    }

                    goto error_return;
                }

                /*
                 * Can't process if message body isn't all here yet.
                 *
                 * (In protocol 2.0 case, we are assuming messages carry at
                 * least 4 bytes of data.)
                 */
                msgLength -= 4;
                avail = conn->inEnd - conn->inCursor;
                if (avail < msgLength)
                {
                    /*
                     * Before returning, try to enlarge the input buffer if
                     * needed to hold the whole message; see notes in
                     * pqParseInput3.
                     */
                    if (pqCheckInBufferSpace(conn->inCursor + (size_t) msgLength,
                                             conn))
                        goto error_return;
                    /* We'll come back when there is more data */
                    return PGRES_POLLING_READING;
                }

                /* Handle errors. */
                if (beresp == 'E')
                {
                    if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                    {
                        if (pqGetErrorNotice3(conn, true))
                        {
                            /* We'll come back when there is more data */
                            return PGRES_POLLING_READING;
                        }
                    }
                    else
                    {
                        if (pqGets_append(&conn->errorMessage, conn))
                        {
                            /* We'll come back when there is more data */
                            return PGRES_POLLING_READING;
                        }
                    }
                    /* OK, we read the message; mark data consumed */
                    conn->inStart = conn->inCursor;

#ifdef USE_SSL

                    /*
                     * if sslmode is "allow" and we haven't tried an SSL
                     * connection already, then retry with an SSL connection
                     */
                    if (conn->sslmode[0] == 'a' /* "allow" */
                        && conn->ssl == NULL
                        && conn->allow_ssl_try
                        && conn->wait_ssl_try)
                    {
                        /* only retry once */
                        conn->wait_ssl_try = false;
                        /* Must drop the old connection */
                        pqDropConnection(conn);
                        conn->status = CONNECTION_NEEDED;
                        goto keep_going;
                    }

                    /*
                     * if sslmode is "prefer" and we're in an SSL connection,
                     * then do a non-SSL retry
                     */
                    if (conn->sslmode[0] == 'p' /* "prefer" */
                        && conn->allow_ssl_try
                        && !conn->wait_ssl_try) /* redundant? */
                    {
                        /* only retry once */
                        conn->allow_ssl_try = false;
                        /* Must drop the old connection */
                        pqDropConnection(conn);
                        conn->status = CONNECTION_NEEDED;
                        goto keep_going;
                    }
#endif

                    goto error_return;
                }

                /* It is an authentication request. */
                conn->auth_req_received = true;

                /* Get the type of request. */
                if (pqGetInt((int *) &areq, 4, conn))
                {
                    /* We'll come back when there are more data */
                    return PGRES_POLLING_READING;
                }

                /* Get the password salt if there is one. */
                if (areq == AUTH_REQ_MD5)
                {
                    if (pqGetnchar(conn->md5Salt,
                                   sizeof(conn->md5Salt), conn))
                    {
                        /* We'll come back when there are more data */
                        return PGRES_POLLING_READING;
                    }
                }
#if defined(ENABLE_GSS) || defined(ENABLE_SSPI)

                /*
                 * Continue GSSAPI/SSPI authentication
                 */
                if (areq == AUTH_REQ_GSS_CONT)
                {
                    int         llen = msgLength - 4;

                    /*
                     * We can be called repeatedly for the same buffer. Avoid
                     * re-allocating the buffer in this case - just re-use the
                     * old buffer.
                     */
                    if (llen != conn->ginbuf.length)
                    {
                        if (conn->ginbuf.value)
                            free(conn->ginbuf.value);

                        conn->ginbuf.length = llen;
                        conn->ginbuf.value = malloc(llen);
                        if (!conn->ginbuf.value)
                        {
                            printfPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("out of memory allocating GSSAPI buffer (%d)"),
                                              llen);
                            goto error_return;
                        }
                    }

                    if (pqGetnchar(conn->ginbuf.value, llen, conn))
                    {
                        /* We'll come back when there is more data. */
                        return PGRES_POLLING_READING;
                    }
                }
#endif

                /*
                 * OK, we successfully read the message; mark data consumed
                 */
                conn->inStart = conn->inCursor;

                /* Respond to the request if necessary. */

                /*
                 * Note that conn->pghost must be non-NULL if we are going to
                 * avoid the Kerberos code doing a hostname look-up.
                 */

                if (pg_fe_sendauth(areq, conn) != STATUS_OK)
                {
                    conn->errorMessage.len = strlen(conn->errorMessage.data);
                    goto error_return;
                }
                conn->errorMessage.len = strlen(conn->errorMessage.data);

                /*
                 * Just make sure that any data sent by pg_fe_sendauth is
                 * flushed out.  Although this theoretically could block, it
                 * really shouldn't since we don't send large auth responses.
                 */
                if (pqFlush(conn))
                    goto error_return;

                if (areq == AUTH_REQ_OK)
                {
                    /* We are done with authentication exchange */
                    conn->status = CONNECTION_AUTH_OK;

                    /*
                     * Set asyncStatus so that PQgetResult will think that
                     * what comes back next is the result of a query.  See
                     * below.
                     */
                    conn->asyncStatus = PGASYNC_BUSY;
                }

                /* Look to see if we have more data yet. */
                goto keep_going;
            }

        case CONNECTION_AUTH_OK:
            {
                /*
                 * Now we expect to hear from the backend. A ReadyForQuery
                 * message indicates that startup is successful, but we might
                 * also get an Error message indicating failure. (Notice
                 * messages indicating nonfatal warnings are also allowed by
                 * the protocol, as are ParameterStatus and BackendKeyData
                 * messages.) Easiest way to handle this is to let
                 * PQgetResult() read the messages. We just have to fake it
                 * out about the state of the connection, by setting
                 * asyncStatus = PGASYNC_BUSY (done above).
                 */

                if (PQisBusy(conn))
                    return PGRES_POLLING_READING;

                res = PQgetResult(conn);

                /*
                 * NULL return indicating we have gone to IDLE state is
                 * expected
                 */
                if (res)
                {
                    if (res->resultStatus != PGRES_FATAL_ERROR)
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("unexpected message from server during startup\n"));
                    else if (conn->send_appname &&
                             (conn->appname || conn->fbappname))
                    {
                        /*
                         * If we tried to send application_name, check to see
                         * if the error is about that --- pre-9.0 servers will
                         * reject it at this stage of the process.  If so,
                         * close the connection and retry without sending
                         * application_name.  We could possibly get a false
                         * SQLSTATE match here and retry uselessly, but there
                         * seems no great harm in that; we'll just get the
                         * same error again if it's unrelated.
                         */
                        const char *sqlstate;

                        sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
                        if (sqlstate &&
                            strcmp(sqlstate, ERRCODE_APPNAME_UNKNOWN) == 0)
                        {
                            PQclear(res);
                            conn->send_appname = false;
                            /* Must drop the old connection */
                            pqDropConnection(conn);
                            conn->status = CONNECTION_NEEDED;
                            goto keep_going;
                        }
                    }

                    /*
                     * if the resultStatus is FATAL, then conn->errorMessage
                     * already has a copy of the error; needn't copy it back.
                     * But add a newline if it's not there already, since
                     * postmaster error messages may not have one.
                     */
                    if (conn->errorMessage.len <= 0 ||
                        conn->errorMessage.data[conn->errorMessage.len - 1] != '\n')
                        appendPQExpBufferChar(&conn->errorMessage, '\n');
                    PQclear(res);
                    goto error_return;
                }

                /* We can release the address list now. */
                pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
                conn->addrlist = NULL;
                conn->addr_cur = NULL;

                /* Fire up post-connection housekeeping if needed */
                if (PG_PROTOCOL_MAJOR(conn->pversion) < 3)
                {
                    conn->status = CONNECTION_SETENV;
                    conn->setenv_state = SETENV_STATE_CLIENT_ENCODING_SEND;
                    conn->next_eo = EnvironmentOptions;
                    return PGRES_POLLING_WRITING;
                }

                /* Otherwise, we are open for business! */
                conn->status = CONNECTION_OK;
                return PGRES_POLLING_OK;
            }

        case CONNECTION_SETENV:

            /*
             * Do post-connection housekeeping (only needed in protocol 2.0).
             *
             * We pretend that the connection is OK for the duration of these
             * queries.
             */
            conn->status = CONNECTION_OK;

            switch (pqSetenvPoll(conn))
            {
                case PGRES_POLLING_OK:  /* Success */
                    break;

                case PGRES_POLLING_READING:     /* Still going */
                    conn->status = CONNECTION_SETENV;
                    return PGRES_POLLING_READING;

                case PGRES_POLLING_WRITING:     /* Still going */
                    conn->status = CONNECTION_SETENV;
                    return PGRES_POLLING_WRITING;

                default:
                    goto error_return;
            }

            /* We are open for business! */
            conn->status = CONNECTION_OK;
            return PGRES_POLLING_OK;

        default:
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("invalid connection state %d, "
                               "probably indicative of memory corruption\n"),
                              conn->status);
            goto error_return;
    }

    /* Unreachable */

error_return:

    dot_pg_pass_warning(conn);

    /*
     * We used to close the socket at this point, but that makes it awkward
     * for those above us if they wish to remove this socket from their own
     * records (an fd_set for example).  We'll just have this socket closed
     * when PQfinish is called (which is compulsory even after an error, since
     * the connection structure must be freed).
     */
    conn->status = CONNECTION_BAD;
    return PGRES_POLLING_FAILED;
}


/*
 * internal_ping
 *      Determine if a server is running and if we can connect to it.
 *
 * The argument is a connection that's been started, but not completed.
 */
static PGPing
internal_ping(PGconn *conn)
{
    /* Say "no attempt" if we never got to PQconnectPoll */
    if (!conn || !conn->options_valid)
        return PQPING_NO_ATTEMPT;

    /* Attempt to complete the connection */
    if (conn->status != CONNECTION_BAD)
        (void) connectDBComplete(conn);

    /* Definitely OK if we succeeded */
    if (conn->status != CONNECTION_BAD)
        return PQPING_OK;

    /*
     * Here begins the interesting part of "ping": determine the cause of the
     * failure in sufficient detail to decide what to return.  We do not want
     * to report that the server is not up just because we didn't have a valid
     * password, for example.  In fact, any sort of authentication request
     * implies the server is up.  (We need this check since the libpq side of
     * things might have pulled the plug on the connection before getting an
     * error as such from the postmaster.)
     */
    if (conn->auth_req_received)
        return PQPING_OK;

    /*
     * If we failed to get any ERROR response from the postmaster, report
     * PQPING_NO_RESPONSE.  This result could be somewhat misleading for a
     * pre-7.4 server, since it won't send back a SQLSTATE, but those are long
     * out of support.  Another corner case where the server could return a
     * failure without a SQLSTATE is fork failure, but NO_RESPONSE isn't
     * totally unreasonable for that anyway.  We expect that every other
     * failure case in a modern server will produce a report with a SQLSTATE.
     *
     * NOTE: whenever we get around to making libpq generate SQLSTATEs for
     * client-side errors, we should either not store those into
     * last_sqlstate, or add an extra flag so we can tell client-side errors
     * apart from server-side ones.
     */
    if (strlen(conn->last_sqlstate) != 5)
        return PQPING_NO_RESPONSE;

    /*
     * Report PQPING_REJECT if server says it's not accepting connections. (We
     * distinguish this case mainly for the convenience of pg_ctl.)
     */
    if (strcmp(conn->last_sqlstate, ERRCODE_CANNOT_CONNECT_NOW) == 0)
        return PQPING_REJECT;

    /*
     * Any other SQLSTATE can be taken to indicate that the server is up.
     * Presumably it didn't like our username, password, or database name; or
     * perhaps it had some transient failure, but that should not be taken as
     * meaning "it's down".
     */
    return PQPING_OK;
}


/*
 * makeEmptyPGconn
 *   - create a PGconn data structure with (as yet) no interesting data
 */
static PGconn *
makeEmptyPGconn(void)
{
    PGconn     *conn;

#ifdef WIN32

    /*
     * Make sure socket support is up and running.
     */
    WSADATA     wsaData;

    if (WSAStartup(MAKEWORD(1, 1), &wsaData))
        return NULL;
    WSASetLastError(0);
#endif

    conn = (PGconn *) malloc(sizeof(PGconn));
    if (conn == NULL)
    {
#ifdef WIN32
        WSACleanup();
#endif
        return conn;
    }

    /* Zero all pointers and booleans */
    MemSet(conn, 0, sizeof(PGconn));

    /* install default notice hooks */
    conn->noticeHooks.noticeRec = defaultNoticeReceiver;
    conn->noticeHooks.noticeProc = defaultNoticeProcessor;

    conn->status = CONNECTION_BAD;
    conn->asyncStatus = PGASYNC_IDLE;
    conn->xactStatus = PQTRANS_IDLE;
    conn->options_valid = false;
    conn->nonblocking = false;
    conn->setenv_state = SETENV_STATE_IDLE;
    conn->client_encoding = PG_SQL_ASCII;
    conn->std_strings = false;  /* unless server says differently */
    conn->verbosity = PQERRORS_DEFAULT;
    conn->sock = -1;
    conn->auth_req_received = false;
    conn->password_needed = false;
    conn->dot_pgpass_used = false;
#ifdef USE_SSL
    conn->allow_ssl_try = true;
    conn->wait_ssl_try = false;
#endif

    /*
     * We try to send at least 8K at a time, which is the usual size of pipe
     * buffers on Unix systems.  That way, when we are sending a large amount
     * of data, we avoid incurring extra kernel context swaps for partial
     * bufferloads.  The output buffer is initially made 16K in size, and we
     * try to dump it after accumulating 8K.
     *
     * With the same goal of minimizing context swaps, the input buffer will
     * be enlarged anytime it has less than 8K free, so we initially allocate
     * twice that.
     */
    conn->inBufSize = 16 * 1024;
    conn->inBuffer = (char *) malloc(conn->inBufSize);
    conn->outBufSize = 16 * 1024;
    conn->outBuffer = (char *) malloc(conn->outBufSize);
    conn->rowBufLen = 32;
    conn->rowBuf = (PGdataValue *) malloc(conn->rowBufLen * sizeof(PGdataValue));
    initPQExpBuffer(&conn->errorMessage);
    initPQExpBuffer(&conn->workBuffer);

    if (conn->inBuffer == NULL ||
        conn->outBuffer == NULL ||
        conn->rowBuf == NULL ||
        PQExpBufferBroken(&conn->errorMessage) ||
        PQExpBufferBroken(&conn->workBuffer))
    {
        /* out of memory already :-( */
        freePGconn(conn);
        conn = NULL;
    }

    return conn;
}

/*
 * freePGconn
 *   - free an idle (closed) PGconn data structure
 *
 * NOTE: this should not overlap any functionality with closePGconn().
 * Clearing/resetting of transient state belongs there; what we do here is
 * release data that is to be held for the life of the PGconn structure.
 * If a value ought to be cleared/freed during PQreset(), do it there not here.
 */
static void
freePGconn(PGconn *conn)
{
    int         i;

    /* let any event procs clean up their state data */
    for (i = 0; i < conn->nEvents; i++)
    {
        PGEventConnDestroy evt;

        evt.conn = conn;
        (void) conn->events[i].proc(PGEVT_CONNDESTROY, &evt,
                                    conn->events[i].passThrough);
        free(conn->events[i].name);
    }

    if (conn->client_encoding_initial)
        free(conn->client_encoding_initial);
    if (conn->events)
        free(conn->events);
    if (conn->pghost)
        free(conn->pghost);
    if (conn->pghostaddr)
        free(conn->pghostaddr);
    if (conn->pgport)
        free(conn->pgport);
    if (conn->pgunixsocket)
        free(conn->pgunixsocket);
    if (conn->pgtty)
        free(conn->pgtty);
    if (conn->connect_timeout)
        free(conn->connect_timeout);
    if (conn->pgoptions)
        free(conn->pgoptions);
    if (conn->appname)
        free(conn->appname);
    if (conn->fbappname)
        free(conn->fbappname);
    if (conn->dbName)
        free(conn->dbName);
    if (conn->replication)
        free(conn->replication);
    if (conn->pguser)
        free(conn->pguser);
    if (conn->pgpass)
        free(conn->pgpass);
    if (conn->keepalives)
        free(conn->keepalives);
    if (conn->keepalives_idle)
        free(conn->keepalives_idle);
    if (conn->keepalives_interval)
        free(conn->keepalives_interval);
    if (conn->keepalives_count)
        free(conn->keepalives_count);
    if (conn->sslmode)
        free(conn->sslmode);
    if (conn->sslcert)
        free(conn->sslcert);
    if (conn->sslkey)
        free(conn->sslkey);
    if (conn->sslrootcert)
        free(conn->sslrootcert);
    if (conn->sslcrl)
        free(conn->sslcrl);
    if (conn->sslcompression)
        free(conn->sslcompression);
    if (conn->requirepeer)
        free(conn->requirepeer);
#if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
    if (conn->krbsrvname)
        free(conn->krbsrvname);
#endif
#if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
    if (conn->gsslib)
        free(conn->gsslib);
#endif
    /* Note that conn->Pfdebug is not ours to close or free */
    if (conn->last_query)
        free(conn->last_query);
    if (conn->inBuffer)
        free(conn->inBuffer);
    if (conn->outBuffer)
        free(conn->outBuffer);
    if (conn->rowBuf)
        free(conn->rowBuf);
    termPQExpBuffer(&conn->errorMessage);
    termPQExpBuffer(&conn->workBuffer);

    free(conn);

#ifdef WIN32
    WSACleanup();
#endif
}

/*
 * closePGconn
 *   - properly close a connection to the backend
 *
 * This should reset or release all transient state, but NOT the connection
 * parameters.  On exit, the PGconn should be in condition to start a fresh
 * connection with the same parameters (see PQreset()).
 */
static void
closePGconn(PGconn *conn)
{
    PGnotify   *notify;
    pgParameterStatus *pstatus;

    /*
     * Note that the protocol doesn't allow us to send Terminate messages
     * during the startup phase.
     */
    if (conn->sock >= 0 && conn->status == CONNECTION_OK)
    {
        /*
         * Try to send "close connection" message to backend. Ignore any
         * error.
         */
        pqPutMsgStart('X', false, conn);
        pqPutMsgEnd(conn);
        pqFlush(conn);
    }

    /*
     * Must reset the blocking status so a possible reconnect will work.
     *
     * Don't call PQsetnonblocking() because it will fail if it's unable to
     * flush the connection.
     */
    conn->nonblocking = FALSE;

    /*
     * Close the connection, reset all transient state, flush I/O buffers.
     */
    pqDropConnection(conn);
    conn->status = CONNECTION_BAD;      /* Well, not really _bad_ - just
                                         * absent */
    conn->asyncStatus = PGASYNC_IDLE;
    pqClearAsyncResult(conn);   /* deallocate result */
    pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
    conn->addrlist = NULL;
    conn->addr_cur = NULL;
    notify = conn->notifyHead;
    while (notify != NULL)
    {
        PGnotify   *prev = notify;

        notify = notify->next;
        free(prev);
    }
    conn->notifyHead = conn->notifyTail = NULL;
    pstatus = conn->pstatus;
    while (pstatus != NULL)
    {
        pgParameterStatus *prev = pstatus;

        pstatus = pstatus->next;
        free(prev);
    }
    conn->pstatus = NULL;
    if (conn->lobjfuncs)
        free(conn->lobjfuncs);
    conn->lobjfuncs = NULL;
#ifdef ENABLE_GSS
    {
        OM_uint32   min_s;

        if (conn->gctx)
            gss_delete_sec_context(&min_s, &conn->gctx, GSS_C_NO_BUFFER);
        if (conn->gtarg_nam)
            gss_release_name(&min_s, &conn->gtarg_nam);
        if (conn->ginbuf.length)
            gss_release_buffer(&min_s, &conn->ginbuf);
        if (conn->goutbuf.length)
            gss_release_buffer(&min_s, &conn->goutbuf);
    }
#endif
#ifdef ENABLE_SSPI
    if (conn->ginbuf.length)
        free(conn->ginbuf.value);
    conn->ginbuf.length = 0;
    conn->ginbuf.value = NULL;
    if (conn->sspitarget)
        free(conn->sspitarget);
    conn->sspitarget = NULL;
    if (conn->sspicred)
    {
        FreeCredentialsHandle(conn->sspicred);
        free(conn->sspicred);
        conn->sspicred = NULL;
    }
    if (conn->sspictx)
    {
        DeleteSecurityContext(conn->sspictx);
        free(conn->sspictx);
        conn->sspictx = NULL;
    }
#endif
}

/*
 * PQfinish: properly close a connection to the backend. Also frees
 * the PGconn data structure so it shouldn't be re-used after this.
 */
void
PQfinish(PGconn *conn)
{
    if (conn)
    {
        closePGconn(conn);
        freePGconn(conn);
    }
}

/*
 * PQreset: resets the connection to the backend by closing the
 * existing connection and creating a new one.
 */
void
PQreset(PGconn *conn)
{
    if (conn)
    {
        closePGconn(conn);

        if (connectDBStart(conn) && connectDBComplete(conn))
        {
            /*
             * Notify event procs of successful reset.  We treat an event proc
             * failure as disabling the connection ... good idea?
             */
            int         i;

            for (i = 0; i < conn->nEvents; i++)
            {
                PGEventConnReset evt;

                evt.conn = conn;
                if (!conn->events[i].proc(PGEVT_CONNRESET, &evt,
                                          conn->events[i].passThrough))
                {
                    conn->status = CONNECTION_BAD;
                    printfPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("PGEventProc \"%s\" failed during PGEVT_CONNRESET event\n"),
                                      conn->events[i].name);
                    break;
                }
            }
        }
    }
}


/*
 * PQresetStart:
 * resets the connection to the backend
 * closes the existing connection and makes a new one
 * Returns 1 on success, 0 on failure.
 */
int
PQresetStart(PGconn *conn)
{
    if (conn)
    {
        closePGconn(conn);

        return connectDBStart(conn);
    }

    return 0;
}


/*
 * PQresetPoll:
 * resets the connection to the backend
 * closes the existing connection and makes a new one
 */
PostgresPollingStatusType
PQresetPoll(PGconn *conn)
{
    if (conn)
    {
        PostgresPollingStatusType status = PQconnectPoll(conn);

        if (status == PGRES_POLLING_OK)
        {
            /*
             * Notify event procs of successful reset.  We treat an event proc
             * failure as disabling the connection ... good idea?
             */
            int         i;

            for (i = 0; i < conn->nEvents; i++)
            {
                PGEventConnReset evt;

                evt.conn = conn;
                if (!conn->events[i].proc(PGEVT_CONNRESET, &evt,
                                          conn->events[i].passThrough))
                {
                    conn->status = CONNECTION_BAD;
                    printfPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("PGEventProc \"%s\" failed during PGEVT_CONNRESET event\n"),
                                      conn->events[i].name);
                    return PGRES_POLLING_FAILED;
                }
            }
        }

        return status;
    }

    return PGRES_POLLING_FAILED;
}

/*
 * PQcancelGet: get a PGcancel structure corresponding to a connection.
 *
 * A copy is needed to be able to cancel a running query from a different
 * thread. If the same structure is used all structure members would have
 * to be individually locked (if the entire structure was locked, it would
 * be impossible to cancel a synchronous query because the structure would
 * have to stay locked for the duration of the query).
 */
PGcancel *
PQgetCancel(PGconn *conn)
{
    PGcancel   *cancel;

    if (!conn)
        return NULL;

    if (conn->sock < 0)
        return NULL;

    cancel = malloc(sizeof(PGcancel));
    if (cancel == NULL)
        return NULL;

    memcpy(&cancel->raddr, &conn->raddr, sizeof(SockAddr));
    cancel->be_pid = conn->be_pid;
    cancel->be_key = conn->be_key;

    return cancel;
}

/* PQfreeCancel: free a cancel structure */
void
PQfreeCancel(PGcancel *cancel)
{
    if (cancel)
        free(cancel);
}


/*
 * PQcancel and PQrequestCancel: attempt to request cancellation of the
 * current operation.
 *
 * The return value is TRUE if the cancel request was successfully
 * dispatched, FALSE if not (in which case an error message is available).
 * Note: successful dispatch is no guarantee that there will be any effect at
 * the backend.  The application must read the operation result as usual.
 *
 * CAUTION: we want this routine to be safely callable from a signal handler
 * (for example, an application might want to call it in a SIGINT handler).
 * This means we cannot use any C library routine that might be non-reentrant.
 * malloc/free are often non-reentrant, and anything that might call them is
 * just as dangerous.  We avoid sprintf here for that reason.  Building up
 * error messages with strcpy/strcat is tedious but should be quite safe.
 * We also save/restore errno in case the signal handler support doesn't.
 *
 * internal_cancel() is an internal helper function to make code-sharing
 * between the two versions of the cancel function possible.
 */
static int
internal_cancel(SockAddr *raddr, int be_pid, int be_key,
                char *errbuf, int errbufsize)
{
    int         save_errno = SOCK_ERRNO;
    int         tmpsock = -1;
    char        sebuf[256];
    int         maxlen;
    struct
    {
        uint32      packetlen;
        CancelRequestPacket cp;
    }           crp;

    /*
     * We need to open a temporary connection to the postmaster. Do this with
     * only kernel calls.
     */
    if ((tmpsock = socket(raddr->addr.ss_family, SOCK_STREAM, 0)) < 0)
    {
        strlcpy(errbuf, "PQcancel() -- socket() failed: ", errbufsize);
        goto cancel_errReturn;
    }
retry3:
    if (connect(tmpsock, (struct sockaddr *) & raddr->addr,
                raddr->salen) < 0)
    {
        if (SOCK_ERRNO == EINTR)
            /* Interrupted system call - we'll just try again */
            goto retry3;
        strlcpy(errbuf, "PQcancel() -- connect() failed: ", errbufsize);
        goto cancel_errReturn;
    }

    /*
     * We needn't set nonblocking I/O or NODELAY options here.
     */

    /* Create and send the cancel request packet. */

    crp.packetlen = htonl((uint32) sizeof(crp));
    crp.cp.cancelRequestCode = (MsgType) htonl(CANCEL_REQUEST_CODE);
    crp.cp.backendPID = htonl(be_pid);
    crp.cp.cancelAuthCode = htonl(be_key);

retry4:
    if (send(tmpsock, (char *) &crp, sizeof(crp), 0) != (int) sizeof(crp))
    {
        if (SOCK_ERRNO == EINTR)
            /* Interrupted system call - we'll just try again */
            goto retry4;
        strlcpy(errbuf, "PQcancel() -- send() failed: ", errbufsize);
        goto cancel_errReturn;
    }

    /*
     * Wait for the postmaster to close the connection, which indicates that
     * it's processed the request.  Without this delay, we might issue another
     * command only to find that our cancel zaps that command instead of the
     * one we thought we were canceling.  Note we don't actually expect this
     * read to obtain any data, we are just waiting for EOF to be signaled.
     */
retry5:
    if (recv(tmpsock, (char *) &crp, 1, 0) < 0)
    {
        if (SOCK_ERRNO == EINTR)
            /* Interrupted system call - we'll just try again */
            goto retry5;
        /* we ignore other error conditions */
    }

    /* All done */
    closesocket(tmpsock);
    SOCK_ERRNO_SET(save_errno);
    return TRUE;

cancel_errReturn:

    /*
     * Make sure we don't overflow the error buffer. Leave space for the \n at
     * the end, and for the terminating zero.
     */
    maxlen = errbufsize - strlen(errbuf) - 2;
    if (maxlen >= 0)
    {
        strncat(errbuf, SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)),
                maxlen);
        strcat(errbuf, "\n");
    }
    if (tmpsock >= 0)
        closesocket(tmpsock);
    SOCK_ERRNO_SET(save_errno);
    return FALSE;
}

/*
 * PQcancel: request query cancel
 *
 * Returns TRUE if able to send the cancel request, FALSE if not.
 *
 * On failure, an error message is stored in *errbuf, which must be of size
 * errbufsize (recommended size is 256 bytes).  *errbuf is not changed on
 * success return.
 */
int
PQcancel(PGcancel *cancel, char *errbuf, int errbufsize)
{
    if (!cancel)
    {
        strlcpy(errbuf, "PQcancel() -- no cancel object supplied", errbufsize);
        return FALSE;
    }

    return internal_cancel(&cancel->raddr, cancel->be_pid, cancel->be_key,
                           errbuf, errbufsize);
}

/*
 * PQrequestCancel: old, not thread-safe function for requesting query cancel
 *
 * Returns TRUE if able to send the cancel request, FALSE if not.
 *
 * On failure, the error message is saved in conn->errorMessage; this means
 * that this can't be used when there might be other active operations on
 * the connection object.
 *
 * NOTE: error messages will be cut off at the current size of the
 * error message buffer, since we dare not try to expand conn->errorMessage!
 */
int
PQrequestCancel(PGconn *conn)
{
    int         r;

    /* Check we have an open connection */
    if (!conn)
        return FALSE;

    if (conn->sock < 0)
    {
        strlcpy(conn->errorMessage.data,
                "PQrequestCancel() -- connection is not open\n",
                conn->errorMessage.maxlen);
        conn->errorMessage.len = strlen(conn->errorMessage.data);

        return FALSE;
    }

    r = internal_cancel(&conn->raddr, conn->be_pid, conn->be_key,
                        conn->errorMessage.data, conn->errorMessage.maxlen);

    if (!r)
        conn->errorMessage.len = strlen(conn->errorMessage.data);

    return r;
}


/*
 * pqPacketSend() -- convenience routine to send a message to server.
 *
 * pack_type: the single-byte message type code.  (Pass zero for startup
 * packets, which have no message type code.)
 *
 * buf, buf_len: contents of message.  The given length includes only what
 * is in buf; the message type and message length fields are added here.
 *
 * RETURNS: STATUS_ERROR if the write fails, STATUS_OK otherwise.
 * SIDE_EFFECTS: may block.
 *
 * Note: all messages sent with this routine have a length word, whether
 * it's protocol 2.0 or 3.0.
 */
int
pqPacketSend(PGconn *conn, char pack_type,
             const void *buf, size_t buf_len)
{
    /* Start the message. */
    if (pqPutMsgStart(pack_type, true, conn))
        return STATUS_ERROR;

    /* Send the message body. */
    if (pqPutnchar(buf, buf_len, conn))
        return STATUS_ERROR;

    /* Finish the message. */
    if (pqPutMsgEnd(conn))
        return STATUS_ERROR;

    /* Flush to ensure backend gets it. */
    if (pqFlush(conn))
        return STATUS_ERROR;

    return STATUS_OK;
}

#ifdef USE_LDAP

#define LDAP_URL    "ldap://"
#define LDAP_DEF_PORT   389
#define PGLDAP_TIMEOUT 2

#define ld_is_sp_tab(x) ((x) == ' ' || (x) == '\t')
#define ld_is_nl_cr(x) ((x) == '\r' || (x) == '\n')


/*
 *      ldapServiceLookup
 *
 * Search the LDAP URL passed as first argument, treat the result as a
 * string of connection options that are parsed and added to the array of
 * options passed as second argument.
 *
 * LDAP URLs must conform to RFC 1959 without escape sequences.
 *  ldap://host:port/dn?attributes?scope?filter?extensions
 *
 * Returns
 *  0 if the lookup was successful,
 *  1 if the connection to the LDAP server could be established but
 *    the search was unsuccessful,
 *  2 if a connection could not be established, and
 *  3 if a fatal error occurred.
 *
 * An error message is returned in the third argument for return codes 1 and 3.
 */
static int
ldapServiceLookup(const char *purl, PQconninfoOption *options,
                  PQExpBuffer errorMessage)
{
    int         port = LDAP_DEF_PORT,
                scope,
                rc,
                msgid,
                size,
                state,
                oldstate,
                i;
    bool        found_keyword;
    char       *url,
               *hostname,
               *portstr,
               *endptr,
               *dn,
               *scopestr,
               *filter,
               *result,
               *p,
               *p1 = NULL,
               *optname = NULL,
               *optval = NULL;
    char       *attrs[2] = {NULL, NULL};
    LDAP       *ld = NULL;
    LDAPMessage *res,
               *entry;
    struct berval **values;
    LDAP_TIMEVAL time = {PGLDAP_TIMEOUT, 0};

    if ((url = strdup(purl)) == NULL)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("out of memory\n"));
        return 3;
    }

    /*
     * Parse URL components, check for correctness.  Basically, url has '\0'
     * placed at component boundaries and variables are pointed at each
     * component.
     */

    if (pg_strncasecmp(url, LDAP_URL, strlen(LDAP_URL)) != 0)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("invalid LDAP URL \"%s\": scheme must be ldap://\n"), purl);
        free(url);
        return 3;
    }

    /* hostname */
    hostname = url + strlen(LDAP_URL);
    if (*hostname == '/')       /* no hostname? */
        hostname = DefaultHost; /* the default */

    /* dn, "distinguished name" */
    p = strchr(url + strlen(LDAP_URL), '/');
    if (p == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
             "invalid LDAP URL \"%s\": missing distinguished name\n"), purl);
        free(url);
        return 3;
    }
    *p = '\0';                  /* terminate hostname */
    dn = p + 1;

    /* attribute */
    if ((p = strchr(dn, '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
        "invalid LDAP URL \"%s\": must have exactly one attribute\n"), purl);
        free(url);
        return 3;
    }
    *p = '\0';
    attrs[0] = p + 1;

    /* scope */
    if ((p = strchr(attrs[0], '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("invalid LDAP URL \"%s\": must have search scope (base/one/sub)\n"), purl);
        free(url);
        return 3;
    }
    *p = '\0';
    scopestr = p + 1;

    /* filter */
    if ((p = strchr(scopestr, '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        printfPQExpBuffer(errorMessage,
                libpq_gettext("invalid LDAP URL \"%s\": no filter\n"), purl);
        free(url);
        return 3;
    }
    *p = '\0';
    filter = p + 1;
    if ((p = strchr(filter, '?')) != NULL)
        *p = '\0';

    /* port number? */
    if ((p1 = strchr(hostname, ':')) != NULL)
    {
        long        lport;

        *p1 = '\0';
        portstr = p1 + 1;
        errno = 0;
        lport = strtol(portstr, &endptr, 10);
        if (*portstr == '\0' || *endptr != '\0' || errno || lport < 0 || lport > 65535)
        {
            printfPQExpBuffer(errorMessage, libpq_gettext(
                    "invalid LDAP URL \"%s\": invalid port number\n"), purl);
            free(url);
            return 3;
        }
        port = (int) lport;
    }

    /* Allow only one attribute */
    if (strchr(attrs[0], ',') != NULL)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
        "invalid LDAP URL \"%s\": must have exactly one attribute\n"), purl);
        free(url);
        return 3;
    }

    /* set scope */
    if (pg_strcasecmp(scopestr, "base") == 0)
        scope = LDAP_SCOPE_BASE;
    else if (pg_strcasecmp(scopestr, "one") == 0)
        scope = LDAP_SCOPE_ONELEVEL;
    else if (pg_strcasecmp(scopestr, "sub") == 0)
        scope = LDAP_SCOPE_SUBTREE;
    else
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("invalid LDAP URL \"%s\": must have search scope (base/one/sub)\n"), purl);
        free(url);
        return 3;
    }

    /* initialize LDAP structure */
    if ((ld = ldap_init(hostname, port)) == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("could not create LDAP structure\n"));
        free(url);
        return 3;
    }

    /*
     * Initialize connection to the server.  We do an explicit bind because we
     * want to return 2 if the bind fails.
     */
    if ((msgid = ldap_simple_bind(ld, NULL, NULL)) == -1)
    {
        /* error in ldap_simple_bind() */
        free(url);
        ldap_unbind(ld);
        return 2;
    }

    /* wait some time for the connection to succeed */
    res = NULL;
    if ((rc = ldap_result(ld, msgid, LDAP_MSG_ALL, &time, &res)) == -1 ||
        res == NULL)
    {
        if (res != NULL)
        {
            /* timeout */
            ldap_msgfree(res);
        }
        /* error in ldap_result() */
        free(url);
        ldap_unbind(ld);
        return 2;
    }
    ldap_msgfree(res);

    /* search */
    res = NULL;
    if ((rc = ldap_search_st(ld, dn, scope, filter, attrs, 0, &time, &res))
        != LDAP_SUCCESS)
    {
        if (res != NULL)
            ldap_msgfree(res);
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("lookup on LDAP server failed: %s\n"),
                          ldap_err2string(rc));
        ldap_unbind(ld);
        free(url);
        return 1;
    }

    /* complain if there was not exactly one result */
    if ((rc = ldap_count_entries(ld, res)) != 1)
    {
        printfPQExpBuffer(errorMessage,
             rc ? libpq_gettext("more than one entry found on LDAP lookup\n")
                          : libpq_gettext("no entry found on LDAP lookup\n"));
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }

    /* get entry */
    if ((entry = ldap_first_entry(ld, res)) == NULL)
    {
        /* should never happen */
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("no entry found on LDAP lookup\n"));
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }

    /* get values */
    if ((values = ldap_get_values_len(ld, entry, attrs[0])) == NULL)
    {
        printfPQExpBuffer(errorMessage,
                  libpq_gettext("attribute has no values on LDAP lookup\n"));
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }

    ldap_msgfree(res);
    free(url);

    if (values[0] == NULL)
    {
        printfPQExpBuffer(errorMessage,
                  libpq_gettext("attribute has no values on LDAP lookup\n"));
        ldap_value_free_len(values);
        ldap_unbind(ld);
        return 1;
    }

    /* concatenate values into a single string with newline terminators */
    size = 1;                   /* for the trailing null */
    for (i = 0; values[i] != NULL; i++)
        size += values[i]->bv_len + 1;
    if ((result = malloc(size)) == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        ldap_value_free_len(values);
        ldap_unbind(ld);
        return 3;
    }
    p = result;
    for (i = 0; values[i] != NULL; i++)
    {
        memcpy(p, values[i]->bv_val, values[i]->bv_len);
        p += values[i]->bv_len;
        *(p++) = '\n';
    }
    *p = '\0';

    ldap_value_free_len(values);
    ldap_unbind(ld);

    /* parse result string */
    oldstate = state = 0;
    for (p = result; *p != '\0'; ++p)
    {
        switch (state)
        {
            case 0:             /* between entries */
                if (!ld_is_sp_tab(*p) && !ld_is_nl_cr(*p))
                {
                    optname = p;
                    state = 1;
                }
                break;
            case 1:             /* in option name */
                if (ld_is_sp_tab(*p))
                {
                    *p = '\0';
                    state = 2;
                }
                else if (ld_is_nl_cr(*p))
                {
                    printfPQExpBuffer(errorMessage, libpq_gettext(
                    "missing \"=\" after \"%s\" in connection info string\n"),
                                      optname);
                    free(result);
                    return 3;
                }
                else if (*p == '=')
                {
                    *p = '\0';
                    state = 3;
                }
                break;
            case 2:             /* after option name */
                if (*p == '=')
                {
                    state = 3;
                }
                else if (!ld_is_sp_tab(*p))
                {
                    printfPQExpBuffer(errorMessage, libpq_gettext(
                    "missing \"=\" after \"%s\" in connection info string\n"),
                                      optname);
                    free(result);
                    return 3;
                }
                break;
            case 3:             /* before option value */
                if (*p == '\'')
                {
                    optval = p + 1;
                    p1 = p + 1;
                    state = 5;
                }
                else if (ld_is_nl_cr(*p))
                {
                    optval = optname + strlen(optname); /* empty */
                    state = 0;
                }
                else if (!ld_is_sp_tab(*p))
                {
                    optval = p;
                    state = 4;
                }
                break;
            case 4:             /* in unquoted option value */
                if (ld_is_sp_tab(*p) || ld_is_nl_cr(*p))
                {
                    *p = '\0';
                    state = 0;
                }
                break;
            case 5:             /* in quoted option value */
                if (*p == '\'')
                {
                    *p1 = '\0';
                    state = 0;
                }
                else if (*p == '\\')
                    state = 6;
                else
                    *(p1++) = *p;
                break;
            case 6:             /* in quoted option value after escape */
                *(p1++) = *p;
                state = 5;
                break;
        }

        if (state == 0 && oldstate != 0)
        {
            found_keyword = false;
            for (i = 0; options[i].keyword; i++)
            {
                if (strcmp(options[i].keyword, optname) == 0)
                {
                    if (options[i].val == NULL)
                        options[i].val = strdup(optval);
                    found_keyword = true;
                    break;
                }
            }
            if (!found_keyword)
            {
                printfPQExpBuffer(errorMessage,
                         libpq_gettext("invalid connection option \"%s\"\n"),
                                  optname);
                free(result);
                return 1;
            }
            optname = NULL;
            optval = NULL;
        }
        oldstate = state;
    }

    free(result);

    if (state == 5 || state == 6)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
                  "unterminated quoted string in connection info string\n"));
        return 3;
    }

    return 0;
}
#endif

#define MAXBUFSIZE 256

static int
parseServiceInfo(PQconninfoOption *options, PQExpBuffer errorMessage)
{
    const char *service = conninfo_getval(options, "service");
    char        serviceFile[MAXPGPATH];
    char       *env;
    bool        group_found = false;
    int         status;
    struct stat stat_buf;

    /*
     * We have to special-case the environment variable PGSERVICE here, since
     * this is and should be called before inserting environment defaults for
     * other connection options.
     */
    if (service == NULL)
        service = getenv("PGSERVICE");

    if (service == NULL)
        return 0;

    if ((env = getenv("PGSERVICEFILE")) != NULL)
        strlcpy(serviceFile, env, sizeof(serviceFile));
    else
    {
        char        homedir[MAXPGPATH];

        if (!pqGetHomeDirectory(homedir, sizeof(homedir)))
        {
            printfPQExpBuffer(errorMessage, libpq_gettext("could not get home directory to locate service definition file"));
            return 1;
        }
        snprintf(serviceFile, MAXPGPATH, "%s/%s", homedir, ".pg_service.conf");
        errno = 0;
        if (stat(serviceFile, &stat_buf) != 0 && errno == ENOENT)
            goto next_file;
    }

    status = parseServiceFile(serviceFile, service, options, errorMessage, &group_found);
    if (group_found || status != 0)
        return status;

next_file:

    /*
     * This could be used by any application so we can't use the binary
     * location to find our config files.
     */
    snprintf(serviceFile, MAXPGPATH, "%s/pg_service.conf",
             getenv("PGSYSCONFDIR") ? getenv("PGSYSCONFDIR") : SYSCONFDIR);
    errno = 0;
    if (stat(serviceFile, &stat_buf) != 0 && errno == ENOENT)
        goto last_file;

    status = parseServiceFile(serviceFile, service, options, errorMessage, &group_found);
    if (status != 0)
        return status;

last_file:
    if (!group_found)
    {
        printfPQExpBuffer(errorMessage,
         libpq_gettext("definition of service \"%s\" not found\n"), service);
        return 3;
    }

    return 0;
}

static int
parseServiceFile(const char *serviceFile,
                 const char *service,
                 PQconninfoOption *options,
                 PQExpBuffer errorMessage,
                 bool *group_found)
{
    int         linenr = 0,
                i;
    FILE       *f;
    char        buf[MAXBUFSIZE],
               *line;

    f = fopen(serviceFile, "r");
    if (f == NULL)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("service file \"%s\" not found\n"),
                          serviceFile);
        return 1;
    }

    while ((line = fgets(buf, sizeof(buf), f)) != NULL)
    {
        linenr++;

        if (strlen(line) >= sizeof(buf) - 1)
        {
            fclose(f);
            printfPQExpBuffer(errorMessage,
                  libpq_gettext("line %d too long in service file \"%s\"\n"),
                              linenr,
                              serviceFile);
            return 2;
        }

        /* ignore EOL at end of line */
        if (strlen(line) && line[strlen(line) - 1] == '\n')
            line[strlen(line) - 1] = 0;

        /* ignore leading blanks */
        while (*line && isspace((unsigned char) line[0]))
            line++;

        /* ignore comments and empty lines */
        if (strlen(line) == 0 || line[0] == '#')
            continue;

        /* Check for right groupname */
        if (line[0] == '[')
        {
            if (*group_found)
            {
                /* group info already read */
                fclose(f);
                return 0;
            }

            if (strncmp(line + 1, service, strlen(service)) == 0 &&
                line[strlen(service) + 1] == ']')
                *group_found = true;
            else
                *group_found = false;
        }
        else
        {
            if (*group_found)
            {
                /*
                 * Finally, we are in the right group and can parse the line
                 */
                char       *key,
                           *val;
                bool        found_keyword;

#ifdef USE_LDAP
                if (strncmp(line, "ldap", 4) == 0)
                {
                    int         rc = ldapServiceLookup(line, options, errorMessage);

                    /* if rc = 2, go on reading for fallback */
                    switch (rc)
                    {
                        case 0:
                            fclose(f);
                            return 0;
                        case 1:
                        case 3:
                            fclose(f);
                            return 3;
                        case 2:
                            continue;
                    }
                }
#endif

                key = line;
                val = strchr(line, '=');
                if (val == NULL)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("syntax error in service file \"%s\", line %d\n"),
                                      serviceFile,
                                      linenr);
                    fclose(f);
                    return 3;
                }
                *val++ = '\0';

                /*
                 * Set the parameter --- but don't override any previous
                 * explicit setting.
                 */
                found_keyword = false;
                for (i = 0; options[i].keyword; i++)
                {
                    if (strcmp(options[i].keyword, key) == 0)
                    {
                        if (options[i].val == NULL)
                            options[i].val = strdup(val);
                        found_keyword = true;
                        break;
                    }
                }

                if (!found_keyword)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("syntax error in service file \"%s\", line %d\n"),
                                      serviceFile,
                                      linenr);
                    fclose(f);
                    return 3;
                }
            }
        }
    }

    fclose(f);

    return 0;
}


/*
 *      PQconninfoParse
 *
 * Parse a string like PQconnectdb() would do and return the
 * resulting connection options array.  NULL is returned on failure.
 * The result contains only options specified directly in the string,
 * not any possible default values.
 *
 * If errmsg isn't NULL, *errmsg is set to NULL on success, or a malloc'd
 * string on failure (use PQfreemem to free it).  In out-of-memory conditions
 * both *errmsg and the result could be NULL.
 *
 * NOTE: the returned array is dynamically allocated and should
 * be freed when no longer needed via PQconninfoFree().
 */
PQconninfoOption *
PQconninfoParse(const char *conninfo, char **errmsg)
{
    PQExpBufferData errorBuf;
    PQconninfoOption *connOptions;

    if (errmsg)
        *errmsg = NULL;         /* default */
    initPQExpBuffer(&errorBuf);
    if (PQExpBufferDataBroken(errorBuf))
        return NULL;            /* out of memory already :-( */
    connOptions = parse_connection_string(conninfo, &errorBuf, false);
    if (connOptions == NULL && errmsg)
        *errmsg = errorBuf.data;
    else
        termPQExpBuffer(&errorBuf);
    return connOptions;
}

/*
 * Build a working copy of the constant PQconninfoOptions array.
 */
static PQconninfoOption *
conninfo_init(PQExpBuffer errorMessage)
{
    PQconninfoOption *options;
    PQconninfoOption *opt_dest;
    const internalPQconninfoOption *cur_opt;

    /*
     * Get enough memory for all options in PQconninfoOptions, even if some
     * end up being filtered out.
     */
    options = (PQconninfoOption *) malloc(sizeof(PQconninfoOption) * sizeof(PQconninfoOptions) / sizeof(PQconninfoOptions[0]));
    if (options == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        return NULL;
    }
    opt_dest = options;

    for (cur_opt = PQconninfoOptions; cur_opt->keyword; cur_opt++)
    {
        /* Only copy the public part of the struct, not the full internal */
        memcpy(opt_dest, cur_opt, sizeof(PQconninfoOption));
        opt_dest++;
    }
    MemSet(opt_dest, 0, sizeof(PQconninfoOption));

    return options;
}

/*
 * Connection string parser
 *
 * Returns a malloc'd PQconninfoOption array, if parsing is successful.
 * Otherwise, NULL is returned and an error message is left in errorMessage.
 *
 * If use_defaults is TRUE, default values are filled in (from a service file,
 * environment variables, etc).
 */
static PQconninfoOption *
parse_connection_string(const char *connstr, PQExpBuffer errorMessage,
                        bool use_defaults)
{
    /* Parse as URI if connection string matches URI prefix */
    if (uri_prefix_length(connstr) != 0)
        return conninfo_uri_parse(connstr, errorMessage, use_defaults);

    /* Parse as default otherwise */
    return conninfo_parse(connstr, errorMessage, use_defaults);
}

/*
 * Checks if connection string starts with either of the valid URI prefix
 * designators.
 *
 * Returns the URI prefix length, 0 if the string doesn't contain a URI prefix.
 */
static int
uri_prefix_length(const char *connstr)
{
    if (strncmp(connstr, uri_designator,
                sizeof(uri_designator) - 1) == 0)
        return sizeof(uri_designator) - 1;

    if (strncmp(connstr, short_uri_designator,
                sizeof(short_uri_designator) - 1) == 0)
        return sizeof(short_uri_designator) - 1;

    return 0;
}

/*
 * Recognized connection string either starts with a valid URI prefix or
 * contains a "=" in it.
 *
 * Must be consistent with parse_connection_string: anything for which this
 * returns true should at least look like it's parseable by that routine.
 */
static bool
recognized_connection_string(const char *connstr)
{
    return uri_prefix_length(connstr) != 0 || strchr(connstr, '=') != NULL;
}

/*
 * Subroutine for parse_connection_string
 *
 * Deal with a string containing key=value pairs.
 */
static PQconninfoOption *
conninfo_parse(const char *conninfo, PQExpBuffer errorMessage,
               bool use_defaults)
{
    char       *pname;
    char       *pval;
    char       *buf;
    char       *cp;
    char       *cp2;
    PQconninfoOption *options;

    /* Make a working copy of PQconninfoOptions */
    options = conninfo_init(errorMessage);
    if (options == NULL)
        return NULL;

    /* Need a modifiable copy of the input string */
    if ((buf = strdup(conninfo)) == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        PQconninfoFree(options);
        return NULL;
    }
    cp = buf;

    while (*cp)
    {
        /* Skip blanks before the parameter name */
        if (isspace((unsigned char) *cp))
        {
            cp++;
            continue;
        }

        /* Get the parameter name */
        pname = cp;
        while (*cp)
        {
            if (*cp == '=')
                break;
            if (isspace((unsigned char) *cp))
            {
                *cp++ = '\0';
                while (*cp)
                {
                    if (!isspace((unsigned char) *cp))
                        break;
                    cp++;
                }
                break;
            }
            cp++;
        }

        /* Check that there is a following '=' */
        if (*cp != '=')
        {
            printfPQExpBuffer(errorMessage,
                              libpq_gettext("missing \"=\" after \"%s\" in connection info string\n"),
                              pname);
            PQconninfoFree(options);
            free(buf);
            return NULL;
        }
        *cp++ = '\0';

        /* Skip blanks after the '=' */
        while (*cp)
        {
            if (!isspace((unsigned char) *cp))
                break;
            cp++;
        }

        /* Get the parameter value */
        pval = cp;

        if (*cp != '\'')
        {
            cp2 = pval;
            while (*cp)
            {
                if (isspace((unsigned char) *cp))
                {
                    *cp++ = '\0';
                    break;
                }
                if (*cp == '\\')
                {
                    cp++;
                    if (*cp != '\0')
                        *cp2++ = *cp++;
                }
                else
                    *cp2++ = *cp++;
            }
            *cp2 = '\0';
        }
        else
        {
            cp2 = pval;
            cp++;
            for (;;)
            {
                if (*cp == '\0')
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("unterminated quoted string in connection info string\n"));
                    PQconninfoFree(options);
                    free(buf);
                    return NULL;
                }
                if (*cp == '\\')
                {
                    cp++;
                    if (*cp != '\0')
                        *cp2++ = *cp++;
                    continue;
                }
                if (*cp == '\'')
                {
                    *cp2 = '\0';
                    cp++;
                    break;
                }
                *cp2++ = *cp++;
            }
        }

        /*
         * Now that we have the name and the value, store the record.
         */
        if (!conninfo_storeval(options, pname, pval, errorMessage, false, false))
        {
            PQconninfoFree(options);
            free(buf);
            return NULL;
        }
    }

    /* Done with the modifiable input string */
    free(buf);

    /*
     * Add in defaults if the caller wants that.
     */
    if (use_defaults)
    {
        if (!conninfo_add_defaults(options, errorMessage))
        {
            PQconninfoFree(options);
            return NULL;
        }
    }

    return options;
}

/*
 * Conninfo array parser routine
 *
 * If successful, a malloc'd PQconninfoOption array is returned.
 * If not successful, NULL is returned and an error message is
 * left in errorMessage.
 * Defaults are supplied (from a service file, environment variables, etc)
 * for unspecified options, but only if use_defaults is TRUE.
 *
 * If expand_dbname is non-zero, and the value passed for keyword "dbname" is a
 * connection string (as indicated by recognized_connection_string) then parse
 * and process it, overriding any previously processed conflicting
 * keywords. Subsequent keywords will take precedence, however.
 */
static PQconninfoOption *
conninfo_array_parse(const char *const * keywords, const char *const * values,
                     PQExpBuffer errorMessage, bool use_defaults,
                     int expand_dbname)
{
    PQconninfoOption *options;
    PQconninfoOption *dbname_options = NULL;
    PQconninfoOption *option;
    int         i = 0;

    /*
     * If expand_dbname is non-zero, check keyword "dbname" to see if val is
     * actually a recognized connection string.
     */
    while (expand_dbname && keywords[i])
    {
        const char *pname = keywords[i];
        const char *pvalue = values[i];

        /* first find "dbname" if any */
        if (strcmp(pname, "dbname") == 0 && pvalue)
        {
            /*
             * If value is a connection string, parse it, but do not use
             * defaults here -- those get picked up later. We only want to
             * override for those parameters actually passed.
             */
            if (recognized_connection_string(pvalue))
            {
                dbname_options = parse_connection_string(pvalue, errorMessage, false);
                if (dbname_options == NULL)
                    return NULL;
            }
            break;
        }
        ++i;
    }

    /* Make a working copy of PQconninfoOptions */
    options = conninfo_init(errorMessage);
    if (options == NULL)
    {
        PQconninfoFree(dbname_options);
        return NULL;
    }

    /* Parse the keywords/values arrays */
    i = 0;
    while (keywords[i])
    {
        const char *pname = keywords[i];
        const char *pvalue = values[i];

        if (pvalue != NULL)
        {
            /* Search for the param record */
            for (option = options; option->keyword != NULL; option++)
            {
                if (strcmp(option->keyword, pname) == 0)
                    break;
            }

            /* Check for invalid connection option */
            if (option->keyword == NULL)
            {
                printfPQExpBuffer(errorMessage,
                         libpq_gettext("invalid connection option \"%s\"\n"),
                                  pname);
                PQconninfoFree(options);
                PQconninfoFree(dbname_options);
                return NULL;
            }

            /*
             * If we are on the dbname parameter, and we have a parsed
             * connection string, copy those parameters across, overriding any
             * existing previous settings.
             */
            if (strcmp(pname, "dbname") == 0 && dbname_options)
            {
                PQconninfoOption *str_option;

                for (str_option = dbname_options; str_option->keyword != NULL; str_option++)
                {
                    if (str_option->val != NULL)
                    {
                        int         k;

                        for (k = 0; options[k].keyword; k++)
                        {
                            if (strcmp(options[k].keyword, str_option->keyword) == 0)
                            {
                                if (options[k].val)
                                    free(options[k].val);
                                options[k].val = strdup(str_option->val);
                                break;
                            }
                        }
                    }
                }
            }
            else
            {
                /*
                 * Store the value, overriding previous settings
                 */
                if (option->val)
                    free(option->val);
                option->val = strdup(pvalue);
                if (!option->val)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("out of memory\n"));
                    PQconninfoFree(options);
                    PQconninfoFree(dbname_options);
                    return NULL;
                }
            }
        }
        ++i;
    }
    PQconninfoFree(dbname_options);

    /*
     * Add in defaults if the caller wants that.
     */
    if (use_defaults)
    {
        if (!conninfo_add_defaults(options, errorMessage))
        {
            PQconninfoFree(options);
            return NULL;
        }
    }

    return options;
}

/*
 * Add the default values for any unspecified options to the connection
 * options array.
 *
 * Defaults are obtained from a service file, environment variables, etc.
 *
 * Returns TRUE if successful, otherwise FALSE; errorMessage is filled in
 * upon failure.  Note that failure to locate a default value is not an
 * error condition here --- we just leave the option's value as NULL.
 */
static bool
conninfo_add_defaults(PQconninfoOption *options, PQExpBuffer errorMessage)
{
    PQconninfoOption *option;
    char       *tmp;

    /*
     * If there's a service spec, use it to obtain any not-explicitly-given
     * parameters.
     */
    if (parseServiceInfo(options, errorMessage) != 0)
        return false;

    /*
     * Get the fallback resources for parameters not specified in the conninfo
     * string nor the service.
     */
    for (option = options; option->keyword != NULL; option++)
    {
        if (option->val != NULL)
            continue;           /* Value was in conninfo or service */

        /*
         * Try to get the environment variable fallback
         */
        if (option->envvar != NULL)
        {
            if ((tmp = getenv(option->envvar)) != NULL)
            {
                option->val = strdup(tmp);
                if (!option->val)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("out of memory\n"));
                    return false;
                }
                continue;
            }
        }

        /*
         * No environment variable specified or the variable isn't set - try
         * compiled-in default
         */
        if (option->compiled != NULL)
        {
            option->val = strdup(option->compiled);
            if (!option->val)
            {
                printfPQExpBuffer(errorMessage,
                                  libpq_gettext("out of memory\n"));
                return false;
            }
            continue;
        }

        /*
         * Special handling for "user" option
         */
        if (strcmp(option->keyword, "user") == 0)
        {
            option->val = pg_fe_getauthname(errorMessage);
            continue;
        }
    }

    return true;
}

/*
 * Subroutine for parse_connection_string
 *
 * Deal with a URI connection string.
 */
static PQconninfoOption *
conninfo_uri_parse(const char *uri, PQExpBuffer errorMessage,
                   bool use_defaults)
{
    PQconninfoOption *options;

    /* Make a working copy of PQconninfoOptions */
    options = conninfo_init(errorMessage);
    if (options == NULL)
        return NULL;

    if (!conninfo_uri_parse_options(options, uri, errorMessage))
    {
        PQconninfoFree(options);
        return NULL;
    }

    /*
     * Add in defaults if the caller wants that.
     */
    if (use_defaults)
    {
        if (!conninfo_add_defaults(options, errorMessage))
        {
            PQconninfoFree(options);
            return NULL;
        }
    }

    return options;
}

/*
 * conninfo_uri_parse_options
 *      Actual URI parser.
 *
 * If successful, returns true while the options array is filled with parsed
 * options from the URI.
 * If not successful, returns false and fills errorMessage accordingly.
 *
 * Parses the connection URI string in 'uri' according to the URI syntax (RFC
 * 3986):
 *
 * postgresql://[user[:password]@][netloc][:port][/dbname][?param1=value1&...]
 *
 * where "netloc" is a hostname, an IPv4 address, or an IPv6 address surrounded
 * by literal square brackets.
 *
 * Any of the URI parts might use percent-encoding (%xy).
 */
static bool
conninfo_uri_parse_options(PQconninfoOption *options, const char *uri,
                           PQExpBuffer errorMessage)
{
    int         prefix_len;
    char       *p;
    char       *buf = strdup(uri);      /* need a modifiable copy of the input
                                         * URI */
    char       *start = buf;
    char        prevchar = '\0';
    char       *user = NULL;
    char       *host = NULL;
    bool        retval = false;

    if (buf == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        return false;
    }

    /* Skip the URI prefix */
    prefix_len = uri_prefix_length(uri);
    if (prefix_len == 0)
    {
        /* Should never happen */
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("invalid URI propagated to internal parser routine: \"%s\"\n"),
                          uri);
        goto cleanup;
    }
    start += prefix_len;
    p = start;

    /* Look ahead for possible user credentials designator */
    while (*p && *p != '@' && *p != '/')
        ++p;
    if (*p == '@')
    {
        /*
         * Found username/password designator, so URI should be of the form
         * "scheme://user[:password]@[netloc]".
         */
        user = start;

        p = user;
        while (*p != ':' && *p != '@')
            ++p;

        /* Save last char and cut off at end of user name */
        prevchar = *p;
        *p = '\0';

        if (*user &&
            !conninfo_storeval(options, "user", user,
                               errorMessage, false, true))
            goto cleanup;

        if (prevchar == ':')
        {
            const char *password = p + 1;

            while (*p != '@')
                ++p;
            *p = '\0';

            if (*password &&
                !conninfo_storeval(options, "password", password,
                                   errorMessage, false, true))
                goto cleanup;
        }

        /* Advance past end of parsed user name or password token */
        ++p;
    }
    else
    {
        /*
         * No username/password designator found.  Reset to start of URI.
         */
        p = start;
    }

    /*
     * "p" has been incremented past optional URI credential information at
     * this point and now points at the "netloc" part of the URI.
     *
     * Look for IPv6 address.
     */
    if (*p == '[')
    {
        host = ++p;
        while (*p && *p != ']')
            ++p;
        if (!*p)
        {
            printfPQExpBuffer(errorMessage,
                              libpq_gettext("end of string reached when looking for matching \"]\" in IPv6 host address in URI: \"%s\"\n"),
                              uri);
            goto cleanup;
        }
        if (p == host)
        {
            printfPQExpBuffer(errorMessage,
                              libpq_gettext("IPv6 host address may not be empty in URI: \"%s\"\n"),
                              uri);
            goto cleanup;
        }

        /* Cut off the bracket and advance */
        *(p++) = '\0';

        /*
         * The address may be followed by a port specifier or a slash or a
         * query.
         */
        if (*p && *p != ':' && *p != '/' && *p != '?')
        {
            printfPQExpBuffer(errorMessage,
                              libpq_gettext("unexpected character \"%c\" at position %d in URI (expected \":\" or \"/\"): \"%s\"\n"),
                              *p, (int) (p - buf + 1), uri);
            goto cleanup;
        }
    }
    else
    {
        /* not an IPv6 address: DNS-named or IPv4 netloc */
        host = p;

        /*
         * Look for port specifier (colon) or end of host specifier (slash),
         * or query (question mark).
         */
        while (*p && *p != ':' && *p != '/' && *p != '?')
            ++p;
    }

    /* Save the hostname terminator before we null it */
    prevchar = *p;
    *p = '\0';

    if (*host &&
        !conninfo_storeval(options, "host", host,
                           errorMessage, false, true))
        goto cleanup;


    if (prevchar == ':')
    {
        const char *port = ++p; /* advance past host terminator */

        while (*p && *p != '/' && *p != '?')
            ++p;

        prevchar = *p;
        *p = '\0';

        if (*port &&
            !conninfo_storeval(options, "port", port,
                               errorMessage, false, true))
            goto cleanup;
    }

    if (prevchar && prevchar != '?')
    {
        const char *dbname = ++p;       /* advance past host terminator */

        /* Look for query parameters */
        while (*p && *p != '?')
            ++p;

        prevchar = *p;
        *p = '\0';

        /*
         * Avoid setting dbname to an empty string, as it forces the default
         * value (username) and ignores $PGDATABASE, as opposed to not setting
         * it at all.
         */
        if (*dbname &&
            !conninfo_storeval(options, "dbname", dbname,
                               errorMessage, false, true))
            goto cleanup;
    }

    if (prevchar)
    {
        ++p;                    /* advance past terminator */

        if (!conninfo_uri_parse_params(p, options, errorMessage))
            goto cleanup;
    }

    /* everything parsed okay */
    retval = true;

cleanup:
    free(buf);
    return retval;
}

/*
 * Connection URI parameters parser routine
 *
 * If successful, returns true while connOptions is filled with parsed
 * parameters.  Otherwise, returns false and fills errorMessage appropriately.
 *
 * Destructively modifies 'params' buffer.
 */
static bool
conninfo_uri_parse_params(char *params,
                          PQconninfoOption *connOptions,
                          PQExpBuffer errorMessage)
{
    while (*params)
    {
        char       *keyword = params;
        char       *value = NULL;
        char       *p = params;
        bool        malloced = false;

        /*
         * Scan the params string for '=' and '&', marking the end of keyword
         * and value respectively.
         */
        for (;;)
        {
            if (*p == '=')
            {
                /* Was there '=' already? */
                if (value != NULL)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("extra key/value separator \"=\" in URI query parameter: \"%s\"\n"),
                                      params);
                    return false;
                }
                /* Cut off keyword, advance to value */
                *p = '\0';
                value = ++p;
            }
            else if (*p == '&' || *p == '\0')
            {
                char        prevchar;

                /* Cut off value, remember old value */
                prevchar = *p;
                *p = '\0';

                /* Was there '=' at all? */
                if (value == NULL)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("missing key/value separator \"=\" in URI query parameter: \"%s\"\n"),
                                      params);
                    return false;
                }

                /*
                 * If not at the end, advance; now pointing to start of the
                 * next parameter, if any.
                 */
                if (prevchar != '\0')
                    ++p;
                break;
            }

            /* Advance, NUL is checked in the 'if' above */
            ++p;
        }

        keyword = conninfo_uri_decode(keyword, errorMessage);
        if (keyword == NULL)
        {
            /* conninfo_uri_decode already set an error message */
            return false;
        }
        value = conninfo_uri_decode(value, errorMessage);
        if (value == NULL)
        {
            /* conninfo_uri_decode already set an error message */
            free(keyword);
            return false;
        }
        malloced = true;

        /*
         * Special keyword handling for improved JDBC compatibility.
         */
        if (strcmp(keyword, "ssl") == 0 &&
            strcmp(value, "true") == 0)
        {
            free(keyword);
            free(value);
            malloced = false;

            keyword = "sslmode";
            value = "require";
        }

        /*
         * Store the value if the corresponding option exists; ignore
         * otherwise.  At this point both keyword and value are not
         * URI-encoded.
         */
        if (!conninfo_storeval(connOptions, keyword, value,
                               errorMessage, true, false))
        {
            /*
             * Check if there was a hard error when decoding or storing the
             * option.
             */
            if (errorMessage->len != 0)
            {
                if (malloced)
                {
                    free(keyword);
                    free(value);
                }
                return false;
            }

            printfPQExpBuffer(errorMessage,
                              libpq_gettext(
                                    "invalid URI query parameter: \"%s\"\n"),
                              keyword);
            if (malloced)
            {
                free(keyword);
                free(value);
            }
            return false;
        }
        if (malloced)
        {
            free(keyword);
            free(value);
        }

        /* Proceed to next key=value pair */
        params = p;
    }

    return true;
}

/*
 * Connection URI decoder routine
 *
 * If successful, returns the malloc'd decoded string.
 * If not successful, returns NULL and fills errorMessage accordingly.
 *
 * The string is decoded by replacing any percent-encoded tokens with
 * corresponding characters, while preserving any non-encoded characters.  A
 * percent-encoded token is a character triplet: a percent sign, followed by a
 * pair of hexadecimal digits (0-9A-F), where lower- and upper-case letters are
 * treated identically.
 */
static char *
conninfo_uri_decode(const char *str, PQExpBuffer errorMessage)
{
    char       *buf = malloc(strlen(str) + 1);
    char       *p = buf;
    const char *q = str;

    if (buf == NULL)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("out of memory\n"));
        return NULL;
    }

    for (;;)
    {
        if (*q != '%')
        {
            /* copy and check for NUL terminator */
            if (!(*(p++) = *(q++)))
                break;
        }
        else
        {
            int         hi;
            int         lo;
            int         c;

            ++q;                /* skip the percent sign itself */

            /*
             * Possible EOL will be caught by the first call to
             * get_hexdigit(), so we never dereference an invalid q pointer.
             */
            if (!(get_hexdigit(*q++, &hi) && get_hexdigit(*q++, &lo)))
            {
                printfPQExpBuffer(errorMessage,
                    libpq_gettext("invalid percent-encoded token: \"%s\"\n"),
                                  str);
                free(buf);
                return NULL;
            }

            c = (hi << 4) | lo;
            if (c == 0)
            {
                printfPQExpBuffer(errorMessage,
                                  libpq_gettext("forbidden value %%00 in percent-encoded value: \"%s\"\n"),
                                  str);
                free(buf);
                return NULL;
            }
            *(p++) = c;
        }
    }

    return buf;
}

/*
 * Convert hexadecimal digit character to its integer value.
 *
 * If successful, returns true and value is filled with digit's base 16 value.
 * If not successful, returns false.
 *
 * Lower- and upper-case letters in the range A-F are treated identically.
 */
static bool
get_hexdigit(char digit, int *value)
{
    if ('0' <= digit && digit <= '9')
        *value = digit - '0';
    else if ('A' <= digit && digit <= 'F')
        *value = digit - 'A' + 10;
    else if ('a' <= digit && digit <= 'f')
        *value = digit - 'a' + 10;
    else
        return false;

    return true;
}

/*
 * Find an option value corresponding to the keyword in the connOptions array.
 *
 * If successful, returns a pointer to the corresponding option's value.
 * If not successful, returns NULL.
 */
static const char *
conninfo_getval(PQconninfoOption *connOptions,
                const char *keyword)
{
    PQconninfoOption *option;

    option = conninfo_find(connOptions, keyword);

    return option ? option->val : NULL;
}

/*
 * Store a (new) value for an option corresponding to the keyword in
 * connOptions array.
 *
 * If uri_decode is true, the value is URI-decoded.  The keyword is always
 * assumed to be non URI-encoded.
 *
 * If successful, returns a pointer to the corresponding PQconninfoOption,
 * which value is replaced with a strdup'd copy of the passed value string.
 * The existing value for the option is free'd before replacing, if any.
 *
 * If not successful, returns NULL and fills errorMessage accordingly.
 * However, if the reason of failure is an invalid keyword being passed and
 * ignoreMissing is TRUE, errorMessage will be left untouched.
 */
static PQconninfoOption *
conninfo_storeval(PQconninfoOption *connOptions,
                  const char *keyword, const char *value,
                  PQExpBuffer errorMessage, bool ignoreMissing,
                  bool uri_decode)
{
    PQconninfoOption *option;
    char       *value_copy;

    /*
     * For backwards compatibility, requiressl=1 gets translated to
     * sslmode=require, and requiressl=0 gets translated to sslmode=prefer
     * (which is the default for sslmode).
     */
    if (strcmp(keyword, "requiressl") == 0)
    {
        keyword = "sslmode";
        if (value[0] == '1')
            value = "require";
        else
            value = "prefer";
    }

    option = conninfo_find(connOptions, keyword);
    if (option == NULL)
    {
        if (!ignoreMissing)
            printfPQExpBuffer(errorMessage,
                         libpq_gettext("invalid connection option \"%s\"\n"),
                              keyword);
        return NULL;
    }

    if (uri_decode)
    {
        value_copy = conninfo_uri_decode(value, errorMessage);
        if (value_copy == NULL)
            /* conninfo_uri_decode already set an error message */
            return NULL;
    }
    else
    {
        value_copy = strdup(value);

        if (value_copy == NULL)
        {
            printfPQExpBuffer(errorMessage, libpq_gettext("out of memory\n"));
            return NULL;
        }
    }

    if (option->val)
        free(option->val);
    option->val = value_copy;

    return option;
}

/*
 * Find a PQconninfoOption option corresponding to the keyword in the
 * connOptions array.
 *
 * If successful, returns a pointer to the corresponding PQconninfoOption
 * structure.
 * If not successful, returns NULL.
 */
static PQconninfoOption *
conninfo_find(PQconninfoOption *connOptions, const char *keyword)
{
    PQconninfoOption *option;

    for (option = connOptions; option->keyword != NULL; option++)
    {
        if (strcmp(option->keyword, keyword) == 0)
            return option;
    }

    return NULL;
}


/*
 * Return the connection options used for the connection
 */
PQconninfoOption *
PQconninfo(PGconn *conn)
{
    PQExpBufferData errorBuf;
    PQconninfoOption *connOptions;

    if (conn == NULL)
        return NULL;

    /* We don't actually report any errors here, but callees want a buffer */
    initPQExpBuffer(&errorBuf);
    if (PQExpBufferDataBroken(errorBuf))
        return NULL;            /* out of memory already :-( */

    connOptions = conninfo_init(&errorBuf);

    if (connOptions != NULL)
    {
        const internalPQconninfoOption *option;

        for (option = PQconninfoOptions; option->keyword; option++)
        {
            char      **connmember;

            if (option->connofs < 0)
                continue;

            connmember = (char **) ((char *) conn + option->connofs);

            if (*connmember)
                conninfo_storeval(connOptions, option->keyword, *connmember,
                                  &errorBuf, true, false);
        }
    }

    termPQExpBuffer(&errorBuf);

    return connOptions;
}


void
PQconninfoFree(PQconninfoOption *connOptions)
{
    PQconninfoOption *option;

    if (connOptions == NULL)
        return;

    for (option = connOptions; option->keyword != NULL; option++)
    {
        if (option->val != NULL)
            free(option->val);
    }
    free(connOptions);
}


/* =========== accessor functions for PGconn ========= */
char *
PQdb(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->dbName;
}

char *
PQuser(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pguser;
}

char *
PQpass(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pgpass;
}

char *
PQhost(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pghost ? conn->pghost : conn->pgunixsocket;
}

char *
PQport(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pgport;
}

char *
PQtty(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pgtty;
}

char *
PQoptions(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pgoptions;
}

ConnStatusType
PQstatus(const PGconn *conn)
{
    if (!conn)
        return CONNECTION_BAD;
    return conn->status;
}

PGTransactionStatusType
PQtransactionStatus(const PGconn *conn)
{
    if (!conn || conn->status != CONNECTION_OK)
        return PQTRANS_UNKNOWN;
    if (conn->asyncStatus != PGASYNC_IDLE)
        return PQTRANS_ACTIVE;
    return conn->xactStatus;
}

const char *
PQparameterStatus(const PGconn *conn, const char *paramName)
{
    const pgParameterStatus *pstatus;

    if (!conn || !paramName)
        return NULL;
    for (pstatus = conn->pstatus; pstatus != NULL; pstatus = pstatus->next)
    {
        if (strcmp(pstatus->name, paramName) == 0)
            return pstatus->value;
    }
    return NULL;
}

int
PQprotocolVersion(const PGconn *conn)
{
    if (!conn)
        return 0;
    if (conn->status == CONNECTION_BAD)
        return 0;
    return PG_PROTOCOL_MAJOR(conn->pversion);
}

int
PQserverVersion(const PGconn *conn)
{
    if (!conn)
        return 0;
    if (conn->status == CONNECTION_BAD)
        return 0;
    return conn->sversion;
}

char *
PQerrorMessage(const PGconn *conn)
{
    if (!conn)
        return libpq_gettext("connection pointer is NULL\n");

    return conn->errorMessage.data;
}

int
PQsocket(const PGconn *conn)
{
    if (!conn)
        return -1;
    return conn->sock;
}

int
PQbackendPID(const PGconn *conn)
{
    if (!conn || conn->status != CONNECTION_OK)
        return 0;
    return conn->be_pid;
}

int
PQconnectionNeedsPassword(const PGconn *conn)
{
    if (!conn)
        return false;
    if (conn->password_needed &&
        (conn->pgpass == NULL || conn->pgpass[0] == '\0'))
        return true;
    else
        return false;
}

int
PQconnectionUsedPassword(const PGconn *conn)
{
    if (!conn)
        return false;
    if (conn->password_needed)
        return true;
    else
        return false;
}

int
PQclientEncoding(const PGconn *conn)
{
    if (!conn || conn->status != CONNECTION_OK)
        return -1;
    return conn->client_encoding;
}

int
PQsetClientEncoding(PGconn *conn, const char *encoding)
{
    char        qbuf[128];
    static const char query[] = "set client_encoding to '%s'";
    PGresult   *res;
    int         status;

    if (!conn || conn->status != CONNECTION_OK)
        return -1;

    if (!encoding)
        return -1;

    /* Resolve special "auto" value from the locale */
    if (strcmp(encoding, "auto") == 0)
        encoding = pg_encoding_to_char(pg_get_encoding_from_locale(NULL, true));

    /* check query buffer overflow */
    if (sizeof(qbuf) < (sizeof(query) + strlen(encoding)))
        return -1;

    /* ok, now send a query */
    sprintf(qbuf, query, encoding);
    res = PQexec(conn, qbuf);

    if (res == NULL)
        return -1;
    if (res->resultStatus != PGRES_COMMAND_OK)
        status = -1;
    else
    {
        /*
         * In protocol 2 we have to assume the setting will stick, and adjust
         * our state immediately.  In protocol 3 and up we can rely on the
         * backend to report the parameter value, and we'll change state at
         * that time.
         */
        if (PG_PROTOCOL_MAJOR(conn->pversion) < 3)
            pqSaveParameterStatus(conn, "client_encoding", encoding);
        status = 0;             /* everything is ok */
    }
    PQclear(res);
    return status;
}

PGVerbosity
PQsetErrorVerbosity(PGconn *conn, PGVerbosity verbosity)
{
    PGVerbosity old;

    if (!conn)
        return PQERRORS_DEFAULT;
    old = conn->verbosity;
    conn->verbosity = verbosity;
    return old;
}

void
PQtrace(PGconn *conn, FILE *debug_port)
{
    if (conn == NULL)
        return;
    PQuntrace(conn);
    conn->Pfdebug = debug_port;
}

void
PQuntrace(PGconn *conn)
{
    if (conn == NULL)
        return;
    if (conn->Pfdebug)
    {
        fflush(conn->Pfdebug);
        conn->Pfdebug = NULL;
    }
}

PQnoticeReceiver
PQsetNoticeReceiver(PGconn *conn, PQnoticeReceiver proc, void *arg)
{
    PQnoticeReceiver old;

    if (conn == NULL)
        return NULL;

    old = conn->noticeHooks.noticeRec;
    if (proc)
    {
        conn->noticeHooks.noticeRec = proc;
        conn->noticeHooks.noticeRecArg = arg;
    }
    return old;
}

PQnoticeProcessor
PQsetNoticeProcessor(PGconn *conn, PQnoticeProcessor proc, void *arg)
{
    PQnoticeProcessor old;

    if (conn == NULL)
        return NULL;

    old = conn->noticeHooks.noticeProc;
    if (proc)
    {
        conn->noticeHooks.noticeProc = proc;
        conn->noticeHooks.noticeProcArg = arg;
    }
    return old;
}

/*
 * The default notice message receiver just gets the standard notice text
 * and sends it to the notice processor.  This two-level setup exists
 * mostly for backwards compatibility; perhaps we should deprecate use of
 * PQsetNoticeProcessor?
 */
static void
defaultNoticeReceiver(void *arg, const PGresult *res)
{
    (void) arg;                 /* not used */
    if (res->noticeHooks.noticeProc != NULL)
        (*res->noticeHooks.noticeProc) (res->noticeHooks.noticeProcArg,
                                        PQresultErrorMessage(res));
}

/*
 * The default notice message processor just prints the
 * message on stderr.  Applications can override this if they
 * want the messages to go elsewhere (a window, for example).
 * Note that simply discarding notices is probably a bad idea.
 */
static void
defaultNoticeProcessor(void *arg, const char *message)
{
    (void) arg;                 /* not used */
    /* Note: we expect the supplied string to end with a newline already. */
    fprintf(stderr, "%s", message);
}

/*
 * returns a pointer to the next token or NULL if the current
 * token doesn't match
 */
static char *
pwdfMatchesString(char *buf, char *token)
{
    char       *tbuf,
               *ttok;
    bool        bslash = false;

    if (buf == NULL || token == NULL)
        return NULL;
    tbuf = buf;
    ttok = token;
    if (tbuf[0] == '*' && tbuf[1] == ':')
        return tbuf + 2;
    while (*tbuf != 0)
    {
        if (*tbuf == '\\' && !bslash)
        {
            tbuf++;
            bslash = true;
        }
        if (*tbuf == ':' && *ttok == 0 && !bslash)
            return tbuf + 1;
        bslash = false;
        if (*ttok == 0)
            return NULL;
        if (*tbuf == *ttok)
        {
            tbuf++;
            ttok++;
        }
        else
            return NULL;
    }
    return NULL;
}

/* Get a password from the password file. Return value is malloc'd. */
static char *
PasswordFromFile(char *hostname, char *port, char *dbname, char *username)
{
    FILE       *fp;
    char        pgpassfile[MAXPGPATH];
    struct stat stat_buf;

#define LINELEN NAMEDATALEN*5
    char        buf[LINELEN];

    if (dbname == NULL || strlen(dbname) == 0)
        return NULL;

    if (username == NULL || strlen(username) == 0)
        return NULL;

    /* 'localhost' matches pghost of '' or the default socket directory */
    if (hostname == NULL)
        hostname = DefaultHost;
    else if (is_absolute_path(hostname))

        /*
         * We should probably use canonicalize_path(), but then we have to
         * bring path.c into libpq, and it doesn't seem worth it.
         */
        if (strcmp(hostname, DEFAULT_PGSOCKET_DIR) == 0)
            hostname = DefaultHost;

    if (port == NULL)
        port = DEF_PGPORT_STR;

    if (!getPgPassFilename(pgpassfile))
        return NULL;

    /* If password file cannot be opened, ignore it. */
    if (stat(pgpassfile, &stat_buf) != 0)
        return NULL;

#ifndef WIN32
    if (!S_ISREG(stat_buf.st_mode))
    {
        fprintf(stderr,
        libpq_gettext("WARNING: password file \"%s\" is not a plain file\n"),
                pgpassfile);
        return NULL;
    }

    /* If password file is insecure, alert the user and ignore it. */
    if (stat_buf.st_mode & (S_IRWXG | S_IRWXO))
    {
        fprintf(stderr,
                libpq_gettext("WARNING: password file \"%s\" has group or world access; permissions should be u=rw (0600) or less\n"),
                pgpassfile);
        return NULL;
    }
#else

    /*
     * On Win32, the directory is protected, so we don't have to check the
     * file.
     */
#endif

    fp = fopen(pgpassfile, "r");
    if (fp == NULL)
        return NULL;

    while (!feof(fp) && !ferror(fp))
    {
        char       *t = buf,
                   *ret,
                   *p1,
                   *p2;
        int         len;

        if (fgets(buf, sizeof(buf), fp) == NULL)
            break;

        len = strlen(buf);
        if (len == 0)
            continue;

        /* Remove trailing newline */
        if (buf[len - 1] == '\n')
            buf[len - 1] = 0;

        if ((t = pwdfMatchesString(t, hostname)) == NULL ||
            (t = pwdfMatchesString(t, port)) == NULL ||
            (t = pwdfMatchesString(t, dbname)) == NULL ||
            (t = pwdfMatchesString(t, username)) == NULL)
            continue;
        ret = strdup(t);
        fclose(fp);

        /* De-escape password. */
        for (p1 = p2 = ret; *p1 != ':' && *p1 != '\0'; ++p1, ++p2)
        {
            if (*p1 == '\\' && p1[1] != '\0')
                ++p1;
            *p2 = *p1;
        }
        *p2 = '\0';

        return ret;
    }

    fclose(fp);
    return NULL;

#undef LINELEN
}


static bool
getPgPassFilename(char *pgpassfile)
{
    char       *passfile_env;

    if ((passfile_env = getenv("PGPASSFILE")) != NULL)
        /* use the literal path from the environment, if set */
        strlcpy(pgpassfile, passfile_env, MAXPGPATH);
    else
    {
        char        homedir[MAXPGPATH];

        if (!pqGetHomeDirectory(homedir, sizeof(homedir)))
            return false;
        snprintf(pgpassfile, MAXPGPATH, "%s/%s", homedir, PGPASSFILE);
    }
    return true;
}

/*
 *  If the connection failed, we should mention if
 *  we got the password from .pgpass in case that
 *  password is wrong.
 */
static void
dot_pg_pass_warning(PGconn *conn)
{
    /* If it was 'invalid authorization', add .pgpass mention */
    /* only works with >= 9.0 servers */
    if (conn->dot_pgpass_used && conn->password_needed && conn->result &&
        strcmp(PQresultErrorField(conn->result, PG_DIAG_SQLSTATE),
               ERRCODE_INVALID_PASSWORD) == 0)
    {
        char        pgpassfile[MAXPGPATH];

        if (!getPgPassFilename(pgpassfile))
            return;
        appendPQExpBuffer(&conn->errorMessage,
                      libpq_gettext("password retrieved from file \"%s\"\n"),
                          pgpassfile);
    }
}


/*
 * Obtain user's home directory, return in given buffer
 *
 * On Unix, this actually returns the user's home directory.  On Windows
 * it returns the PostgreSQL-specific application data folder.
 *
 * This is essentially the same as get_home_path(), but we don't use that
 * because we don't want to pull path.c into libpq (it pollutes application
 * namespace)
 */
bool
pqGetHomeDirectory(char *buf, int bufsize)
{
#ifndef WIN32
    char        pwdbuf[BUFSIZ];
    struct passwd pwdstr;
    struct passwd *pwd = NULL;

    if (pqGetpwuid(geteuid(), &pwdstr, pwdbuf, sizeof(pwdbuf), &pwd) != 0)
        return false;
    strlcpy(buf, pwd->pw_dir, bufsize);
    return true;
#else
    char        tmppath[MAX_PATH];

    ZeroMemory(tmppath, sizeof(tmppath));
    if (SHGetFolderPath(NULL, CSIDL_APPDATA, NULL, 0, tmppath) != S_OK)
        return false;
    snprintf(buf, bufsize, "%s/postgresql", tmppath);
    return true;
#endif
}

/*
 * To keep the API consistent, the locking stubs are always provided, even
 * if they are not required.
 */

static void
default_threadlock(int acquire)
{
#ifdef ENABLE_THREAD_SAFETY
#ifndef WIN32
    static pthread_mutex_t singlethread_lock = PTHREAD_MUTEX_INITIALIZER;
#else
    static pthread_mutex_t singlethread_lock = NULL;
    static long mutex_initlock = 0;

    if (singlethread_lock == NULL)
    {
        while (InterlockedExchange(&mutex_initlock, 1) == 1)
             /* loop, another thread own the lock */ ;
        if (singlethread_lock == NULL)
        {
            if (pthread_mutex_init(&singlethread_lock, NULL))
                PGTHREAD_ERROR("failed to initialize mutex");
        }
        InterlockedExchange(&mutex_initlock, 0);
    }
#endif
    if (acquire)
    {
        if (pthread_mutex_lock(&singlethread_lock))
            PGTHREAD_ERROR("failed to lock mutex");
    }
    else
    {
        if (pthread_mutex_unlock(&singlethread_lock))
            PGTHREAD_ERROR("failed to unlock mutex");
    }
#endif
}

pgthreadlock_t
PQregisterThreadLock(pgthreadlock_t newhandler)
{
    pgthreadlock_t prev = pg_g_threadlock;

    if (newhandler)
        pg_g_threadlock = newhandler;
    else
        pg_g_threadlock = default_threadlock;

    return prev;
}