Example Matching Rule Plug-In

The example code cited in this chapter, from install-path/examples/matchingrule.c, mimics functionality installed by default with Directory Server. For this reason, you do not need to build and load the plug-in unless you modify the plug-in to implement your own matching rule. The example uses a different OID from the plug-in that is provided with Directory Server. Therefore, the sample plug-in does not interfere with the existing plug-in if you do choose to load the sample.

Configuring Matching Rule Plug-Ins

Matching rule plug-ins have type matchingrule. Directory Server plug-ins can depend on matching rule plug-ins by type. Directory Server cannot load plug-ins unless plug-ins of the type the plug-ins depend on load without error.

Refer to Plugging Libraries Into Directory Server for details on loading plug-in configuration entries into Directory Server.

Registering Matching Rule Plug-Ins

Matching rule plug-ins include factory functions. Factory functions provide function pointers to the indexing or filter match routines dynamically. You therefore register only the factory functions as part of the plug-in initialization function.

A plug-in that handles both indexing and matching registers both factory functions and a description, as shown in the following example.

Example 10–1 Registering Matching Rule Factory Functions (matchingrule.c)

#include "slapi-plugin.h"

static Slapi_PluginDesc plg_desc = {
    "caseExactMatchingRule",           /* Plug-in identifier           */
    "Sun Microsystems, Inc.",          /* Vendor name                  */
    "6.0",                             /* Plug-in revision number      */
    "Case Exact Matching Rule plug-in" /* Plug-in description          */
};

#ifdef _WIN32
__declspec(dllexport)
#endif
int
plg_init(Slapi_PBlock * pb)
{
    int                       rc;
        
    /* Matching rule factory functions are registered using
     * the parameter block structure. Other functions are then
     * registered dynamically by the factory functions.
     *
     * This means that a single matching rule plug-in may handle
     * a number of different matching rules.                           */
    rc  = slapi_pblock_set(
        pb,
        SLAPI_PLUGIN_MR_INDEXER_CREATE_FN,
        (void *)plg_indexer_create
    );
    rc |= slapi_pblock_set(
        pb,
        SLAPI_PLUGIN_MR_FILTER_CREATE_FN,
        (void *)plg_filter_create
    );
    rc |= slapi_pblock_set(
        pb,
        SLAPI_PLUGIN_DESCRIPTION,
        (void *)&plg_desc
    );

    /* Register the matching rules themselves. */

    return rc;
}

Here, plg_init() is the plug-in initialization function, plg_indexer_create() is the indexer factory, plg_filter_create() is the filter factory, and plg_desc is the plug-in description structure.

If your plug-in uses private data, set SLAPI_PLUGIN_PRIVATE in the parameter block as a pointer to the private data structure.

Example 10–2 Registering a Matching Rule (matchingrule.c)

Register matching rules by using slapi_matchingrule_register() as shown here rather than using slapi_pblock_set() in the initialization function.

#include "slapi-plugin.h"

#define PLG_DESC      "Case Exact Matching on Directory String" \
                      " [defined in X.520]"
#define PLG_NAME      "caseExactMatch"
/* This OID is for examples only and is not intended for reuse. The
 * official OID for this matching rule is 2.5.13.5.                    */
#define PLG_OID       "1.3.6.1.4.1.42.2.27.999.4.1"

#ifdef _WIN32
__declspec(dllexport)
#endif
int
plg_init(Slapi_PBlock * pb)
{
    Slapi_MatchingRuleEntry * mrentry = slapi_matchingrule_new();
    int                       rc;
        
    /* Register matching rule factory functions.*/

    /* Matching rules themselves are registered using a
     * Slapi_MatchingRuleEntry structure, not the parameter
     * block structure used when registering plug-in functions.
     *
     * This plug-in registers only one matching rule. Yours
     * may register many matching rules.                               */
    rc |= slapi_matchingrule_set(
        mrentry,
        SLAPI_MATCHINGRULE_DESC,
        (void *)slapi_ch_strdup(PLG_DESC)
    );
    rc |= slapi_matchingrule_set(
        mrentry,
        SLAPI_MATCHINGRULE_NAME,
        (void *)slapi_ch_strdup(PLG_NAME)
    );
    rc |= slapi_matchingrule_set(
        mrentry,
        SLAPI_MATCHINGRULE_OID,
        (void *)slapi_ch_strdup(PLG_OID)
    );
    rc |= slapi_matchingrule_set(
        mrentry,
        SLAPI_MATCHINGRULE_SYNTAX,     /* Here you use DirectoryString.*/
        (void *)slapi_ch_strdup("1.3.6.1.4.1.1466.115.121.1.15")
    );
    rc |= slapi_matchingrule_register(mrentry);
    slapi_matchingrule_free(&mrentry, 1);

    return rc;
}

• PLG_DESC is a string that describes the matching rule.

• PLG_NAME is a string identifier for the matching rule.

• PLG_OID is the object identifier for the matching rule.

  The sample plug-in #defines every item. If the plug-in implements several matching rules, the initialization function must register each item.

  Notice that plug-ins must register factory functions separately, using slapi_pblock_set().