ex_btrec.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1997-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: ex_btrec.c,v 12.1 2005/06/16 20:22:00 bostic Exp $
 */

#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include <db.h>

#define DATABASE        "access.db"
#define WORDLIST        "../test/wordlist"
int     main __P((void));

int     ex_btrec __P((void));
void    show __P((const char *, DBT *, DBT *));

int
main()
{
        return (ex_btrec() == 1 ? EXIT_FAILURE : EXIT_SUCCESS);
}

int
ex_btrec()
{
        DB *dbp;
        DBC *dbcp;
        DBT key, data;
        DB_BTREE_STAT *statp;
        FILE *fp;
        db_recno_t recno;
        size_t len;
        int cnt, ret;
        char *p, *t, buf[1024], rbuf[1024];
        const char *progname = "ex_btrec";              /* Program name. */

        /* Open the word database. */
        if ((fp = fopen(WORDLIST, "r")) == NULL) {
                fprintf(stderr, "%s: open %s: %s\n",
                    progname, WORDLIST, db_strerror(errno));
                return (1);
        }

        /* Remove the previous database. */
        (void)remove(DATABASE);

        /* Create and initialize database object, open the database. */
        if ((ret = db_create(&dbp, NULL, 0)) != 0) {
                fprintf(stderr,
                    "%s: db_create: %s\n", progname, db_strerror(ret));
                return (1);
        }
        dbp->set_errfile(dbp, stderr);
        dbp->set_errpfx(dbp, progname);                 /* 1K page sizes. */
        if ((ret = dbp->set_pagesize(dbp, 1024)) != 0) {
                dbp->err(dbp, ret, "set_pagesize");
                return (1);
        }                                               /* Record numbers. */
        if ((ret = dbp->set_flags(dbp, DB_RECNUM)) != 0) {
                dbp->err(dbp, ret, "set_flags: DB_RECNUM");
                return (1);
        }
        if ((ret = dbp->open(dbp,
            NULL, DATABASE, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
                dbp->err(dbp, ret, "open: %s", DATABASE);
                return (1);
        }

        /*
         * Insert records into the database, where the key is the word
         * preceded by its record number, and the data is the same, but
         * in reverse order.
         */
        memset(&key, 0, sizeof(DBT));
        memset(&data, 0, sizeof(DBT));
        for (cnt = 1; cnt <= 1000; ++cnt) {
                (void)sprintf(buf, "%04d_", cnt);
                if (fgets(buf + 4, sizeof(buf) - 4, fp) == NULL)
                        break;
                len = strlen(buf);
                for (t = rbuf, p = buf + (len - 2); p >= buf;)
                        *t++ = *p--;
                *t++ = '\0';

                key.data = buf;
                data.data = rbuf;
                data.size = key.size = (u_int32_t)len - 1;

                if ((ret =
                    dbp->put(dbp, NULL, &key, &data, DB_NOOVERWRITE)) != 0) {
                        dbp->err(dbp, ret, "DB->put");
                        if (ret != DB_KEYEXIST)
                                goto err1;
                }
        }

        /* Close the word database. */
        (void)fclose(fp);

        /* Print out the number of records in the database. */
        if ((ret = dbp->stat(dbp, NULL, &statp, 0)) != 0) {
                dbp->err(dbp, ret, "DB->stat");
                goto err1;
        }
        printf("%s: database contains %lu records\n",
            progname, (u_long)statp->bt_ndata);
        free(statp);

        /* Acquire a cursor for the database. */
        if ((ret = dbp->cursor(dbp, NULL, &dbcp, 0)) != 0) {
                dbp->err(dbp, ret, "DB->cursor");
                goto err1;
        }

        /*
         * Prompt the user for a record number, then retrieve and display
         * that record.
         */
        for (;;) {
                /* Get a record number. */
                printf("recno #> ");
                fflush(stdout);
                if (fgets(buf, sizeof(buf), stdin) == NULL)
                        break;
                recno = atoi(buf);

                /*
                 * Reset the key each time, the dbp->c_get() routine returns
                 * the key and data pair, not just the key!
                 */
                key.data = &recno;
                key.size = sizeof(recno);
                if ((ret = dbcp->c_get(dbcp, &key, &data, DB_SET_RECNO)) != 0)
                        goto get_err;

                /* Display the key and data. */
                show("k/d\t", &key, &data);

                /* Move the cursor a record forward. */
                if ((ret = dbcp->c_get(dbcp, &key, &data, DB_NEXT)) != 0)
                        goto get_err;

                /* Display the key and data. */
                show("next\t", &key, &data);

                /*
                 * Retrieve the record number for the following record into
                 * local memory.
                 */
                data.data = &recno;
                data.size = sizeof(recno);
                data.ulen = sizeof(recno);
                data.flags |= DB_DBT_USERMEM;
                if ((ret = dbcp->c_get(dbcp, &key, &data, DB_GET_RECNO)) != 0) {
get_err:                dbp->err(dbp, ret, "DBcursor->get");
                        if (ret != DB_NOTFOUND && ret != DB_KEYEMPTY)
                                goto err2;
                } else
                        printf("retrieved recno: %lu\n", (u_long)recno);

                /* Reset the data DBT. */
                memset(&data, 0, sizeof(data));
        }

        if ((ret = dbcp->c_close(dbcp)) != 0) {
                dbp->err(dbp, ret, "DBcursor->close");
                goto err1;
        }
        if ((ret = dbp->close(dbp, 0)) != 0) {
                fprintf(stderr,
                    "%s: DB->close: %s\n", progname, db_strerror(ret));
                return (1);
        }

        return (0);

err2:   (void)dbcp->c_close(dbcp);
err1:   (void)dbp->close(dbp, 0);
        return (ret);

}

/*
 * show --
 *      Display a key/data pair.
 */
void
show(msg, key, data)
        const char *msg;
        DBT *key, *data;
{
        printf("%s%.*s : %.*s\n", msg,
            (int)key->size, (char *)key->data,
            (int)data->size, (char *)data->data);
}

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