ex_extending.c

Shows how to extend WiredTiger with application-specific collations, extractors and cursor types.

/*-
 * Public Domain 2014-present MongoDB, Inc.
 * Public Domain 2008-2014 WiredTiger, Inc.
 *
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * ex_extending.c
 *      This is an example demonstrating ways to extend WiredTiger with
 *      extractors, collators and loadable modules.
 */
#include <test_util.h>

static const char *home;

/* A simple case insensitive comparator. */
static int
__compare_nocase(
  WT_COLLATOR *collator, WT_SESSION *session, const WT_ITEM *v1, const WT_ITEM *v2, int *cmp)
{
    const char *s1 = (const char *)v1->data;
    const char *s2 = (const char *)v2->data;

    (void)session;  /* unused variable */
    (void)collator; /* unused variable */

    *cmp = strcasecmp(s1, s2);
    return (0);
}

static WT_COLLATOR nocasecoll = {__compare_nocase, NULL, NULL};
/*
 * Comparator that only compares the first N prefix characters of the string. This has associated
 * data, so we need to extend WT_COLLATOR.
 */
typedef struct {
    WT_COLLATOR iface;
    uint32_t maxlen;
} PREFIX_COLLATOR;

static int
__compare_prefixes(
  WT_COLLATOR *collator, WT_SESSION *session, const WT_ITEM *v1, const WT_ITEM *v2, int *cmp)
{
    PREFIX_COLLATOR *pcoll = (PREFIX_COLLATOR *)collator;
    const char *s1 = (const char *)v1->data;
    const char *s2 = (const char *)v2->data;

    (void)session; /* unused */

    *cmp = strncmp(s1, s2, pcoll->maxlen);
    return (0);
}

static PREFIX_COLLATOR pcoll10 = {{__compare_prefixes, NULL, NULL}, 10};
int
main(int argc, char *argv[])
{
    WT_CONNECTION *conn;
    WT_SESSION *session;

    home = example_setup(argc, argv);

    /* Open a connection to the database, creating it if necessary. */
    error_check(wiredtiger_open(home, NULL, "create", &conn));

    error_check(conn->add_collator(conn, "nocase", &nocasecoll, NULL));
    error_check(conn->add_collator(conn, "prefix10", &pcoll10.iface, NULL));

    /* Open a session for the current thread's work. */
    error_check(conn->open_session(conn, NULL, NULL, &session));

    /* Do some work... */

    error_check(conn->close(conn, NULL));
    return (EXIT_SUCCESS);
}