A toy/demo overlay for collective attributes.

diff --git a/servers/slapd/overlays/collect.c b/servers/slapd/overlays/collect.c
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+++ b/servers/slapd/overlays/collect.c
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+/* collect.c - Demonstration of overlay code */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2003-2004 The OpenLDAP Foundation.
+ * Portions Copyright 2003 Howard Chu.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/* ACKNOWLEDGEMENTS:
+ * This work was initially developed by the Howard Chu for inclusion
+ * in OpenLDAP Software.
+ */
+
+#include "portable.h"
+
+#ifdef SLAPD_OVER_COLLECT
+
+#include <stdio.h>
+
+#include <ac/string.h>
+#include <ac/socket.h>
+
+#include "slap.h"
+
+
+/* This is a cheap hack to implement a collective attribute.
+ *
+ * This demonstration overlay looks for a specified attribute in an
+ * ancestor of a given entry and adds that attribute to the given
+ * entry when it is returned in a search response. It takes no effect
+ * for any other operations. If the ancestor does not exist, there
+ * is no effect. If no attribute was configured, there is no effect.
+ */
+
+typedef struct collect_info {
+       struct collect_info *ci_next;
+       struct berval ci_dn;
+       AttributeDescription *ci_ad;
+} collect_info;
+
+static int
+collect_response( Operation *op, SlapReply *rs )
+{
+       slap_overinst *on = (slap_overinst *) op->o_bd->bd_info;
+       collect_info *ci = on->on_bi.bi_private;
+
+       /* If we've been configured and the current response is
+        * a search entry
+        */
+       if ( ci && rs->sr_type == REP_SEARCH ) {
+               Entry *new = NULL;
+               int rc;
+
+               op->o_bd->bd_info = (BackendInfo *)on->on_info;
+
+               for (; ci; ci=ci->ci_next ) {
+                       BerVarray vals = NULL;
+
+                       /* Is our configured entry an ancestor of this one? */
+                       rc = rs->sr_entry->e_nname.bv_len - ci->ci_dn.bv_len;
+                       if ( rc < 1 || strcmp( rs->sr_entry->e_nname.bv_val + rc,
+                               ci->ci_dn.bv_val )) continue;
+
+                       /* Extract the values of the desired attribute from
+                        * the ancestor entry
+                        */
+                       rc = backend_attribute( op, NULL, &ci->ci_dn, ci->ci_ad, &vals );
+
+                       /* If there are any values, merge them into the
+                        * current entry
+                        */
+                       if ( vals ) {
+                               /* The current entry may live in a cache, so
+                                * don't modify it directly. Make a copy and
+                                * work with that instead.
+                                */
+                               if ( !new ) {
+                                       new = entry_dup( rs->sr_entry );
+                               }
+                               attr_merge( new, ci->ci_ad, vals, NULL );
+                               ber_bvarray_free_x( vals, op->o_tmpmemctx );
+                       }
+               }
+
+               if ( new ) {
+                       rs->sr_entry = new;
+                       rs->sr_flags |= REP_ENTRY_MUSTBEFREED;
+               }
+       }
+       /* Default is to just fall through to the normal processing */
+       return SLAP_CB_CONTINUE;
+}
+
+static int collect_config(
+    BackendDB  *be,
+    const char *fname,
+    int                lineno,
+    int                argc,
+    char       **argv
+)
+{
+       slap_overinst *on = (slap_overinst *) be->bd_info;
+       AttributeDescription *ad = NULL;
+
+       /* The config syntax is "collectinfo <dn> <attribute-description>"
+        * and only one directive may be specified per overlay instance.
+        */
+
+       if ( strcasecmp( argv[0], "collectinfo" ) == 0 ) {
+               collect_info *ci;
+               struct berval bv, dn;
+               const char *text;
+               if ( argc != 3 ) {
+                       Debug( LDAP_DEBUG_ANY,
+               "%s: line %d: argument missing in \"collectinfo <dn> <attribute-description>\" line.\n",
+                       fname, lineno, 0 );
+                       return( 1 );
+               }
+               ber_str2bv( argv[1], 0, 0, &bv );
+               if ( dnNormalize( 0, NULL, NULL, &bv, &dn, NULL ) ) {
+                       Debug( LDAP_DEBUG_ANY,
+               "%s: line %d: invalid DN in \"collectinfo\" line: %s.\n",
+                       fname, lineno, text );
+                       return( 1 );
+               }
+               if ( slap_str2ad( argv[2], &ad, &text ) ) {
+                       Debug( LDAP_DEBUG_ANY,
+               "%s: line %d: attribute description unknown in \"collectinfo\" line: %s.\n",
+                       fname, lineno, text );
+                       return( 1 );
+               }
+
+               /* The on->on_bi.bi_private pointer can be used for
+                * anything this instance of the overlay needs.
+                */
+               ci = ch_malloc( sizeof( collect_info ));
+               ci->ci_ad = ad;
+               ci->ci_dn = dn;
+               ci->ci_next = on->on_bi.bi_private;
+               on->on_bi.bi_private = ci;
+               return 0;
+       }
+       return SLAP_CONF_UNKNOWN;
+}
+
+static slap_overinst collect;
+
+int collect_init() {
+       collect.on_bi.bi_type = "collect";
+       collect.on_bi.bi_db_config = collect_config;
+       collect.on_response = collect_response;
+
+       return overlay_register( &collect );
+}
+
+#if SLAPD_OVER_COLLECT == SLAPD_MOD_DYNAMIC
+int init_module(int argc, char *argv[]) {
+       return collect_init();
+}
+#endif
+
+#endif /* SLAPD_OVER_COLLECT */