varlena.c

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/*-------------------------------------------------------------------------
 *
 * varlena.c
 *    Functions for the variable-length built-in types.
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/varlena.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <limits.h>

#include "access/tuptoaster.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_type.h"
#include "libpq/md5.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "parser/scansup.h"
#include "regex/regex.h"
#include "utils/builtins.h"
#include "utils/bytea.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"


/* GUC variable */
int         bytea_output = BYTEA_OUTPUT_HEX;

typedef struct varlena unknown;

typedef struct
{
    bool        use_wchar;      /* T if multibyte encoding */
    char       *str1;           /* use these if not use_wchar */
    char       *str2;           /* note: these point to original texts */
    pg_wchar   *wstr1;          /* use these if use_wchar */
    pg_wchar   *wstr2;          /* note: these are palloc'd */
    int         len1;           /* string lengths in logical characters */
    int         len2;
    /* Skip table for Boyer-Moore-Horspool search algorithm: */
    int         skiptablemask;  /* mask for ANDing with skiptable subscripts */
    int         skiptable[256]; /* skip distance for given mismatched char */
} TextPositionState;

#define DatumGetUnknownP(X)         ((unknown *) PG_DETOAST_DATUM(X))
#define DatumGetUnknownPCopy(X)     ((unknown *) PG_DETOAST_DATUM_COPY(X))
#define PG_GETARG_UNKNOWN_P(n)      DatumGetUnknownP(PG_GETARG_DATUM(n))
#define PG_GETARG_UNKNOWN_P_COPY(n) DatumGetUnknownPCopy(PG_GETARG_DATUM(n))
#define PG_RETURN_UNKNOWN_P(x)      PG_RETURN_POINTER(x)

static int32 text_length(Datum str);
static text *text_catenate(text *t1, text *t2);
static text *text_substring(Datum str,
               int32 start,
               int32 length,
               bool length_not_specified);
static text *text_overlay(text *t1, text *t2, int sp, int sl);
static int  text_position(text *t1, text *t2);
static void text_position_setup(text *t1, text *t2, TextPositionState *state);
static int  text_position_next(int start_pos, TextPositionState *state);
static void text_position_cleanup(TextPositionState *state);
static int  text_cmp(text *arg1, text *arg2, Oid collid);
static bytea *bytea_catenate(bytea *t1, bytea *t2);
static bytea *bytea_substring(Datum str,
                int S,
                int L,
                bool length_not_specified);
static bytea *bytea_overlay(bytea *t1, bytea *t2, int sp, int sl);
static void appendStringInfoText(StringInfo str, const text *t);
static Datum text_to_array_internal(PG_FUNCTION_ARGS);
static text *array_to_text_internal(FunctionCallInfo fcinfo, ArrayType *v,
                       const char *fldsep, const char *null_string);
static StringInfo makeStringAggState(FunctionCallInfo fcinfo);
static bool text_format_parse_digits(const char **ptr, const char *end_ptr,
                         int *value);
static const char *text_format_parse_format(const char *start_ptr,
                         const char *end_ptr,
                         int *argpos, int *widthpos,
                         int *flags, int *width);
static void text_format_string_conversion(StringInfo buf, char conversion,
                              FmgrInfo *typOutputInfo,
                              Datum value, bool isNull,
                              int flags, int width);
static void text_format_append_string(StringInfo buf, const char *str,
                          int flags, int width);


/*****************************************************************************
 *   CONVERSION ROUTINES EXPORTED FOR USE BY C CODE                          *
 *****************************************************************************/

/*
 * cstring_to_text
 *
 * Create a text value from a null-terminated C string.
 *
 * The new text value is freshly palloc'd with a full-size VARHDR.
 */
text *
cstring_to_text(const char *s)
{
    return cstring_to_text_with_len(s, strlen(s));
}

/*
 * cstring_to_text_with_len
 *
 * Same as cstring_to_text except the caller specifies the string length;
 * the string need not be null_terminated.
 */
text *
cstring_to_text_with_len(const char *s, int len)
{
    text       *result = (text *) palloc(len + VARHDRSZ);

    SET_VARSIZE(result, len + VARHDRSZ);
    memcpy(VARDATA(result), s, len);

    return result;
}

/*
 * text_to_cstring
 *
 * Create a palloc'd, null-terminated C string from a text value.
 *
 * We support being passed a compressed or toasted text value.
 * This is a bit bogus since such values shouldn't really be referred to as
 * "text *", but it seems useful for robustness.  If we didn't handle that
 * case here, we'd need another routine that did, anyway.
 */
char *
text_to_cstring(const text *t)
{
    /* must cast away the const, unfortunately */
    text       *tunpacked = pg_detoast_datum_packed((struct varlena *) t);
    int         len = VARSIZE_ANY_EXHDR(tunpacked);
    char       *result;

    result = (char *) palloc(len + 1);
    memcpy(result, VARDATA_ANY(tunpacked), len);
    result[len] = '\0';

    if (tunpacked != t)
        pfree(tunpacked);

    return result;
}

/*
 * text_to_cstring_buffer
 *
 * Copy a text value into a caller-supplied buffer of size dst_len.
 *
 * The text string is truncated if necessary to fit.  The result is
 * guaranteed null-terminated (unless dst_len == 0).
 *
 * We support being passed a compressed or toasted text value.
 * This is a bit bogus since such values shouldn't really be referred to as
 * "text *", but it seems useful for robustness.  If we didn't handle that
 * case here, we'd need another routine that did, anyway.
 */
void
text_to_cstring_buffer(const text *src, char *dst, size_t dst_len)
{
    /* must cast away the const, unfortunately */
    text       *srcunpacked = pg_detoast_datum_packed((struct varlena *) src);
    size_t      src_len = VARSIZE_ANY_EXHDR(srcunpacked);

    if (dst_len > 0)
    {
        dst_len--;
        if (dst_len >= src_len)
            dst_len = src_len;
        else    /* ensure truncation is encoding-safe */
            dst_len = pg_mbcliplen(VARDATA_ANY(srcunpacked), src_len, dst_len);
        memcpy(dst, VARDATA_ANY(srcunpacked), dst_len);
        dst[dst_len] = '\0';
    }

    if (srcunpacked != src)
        pfree(srcunpacked);
}


/*****************************************************************************
 *   USER I/O ROUTINES                                                       *
 *****************************************************************************/


#define VAL(CH)         ((CH) - '0')
#define DIG(VAL)        ((VAL) + '0')

/*
 *      byteain         - converts from printable representation of byte array
 *
 *      Non-printable characters must be passed as '\nnn' (octal) and are
 *      converted to internal form.  '\' must be passed as '\\'.
 *      ereport(ERROR, ...) if bad form.
 *
 *      BUGS:
 *              The input is scanned twice.
 *              The error checking of input is minimal.
 */
Datum
byteain(PG_FUNCTION_ARGS)
{
    char       *inputText = PG_GETARG_CSTRING(0);
    char       *tp;
    char       *rp;
    int         bc;
    bytea      *result;

    /* Recognize hex input */
    if (inputText[0] == '\\' && inputText[1] == 'x')
    {
        size_t      len = strlen(inputText);

        bc = (len - 2) / 2 + VARHDRSZ;  /* maximum possible length */
        result = palloc(bc);
        bc = hex_decode(inputText + 2, len - 2, VARDATA(result));
        SET_VARSIZE(result, bc + VARHDRSZ);     /* actual length */

        PG_RETURN_BYTEA_P(result);
    }

    /* Else, it's the traditional escaped style */
    for (bc = 0, tp = inputText; *tp != '\0'; bc++)
    {
        if (tp[0] != '\\')
            tp++;
        else if ((tp[0] == '\\') &&
                 (tp[1] >= '0' && tp[1] <= '3') &&
                 (tp[2] >= '0' && tp[2] <= '7') &&
                 (tp[3] >= '0' && tp[3] <= '7'))
            tp += 4;
        else if ((tp[0] == '\\') &&
                 (tp[1] == '\\'))
            tp += 2;
        else
        {
            /*
             * one backslash, not followed by another or ### valid octal
             */
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                     errmsg("invalid input syntax for type bytea")));
        }
    }

    bc += VARHDRSZ;

    result = (bytea *) palloc(bc);
    SET_VARSIZE(result, bc);

    tp = inputText;
    rp = VARDATA(result);
    while (*tp != '\0')
    {
        if (tp[0] != '\\')
            *rp++ = *tp++;
        else if ((tp[0] == '\\') &&
                 (tp[1] >= '0' && tp[1] <= '3') &&
                 (tp[2] >= '0' && tp[2] <= '7') &&
                 (tp[3] >= '0' && tp[3] <= '7'))
        {
            bc = VAL(tp[1]);
            bc <<= 3;
            bc += VAL(tp[2]);
            bc <<= 3;
            *rp++ = bc + VAL(tp[3]);

            tp += 4;
        }
        else if ((tp[0] == '\\') &&
                 (tp[1] == '\\'))
        {
            *rp++ = '\\';
            tp += 2;
        }
        else
        {
            /*
             * We should never get here. The first pass should not allow it.
             */
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                     errmsg("invalid input syntax for type bytea")));
        }
    }

    PG_RETURN_BYTEA_P(result);
}

/*
 *      byteaout        - converts to printable representation of byte array
 *
 *      In the traditional escaped format, non-printable characters are
 *      printed as '\nnn' (octal) and '\' as '\\'.
 */
Datum
byteaout(PG_FUNCTION_ARGS)
{
    bytea      *vlena = PG_GETARG_BYTEA_PP(0);
    char       *result;
    char       *rp;

    if (bytea_output == BYTEA_OUTPUT_HEX)
    {
        /* Print hex format */
        rp = result = palloc(VARSIZE_ANY_EXHDR(vlena) * 2 + 2 + 1);
        *rp++ = '\\';
        *rp++ = 'x';
        rp += hex_encode(VARDATA_ANY(vlena), VARSIZE_ANY_EXHDR(vlena), rp);
    }
    else if (bytea_output == BYTEA_OUTPUT_ESCAPE)
    {
        /* Print traditional escaped format */
        char       *vp;
        int         len;
        int         i;

        len = 1;                /* empty string has 1 char */
        vp = VARDATA_ANY(vlena);
        for (i = VARSIZE_ANY_EXHDR(vlena); i != 0; i--, vp++)
        {
            if (*vp == '\\')
                len += 2;
            else if ((unsigned char) *vp < 0x20 || (unsigned char) *vp > 0x7e)
                len += 4;
            else
                len++;
        }
        rp = result = (char *) palloc(len);
        vp = VARDATA_ANY(vlena);
        for (i = VARSIZE_ANY_EXHDR(vlena); i != 0; i--, vp++)
        {
            if (*vp == '\\')
            {
                *rp++ = '\\';
                *rp++ = '\\';
            }
            else if ((unsigned char) *vp < 0x20 || (unsigned char) *vp > 0x7e)
            {
                int         val;    /* holds unprintable chars */

                val = *vp;
                rp[0] = '\\';
                rp[3] = DIG(val & 07);
                val >>= 3;
                rp[2] = DIG(val & 07);
                val >>= 3;
                rp[1] = DIG(val & 03);
                rp += 4;
            }
            else
                *rp++ = *vp;
        }
    }
    else
    {
        elog(ERROR, "unrecognized bytea_output setting: %d",
             bytea_output);
        rp = result = NULL;     /* keep compiler quiet */
    }
    *rp = '\0';
    PG_RETURN_CSTRING(result);
}

/*
 *      bytearecv           - converts external binary format to bytea
 */
Datum
bytearecv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    bytea      *result;
    int         nbytes;

    nbytes = buf->len - buf->cursor;
    result = (bytea *) palloc(nbytes + VARHDRSZ);
    SET_VARSIZE(result, nbytes + VARHDRSZ);
    pq_copymsgbytes(buf, VARDATA(result), nbytes);
    PG_RETURN_BYTEA_P(result);
}

/*
 *      byteasend           - converts bytea to binary format
 *
 * This is a special case: just copy the input...
 */
Datum
byteasend(PG_FUNCTION_ARGS)
{
    bytea      *vlena = PG_GETARG_BYTEA_P_COPY(0);

    PG_RETURN_BYTEA_P(vlena);
}

Datum
bytea_string_agg_transfn(PG_FUNCTION_ARGS)
{
    StringInfo  state;

    state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);

    /* Append the value unless null. */
    if (!PG_ARGISNULL(1))
    {
        bytea      *value = PG_GETARG_BYTEA_PP(1);

        /* On the first time through, we ignore the delimiter. */
        if (state == NULL)
            state = makeStringAggState(fcinfo);
        else if (!PG_ARGISNULL(2))
        {
            bytea      *delim = PG_GETARG_BYTEA_PP(2);

            appendBinaryStringInfo(state, VARDATA_ANY(delim), VARSIZE_ANY_EXHDR(delim));
        }

        appendBinaryStringInfo(state, VARDATA_ANY(value), VARSIZE_ANY_EXHDR(value));
    }

    /*
     * The transition type for string_agg() is declared to be "internal",
     * which is a pass-by-value type the same size as a pointer.
     */
    PG_RETURN_POINTER(state);
}

Datum
bytea_string_agg_finalfn(PG_FUNCTION_ARGS)
{
    StringInfo  state;

    /* cannot be called directly because of internal-type argument */
    Assert(AggCheckCallContext(fcinfo, NULL));

    state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);

    if (state != NULL)
    {
        bytea      *result;

        result = (bytea *) palloc(state->len + VARHDRSZ);
        SET_VARSIZE(result, state->len + VARHDRSZ);
        memcpy(VARDATA(result), state->data, state->len);
        PG_RETURN_BYTEA_P(result);
    }
    else
        PG_RETURN_NULL();
}

/*
 *      textin          - converts "..." to internal representation
 */
Datum
textin(PG_FUNCTION_ARGS)
{
    char       *inputText = PG_GETARG_CSTRING(0);

    PG_RETURN_TEXT_P(cstring_to_text(inputText));
}

/*
 *      textout         - converts internal representation to "..."
 */
Datum
textout(PG_FUNCTION_ARGS)
{
    Datum       txt = PG_GETARG_DATUM(0);

    PG_RETURN_CSTRING(TextDatumGetCString(txt));
}

/*
 *      textrecv            - converts external binary format to text
 */
Datum
textrecv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    text       *result;
    char       *str;
    int         nbytes;

    str = pq_getmsgtext(buf, buf->len - buf->cursor, &nbytes);

    result = cstring_to_text_with_len(str, nbytes);
    pfree(str);
    PG_RETURN_TEXT_P(result);
}

/*
 *      textsend            - converts text to binary format
 */
Datum
textsend(PG_FUNCTION_ARGS)
{
    text       *t = PG_GETARG_TEXT_PP(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendtext(&buf, VARDATA_ANY(t), VARSIZE_ANY_EXHDR(t));
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}


/*
 *      unknownin           - converts "..." to internal representation
 */
Datum
unknownin(PG_FUNCTION_ARGS)
{
    char       *str = PG_GETARG_CSTRING(0);

    /* representation is same as cstring */
    PG_RETURN_CSTRING(pstrdup(str));
}

/*
 *      unknownout          - converts internal representation to "..."
 */
Datum
unknownout(PG_FUNCTION_ARGS)
{
    /* representation is same as cstring */
    char       *str = PG_GETARG_CSTRING(0);

    PG_RETURN_CSTRING(pstrdup(str));
}

/*
 *      unknownrecv         - converts external binary format to unknown
 */
Datum
unknownrecv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    char       *str;
    int         nbytes;

    str = pq_getmsgtext(buf, buf->len - buf->cursor, &nbytes);
    /* representation is same as cstring */
    PG_RETURN_CSTRING(str);
}

/*
 *      unknownsend         - converts unknown to binary format
 */
Datum
unknownsend(PG_FUNCTION_ARGS)
{
    /* representation is same as cstring */
    char       *str = PG_GETARG_CSTRING(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendtext(&buf, str, strlen(str));
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}


/* ========== PUBLIC ROUTINES ========== */

/*
 * textlen -
 *    returns the logical length of a text*
 *     (which is less than the VARSIZE of the text*)
 */
Datum
textlen(PG_FUNCTION_ARGS)
{
    Datum       str = PG_GETARG_DATUM(0);

    /* try to avoid decompressing argument */
    PG_RETURN_INT32(text_length(str));
}

/*
 * text_length -
 *  Does the real work for textlen()
 *
 *  This is broken out so it can be called directly by other string processing
 *  functions.  Note that the argument is passed as a Datum, to indicate that
 *  it may still be in compressed form.  We can avoid decompressing it at all
 *  in some cases.
 */
static int32
text_length(Datum str)
{
    /* fastpath when max encoding length is one */
    if (pg_database_encoding_max_length() == 1)
        PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
    else
    {
        text       *t = DatumGetTextPP(str);

        PG_RETURN_INT32(pg_mbstrlen_with_len(VARDATA_ANY(t),
                                             VARSIZE_ANY_EXHDR(t)));
    }
}

/*
 * textoctetlen -
 *    returns the physical length of a text*
 *     (which is less than the VARSIZE of the text*)
 */
Datum
textoctetlen(PG_FUNCTION_ARGS)
{
    Datum       str = PG_GETARG_DATUM(0);

    /* We need not detoast the input at all */
    PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
}

/*
 * textcat -
 *    takes two text* and returns a text* that is the concatenation of
 *    the two.
 *
 * Rewritten by Sapa, [email protected]. 8-Jul-96.
 * Updated by Thomas, [email protected] 1997-07-10.
 * Allocate space for output in all cases.
 * XXX - thomas 1997-07-10
 */
Datum
textcat(PG_FUNCTION_ARGS)
{
    text       *t1 = PG_GETARG_TEXT_PP(0);
    text       *t2 = PG_GETARG_TEXT_PP(1);

    PG_RETURN_TEXT_P(text_catenate(t1, t2));
}

/*
 * text_catenate
 *  Guts of textcat(), broken out so it can be used by other functions
 *
 * Arguments can be in short-header form, but not compressed or out-of-line
 */
static text *
text_catenate(text *t1, text *t2)
{
    text       *result;
    int         len1,
                len2,
                len;
    char       *ptr;

    len1 = VARSIZE_ANY_EXHDR(t1);
    len2 = VARSIZE_ANY_EXHDR(t2);

    /* paranoia ... probably should throw error instead? */
    if (len1 < 0)
        len1 = 0;
    if (len2 < 0)
        len2 = 0;

    len = len1 + len2 + VARHDRSZ;
    result = (text *) palloc(len);

    /* Set size of result string... */
    SET_VARSIZE(result, len);

    /* Fill data field of result string... */
    ptr = VARDATA(result);
    if (len1 > 0)
        memcpy(ptr, VARDATA_ANY(t1), len1);
    if (len2 > 0)
        memcpy(ptr + len1, VARDATA_ANY(t2), len2);

    return result;
}

/*
 * charlen_to_bytelen()
 *  Compute the number of bytes occupied by n characters starting at *p
 *
 * It is caller's responsibility that there actually are n characters;
 * the string need not be null-terminated.
 */
static int
charlen_to_bytelen(const char *p, int n)
{
    if (pg_database_encoding_max_length() == 1)
    {
        /* Optimization for single-byte encodings */
        return n;
    }
    else
    {
        const char *s;

        for (s = p; n > 0; n--)
            s += pg_mblen(s);

        return s - p;
    }
}

/*
 * text_substr()
 * Return a substring starting at the specified position.
 * - thomas 1997-12-31
 *
 * Input:
 *  - string
 *  - starting position (is one-based)
 *  - string length
 *
 * If the starting position is zero or less, then return from the start of the string
 *  adjusting the length to be consistent with the "negative start" per SQL.
 * If the length is less than zero, return the remaining string.
 *
 * Added multibyte support.
 * - Tatsuo Ishii 1998-4-21
 * Changed behavior if starting position is less than one to conform to SQL behavior.
 * Formerly returned the entire string; now returns a portion.
 * - Thomas Lockhart 1998-12-10
 * Now uses faster TOAST-slicing interface
 * - John Gray 2002-02-22
 * Remove "#ifdef MULTIBYTE" and test for encoding_max_length instead. Change
 * behaviors conflicting with SQL to meet SQL (if E = S + L < S throw
 * error; if E < 1, return '', not entire string). Fixed MB related bug when
 * S > LC and < LC + 4 sometimes garbage characters are returned.
 * - Joe Conway 2002-08-10
 */
Datum
text_substr(PG_FUNCTION_ARGS)
{
    PG_RETURN_TEXT_P(text_substring(PG_GETARG_DATUM(0),
                                    PG_GETARG_INT32(1),
                                    PG_GETARG_INT32(2),
                                    false));
}

/*
 * text_substr_no_len -
 *    Wrapper to avoid opr_sanity failure due to
 *    one function accepting a different number of args.
 */
Datum
text_substr_no_len(PG_FUNCTION_ARGS)
{
    PG_RETURN_TEXT_P(text_substring(PG_GETARG_DATUM(0),
                                    PG_GETARG_INT32(1),
                                    -1, true));
}

/*
 * text_substring -
 *  Does the real work for text_substr() and text_substr_no_len()
 *
 *  This is broken out so it can be called directly by other string processing
 *  functions.  Note that the argument is passed as a Datum, to indicate that
 *  it may still be in compressed/toasted form.  We can avoid detoasting all
 *  of it in some cases.
 *
 *  The result is always a freshly palloc'd datum.
 */
static text *
text_substring(Datum str, int32 start, int32 length, bool length_not_specified)
{
    int32       eml = pg_database_encoding_max_length();
    int32       S = start;      /* start position */
    int32       S1;             /* adjusted start position */
    int32       L1;             /* adjusted substring length */

    /* life is easy if the encoding max length is 1 */
    if (eml == 1)
    {
        S1 = Max(S, 1);

        if (length_not_specified)       /* special case - get length to end of
                                         * string */
            L1 = -1;
        else
        {
            /* end position */
            int         E = S + length;

            /*
             * A negative value for L is the only way for the end position to
             * be before the start. SQL99 says to throw an error.
             */
            if (E < S)
                ereport(ERROR,
                        (errcode(ERRCODE_SUBSTRING_ERROR),
                         errmsg("negative substring length not allowed")));

            /*
             * A zero or negative value for the end position can happen if the
             * start was negative or one. SQL99 says to return a zero-length
             * string.
             */
            if (E < 1)
                return cstring_to_text("");

            L1 = E - S1;
        }

        /*
         * If the start position is past the end of the string, SQL99 says to
         * return a zero-length string -- PG_GETARG_TEXT_P_SLICE() will do
         * that for us. Convert to zero-based starting position
         */
        return DatumGetTextPSlice(str, S1 - 1, L1);
    }
    else if (eml > 1)
    {
        /*
         * When encoding max length is > 1, we can't get LC without
         * detoasting, so we'll grab a conservatively large slice now and go
         * back later to do the right thing
         */
        int32       slice_start;
        int32       slice_size;
        int32       slice_strlen;
        text       *slice;
        int32       E1;
        int32       i;
        char       *p;
        char       *s;
        text       *ret;

        /*
         * if S is past the end of the string, the tuple toaster will return a
         * zero-length string to us
         */
        S1 = Max(S, 1);

        /*
         * We need to start at position zero because there is no way to know
         * in advance which byte offset corresponds to the supplied start
         * position.
         */
        slice_start = 0;

        if (length_not_specified)       /* special case - get length to end of
                                         * string */
            slice_size = L1 = -1;
        else
        {
            int         E = S + length;

            /*
             * A negative value for L is the only way for the end position to
             * be before the start. SQL99 says to throw an error.
             */
            if (E < S)
                ereport(ERROR,
                        (errcode(ERRCODE_SUBSTRING_ERROR),
                         errmsg("negative substring length not allowed")));

            /*
             * A zero or negative value for the end position can happen if the
             * start was negative or one. SQL99 says to return a zero-length
             * string.
             */
            if (E < 1)
                return cstring_to_text("");

            /*
             * if E is past the end of the string, the tuple toaster will
             * truncate the length for us
             */
            L1 = E - S1;

            /*
             * Total slice size in bytes can't be any longer than the start
             * position plus substring length times the encoding max length.
             */
            slice_size = (S1 + L1) * eml;
        }

        /*
         * If we're working with an untoasted source, no need to do an extra
         * copying step.
         */
        if (VARATT_IS_COMPRESSED(DatumGetPointer(str)) ||
            VARATT_IS_EXTERNAL(DatumGetPointer(str)))
            slice = DatumGetTextPSlice(str, slice_start, slice_size);
        else
            slice = (text *) DatumGetPointer(str);

        /* see if we got back an empty string */
        if (VARSIZE_ANY_EXHDR(slice) == 0)
        {
            if (slice != (text *) DatumGetPointer(str))
                pfree(slice);
            return cstring_to_text("");
        }

        /* Now we can get the actual length of the slice in MB characters */
        slice_strlen = pg_mbstrlen_with_len(VARDATA_ANY(slice),
                                            VARSIZE_ANY_EXHDR(slice));

        /*
         * Check that the start position wasn't > slice_strlen. If so, SQL99
         * says to return a zero-length string.
         */
        if (S1 > slice_strlen)
        {
            if (slice != (text *) DatumGetPointer(str))
                pfree(slice);
            return cstring_to_text("");
        }

        /*
         * Adjust L1 and E1 now that we know the slice string length. Again
         * remember that S1 is one based, and slice_start is zero based.
         */
        if (L1 > -1)
            E1 = Min(S1 + L1, slice_start + 1 + slice_strlen);
        else
            E1 = slice_start + 1 + slice_strlen;

        /*
         * Find the start position in the slice; remember S1 is not zero based
         */
        p = VARDATA_ANY(slice);
        for (i = 0; i < S1 - 1; i++)
            p += pg_mblen(p);

        /* hang onto a pointer to our start position */
        s = p;

        /*
         * Count the actual bytes used by the substring of the requested
         * length.
         */
        for (i = S1; i < E1; i++)
            p += pg_mblen(p);

        ret = (text *) palloc(VARHDRSZ + (p - s));
        SET_VARSIZE(ret, VARHDRSZ + (p - s));
        memcpy(VARDATA(ret), s, (p - s));

        if (slice != (text *) DatumGetPointer(str))
            pfree(slice);

        return ret;
    }
    else
        elog(ERROR, "invalid backend encoding: encoding max length < 1");

    /* not reached: suppress compiler warning */
    return NULL;
}

/*
 * textoverlay
 *  Replace specified substring of first string with second
 *
 * The SQL standard defines OVERLAY() in terms of substring and concatenation.
 * This code is a direct implementation of what the standard says.
 */
Datum
textoverlay(PG_FUNCTION_ARGS)
{
    text       *t1 = PG_GETARG_TEXT_PP(0);
    text       *t2 = PG_GETARG_TEXT_PP(1);
    int         sp = PG_GETARG_INT32(2);        /* substring start position */
    int         sl = PG_GETARG_INT32(3);        /* substring length */

    PG_RETURN_TEXT_P(text_overlay(t1, t2, sp, sl));
}

Datum
textoverlay_no_len(PG_FUNCTION_ARGS)
{
    text       *t1 = PG_GETARG_TEXT_PP(0);
    text       *t2 = PG_GETARG_TEXT_PP(1);
    int         sp = PG_GETARG_INT32(2);        /* substring start position */
    int         sl;

    sl = text_length(PointerGetDatum(t2));      /* defaults to length(t2) */
    PG_RETURN_TEXT_P(text_overlay(t1, t2, sp, sl));
}

static text *
text_overlay(text *t1, text *t2, int sp, int sl)
{
    text       *result;
    text       *s1;
    text       *s2;
    int         sp_pl_sl;

    /*
     * Check for possible integer-overflow cases.  For negative sp, throw a
     * "substring length" error because that's what should be expected
     * according to the spec's definition of OVERLAY().
     */
    if (sp <= 0)
        ereport(ERROR,
                (errcode(ERRCODE_SUBSTRING_ERROR),
                 errmsg("negative substring length not allowed")));
    sp_pl_sl = sp + sl;
    if (sp_pl_sl <= sl)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));

    s1 = text_substring(PointerGetDatum(t1), 1, sp - 1, false);
    s2 = text_substring(PointerGetDatum(t1), sp_pl_sl, -1, true);
    result = text_catenate(s1, t2);
    result = text_catenate(result, s2);

    return result;
}

/*
 * textpos -
 *    Return the position of the specified substring.
 *    Implements the SQL POSITION() function.
 *    Ref: A Guide To The SQL Standard, Date & Darwen, 1997
 * - thomas 1997-07-27
 */
Datum
textpos(PG_FUNCTION_ARGS)
{
    text       *str = PG_GETARG_TEXT_PP(0);
    text       *search_str = PG_GETARG_TEXT_PP(1);

    PG_RETURN_INT32((int32) text_position(str, search_str));
}

/*
 * text_position -
 *  Does the real work for textpos()
 *
 * Inputs:
 *      t1 - string to be searched
 *      t2 - pattern to match within t1
 * Result:
 *      Character index of the first matched char, starting from 1,
 *      or 0 if no match.
 *
 *  This is broken out so it can be called directly by other string processing
 *  functions.
 */
static int
text_position(text *t1, text *t2)
{
    TextPositionState state;
    int         result;

    text_position_setup(t1, t2, &state);
    result = text_position_next(1, &state);
    text_position_cleanup(&state);
    return result;
}


/*
 * text_position_setup, text_position_next, text_position_cleanup -
 *  Component steps of text_position()
 *
 * These are broken out so that a string can be efficiently searched for
 * multiple occurrences of the same pattern.  text_position_next may be
 * called multiple times with increasing values of start_pos, which is
 * the 1-based character position to start the search from.  The "state"
 * variable is normally just a local variable in the caller.
 */

static void
text_position_setup(text *t1, text *t2, TextPositionState *state)
{
    int         len1 = VARSIZE_ANY_EXHDR(t1);
    int         len2 = VARSIZE_ANY_EXHDR(t2);

    if (pg_database_encoding_max_length() == 1)
    {
        /* simple case - single byte encoding */
        state->use_wchar = false;
        state->str1 = VARDATA_ANY(t1);
        state->str2 = VARDATA_ANY(t2);
        state->len1 = len1;
        state->len2 = len2;
    }
    else
    {
        /* not as simple - multibyte encoding */
        pg_wchar   *p1,
                   *p2;

        p1 = (pg_wchar *) palloc((len1 + 1) * sizeof(pg_wchar));
        len1 = pg_mb2wchar_with_len(VARDATA_ANY(t1), p1, len1);
        p2 = (pg_wchar *) palloc((len2 + 1) * sizeof(pg_wchar));
        len2 = pg_mb2wchar_with_len(VARDATA_ANY(t2), p2, len2);

        state->use_wchar = true;
        state->wstr1 = p1;
        state->wstr2 = p2;
        state->len1 = len1;
        state->len2 = len2;
    }

    /*
     * Prepare the skip table for Boyer-Moore-Horspool searching.  In these
     * notes we use the terminology that the "haystack" is the string to be
     * searched (t1) and the "needle" is the pattern being sought (t2).
     *
     * If the needle is empty or bigger than the haystack then there is no
     * point in wasting cycles initializing the table.  We also choose not to
     * use B-M-H for needles of length 1, since the skip table can't possibly
     * save anything in that case.
     */
    if (len1 >= len2 && len2 > 1)
    {
        int         searchlength = len1 - len2;
        int         skiptablemask;
        int         last;
        int         i;

        /*
         * First we must determine how much of the skip table to use.  The
         * declaration of TextPositionState allows up to 256 elements, but for
         * short search problems we don't really want to have to initialize so
         * many elements --- it would take too long in comparison to the
         * actual search time.  So we choose a useful skip table size based on
         * the haystack length minus the needle length.  The closer the needle
         * length is to the haystack length the less useful skipping becomes.
         *
         * Note: since we use bit-masking to select table elements, the skip
         * table size MUST be a power of 2, and so the mask must be 2^N-1.
         */
        if (searchlength < 16)
            skiptablemask = 3;
        else if (searchlength < 64)
            skiptablemask = 7;
        else if (searchlength < 128)
            skiptablemask = 15;
        else if (searchlength < 512)
            skiptablemask = 31;
        else if (searchlength < 2048)
            skiptablemask = 63;
        else if (searchlength < 4096)
            skiptablemask = 127;
        else
            skiptablemask = 255;
        state->skiptablemask = skiptablemask;

        /*
         * Initialize the skip table.  We set all elements to the needle
         * length, since this is the correct skip distance for any character
         * not found in the needle.
         */
        for (i = 0; i <= skiptablemask; i++)
            state->skiptable[i] = len2;

        /*
         * Now examine the needle.  For each character except the last one,
         * set the corresponding table element to the appropriate skip
         * distance.  Note that when two characters share the same skip table
         * entry, the one later in the needle must determine the skip
         * distance.
         */
        last = len2 - 1;

        if (!state->use_wchar)
        {
            const char *str2 = state->str2;

            for (i = 0; i < last; i++)
                state->skiptable[(unsigned char) str2[i] & skiptablemask] = last - i;
        }
        else
        {
            const pg_wchar *wstr2 = state->wstr2;

            for (i = 0; i < last; i++)
                state->skiptable[wstr2[i] & skiptablemask] = last - i;
        }
    }
}

static int
text_position_next(int start_pos, TextPositionState *state)
{
    int         haystack_len = state->len1;
    int         needle_len = state->len2;
    int         skiptablemask = state->skiptablemask;

    Assert(start_pos > 0);      /* else caller error */

    if (needle_len <= 0)
        return start_pos;       /* result for empty pattern */

    start_pos--;                /* adjust for zero based arrays */

    /* Done if the needle can't possibly fit */
    if (haystack_len < start_pos + needle_len)
        return 0;

    if (!state->use_wchar)
    {
        /* simple case - single byte encoding */
        const char *haystack = state->str1;
        const char *needle = state->str2;
        const char *haystack_end = &haystack[haystack_len];
        const char *hptr;

        if (needle_len == 1)
        {
            /* No point in using B-M-H for a one-character needle */
            char        nchar = *needle;

            hptr = &haystack[start_pos];
            while (hptr < haystack_end)
            {
                if (*hptr == nchar)
                    return hptr - haystack + 1;
                hptr++;
            }
        }
        else
        {
            const char *needle_last = &needle[needle_len - 1];

            /* Start at startpos plus the length of the needle */
            hptr = &haystack[start_pos + needle_len - 1];
            while (hptr < haystack_end)
            {
                /* Match the needle scanning *backward* */
                const char *nptr;
                const char *p;

                nptr = needle_last;
                p = hptr;
                while (*nptr == *p)
                {
                    /* Matched it all?  If so, return 1-based position */
                    if (nptr == needle)
                        return p - haystack + 1;
                    nptr--, p--;
                }

                /*
                 * No match, so use the haystack char at hptr to decide how
                 * far to advance.  If the needle had any occurrence of that
                 * character (or more precisely, one sharing the same
                 * skiptable entry) before its last character, then we advance
                 * far enough to align the last such needle character with
                 * that haystack position.  Otherwise we can advance by the
                 * whole needle length.
                 */
                hptr += state->skiptable[(unsigned char) *hptr & skiptablemask];
            }
        }
    }
    else
    {
        /* The multibyte char version. This works exactly the same way. */
        const pg_wchar *haystack = state->wstr1;
        const pg_wchar *needle = state->wstr2;
        const pg_wchar *haystack_end = &haystack[haystack_len];
        const pg_wchar *hptr;

        if (needle_len == 1)
        {
            /* No point in using B-M-H for a one-character needle */
            pg_wchar    nchar = *needle;

            hptr = &haystack[start_pos];
            while (hptr < haystack_end)
            {
                if (*hptr == nchar)
                    return hptr - haystack + 1;
                hptr++;
            }
        }
        else
        {
            const pg_wchar *needle_last = &needle[needle_len - 1];

            /* Start at startpos plus the length of the needle */
            hptr = &haystack[start_pos + needle_len - 1];
            while (hptr < haystack_end)
            {
                /* Match the needle scanning *backward* */
                const pg_wchar *nptr;
                const pg_wchar *p;

                nptr = needle_last;
                p = hptr;
                while (*nptr == *p)
                {
                    /* Matched it all?  If so, return 1-based position */
                    if (nptr == needle)
                        return p - haystack + 1;
                    nptr--, p--;
                }

                /*
                 * No match, so use the haystack char at hptr to decide how
                 * far to advance.  If the needle had any occurrence of that
                 * character (or more precisely, one sharing the same
                 * skiptable entry) before its last character, then we advance
                 * far enough to align the last such needle character with
                 * that haystack position.  Otherwise we can advance by the
                 * whole needle length.
                 */
                hptr += state->skiptable[*hptr & skiptablemask];
            }
        }
    }

    return 0;                   /* not found */
}

static void
text_position_cleanup(TextPositionState *state)
{
    if (state->use_wchar)
    {
        pfree(state->wstr1);
        pfree(state->wstr2);
    }
}

/* varstr_cmp()
 * Comparison function for text strings with given lengths.
 * Includes locale support, but must copy strings to temporary memory
 *  to allow null-termination for inputs to strcoll().
 * Returns an integer less than, equal to, or greater than zero, indicating
 * whether arg1 is less than, equal to, or greater than arg2.
 */
int
varstr_cmp(char *arg1, int len1, char *arg2, int len2, Oid collid)
{
    int         result;

    /*
     * Unfortunately, there is no strncoll(), so in the non-C locale case we
     * have to do some memory copying.  This turns out to be significantly
     * slower, so we optimize the case where LC_COLLATE is C.  We also try to
     * optimize relatively-short strings by avoiding palloc/pfree overhead.
     */
    if (lc_collate_is_c(collid))
    {
        result = memcmp(arg1, arg2, Min(len1, len2));
        if ((result == 0) && (len1 != len2))
            result = (len1 < len2) ? -1 : 1;
    }
    else
    {
#define STACKBUFLEN     1024

        char        a1buf[STACKBUFLEN];
        char        a2buf[STACKBUFLEN];
        char       *a1p,
                   *a2p;

#ifdef HAVE_LOCALE_T
        pg_locale_t mylocale = 0;
#endif

        if (collid != DEFAULT_COLLATION_OID)
        {
            if (!OidIsValid(collid))
            {
                /*
                 * This typically means that the parser could not resolve a
                 * conflict of implicit collations, so report it that way.
                 */
                ereport(ERROR,
                        (errcode(ERRCODE_INDETERMINATE_COLLATION),
                         errmsg("could not determine which collation to use for string comparison"),
                         errhint("Use the COLLATE clause to set the collation explicitly.")));
            }
#ifdef HAVE_LOCALE_T
            mylocale = pg_newlocale_from_collation(collid);
#endif
        }

#ifdef WIN32
        /* Win32 does not have UTF-8, so we need to map to UTF-16 */
        if (GetDatabaseEncoding() == PG_UTF8)
        {
            int         a1len;
            int         a2len;
            int         r;

            if (len1 >= STACKBUFLEN / 2)
            {
                a1len = len1 * 2 + 2;
                a1p = palloc(a1len);
            }
            else
            {
                a1len = STACKBUFLEN;
                a1p = a1buf;
            }
            if (len2 >= STACKBUFLEN / 2)
            {
                a2len = len2 * 2 + 2;
                a2p = palloc(a2len);
            }
            else
            {
                a2len = STACKBUFLEN;
                a2p = a2buf;
            }

            /* stupid Microsloth API does not work for zero-length input */
            if (len1 == 0)
                r = 0;
            else
            {
                r = MultiByteToWideChar(CP_UTF8, 0, arg1, len1,
                                        (LPWSTR) a1p, a1len / 2);
                if (!r)
                    ereport(ERROR,
                            (errmsg("could not convert string to UTF-16: error code %lu",
                                    GetLastError())));
            }
            ((LPWSTR) a1p)[r] = 0;

            if (len2 == 0)
                r = 0;
            else
            {
                r = MultiByteToWideChar(CP_UTF8, 0, arg2, len2,
                                        (LPWSTR) a2p, a2len / 2);
                if (!r)
                    ereport(ERROR,
                            (errmsg("could not convert string to UTF-16: error code %lu",
                                    GetLastError())));
            }
            ((LPWSTR) a2p)[r] = 0;

            errno = 0;
#ifdef HAVE_LOCALE_T
            if (mylocale)
                result = wcscoll_l((LPWSTR) a1p, (LPWSTR) a2p, mylocale);
            else
#endif
                result = wcscoll((LPWSTR) a1p, (LPWSTR) a2p);
            if (result == 2147483647)   /* _NLSCMPERROR; missing from mingw
                                         * headers */
                ereport(ERROR,
                        (errmsg("could not compare Unicode strings: %m")));

            /*
             * In some locales wcscoll() can claim that nonidentical strings
             * are equal.  Believing that would be bad news for a number of
             * reasons, so we follow Perl's lead and sort "equal" strings
             * according to strcmp (on the UTF-8 representation).
             */
            if (result == 0)
            {
                result = memcmp(arg1, arg2, Min(len1, len2));
                if ((result == 0) && (len1 != len2))
                    result = (len1 < len2) ? -1 : 1;
            }

            if (a1p != a1buf)
                pfree(a1p);
            if (a2p != a2buf)
                pfree(a2p);

            return result;
        }
#endif   /* WIN32 */

        if (len1 >= STACKBUFLEN)
            a1p = (char *) palloc(len1 + 1);
        else
            a1p = a1buf;
        if (len2 >= STACKBUFLEN)
            a2p = (char *) palloc(len2 + 1);
        else
            a2p = a2buf;

        memcpy(a1p, arg1, len1);
        a1p[len1] = '\0';
        memcpy(a2p, arg2, len2);
        a2p[len2] = '\0';

#ifdef HAVE_LOCALE_T
        if (mylocale)
            result = strcoll_l(a1p, a2p, mylocale);
        else
#endif
            result = strcoll(a1p, a2p);

        /*
         * In some locales strcoll() can claim that nonidentical strings are
         * equal.  Believing that would be bad news for a number of reasons,
         * so we follow Perl's lead and sort "equal" strings according to
         * strcmp().
         */
        if (result == 0)
            result = strcmp(a1p, a2p);

        if (a1p != a1buf)
            pfree(a1p);
        if (a2p != a2buf)
            pfree(a2p);
    }

    return result;
}


/* text_cmp()
 * Internal comparison function for text strings.
 * Returns -1, 0 or 1
 */
static int
text_cmp(text *arg1, text *arg2, Oid collid)
{
    char       *a1p,
               *a2p;
    int         len1,
                len2;

    a1p = VARDATA_ANY(arg1);
    a2p = VARDATA_ANY(arg2);

    len1 = VARSIZE_ANY_EXHDR(arg1);
    len2 = VARSIZE_ANY_EXHDR(arg2);

    return varstr_cmp(a1p, len1, a2p, len2, collid);
}

/*
 * Comparison functions for text strings.
 *
 * Note: btree indexes need these routines not to leak memory; therefore,
 * be careful to free working copies of toasted datums.  Most places don't
 * need to be so careful.
 */

Datum
texteq(PG_FUNCTION_ARGS)
{
    Datum       arg1 = PG_GETARG_DATUM(0);
    Datum       arg2 = PG_GETARG_DATUM(1);
    bool        result;
    Size        len1,
                len2;

    /*
     * Since we only care about equality or not-equality, we can avoid all the
     * expense of strcoll() here, and just do bitwise comparison.  In fact, we
     * don't even have to do a bitwise comparison if we can show the lengths
     * of the strings are unequal; which might save us from having to detoast
     * one or both values.
     */
    len1 = toast_raw_datum_size(arg1);
    len2 = toast_raw_datum_size(arg2);
    if (len1 != len2)
        result = false;
    else
    {
        text       *targ1 = DatumGetTextPP(arg1);
        text       *targ2 = DatumGetTextPP(arg2);

        result = (memcmp(VARDATA_ANY(targ1), VARDATA_ANY(targ2),
                         len1 - VARHDRSZ) == 0);

        PG_FREE_IF_COPY(targ1, 0);
        PG_FREE_IF_COPY(targ2, 1);
    }

    PG_RETURN_BOOL(result);
}

Datum
textne(PG_FUNCTION_ARGS)
{
    Datum       arg1 = PG_GETARG_DATUM(0);
    Datum       arg2 = PG_GETARG_DATUM(1);
    bool        result;
    Size        len1,
                len2;

    /* See comment in texteq() */
    len1 = toast_raw_datum_size(arg1);
    len2 = toast_raw_datum_size(arg2);
    if (len1 != len2)
        result = true;
    else
    {
        text       *targ1 = DatumGetTextPP(arg1);
        text       *targ2 = DatumGetTextPP(arg2);

        result = (memcmp(VARDATA_ANY(targ1), VARDATA_ANY(targ2),
                         len1 - VARHDRSZ) != 0);

        PG_FREE_IF_COPY(targ1, 0);
        PG_FREE_IF_COPY(targ2, 1);
    }

    PG_RETURN_BOOL(result);
}

Datum
text_lt(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    bool        result;

    result = (text_cmp(arg1, arg2, PG_GET_COLLATION()) < 0);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result);
}

Datum
text_le(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    bool        result;

    result = (text_cmp(arg1, arg2, PG_GET_COLLATION()) <= 0);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result);
}

Datum
text_gt(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    bool        result;

    result = (text_cmp(arg1, arg2, PG_GET_COLLATION()) > 0);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result);
}

Datum
text_ge(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    bool        result;

    result = (text_cmp(arg1, arg2, PG_GET_COLLATION()) >= 0);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result);
}

Datum
bttextcmp(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    int32       result;

    result = text_cmp(arg1, arg2, PG_GET_COLLATION());

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_INT32(result);
}


Datum
text_larger(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    text       *result;

    result = ((text_cmp(arg1, arg2, PG_GET_COLLATION()) > 0) ? arg1 : arg2);

    PG_RETURN_TEXT_P(result);
}

Datum
text_smaller(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    text       *result;

    result = ((text_cmp(arg1, arg2, PG_GET_COLLATION()) < 0) ? arg1 : arg2);

    PG_RETURN_TEXT_P(result);
}


/*
 * The following operators support character-by-character comparison
 * of text datums, to allow building indexes suitable for LIKE clauses.
 * Note that the regular texteq/textne comparison operators are assumed
 * to be compatible with these!
 */

static int
internal_text_pattern_compare(text *arg1, text *arg2)
{
    int         result;
    int         len1,
                len2;

    len1 = VARSIZE_ANY_EXHDR(arg1);
    len2 = VARSIZE_ANY_EXHDR(arg2);

    result = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
    if (result != 0)
        return result;
    else if (len1 < len2)
        return -1;
    else if (len1 > len2)
        return 1;
    else
        return 0;
}


Datum
text_pattern_lt(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    int         result;

    result = internal_text_pattern_compare(arg1, arg2);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result < 0);
}


Datum
text_pattern_le(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    int         result;

    result = internal_text_pattern_compare(arg1, arg2);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result <= 0);
}


Datum
text_pattern_ge(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    int         result;

    result = internal_text_pattern_compare(arg1, arg2);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result >= 0);
}


Datum
text_pattern_gt(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    int         result;

    result = internal_text_pattern_compare(arg1, arg2);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL(result > 0);
}


Datum
bttext_pattern_cmp(PG_FUNCTION_ARGS)
{
    text       *arg1 = PG_GETARG_TEXT_PP(0);
    text       *arg2 = PG_GETARG_TEXT_PP(1);
    int         result;

    result = internal_text_pattern_compare(arg1, arg2);

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_INT32(result);
}


/*-------------------------------------------------------------
 * byteaoctetlen
 *
 * get the number of bytes contained in an instance of type 'bytea'
 *-------------------------------------------------------------
 */
Datum
byteaoctetlen(PG_FUNCTION_ARGS)
{
    Datum       str = PG_GETARG_DATUM(0);

    /* We need not detoast the input at all */
    PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
}

/*
 * byteacat -
 *    takes two bytea* and returns a bytea* that is the concatenation of
 *    the two.
 *
 * Cloned from textcat and modified as required.
 */
Datum
byteacat(PG_FUNCTION_ARGS)
{
    bytea      *t1 = PG_GETARG_BYTEA_PP(0);
    bytea      *t2 = PG_GETARG_BYTEA_PP(1);

    PG_RETURN_BYTEA_P(bytea_catenate(t1, t2));
}

/*
 * bytea_catenate
 *  Guts of byteacat(), broken out so it can be used by other functions
 *
 * Arguments can be in short-header form, but not compressed or out-of-line
 */
static bytea *
bytea_catenate(bytea *t1, bytea *t2)
{
    bytea      *result;
    int         len1,
                len2,
                len;
    char       *ptr;

    len1 = VARSIZE_ANY_EXHDR(t1);
    len2 = VARSIZE_ANY_EXHDR(t2);

    /* paranoia ... probably should throw error instead? */
    if (len1 < 0)
        len1 = 0;
    if (len2 < 0)
        len2 = 0;

    len = len1 + len2 + VARHDRSZ;
    result = (bytea *) palloc(len);

    /* Set size of result string... */
    SET_VARSIZE(result, len);

    /* Fill data field of result string... */
    ptr = VARDATA(result);
    if (len1 > 0)
        memcpy(ptr, VARDATA_ANY(t1), len1);
    if (len2 > 0)
        memcpy(ptr + len1, VARDATA_ANY(t2), len2);

    return result;
}

#define PG_STR_GET_BYTEA(str_) \
    DatumGetByteaP(DirectFunctionCall1(byteain, CStringGetDatum(str_)))

/*
 * bytea_substr()
 * Return a substring starting at the specified position.
 * Cloned from text_substr and modified as required.
 *
 * Input:
 *  - string
 *  - starting position (is one-based)
 *  - string length (optional)
 *
 * If the starting position is zero or less, then return from the start of the string
 * adjusting the length to be consistent with the "negative start" per SQL.
 * If the length is less than zero, an ERROR is thrown. If no third argument
 * (length) is provided, the length to the end of the string is assumed.
 */
Datum
bytea_substr(PG_FUNCTION_ARGS)
{
    PG_RETURN_BYTEA_P(bytea_substring(PG_GETARG_DATUM(0),
                                      PG_GETARG_INT32(1),
                                      PG_GETARG_INT32(2),
                                      false));
}

/*
 * bytea_substr_no_len -
 *    Wrapper to avoid opr_sanity failure due to
 *    one function accepting a different number of args.
 */
Datum
bytea_substr_no_len(PG_FUNCTION_ARGS)
{
    PG_RETURN_BYTEA_P(bytea_substring(PG_GETARG_DATUM(0),
                                      PG_GETARG_INT32(1),
                                      -1,
                                      true));
}

static bytea *
bytea_substring(Datum str,
                int S,
                int L,
                bool length_not_specified)
{
    int         S1;             /* adjusted start position */
    int         L1;             /* adjusted substring length */

    S1 = Max(S, 1);

    if (length_not_specified)
    {
        /*
         * Not passed a length - DatumGetByteaPSlice() grabs everything to the
         * end of the string if we pass it a negative value for length.
         */
        L1 = -1;
    }
    else
    {
        /* end position */
        int         E = S + L;

        /*
         * A negative value for L is the only way for the end position to be
         * before the start. SQL99 says to throw an error.
         */
        if (E < S)
            ereport(ERROR,
                    (errcode(ERRCODE_SUBSTRING_ERROR),
                     errmsg("negative substring length not allowed")));

        /*
         * A zero or negative value for the end position can happen if the
         * start was negative or one. SQL99 says to return a zero-length
         * string.
         */
        if (E < 1)
            return PG_STR_GET_BYTEA("");

        L1 = E - S1;
    }

    /*
     * If the start position is past the end of the string, SQL99 says to
     * return a zero-length string -- DatumGetByteaPSlice() will do that for
     * us. Convert to zero-based starting position
     */
    return DatumGetByteaPSlice(str, S1 - 1, L1);
}

/*
 * byteaoverlay
 *  Replace specified substring of first string with second
 *
 * The SQL standard defines OVERLAY() in terms of substring and concatenation.
 * This code is a direct implementation of what the standard says.
 */
Datum
byteaoverlay(PG_FUNCTION_ARGS)
{
    bytea      *t1 = PG_GETARG_BYTEA_PP(0);
    bytea      *t2 = PG_GETARG_BYTEA_PP(1);
    int         sp = PG_GETARG_INT32(2);        /* substring start position */
    int         sl = PG_GETARG_INT32(3);        /* substring length */

    PG_RETURN_BYTEA_P(bytea_overlay(t1, t2, sp, sl));
}

Datum
byteaoverlay_no_len(PG_FUNCTION_ARGS)
{
    bytea      *t1 = PG_GETARG_BYTEA_PP(0);
    bytea      *t2 = PG_GETARG_BYTEA_PP(1);
    int         sp = PG_GETARG_INT32(2);        /* substring start position */
    int         sl;

    sl = VARSIZE_ANY_EXHDR(t2); /* defaults to length(t2) */
    PG_RETURN_BYTEA_P(bytea_overlay(t1, t2, sp, sl));
}

static bytea *
bytea_overlay(bytea *t1, bytea *t2, int sp, int sl)
{
    bytea      *result;
    bytea      *s1;
    bytea      *s2;
    int         sp_pl_sl;

    /*
     * Check for possible integer-overflow cases.  For negative sp, throw a
     * "substring length" error because that's what should be expected
     * according to the spec's definition of OVERLAY().
     */
    if (sp <= 0)
        ereport(ERROR,
                (errcode(ERRCODE_SUBSTRING_ERROR),
                 errmsg("negative substring length not allowed")));
    sp_pl_sl = sp + sl;
    if (sp_pl_sl <= sl)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));

    s1 = bytea_substring(PointerGetDatum(t1), 1, sp - 1, false);
    s2 = bytea_substring(PointerGetDatum(t1), sp_pl_sl, -1, true);
    result = bytea_catenate(s1, t2);
    result = bytea_catenate(result, s2);

    return result;
}

/*
 * byteapos -
 *    Return the position of the specified substring.
 *    Implements the SQL POSITION() function.
 * Cloned from textpos and modified as required.
 */
Datum
byteapos(PG_FUNCTION_ARGS)
{
    bytea      *t1 = PG_GETARG_BYTEA_PP(0);
    bytea      *t2 = PG_GETARG_BYTEA_PP(1);
    int         pos;
    int         px,
                p;
    int         len1,
                len2;
    char       *p1,
               *p2;

    len1 = VARSIZE_ANY_EXHDR(t1);
    len2 = VARSIZE_ANY_EXHDR(t2);

    if (len2 <= 0)
        PG_RETURN_INT32(1);     /* result for empty pattern */

    p1 = VARDATA_ANY(t1);
    p2 = VARDATA_ANY(t2);

    pos = 0;
    px = (len1 - len2);
    for (p = 0; p <= px; p++)
    {
        if ((*p2 == *p1) && (memcmp(p1, p2, len2) == 0))
        {
            pos = p + 1;
            break;
        };
        p1++;
    };

    PG_RETURN_INT32(pos);
}

/*-------------------------------------------------------------
 * byteaGetByte
 *
 * this routine treats "bytea" as an array of bytes.
 * It returns the Nth byte (a number between 0 and 255).
 *-------------------------------------------------------------
 */
Datum
byteaGetByte(PG_FUNCTION_ARGS)
{
    bytea      *v = PG_GETARG_BYTEA_PP(0);
    int32       n = PG_GETARG_INT32(1);
    int         len;
    int         byte;

    len = VARSIZE_ANY_EXHDR(v);

    if (n < 0 || n >= len)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("index %d out of valid range, 0..%d",
                        n, len - 1)));

    byte = ((unsigned char *) VARDATA_ANY(v))[n];

    PG_RETURN_INT32(byte);
}

/*-------------------------------------------------------------
 * byteaGetBit
 *
 * This routine treats a "bytea" type like an array of bits.
 * It returns the value of the Nth bit (0 or 1).
 *
 *-------------------------------------------------------------
 */
Datum
byteaGetBit(PG_FUNCTION_ARGS)
{
    bytea      *v = PG_GETARG_BYTEA_PP(0);
    int32       n = PG_GETARG_INT32(1);
    int         byteNo,
                bitNo;
    int         len;
    int         byte;

    len = VARSIZE_ANY_EXHDR(v);

    if (n < 0 || n >= len * 8)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("index %d out of valid range, 0..%d",
                        n, len * 8 - 1)));

    byteNo = n / 8;
    bitNo = n % 8;

    byte = ((unsigned char *) VARDATA_ANY(v))[byteNo];

    if (byte & (1 << bitNo))
        PG_RETURN_INT32(1);
    else
        PG_RETURN_INT32(0);
}

/*-------------------------------------------------------------
 * byteaSetByte
 *
 * Given an instance of type 'bytea' creates a new one with
 * the Nth byte set to the given value.
 *
 *-------------------------------------------------------------
 */
Datum
byteaSetByte(PG_FUNCTION_ARGS)
{
    bytea      *v = PG_GETARG_BYTEA_P(0);
    int32       n = PG_GETARG_INT32(1);
    int32       newByte = PG_GETARG_INT32(2);
    int         len;
    bytea      *res;

    len = VARSIZE(v) - VARHDRSZ;

    if (n < 0 || n >= len)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("index %d out of valid range, 0..%d",
                        n, len - 1)));

    /*
     * Make a copy of the original varlena.
     */
    res = (bytea *) palloc(VARSIZE(v));
    memcpy((char *) res, (char *) v, VARSIZE(v));

    /*
     * Now set the byte.
     */
    ((unsigned char *) VARDATA(res))[n] = newByte;

    PG_RETURN_BYTEA_P(res);
}

/*-------------------------------------------------------------
 * byteaSetBit
 *
 * Given an instance of type 'bytea' creates a new one with
 * the Nth bit set to the given value.
 *
 *-------------------------------------------------------------
 */
Datum
byteaSetBit(PG_FUNCTION_ARGS)
{
    bytea      *v = PG_GETARG_BYTEA_P(0);
    int32       n = PG_GETARG_INT32(1);
    int32       newBit = PG_GETARG_INT32(2);
    bytea      *res;
    int         len;
    int         oldByte,
                newByte;
    int         byteNo,
                bitNo;

    len = VARSIZE(v) - VARHDRSZ;

    if (n < 0 || n >= len * 8)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("index %d out of valid range, 0..%d",
                        n, len * 8 - 1)));

    byteNo = n / 8;
    bitNo = n % 8;

    /*
     * sanity check!
     */
    if (newBit != 0 && newBit != 1)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("new bit must be 0 or 1")));

    /*
     * Make a copy of the original varlena.
     */
    res = (bytea *) palloc(VARSIZE(v));
    memcpy((char *) res, (char *) v, VARSIZE(v));

    /*
     * Update the byte.
     */
    oldByte = ((unsigned char *) VARDATA(res))[byteNo];

    if (newBit == 0)
        newByte = oldByte & (~(1 << bitNo));
    else
        newByte = oldByte | (1 << bitNo);

    ((unsigned char *) VARDATA(res))[byteNo] = newByte;

    PG_RETURN_BYTEA_P(res);
}


/* text_name()
 * Converts a text type to a Name type.
 */
Datum
text_name(PG_FUNCTION_ARGS)
{
    text       *s = PG_GETARG_TEXT_PP(0);
    Name        result;
    int         len;

    len = VARSIZE_ANY_EXHDR(s);

    /* Truncate oversize input */
    if (len >= NAMEDATALEN)
        len = pg_mbcliplen(VARDATA_ANY(s), len, NAMEDATALEN - 1);

    /* We use palloc0 here to ensure result is zero-padded */
    result = (Name) palloc0(NAMEDATALEN);
    memcpy(NameStr(*result), VARDATA_ANY(s), len);

    PG_RETURN_NAME(result);
}

/* name_text()
 * Converts a Name type to a text type.
 */
Datum
name_text(PG_FUNCTION_ARGS)
{
    Name        s = PG_GETARG_NAME(0);

    PG_RETURN_TEXT_P(cstring_to_text(NameStr(*s)));
}


/*
 * textToQualifiedNameList - convert a text object to list of names
 *
 * This implements the input parsing needed by nextval() and other
 * functions that take a text parameter representing a qualified name.
 * We split the name at dots, downcase if not double-quoted, and
 * truncate names if they're too long.
 */
List *
textToQualifiedNameList(text *textval)
{
    char       *rawname;
    List       *result = NIL;
    List       *namelist;
    ListCell   *l;

    /* Convert to C string (handles possible detoasting). */
    /* Note we rely on being able to modify rawname below. */
    rawname = text_to_cstring(textval);

    if (!SplitIdentifierString(rawname, '.', &namelist))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_NAME),
                 errmsg("invalid name syntax")));

    if (namelist == NIL)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_NAME),
                 errmsg("invalid name syntax")));

    foreach(l, namelist)
    {
        char       *curname = (char *) lfirst(l);

        result = lappend(result, makeString(pstrdup(curname)));
    }

    pfree(rawname);
    list_free(namelist);

    return result;
}

/*
 * SplitIdentifierString --- parse a string containing identifiers
 *
 * This is the guts of textToQualifiedNameList, and is exported for use in
 * other situations such as parsing GUC variables.  In the GUC case, it's
 * important to avoid memory leaks, so the API is designed to minimize the
 * amount of stuff that needs to be allocated and freed.
 *
 * Inputs:
 *  rawstring: the input string; must be overwritable!  On return, it's
 *             been modified to contain the separated identifiers.
 *  separator: the separator punctuation expected between identifiers
 *             (typically '.' or ',').  Whitespace may also appear around
 *             identifiers.
 * Outputs:
 *  namelist: filled with a palloc'd list of pointers to identifiers within
 *            rawstring.  Caller should list_free() this even on error return.
 *
 * Returns TRUE if okay, FALSE if there is a syntax error in the string.
 *
 * Note that an empty string is considered okay here, though not in
 * textToQualifiedNameList.
 */
bool
SplitIdentifierString(char *rawstring, char separator,
                      List **namelist)
{
    char       *nextp = rawstring;
    bool        done = false;

    *namelist = NIL;

    while (isspace((unsigned char) *nextp))
        nextp++;                /* skip leading whitespace */

    if (*nextp == '\0')
        return true;            /* allow empty string */

    /* At the top of the loop, we are at start of a new identifier. */
    do
    {
        char       *curname;
        char       *endp;

        if (*nextp == '\"')
        {
            /* Quoted name --- collapse quote-quote pairs, no downcasing */
            curname = nextp + 1;
            for (;;)
            {
                endp = strchr(nextp + 1, '\"');
                if (endp == NULL)
                    return false;       /* mismatched quotes */
                if (endp[1] != '\"')
                    break;      /* found end of quoted name */
                /* Collapse adjacent quotes into one quote, and look again */
                memmove(endp, endp + 1, strlen(endp));
                nextp = endp;
            }
            /* endp now points at the terminating quote */
            nextp = endp + 1;
        }
        else
        {
            /* Unquoted name --- extends to separator or whitespace */
            char       *downname;
            int         len;

            curname = nextp;
            while (*nextp && *nextp != separator &&
                   !isspace((unsigned char) *nextp))
                nextp++;
            endp = nextp;
            if (curname == nextp)
                return false;   /* empty unquoted name not allowed */

            /*
             * Downcase the identifier, using same code as main lexer does.
             *
             * XXX because we want to overwrite the input in-place, we cannot
             * support a downcasing transformation that increases the string
             * length.  This is not a problem given the current implementation
             * of downcase_truncate_identifier, but we'll probably have to do
             * something about this someday.
             */
            len = endp - curname;
            downname = downcase_truncate_identifier(curname, len, false);
            Assert(strlen(downname) <= len);
            strncpy(curname, downname, len);
            pfree(downname);
        }

        while (isspace((unsigned char) *nextp))
            nextp++;            /* skip trailing whitespace */

        if (*nextp == separator)
        {
            nextp++;
            while (isspace((unsigned char) *nextp))
                nextp++;        /* skip leading whitespace for next */
            /* we expect another name, so done remains false */
        }
        else if (*nextp == '\0')
            done = true;
        else
            return false;       /* invalid syntax */

        /* Now safe to overwrite separator with a null */
        *endp = '\0';

        /* Truncate name if it's overlength */
        truncate_identifier(curname, strlen(curname), false);

        /*
         * Finished isolating current name --- add it to list
         */
        *namelist = lappend(*namelist, curname);

        /* Loop back if we didn't reach end of string */
    } while (!done);

    return true;
}


/*
 * SplitDirectoriesString --- parse a string containing directory names
 *
 * This is similar to SplitIdentifierString, except that the parsing
 * rules are meant to handle pathnames instead of identifiers: there is
 * no downcasing, embedded spaces are allowed, the max length is MAXPGPATH-1,
 * and we apply canonicalize_path() to each extracted string.  Because of the
 * last, the returned strings are separately palloc'd rather than being
 * pointers into rawstring --- but we still scribble on rawstring.
 *
 * Inputs:
 *  rawstring: the input string; must be modifiable!
 *  separator: the separator punctuation expected between directories
 *             (typically ',' or ';').  Whitespace may also appear around
 *             directories.
 * Outputs:
 *  namelist: filled with a palloc'd list of directory names.
 *            Caller should list_free_deep() this even on error return.
 *
 * Returns TRUE if okay, FALSE if there is a syntax error in the string.
 *
 * Note that an empty string is considered okay here.
 */
bool
SplitDirectoriesString(char *rawstring, char separator,
                       List **namelist)
{
    char       *nextp = rawstring;
    bool        done = false;

    *namelist = NIL;

    while (isspace((unsigned char) *nextp))
        nextp++;                /* skip leading whitespace */

    if (*nextp == '\0')
        return true;            /* allow empty string */

    /* At the top of the loop, we are at start of a new directory. */
    do
    {
        char       *curname;
        char       *endp;

        if (*nextp == '\"')
        {
            /* Quoted name --- collapse quote-quote pairs */
            curname = nextp + 1;
            for (;;)
            {
                endp = strchr(nextp + 1, '\"');
                if (endp == NULL)
                    return false;       /* mismatched quotes */
                if (endp[1] != '\"')
                    break;      /* found end of quoted name */
                /* Collapse adjacent quotes into one quote, and look again */
                memmove(endp, endp + 1, strlen(endp));
                nextp = endp;
            }
            /* endp now points at the terminating quote */
            nextp = endp + 1;
        }
        else
        {
            /* Unquoted name --- extends to separator or end of string */
            curname = endp = nextp;
            while (*nextp && *nextp != separator)
            {
                /* trailing whitespace should not be included in name */
                if (!isspace((unsigned char) *nextp))
                    endp = nextp + 1;
                nextp++;
            }
            if (curname == endp)
                return false;   /* empty unquoted name not allowed */
        }

        while (isspace((unsigned char) *nextp))
            nextp++;            /* skip trailing whitespace */

        if (*nextp == separator)
        {
            nextp++;
            while (isspace((unsigned char) *nextp))
                nextp++;        /* skip leading whitespace for next */
            /* we expect another name, so done remains false */
        }
        else if (*nextp == '\0')
            done = true;
        else
            return false;       /* invalid syntax */

        /* Now safe to overwrite separator with a null */
        *endp = '\0';

        /* Truncate path if it's overlength */
        if (strlen(curname) >= MAXPGPATH)
            curname[MAXPGPATH - 1] = '\0';

        /*
         * Finished isolating current name --- add it to list
         */
        curname = pstrdup(curname);
        canonicalize_path(curname);
        *namelist = lappend(*namelist, curname);

        /* Loop back if we didn't reach end of string */
    } while (!done);

    return true;
}


/*****************************************************************************
 *  Comparison Functions used for bytea
 *
 * Note: btree indexes need these routines not to leak memory; therefore,
 * be careful to free working copies of toasted datums.  Most places don't
 * need to be so careful.
 *****************************************************************************/

Datum
byteaeq(PG_FUNCTION_ARGS)
{
    Datum       arg1 = PG_GETARG_DATUM(0);
    Datum       arg2 = PG_GETARG_DATUM(1);
    bool        result;
    Size        len1,
                len2;

    /*
     * We can use a fast path for unequal lengths, which might save us from
     * having to detoast one or both values.
     */
    len1 = toast_raw_datum_size(arg1);
    len2 = toast_raw_datum_size(arg2);
    if (len1 != len2)
        result = false;
    else
    {
        bytea      *barg1 = DatumGetByteaPP(arg1);
        bytea      *barg2 = DatumGetByteaPP(arg2);

        result = (memcmp(VARDATA_ANY(barg1), VARDATA_ANY(barg2),
                         len1 - VARHDRSZ) == 0);

        PG_FREE_IF_COPY(barg1, 0);
        PG_FREE_IF_COPY(barg2, 1);
    }

    PG_RETURN_BOOL(result);
}

Datum
byteane(PG_FUNCTION_ARGS)
{
    Datum       arg1 = PG_GETARG_DATUM(0);
    Datum       arg2 = PG_GETARG_DATUM(1);
    bool        result;
    Size        len1,
                len2;

    /*
     * We can use a fast path for unequal lengths, which might save us from
     * having to detoast one or both values.
     */
    len1 = toast_raw_datum_size(arg1);
    len2 = toast_raw_datum_size(arg2);
    if (len1 != len2)
        result = true;
    else
    {
        bytea      *barg1 = DatumGetByteaPP(arg1);
        bytea      *barg2 = DatumGetByteaPP(arg2);

        result = (memcmp(VARDATA_ANY(barg1), VARDATA_ANY(barg2),
                         len1 - VARHDRSZ) != 0);

        PG_FREE_IF_COPY(barg1, 0);
        PG_FREE_IF_COPY(barg2, 1);
    }

    PG_RETURN_BOOL(result);
}

Datum
bytealt(PG_FUNCTION_ARGS)
{
    bytea      *arg1 = PG_GETARG_BYTEA_PP(0);
    bytea      *arg2 = PG_GETARG_BYTEA_PP(1);
    int         len1,
                len2;
    int         cmp;

    len1 = VARSIZE_ANY_EXHDR(arg1);
    len2 = VARSIZE_ANY_EXHDR(arg2);

    cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL((cmp < 0) || ((cmp == 0) && (len1 < len2)));
}

Datum
byteale(PG_FUNCTION_ARGS)
{
    bytea      *arg1 = PG_GETARG_BYTEA_PP(0);
    bytea      *arg2 = PG_GETARG_BYTEA_PP(1);
    int         len1,
                len2;
    int         cmp;

    len1 = VARSIZE_ANY_EXHDR(arg1);
    len2 = VARSIZE_ANY_EXHDR(arg2);

    cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL((cmp < 0) || ((cmp == 0) && (len1 <= len2)));
}

Datum
byteagt(PG_FUNCTION_ARGS)
{
    bytea      *arg1 = PG_GETARG_BYTEA_PP(0);
    bytea      *arg2 = PG_GETARG_BYTEA_PP(1);
    int         len1,
                len2;
    int         cmp;

    len1 = VARSIZE_ANY_EXHDR(arg1);
    len2 = VARSIZE_ANY_EXHDR(arg2);

    cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL((cmp > 0) || ((cmp == 0) && (len1 > len2)));
}

Datum
byteage(PG_FUNCTION_ARGS)
{
    bytea      *arg1 = PG_GETARG_BYTEA_PP(0);
    bytea      *arg2 = PG_GETARG_BYTEA_PP(1);
    int         len1,
                len2;
    int         cmp;

    len1 = VARSIZE_ANY_EXHDR(arg1);
    len2 = VARSIZE_ANY_EXHDR(arg2);

    cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_BOOL((cmp > 0) || ((cmp == 0) && (len1 >= len2)));
}

Datum
byteacmp(PG_FUNCTION_ARGS)
{
    bytea      *arg1 = PG_GETARG_BYTEA_PP(0);
    bytea      *arg2 = PG_GETARG_BYTEA_PP(1);
    int         len1,
                len2;
    int         cmp;

    len1 = VARSIZE_ANY_EXHDR(arg1);
    len2 = VARSIZE_ANY_EXHDR(arg2);

    cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
    if ((cmp == 0) && (len1 != len2))
        cmp = (len1 < len2) ? -1 : 1;

    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);

    PG_RETURN_INT32(cmp);
}

/*
 * appendStringInfoText
 *
 * Append a text to str.
 * Like appendStringInfoString(str, text_to_cstring(t)) but faster.
 */
static void
appendStringInfoText(StringInfo str, const text *t)
{
    appendBinaryStringInfo(str, VARDATA_ANY(t), VARSIZE_ANY_EXHDR(t));
}

/*
 * replace_text
 * replace all occurrences of 'old_sub_str' in 'orig_str'
 * with 'new_sub_str' to form 'new_str'
 *
 * returns 'orig_str' if 'old_sub_str' == '' or 'orig_str' == ''
 * otherwise returns 'new_str'
 */
Datum
replace_text(PG_FUNCTION_ARGS)
{
    text       *src_text = PG_GETARG_TEXT_PP(0);
    text       *from_sub_text = PG_GETARG_TEXT_PP(1);
    text       *to_sub_text = PG_GETARG_TEXT_PP(2);
    int         src_text_len;
    int         from_sub_text_len;
    TextPositionState state;
    text       *ret_text;
    int         start_posn;
    int         curr_posn;
    int         chunk_len;
    char       *start_ptr;
    StringInfoData str;

    text_position_setup(src_text, from_sub_text, &state);

    /*
     * Note: we check the converted string length, not the original, because
     * they could be different if the input contained invalid encoding.
     */
    src_text_len = state.len1;
    from_sub_text_len = state.len2;

    /* Return unmodified source string if empty source or pattern */
    if (src_text_len < 1 || from_sub_text_len < 1)
    {
        text_position_cleanup(&state);
        PG_RETURN_TEXT_P(src_text);
    }

    start_posn = 1;
    curr_posn = text_position_next(1, &state);

    /* When the from_sub_text is not found, there is nothing to do. */
    if (curr_posn == 0)
    {
        text_position_cleanup(&state);
        PG_RETURN_TEXT_P(src_text);
    }

    /* start_ptr points to the start_posn'th character of src_text */
    start_ptr = VARDATA_ANY(src_text);

    initStringInfo(&str);

    do
    {
        CHECK_FOR_INTERRUPTS();

        /* copy the data skipped over by last text_position_next() */
        chunk_len = charlen_to_bytelen(start_ptr, curr_posn - start_posn);
        appendBinaryStringInfo(&str, start_ptr, chunk_len);

        appendStringInfoText(&str, to_sub_text);

        start_posn = curr_posn;
        start_ptr += chunk_len;
        start_posn += from_sub_text_len;
        start_ptr += charlen_to_bytelen(start_ptr, from_sub_text_len);

        curr_posn = text_position_next(start_posn, &state);
    }
    while (curr_posn > 0);

    /* copy trailing data */
    chunk_len = ((char *) src_text + VARSIZE_ANY(src_text)) - start_ptr;
    appendBinaryStringInfo(&str, start_ptr, chunk_len);

    text_position_cleanup(&state);

    ret_text = cstring_to_text_with_len(str.data, str.len);
    pfree(str.data);

    PG_RETURN_TEXT_P(ret_text);
}

/*
 * check_replace_text_has_escape_char
 *
 * check whether replace_text contains escape char.
 */
static bool
check_replace_text_has_escape_char(const text *replace_text)
{
    const char *p = VARDATA_ANY(replace_text);
    const char *p_end = p + VARSIZE_ANY_EXHDR(replace_text);

    if (pg_database_encoding_max_length() == 1)
    {
        for (; p < p_end; p++)
        {
            if (*p == '\\')
                return true;
        }
    }
    else
    {
        for (; p < p_end; p += pg_mblen(p))
        {
            if (*p == '\\')
                return true;
        }
    }

    return false;
}

/*
 * appendStringInfoRegexpSubstr
 *
 * Append replace_text to str, substituting regexp back references for
 * \n escapes.  start_ptr is the start of the match in the source string,
 * at logical character position data_pos.
 */
static void
appendStringInfoRegexpSubstr(StringInfo str, text *replace_text,
                             regmatch_t *pmatch,
                             char *start_ptr, int data_pos)
{
    const char *p = VARDATA_ANY(replace_text);
    const char *p_end = p + VARSIZE_ANY_EXHDR(replace_text);
    int         eml = pg_database_encoding_max_length();

    for (;;)
    {
        const char *chunk_start = p;
        int         so;
        int         eo;

        /* Find next escape char. */
        if (eml == 1)
        {
            for (; p < p_end && *p != '\\'; p++)
                 /* nothing */ ;
        }
        else
        {
            for (; p < p_end && *p != '\\'; p += pg_mblen(p))
                 /* nothing */ ;
        }

        /* Copy the text we just scanned over, if any. */
        if (p > chunk_start)
            appendBinaryStringInfo(str, chunk_start, p - chunk_start);

        /* Done if at end of string, else advance over escape char. */
        if (p >= p_end)
            break;
        p++;

        if (p >= p_end)
        {
            /* Escape at very end of input.  Treat same as unexpected char */
            appendStringInfoChar(str, '\\');
            break;
        }

        if (*p >= '1' && *p <= '9')
        {
            /* Use the back reference of regexp. */
            int         idx = *p - '0';

            so = pmatch[idx].rm_so;
            eo = pmatch[idx].rm_eo;
            p++;
        }
        else if (*p == '&')
        {
            /* Use the entire matched string. */
            so = pmatch[0].rm_so;
            eo = pmatch[0].rm_eo;
            p++;
        }
        else if (*p == '\\')
        {
            /* \\ means transfer one \ to output. */
            appendStringInfoChar(str, '\\');
            p++;
            continue;
        }
        else
        {
            /*
             * If escape char is not followed by any expected char, just treat
             * it as ordinary data to copy.  (XXX would it be better to throw
             * an error?)
             */
            appendStringInfoChar(str, '\\');
            continue;
        }

        if (so != -1 && eo != -1)
        {
            /*
             * Copy the text that is back reference of regexp.  Note so and eo
             * are counted in characters not bytes.
             */
            char       *chunk_start;
            int         chunk_len;

            Assert(so >= data_pos);
            chunk_start = start_ptr;
            chunk_start += charlen_to_bytelen(chunk_start, so - data_pos);
            chunk_len = charlen_to_bytelen(chunk_start, eo - so);
            appendBinaryStringInfo(str, chunk_start, chunk_len);
        }
    }
}

#define REGEXP_REPLACE_BACKREF_CNT      10

/*
 * replace_text_regexp
 *
 * replace text that matches to regexp in src_text to replace_text.
 *
 * Note: to avoid having to include regex.h in builtins.h, we declare
 * the regexp argument as void *, but really it's regex_t *.
 */
text *
replace_text_regexp(text *src_text, void *regexp,
                    text *replace_text, bool glob)
{
    text       *ret_text;
    regex_t    *re = (regex_t *) regexp;
    int         src_text_len = VARSIZE_ANY_EXHDR(src_text);
    StringInfoData buf;
    regmatch_t  pmatch[REGEXP_REPLACE_BACKREF_CNT];
    pg_wchar   *data;
    size_t      data_len;
    int         search_start;
    int         data_pos;
    char       *start_ptr;
    bool        have_escape;

    initStringInfo(&buf);

    /* Convert data string to wide characters. */
    data = (pg_wchar *) palloc((src_text_len + 1) * sizeof(pg_wchar));
    data_len = pg_mb2wchar_with_len(VARDATA_ANY(src_text), data, src_text_len);

    /* Check whether replace_text has escape char. */
    have_escape = check_replace_text_has_escape_char(replace_text);

    /* start_ptr points to the data_pos'th character of src_text */
    start_ptr = (char *) VARDATA_ANY(src_text);
    data_pos = 0;

    search_start = 0;
    while (search_start <= data_len)
    {
        int         regexec_result;

        CHECK_FOR_INTERRUPTS();

        regexec_result = pg_regexec(re,
                                    data,
                                    data_len,
                                    search_start,
                                    NULL,       /* no details */
                                    REGEXP_REPLACE_BACKREF_CNT,
                                    pmatch,
                                    0);

        if (regexec_result == REG_NOMATCH)
            break;

        if (regexec_result != REG_OKAY)
        {
            char        errMsg[100];

            pg_regerror(regexec_result, re, errMsg, sizeof(errMsg));
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_REGULAR_EXPRESSION),
                     errmsg("regular expression failed: %s", errMsg)));
        }

        /*
         * Copy the text to the left of the match position.  Note we are given
         * character not byte indexes.
         */
        if (pmatch[0].rm_so - data_pos > 0)
        {
            int         chunk_len;

            chunk_len = charlen_to_bytelen(start_ptr,
                                           pmatch[0].rm_so - data_pos);
            appendBinaryStringInfo(&buf, start_ptr, chunk_len);

            /*
             * Advance start_ptr over that text, to avoid multiple rescans of
             * it if the replace_text contains multiple back-references.
             */
            start_ptr += chunk_len;
            data_pos = pmatch[0].rm_so;
        }

        /*
         * Copy the replace_text. Process back references when the
         * replace_text has escape characters.
         */
        if (have_escape)
            appendStringInfoRegexpSubstr(&buf, replace_text, pmatch,
                                         start_ptr, data_pos);
        else
            appendStringInfoText(&buf, replace_text);

        /* Advance start_ptr and data_pos over the matched text. */
        start_ptr += charlen_to_bytelen(start_ptr,
                                        pmatch[0].rm_eo - data_pos);
        data_pos = pmatch[0].rm_eo;

        /*
         * When global option is off, replace the first instance only.
         */
        if (!glob)
            break;

        /*
         * Search from next character when the matching text is zero width.
         */
        search_start = data_pos;
        if (pmatch[0].rm_so == pmatch[0].rm_eo)
            search_start++;
    }

    /*
     * Copy the text to the right of the last match.
     */
    if (data_pos < data_len)
    {
        int         chunk_len;

        chunk_len = ((char *) src_text + VARSIZE_ANY(src_text)) - start_ptr;
        appendBinaryStringInfo(&buf, start_ptr, chunk_len);
    }

    ret_text = cstring_to_text_with_len(buf.data, buf.len);
    pfree(buf.data);
    pfree(data);

    return ret_text;
}

/*
 * split_text
 * parse input string
 * return ord item (1 based)
 * based on provided field separator
 */
Datum
split_text(PG_FUNCTION_ARGS)
{
    text       *inputstring = PG_GETARG_TEXT_PP(0);
    text       *fldsep = PG_GETARG_TEXT_PP(1);
    int         fldnum = PG_GETARG_INT32(2);
    int         inputstring_len;
    int         fldsep_len;
    TextPositionState state;
    int         start_posn;
    int         end_posn;
    text       *result_text;

    /* field number is 1 based */
    if (fldnum < 1)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("field position must be greater than zero")));

    text_position_setup(inputstring, fldsep, &state);

    /*
     * Note: we check the converted string length, not the original, because
     * they could be different if the input contained invalid encoding.
     */
    inputstring_len = state.len1;
    fldsep_len = state.len2;

    /* return empty string for empty input string */
    if (inputstring_len < 1)
    {
        text_position_cleanup(&state);
        PG_RETURN_TEXT_P(cstring_to_text(""));
    }

    /* empty field separator */
    if (fldsep_len < 1)
    {
        text_position_cleanup(&state);
        /* if first field, return input string, else empty string */
        if (fldnum == 1)
            PG_RETURN_TEXT_P(inputstring);
        else
            PG_RETURN_TEXT_P(cstring_to_text(""));
    }

    /* identify bounds of first field */
    start_posn = 1;
    end_posn = text_position_next(1, &state);

    /* special case if fldsep not found at all */
    if (end_posn == 0)
    {
        text_position_cleanup(&state);
        /* if field 1 requested, return input string, else empty string */
        if (fldnum == 1)
            PG_RETURN_TEXT_P(inputstring);
        else
            PG_RETURN_TEXT_P(cstring_to_text(""));
    }

    while (end_posn > 0 && --fldnum > 0)
    {
        /* identify bounds of next field */
        start_posn = end_posn + fldsep_len;
        end_posn = text_position_next(start_posn, &state);
    }

    text_position_cleanup(&state);

    if (fldnum > 0)
    {
        /* N'th field separator not found */
        /* if last field requested, return it, else empty string */
        if (fldnum == 1)
            result_text = text_substring(PointerGetDatum(inputstring),
                                         start_posn,
                                         -1,
                                         true);
        else
            result_text = cstring_to_text("");
    }
    else
    {
        /* non-last field requested */
        result_text = text_substring(PointerGetDatum(inputstring),
                                     start_posn,
                                     end_posn - start_posn,
                                     false);
    }

    PG_RETURN_TEXT_P(result_text);
}

/*
 * Convenience function to return true when two text params are equal.
 */
static bool
text_isequal(text *txt1, text *txt2)
{
    return DatumGetBool(DirectFunctionCall2(texteq,
                                            PointerGetDatum(txt1),
                                            PointerGetDatum(txt2)));
}

/*
 * text_to_array
 * parse input string and return text array of elements,
 * based on provided field separator
 */
Datum
text_to_array(PG_FUNCTION_ARGS)
{
    return text_to_array_internal(fcinfo);
}

/*
 * text_to_array_null
 * parse input string and return text array of elements,
 * based on provided field separator and null string
 *
 * This is a separate entry point only to prevent the regression tests from
 * complaining about different argument sets for the same internal function.
 */
Datum
text_to_array_null(PG_FUNCTION_ARGS)
{
    return text_to_array_internal(fcinfo);
}

/*
 * common code for text_to_array and text_to_array_null functions
 *
 * These are not strict so we have to test for null inputs explicitly.
 */
static Datum
text_to_array_internal(PG_FUNCTION_ARGS)
{
    text       *inputstring;
    text       *fldsep;
    text       *null_string;
    int         inputstring_len;
    int         fldsep_len;
    char       *start_ptr;
    text       *result_text;
    bool        is_null;
    ArrayBuildState *astate = NULL;

    /* when input string is NULL, then result is NULL too */
    if (PG_ARGISNULL(0))
        PG_RETURN_NULL();

    inputstring = PG_GETARG_TEXT_PP(0);

    /* fldsep can be NULL */
    if (!PG_ARGISNULL(1))
        fldsep = PG_GETARG_TEXT_PP(1);
    else
        fldsep = NULL;

    /* null_string can be NULL or omitted */
    if (PG_NARGS() > 2 && !PG_ARGISNULL(2))
        null_string = PG_GETARG_TEXT_PP(2);
    else
        null_string = NULL;

    if (fldsep != NULL)
    {
        /*
         * Normal case with non-null fldsep.  Use the text_position machinery
         * to search for occurrences of fldsep.
         */
        TextPositionState state;
        int         fldnum;
        int         start_posn;
        int         end_posn;
        int         chunk_len;

        text_position_setup(inputstring, fldsep, &state);

        /*
         * Note: we check the converted string length, not the original,
         * because they could be different if the input contained invalid
         * encoding.
         */
        inputstring_len = state.len1;
        fldsep_len = state.len2;

        /* return empty array for empty input string */
        if (inputstring_len < 1)
        {
            text_position_cleanup(&state);
            PG_RETURN_ARRAYTYPE_P(construct_empty_array(TEXTOID));
        }

        /*
         * empty field separator: return the input string as a one-element
         * array
         */
        if (fldsep_len < 1)
        {
            text_position_cleanup(&state);
            /* single element can be a NULL too */
            is_null = null_string ? text_isequal(inputstring, null_string) : false;
            PG_RETURN_ARRAYTYPE_P(create_singleton_array(fcinfo, TEXTOID,
                                                PointerGetDatum(inputstring),
                                                         is_null, 1));
        }

        start_posn = 1;
        /* start_ptr points to the start_posn'th character of inputstring */
        start_ptr = VARDATA_ANY(inputstring);

        for (fldnum = 1;; fldnum++)     /* field number is 1 based */
        {
            CHECK_FOR_INTERRUPTS();

            end_posn = text_position_next(start_posn, &state);

            if (end_posn == 0)
            {
                /* fetch last field */
                chunk_len = ((char *) inputstring + VARSIZE_ANY(inputstring)) - start_ptr;
            }
            else
            {
                /* fetch non-last field */
                chunk_len = charlen_to_bytelen(start_ptr, end_posn - start_posn);
            }

            /* must build a temp text datum to pass to accumArrayResult */
            result_text = cstring_to_text_with_len(start_ptr, chunk_len);
            is_null = null_string ? text_isequal(result_text, null_string) : false;

            /* stash away this field */
            astate = accumArrayResult(astate,
                                      PointerGetDatum(result_text),
                                      is_null,
                                      TEXTOID,
                                      CurrentMemoryContext);

            pfree(result_text);

            if (end_posn == 0)
                break;

            start_posn = end_posn;
            start_ptr += chunk_len;
            start_posn += fldsep_len;
            start_ptr += charlen_to_bytelen(start_ptr, fldsep_len);
        }

        text_position_cleanup(&state);
    }
    else
    {
        /*
         * When fldsep is NULL, each character in the inputstring becomes an
         * element in the result array.  The separator is effectively the
         * space between characters.
         */
        inputstring_len = VARSIZE_ANY_EXHDR(inputstring);

        /* return empty array for empty input string */
        if (inputstring_len < 1)
            PG_RETURN_ARRAYTYPE_P(construct_empty_array(TEXTOID));

        start_ptr = VARDATA_ANY(inputstring);

        while (inputstring_len > 0)
        {
            int         chunk_len = pg_mblen(start_ptr);

            CHECK_FOR_INTERRUPTS();

            /* must build a temp text datum to pass to accumArrayResult */
            result_text = cstring_to_text_with_len(start_ptr, chunk_len);
            is_null = null_string ? text_isequal(result_text, null_string) : false;

            /* stash away this field */
            astate = accumArrayResult(astate,
                                      PointerGetDatum(result_text),
                                      is_null,
                                      TEXTOID,
                                      CurrentMemoryContext);

            pfree(result_text);

            start_ptr += chunk_len;
            inputstring_len -= chunk_len;
        }
    }

    PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate,
                                          CurrentMemoryContext));
}

/*
 * array_to_text
 * concatenate Cstring representation of input array elements
 * using provided field separator
 */
Datum
array_to_text(PG_FUNCTION_ARGS)
{
    ArrayType  *v = PG_GETARG_ARRAYTYPE_P(0);
    char       *fldsep = text_to_cstring(PG_GETARG_TEXT_PP(1));

    PG_RETURN_TEXT_P(array_to_text_internal(fcinfo, v, fldsep, NULL));
}

/*
 * array_to_text_null
 * concatenate Cstring representation of input array elements
 * using provided field separator and null string
 *
 * This version is not strict so we have to test for null inputs explicitly.
 */
Datum
array_to_text_null(PG_FUNCTION_ARGS)
{
    ArrayType  *v;
    char       *fldsep;
    char       *null_string;

    /* returns NULL when first or second parameter is NULL */
    if (PG_ARGISNULL(0) || PG_ARGISNULL(1))
        PG_RETURN_NULL();

    v = PG_GETARG_ARRAYTYPE_P(0);
    fldsep = text_to_cstring(PG_GETARG_TEXT_PP(1));

    /* NULL null string is passed through as a null pointer */
    if (!PG_ARGISNULL(2))
        null_string = text_to_cstring(PG_GETARG_TEXT_PP(2));
    else
        null_string = NULL;

    PG_RETURN_TEXT_P(array_to_text_internal(fcinfo, v, fldsep, null_string));
}

/*
 * common code for array_to_text and array_to_text_null functions
 */
static text *
array_to_text_internal(FunctionCallInfo fcinfo, ArrayType *v,
                       const char *fldsep, const char *null_string)
{
    text       *result;
    int         nitems,
               *dims,
                ndims;
    Oid         element_type;
    int         typlen;
    bool        typbyval;
    char        typalign;
    StringInfoData buf;
    bool        printed = false;
    char       *p;
    bits8      *bitmap;
    int         bitmask;
    int         i;
    ArrayMetaState *my_extra;

    ndims = ARR_NDIM(v);
    dims = ARR_DIMS(v);
    nitems = ArrayGetNItems(ndims, dims);

    /* if there are no elements, return an empty string */
    if (nitems == 0)
        return cstring_to_text_with_len("", 0);

    element_type = ARR_ELEMTYPE(v);
    initStringInfo(&buf);

    /*
     * We arrange to look up info about element type, including its output
     * conversion proc, only once per series of calls, assuming the element
     * type doesn't change underneath us.
     */
    my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
    if (my_extra == NULL)
    {
        fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                                                      sizeof(ArrayMetaState));
        my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
        my_extra->element_type = ~element_type;
    }

    if (my_extra->element_type != element_type)
    {
        /*
         * Get info about element type, including its output conversion proc
         */
        get_type_io_data(element_type, IOFunc_output,
                         &my_extra->typlen, &my_extra->typbyval,
                         &my_extra->typalign, &my_extra->typdelim,
                         &my_extra->typioparam, &my_extra->typiofunc);
        fmgr_info_cxt(my_extra->typiofunc, &my_extra->proc,
                      fcinfo->flinfo->fn_mcxt);
        my_extra->element_type = element_type;
    }
    typlen = my_extra->typlen;
    typbyval = my_extra->typbyval;
    typalign = my_extra->typalign;

    p = ARR_DATA_PTR(v);
    bitmap = ARR_NULLBITMAP(v);
    bitmask = 1;

    for (i = 0; i < nitems; i++)
    {
        Datum       itemvalue;
        char       *value;

        /* Get source element, checking for NULL */
        if (bitmap && (*bitmap & bitmask) == 0)
        {
            /* if null_string is NULL, we just ignore null elements */
            if (null_string != NULL)
            {
                if (printed)
                    appendStringInfo(&buf, "%s%s", fldsep, null_string);
                else
                    appendStringInfoString(&buf, null_string);
                printed = true;
            }
        }
        else
        {
            itemvalue = fetch_att(p, typbyval, typlen);

            value = OutputFunctionCall(&my_extra->proc, itemvalue);

            if (printed)
                appendStringInfo(&buf, "%s%s", fldsep, value);
            else
                appendStringInfoString(&buf, value);
            printed = true;

            p = att_addlength_pointer(p, typlen, p);
            p = (char *) att_align_nominal(p, typalign);
        }

        /* advance bitmap pointer if any */
        if (bitmap)
        {
            bitmask <<= 1;
            if (bitmask == 0x100)
            {
                bitmap++;
                bitmask = 1;
            }
        }
    }

    result = cstring_to_text_with_len(buf.data, buf.len);
    pfree(buf.data);

    return result;
}

#define HEXBASE 16
/*
 * Convert a int32 to a string containing a base 16 (hex) representation of
 * the number.
 */
Datum
to_hex32(PG_FUNCTION_ARGS)
{
    uint32      value = (uint32) PG_GETARG_INT32(0);
    char       *ptr;
    const char *digits = "0123456789abcdef";
    char        buf[32];        /* bigger than needed, but reasonable */

    ptr = buf + sizeof(buf) - 1;
    *ptr = '\0';

    do
    {
        *--ptr = digits[value % HEXBASE];
        value /= HEXBASE;
    } while (ptr > buf && value);

    PG_RETURN_TEXT_P(cstring_to_text(ptr));
}

/*
 * Convert a int64 to a string containing a base 16 (hex) representation of
 * the number.
 */
Datum
to_hex64(PG_FUNCTION_ARGS)
{
    uint64      value = (uint64) PG_GETARG_INT64(0);
    char       *ptr;
    const char *digits = "0123456789abcdef";
    char        buf[32];        /* bigger than needed, but reasonable */

    ptr = buf + sizeof(buf) - 1;
    *ptr = '\0';

    do
    {
        *--ptr = digits[value % HEXBASE];
        value /= HEXBASE;
    } while (ptr > buf && value);

    PG_RETURN_TEXT_P(cstring_to_text(ptr));
}

/*
 * Create an md5 hash of a text string and return it as hex
 *
 * md5 produces a 16 byte (128 bit) hash; double it for hex
 */
#define MD5_HASH_LEN  32

Datum
md5_text(PG_FUNCTION_ARGS)
{
    text       *in_text = PG_GETARG_TEXT_PP(0);
    size_t      len;
    char        hexsum[MD5_HASH_LEN + 1];

    /* Calculate the length of the buffer using varlena metadata */
    len = VARSIZE_ANY_EXHDR(in_text);

    /* get the hash result */
    if (pg_md5_hash(VARDATA_ANY(in_text), len, hexsum) == false)
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));

    /* convert to text and return it */
    PG_RETURN_TEXT_P(cstring_to_text(hexsum));
}

/*
 * Create an md5 hash of a bytea field and return it as a hex string:
 * 16-byte md5 digest is represented in 32 hex characters.
 */
Datum
md5_bytea(PG_FUNCTION_ARGS)
{
    bytea      *in = PG_GETARG_BYTEA_PP(0);
    size_t      len;
    char        hexsum[MD5_HASH_LEN + 1];

    len = VARSIZE_ANY_EXHDR(in);
    if (pg_md5_hash(VARDATA_ANY(in), len, hexsum) == false)
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));

    PG_RETURN_TEXT_P(cstring_to_text(hexsum));
}

/*
 * Return the size of a datum, possibly compressed
 *
 * Works on any data type
 */
Datum
pg_column_size(PG_FUNCTION_ARGS)
{
    Datum       value = PG_GETARG_DATUM(0);
    int32       result;
    int         typlen;

    /* On first call, get the input type's typlen, and save at *fn_extra */
    if (fcinfo->flinfo->fn_extra == NULL)
    {
        /* Lookup the datatype of the supplied argument */
        Oid         argtypeid = get_fn_expr_argtype(fcinfo->flinfo, 0);

        typlen = get_typlen(argtypeid);
        if (typlen == 0)        /* should not happen */
            elog(ERROR, "cache lookup failed for type %u", argtypeid);

        fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                                                      sizeof(int));
        *((int *) fcinfo->flinfo->fn_extra) = typlen;
    }
    else
        typlen = *((int *) fcinfo->flinfo->fn_extra);

    if (typlen == -1)
    {
        /* varlena type, possibly toasted */
        result = toast_datum_size(value);
    }
    else if (typlen == -2)
    {
        /* cstring */
        result = strlen(DatumGetCString(value)) + 1;
    }
    else
    {
        /* ordinary fixed-width type */
        result = typlen;
    }

    PG_RETURN_INT32(result);
}

/*
 * string_agg - Concatenates values and returns string.
 *
 * Syntax: string_agg(value text, delimiter text) RETURNS text
 *
 * Note: Any NULL values are ignored. The first-call delimiter isn't
 * actually used at all, and on subsequent calls the delimiter precedes
 * the associated value.
 */

/* subroutine to initialize state */
static StringInfo
makeStringAggState(FunctionCallInfo fcinfo)
{
    StringInfo  state;
    MemoryContext aggcontext;
    MemoryContext oldcontext;

    if (!AggCheckCallContext(fcinfo, &aggcontext))
    {
        /* cannot be called directly because of internal-type argument */
        elog(ERROR, "string_agg_transfn called in non-aggregate context");
    }

    /*
     * Create state in aggregate context.  It'll stay there across subsequent
     * calls.
     */
    oldcontext = MemoryContextSwitchTo(aggcontext);
    state = makeStringInfo();
    MemoryContextSwitchTo(oldcontext);

    return state;
}

Datum
string_agg_transfn(PG_FUNCTION_ARGS)
{
    StringInfo  state;

    state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);

    /* Append the value unless null. */
    if (!PG_ARGISNULL(1))
    {
        /* On the first time through, we ignore the delimiter. */
        if (state == NULL)
            state = makeStringAggState(fcinfo);
        else if (!PG_ARGISNULL(2))
            appendStringInfoText(state, PG_GETARG_TEXT_PP(2));  /* delimiter */

        appendStringInfoText(state, PG_GETARG_TEXT_PP(1));      /* value */
    }

    /*
     * The transition type for string_agg() is declared to be "internal",
     * which is a pass-by-value type the same size as a pointer.
     */
    PG_RETURN_POINTER(state);
}

Datum
string_agg_finalfn(PG_FUNCTION_ARGS)
{
    StringInfo  state;

    /* cannot be called directly because of internal-type argument */
    Assert(AggCheckCallContext(fcinfo, NULL));

    state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);

    if (state != NULL)
        PG_RETURN_TEXT_P(cstring_to_text_with_len(state->data, state->len));
    else
        PG_RETURN_NULL();
}

/*
 * Implementation of both concat() and concat_ws().
 *
 * sepstr is the separator string to place between values.
 * argidx identifies the first argument to concatenate (counting from zero).
 * Returns NULL if result should be NULL, else text value.
 */
static text *
concat_internal(const char *sepstr, int argidx,
                FunctionCallInfo fcinfo)
{
    text       *result;
    StringInfoData str;
    bool        first_arg = true;
    int         i;

    /*
     * concat(VARIADIC some-array) is essentially equivalent to
     * array_to_text(), ie concat the array elements with the given separator.
     * So we just pass the case off to that code.
     */
    if (get_fn_expr_variadic(fcinfo->flinfo))
    {
        Oid         arr_typid;
        ArrayType  *arr;

        /* Should have just the one argument */
        Assert(argidx == PG_NARGS() - 1);

        /* concat(VARIADIC NULL) is defined as NULL */
        if (PG_ARGISNULL(argidx))
            return NULL;

        /*
         * Non-null argument had better be an array.  The parser doesn't
         * enforce this for VARIADIC ANY functions (maybe it should?), so that
         * check uses ereport not just elog.
         */
        arr_typid = get_fn_expr_argtype(fcinfo->flinfo, argidx);
        if (!OidIsValid(arr_typid))
            elog(ERROR, "could not determine data type of concat() input");

        if (!OidIsValid(get_element_type(arr_typid)))
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("VARIADIC argument must be an array")));

        /* OK, safe to fetch the array value */
        arr = PG_GETARG_ARRAYTYPE_P(argidx);

        /*
         * And serialize the array.  We tell array_to_text to ignore null
         * elements, which matches the behavior of the loop below.
         */
        return array_to_text_internal(fcinfo, arr, sepstr, NULL);
    }

    /* Normal case without explicit VARIADIC marker */
    initStringInfo(&str);

    for (i = argidx; i < PG_NARGS(); i++)
    {
        if (!PG_ARGISNULL(i))
        {
            Datum       value = PG_GETARG_DATUM(i);
            Oid         valtype;
            Oid         typOutput;
            bool        typIsVarlena;

            /* add separator if appropriate */
            if (first_arg)
                first_arg = false;
            else
                appendStringInfoString(&str, sepstr);

            /* call the appropriate type output function, append the result */
            valtype = get_fn_expr_argtype(fcinfo->flinfo, i);
            if (!OidIsValid(valtype))
                elog(ERROR, "could not determine data type of concat() input");
            getTypeOutputInfo(valtype, &typOutput, &typIsVarlena);
            appendStringInfoString(&str,
                                   OidOutputFunctionCall(typOutput, value));
        }
    }

    result = cstring_to_text_with_len(str.data, str.len);
    pfree(str.data);

    return result;
}

/*
 * Concatenate all arguments. NULL arguments are ignored.
 */
Datum
text_concat(PG_FUNCTION_ARGS)
{
    text       *result;

    result = concat_internal("", 0, fcinfo);
    if (result == NULL)
        PG_RETURN_NULL();
    PG_RETURN_TEXT_P(result);
}

/*
 * Concatenate all but first argument value with separators. The first
 * parameter is used as the separator. NULL arguments are ignored.
 */
Datum
text_concat_ws(PG_FUNCTION_ARGS)
{
    char       *sep;
    text       *result;

    /* return NULL when separator is NULL */
    if (PG_ARGISNULL(0))
        PG_RETURN_NULL();
    sep = text_to_cstring(PG_GETARG_TEXT_PP(0));

    result = concat_internal(sep, 1, fcinfo);
    if (result == NULL)
        PG_RETURN_NULL();
    PG_RETURN_TEXT_P(result);
}

/*
 * Return first n characters in the string. When n is negative,
 * return all but last |n| characters.
 */
Datum
text_left(PG_FUNCTION_ARGS)
{
    text       *str = PG_GETARG_TEXT_PP(0);
    const char *p = VARDATA_ANY(str);
    int         len = VARSIZE_ANY_EXHDR(str);
    int         n = PG_GETARG_INT32(1);
    int         rlen;

    if (n < 0)
        n = pg_mbstrlen_with_len(p, len) + n;
    rlen = pg_mbcharcliplen(p, len, n);

    PG_RETURN_TEXT_P(cstring_to_text_with_len(p, rlen));
}

/*
 * Return last n characters in the string. When n is negative,
 * return all but first |n| characters.
 */
Datum
text_right(PG_FUNCTION_ARGS)
{
    text       *str = PG_GETARG_TEXT_PP(0);
    const char *p = VARDATA_ANY(str);
    int         len = VARSIZE_ANY_EXHDR(str);
    int         n = PG_GETARG_INT32(1);
    int         off;

    if (n < 0)
        n = -n;
    else
        n = pg_mbstrlen_with_len(p, len) - n;
    off = pg_mbcharcliplen(p, len, n);

    PG_RETURN_TEXT_P(cstring_to_text_with_len(p + off, len - off));
}

/*
 * Return reversed string
 */
Datum
text_reverse(PG_FUNCTION_ARGS)
{
    text       *str = PG_GETARG_TEXT_PP(0);
    const char *p = VARDATA_ANY(str);
    int         len = VARSIZE_ANY_EXHDR(str);
    const char *endp = p + len;
    text       *result;
    char       *dst;

    result = palloc(len + VARHDRSZ);
    dst = (char *) VARDATA(result) + len;
    SET_VARSIZE(result, len + VARHDRSZ);

    if (pg_database_encoding_max_length() > 1)
    {
        /* multibyte version */
        while (p < endp)
        {
            int         sz;

            sz = pg_mblen(p);
            dst -= sz;
            memcpy(dst, p, sz);
            p += sz;
        }
    }
    else
    {
        /* single byte version */
        while (p < endp)
            *(--dst) = *p++;
    }

    PG_RETURN_TEXT_P(result);
}


/*
 * Support macros for text_format()
 */
#define TEXT_FORMAT_FLAG_MINUS  0x0001  /* is minus flag present? */

#define ADVANCE_PARSE_POINTER(ptr,end_ptr) \
    do { \
        if (++(ptr) >= (end_ptr)) \
            ereport(ERROR, \
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE), \
                     errmsg("unterminated format specifier"))); \
    } while (0)

/*
 * Returns a formatted string
 */
Datum
text_format(PG_FUNCTION_ARGS)
{
    text       *fmt;
    StringInfoData str;
    const char *cp;
    const char *start_ptr;
    const char *end_ptr;
    text       *result;
    int         arg;
    bool        funcvariadic;
    int         nargs;
    Datum      *elements = NULL;
    bool       *nulls = NULL;
    Oid         element_type = InvalidOid;
    Oid         prev_type = InvalidOid;
    Oid         prev_width_type = InvalidOid;
    FmgrInfo    typoutputfinfo;
    FmgrInfo    typoutputinfo_width;

    /* When format string is null, immediately return null */
    if (PG_ARGISNULL(0))
        PG_RETURN_NULL();

    /* If argument is marked VARIADIC, expand array into elements */
    if (get_fn_expr_variadic(fcinfo->flinfo))
    {
        Oid         arr_typid;
        ArrayType  *arr;
        int16       elmlen;
        bool        elmbyval;
        char        elmalign;
        int         nitems;

        /* Should have just the one argument */
        Assert(PG_NARGS() == 2);

        /* If argument is NULL, we treat it as zero-length array */
        if (PG_ARGISNULL(1))
            nitems = 0;
        else
        {
            /*
             * Non-null argument had better be an array.  The parser doesn't
             * enforce this for VARIADIC ANY functions (maybe it should?), so
             * that check uses ereport not just elog.
             */
            arr_typid = get_fn_expr_argtype(fcinfo->flinfo, 1);
            if (!OidIsValid(arr_typid))
                elog(ERROR, "could not determine data type of format() input");

            if (!OidIsValid(get_element_type(arr_typid)))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("VARIADIC argument must be an array")));

            /* OK, safe to fetch the array value */
            arr = PG_GETARG_ARRAYTYPE_P(1);

            /* Get info about array element type */
            element_type = ARR_ELEMTYPE(arr);
            get_typlenbyvalalign(element_type,
                                 &elmlen, &elmbyval, &elmalign);

            /* Extract all array elements */
            deconstruct_array(arr, element_type, elmlen, elmbyval, elmalign,
                              &elements, &nulls, &nitems);
        }

        nargs = nitems + 1;
        funcvariadic = true;
    }
    else
    {
        /* Non-variadic case, we'll process the arguments individually */
        nargs = PG_NARGS();
        funcvariadic = false;
    }

    /* Setup for main loop. */
    fmt = PG_GETARG_TEXT_PP(0);
    start_ptr = VARDATA_ANY(fmt);
    end_ptr = start_ptr + VARSIZE_ANY_EXHDR(fmt);
    initStringInfo(&str);
    arg = 1;                    /* next argument position to print */

    /* Scan format string, looking for conversion specifiers. */
    for (cp = start_ptr; cp < end_ptr; cp++)
    {
        int         argpos;
        int         widthpos;
        int         flags;
        int         width;
        Datum       value;
        bool        isNull;
        Oid         typid;

        /*
         * If it's not the start of a conversion specifier, just copy it to
         * the output buffer.
         */
        if (*cp != '%')
        {
            appendStringInfoCharMacro(&str, *cp);
            continue;
        }

        ADVANCE_PARSE_POINTER(cp, end_ptr);

        /* Easy case: %% outputs a single % */
        if (*cp == '%')
        {
            appendStringInfoCharMacro(&str, *cp);
            continue;
        }

        /* Parse the optional portions of the format specifier */
        cp = text_format_parse_format(cp, end_ptr,
                                      &argpos, &widthpos,
                                      &flags, &width);

        /*
         * Next we should see the main conversion specifier.  Whether or not
         * an argument position was present, it's known that at least one
         * character remains in the string at this point.  Experience suggests
         * that it's worth checking that that character is one of the expected
         * ones before we try to fetch arguments, so as to produce the least
         * confusing response to a mis-formatted specifier.
         */
        if (strchr("sIL", *cp) == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("unrecognized conversion type specifier \"%c\"",
                            *cp)));

        /* If indirect width was specified, get its value */
        if (widthpos >= 0)
        {
            /* Collect the specified or next argument position */
            if (widthpos > 0)
                arg = widthpos;
            if (arg >= nargs)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("too few arguments for format")));

            /* Get the value and type of the selected argument */
            if (!funcvariadic)
            {
                value = PG_GETARG_DATUM(arg);
                isNull = PG_ARGISNULL(arg);
                typid = get_fn_expr_argtype(fcinfo->flinfo, arg);
            }
            else
            {
                value = elements[arg - 1];
                isNull = nulls[arg - 1];
                typid = element_type;
            }
            if (!OidIsValid(typid))
                elog(ERROR, "could not determine data type of format() input");

            arg++;

            /* We can treat NULL width the same as zero */
            if (isNull)
                width = 0;
            else if (typid == INT4OID)
                width = DatumGetInt32(value);
            else if (typid == INT2OID)
                width = DatumGetInt16(value);
            else
            {
                /* For less-usual datatypes, convert to text then to int */
                char       *str;

                if (typid != prev_width_type)
                {
                    Oid         typoutputfunc;
                    bool        typIsVarlena;

                    getTypeOutputInfo(typid, &typoutputfunc, &typIsVarlena);
                    fmgr_info(typoutputfunc, &typoutputinfo_width);
                    prev_width_type = typid;
                }

                str = OutputFunctionCall(&typoutputinfo_width, value);

                /* pg_atoi will complain about bad data or overflow */
                width = pg_atoi(str, sizeof(int), '\0');

                pfree(str);
            }
        }

        /* Collect the specified or next argument position */
        if (argpos > 0)
            arg = argpos;
        if (arg >= nargs)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("too few arguments for format")));

        /* Get the value and type of the selected argument */
        if (!funcvariadic)
        {
            value = PG_GETARG_DATUM(arg);
            isNull = PG_ARGISNULL(arg);
            typid = get_fn_expr_argtype(fcinfo->flinfo, arg);
        }
        else
        {
            value = elements[arg - 1];
            isNull = nulls[arg - 1];
            typid = element_type;
        }
        if (!OidIsValid(typid))
            elog(ERROR, "could not determine data type of format() input");

        arg++;

        /*
         * Get the appropriate typOutput function, reusing previous one if
         * same type as previous argument.  That's particularly useful in the
         * variadic-array case, but often saves work even for ordinary calls.
         */
        if (typid != prev_type)
        {
            Oid         typoutputfunc;
            bool        typIsVarlena;

            getTypeOutputInfo(typid, &typoutputfunc, &typIsVarlena);
            fmgr_info(typoutputfunc, &typoutputfinfo);
            prev_type = typid;
        }

        /*
         * And now we can format the value.
         */
        switch (*cp)
        {
            case 's':
            case 'I':
            case 'L':
                text_format_string_conversion(&str, *cp, &typoutputfinfo,
                                              value, isNull,
                                              flags, width);
                break;
            default:
                /* should not get here, because of previous check */
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("unrecognized conversion type specifier \"%c\"",
                                *cp)));
                break;
        }
    }

    /* Don't need deconstruct_array results anymore. */
    if (elements != NULL)
        pfree(elements);
    if (nulls != NULL)
        pfree(nulls);

    /* Generate results. */
    result = cstring_to_text_with_len(str.data, str.len);
    pfree(str.data);

    PG_RETURN_TEXT_P(result);
}

/*
 * Parse contiguous digits as a decimal number.
 *
 * Returns true if some digits could be parsed.
 * The value is returned into *value, and *ptr is advanced to the next
 * character to be parsed.
 *
 * Note parsing invariant: at least one character is known available before
 * string end (end_ptr) at entry, and this is still true at exit.
 */
static bool
text_format_parse_digits(const char **ptr, const char *end_ptr, int *value)
{
    bool        found = false;
    const char *cp = *ptr;
    int         val = 0;

    while (*cp >= '0' && *cp <= '9')
    {
        int         newval = val * 10 + (*cp - '0');

        if (newval / 10 != val) /* overflow? */
            ereport(ERROR,
                    (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                     errmsg("number is out of range")));
        val = newval;
        ADVANCE_PARSE_POINTER(cp, end_ptr);
        found = true;
    }

    *ptr = cp;
    *value = val;

    return found;
}

/*
 * Parse a format specifier (generally following the SUS printf spec).
 *
 * We have already advanced over the initial '%', and we are looking for
 * [argpos][flags][width]type (but the type character is not consumed here).
 *
 * Inputs are start_ptr (the position after '%') and end_ptr (string end + 1).
 * Output parameters:
 *  argpos: argument position for value to be printed.  -1 means unspecified.
 *  widthpos: argument position for width.  Zero means the argument position
 *          was unspecified (ie, take the next arg) and -1 means no width
 *          argument (width was omitted or specified as a constant).
 *  flags: bitmask of flags.
 *  width: directly-specified width value.  Zero means the width was omitted
 *          (note it's not necessary to distinguish this case from an explicit
 *          zero width value).
 *
 * The function result is the next character position to be parsed, ie, the
 * location where the type character is/should be.
 *
 * Note parsing invariant: at least one character is known available before
 * string end (end_ptr) at entry, and this is still true at exit.
 */
static const char *
text_format_parse_format(const char *start_ptr, const char *end_ptr,
                         int *argpos, int *widthpos,
                         int *flags, int *width)
{
    const char *cp = start_ptr;
    int         n;

    /* set defaults for output parameters */
    *argpos = -1;
    *widthpos = -1;
    *flags = 0;
    *width = 0;

    /* try to identify first number */
    if (text_format_parse_digits(&cp, end_ptr, &n))
    {
        if (*cp != '$')
        {
            /* Must be just a width and a type, so we're done */
            *width = n;
            return cp;
        }
        /* The number was argument position */
        *argpos = n;
        /* Explicit 0 for argument index is immediately refused */
        if (n == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("format specifies argument 0, but arguments are numbered from 1")));
        ADVANCE_PARSE_POINTER(cp, end_ptr);
    }

    /* Handle flags (only minus is supported now) */
    while (*cp == '-')
    {
        *flags |= TEXT_FORMAT_FLAG_MINUS;
        ADVANCE_PARSE_POINTER(cp, end_ptr);
    }

    if (*cp == '*')
    {
        /* Handle indirect width */
        ADVANCE_PARSE_POINTER(cp, end_ptr);
        if (text_format_parse_digits(&cp, end_ptr, &n))
        {
            /* number in this position must be closed by $ */
            if (*cp != '$')
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                  errmsg("width argument position must be ended by \"$\"")));
            /* The number was width argument position */
            *widthpos = n;
            /* Explicit 0 for argument index is immediately refused */
            if (n == 0)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("format specifies argument 0, but arguments are numbered from 1")));
            ADVANCE_PARSE_POINTER(cp, end_ptr);
        }
        else
            *widthpos = 0;      /* width's argument position is unspecified */
    }
    else
    {
        /* Check for direct width specification */
        if (text_format_parse_digits(&cp, end_ptr, &n))
            *width = n;
    }

    /* cp should now be pointing at type character */
    return cp;
}

/*
 * Format a %s, %I, or %L conversion
 */
static void
text_format_string_conversion(StringInfo buf, char conversion,
                              FmgrInfo *typOutputInfo,
                              Datum value, bool isNull,
                              int flags, int width)
{
    char       *str;

    /* Handle NULL arguments before trying to stringify the value. */
    if (isNull)
    {
        if (conversion == 's')
            text_format_append_string(buf, "", flags, width);
        else if (conversion == 'L')
            text_format_append_string(buf, "NULL", flags, width);
        else if (conversion == 'I')
            ereport(ERROR,
                    (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
            errmsg("null values cannot be formatted as an SQL identifier")));
        return;
    }

    /* Stringify. */
    str = OutputFunctionCall(typOutputInfo, value);

    /* Escape. */
    if (conversion == 'I')
    {
        /* quote_identifier may or may not allocate a new string. */
        text_format_append_string(buf, quote_identifier(str), flags, width);
    }
    else if (conversion == 'L')
    {
        char       *qstr = quote_literal_cstr(str);

        text_format_append_string(buf, qstr, flags, width);
        /* quote_literal_cstr() always allocates a new string */
        pfree(qstr);
    }
    else
        text_format_append_string(buf, str, flags, width);

    /* Cleanup. */
    pfree(str);
}

/*
 * Append str to buf, padding as directed by flags/width
 */
static void
text_format_append_string(StringInfo buf, const char *str,
                          int flags, int width)
{
    bool        align_to_left = false;
    int         len;

    /* fast path for typical easy case */
    if (width == 0)
    {
        appendStringInfoString(buf, str);
        return;
    }

    if (width < 0)
    {
        /* Negative width: implicit '-' flag, then take absolute value */
        align_to_left = true;
        /* -INT_MIN is undefined */
        if (width <= INT_MIN)
            ereport(ERROR,
                    (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                     errmsg("number is out of range")));
        width = -width;
    }
    else if (flags & TEXT_FORMAT_FLAG_MINUS)
        align_to_left = true;

    len = pg_mbstrlen(str);
    if (align_to_left)
    {
        /* left justify */
        appendStringInfoString(buf, str);
        if (len < width)
            appendStringInfoSpaces(buf, width - len);
    }
    else
    {
        /* right justify */
        if (len < width)
            appendStringInfoSpaces(buf, width - len);
        appendStringInfoString(buf, str);
    }
}

/*
 * text_format_nv - nonvariadic wrapper for text_format function.
 *
 * note: this wrapper is necessary to pass the sanity check in opr_sanity,
 * which checks that all built-in functions that share the implementing C
 * function take the same number of arguments.
 */
Datum
text_format_nv(PG_FUNCTION_ARGS)
{
    return text_format(fcinfo);
}