PUBSUB command implemented.

Currently it implements three subcommands:

PUBSUB CHANNELS [<pattern>]    List channels with non-zero subscribers.
PUBSUB NUMSUB [channel_1 ...]  List number of subscribers for channels.
PUBSUB NUMPAT                  Return number of subscribed patterns.

src/pubsub.c

@@ -308,3 +308,50 @@ void publishCommand(redisClient *c) {
     int receivers = pubsubPublishMessage(c->argv[1],c->argv[2]);
     addReplyLongLong(c,receivers);
 }
+
+/* PUBSUB command for Pub/Sub introspection. */
+void pubsubCommand(redisClient *c) {
+    if (!strcasecmp(c->argv[1]->ptr,"channels") &&
+        (c->argc == 2 || c->argc ==3))
+    {
+        /* PUBSUB CHANNELS [<pattern>] */
+        sds pat = (c->argc == 2) ? NULL : c->argv[2]->ptr;
+        dictIterator *di = dictGetIterator(server.pubsub_channels);
+        dictEntry *de;
+        long mblen = 0;
+        void *replylen;
+
+        replylen = addDeferredMultiBulkLength(c);
+        while((de = dictNext(di)) != NULL) {
+            robj *cobj = dictGetKey(de);
+            sds channel = cobj->ptr;
+
+            if (!pat || stringmatchlen(pat, sdslen(pat),
+                                       channel, sdslen(channel),0))
+            {
+                addReplyBulk(c,cobj);
+                mblen++;
+            }
+        }
+        dictReleaseIterator(di);
+        setDeferredMultiBulkLength(c,replylen,mblen);
+    } else if (!strcasecmp(c->argv[1]->ptr,"numsub") && c->argc > 2) {
+        /* PUBSUB NUMSUB Channel_1 [... Channel_N] */
+        int j;
+
+        addReplyMultiBulkLen(c,(c->argc-2)*2);
+        for (j = 2; j < c->argc; j++) {
+            list *l = dictFetchValue(server.pubsub_channels,c->argv[j]);
+
+            addReplyBulk(c,c->argv[j]);
+            addReplyBulkLongLong(c,l ? listLength(l) : 0);
+        }
+    } else if (!strcasecmp(c->argv[1]->ptr,"numpat") && c->argc == 2) {
+        /* PUBSUB NUMPAT */
+        addReplyLongLong(c,listLength(server.pubsub_patterns));
+    } else {
+        addReplyErrorFormat(c,
+            "Unknown PUBSUB subcommand or wrong number of arguments for '%s'",
+            (char*)c->argv[1]->ptr);
+    }
+}

src/redis.c

@@ -238,6 +238,7 @@ struct redisCommand redisCommandTable[] = {
     {"psubscribe",psubscribeCommand,-2,"rpslt",0,NULL,0,0,0,0,0},
     {"punsubscribe",punsubscribeCommand,-1,"rpslt",0,NULL,0,0,0,0,0},
     {"publish",publishCommand,3,"pfltr",0,NULL,0,0,0,0,0},
+    {"pubsub",pubsubCommand,-2,"pltrR",0,NULL,0,0,0,0,0},
     {"watch",watchCommand,-2,"rs",0,noPreloadGetKeys,1,-1,1,0,0},
     {"unwatch",unwatchCommand,1,"rs",0,NULL,0,0,0,0,0},
     {"restore",restoreCommand,4,"awm",0,NULL,1,1,1,0,0},

src/redis.h

@@ -1277,6 +1277,7 @@ void unsubscribeCommand(redisClient *c);
 void psubscribeCommand(redisClient *c);
 void punsubscribeCommand(redisClient *c);
 void publishCommand(redisClient *c);
+void pubsubCommand(redisClient *c);
 void watchCommand(redisClient *c);
 void unwatchCommand(redisClient *c);
 void restoreCommand(redisClient *c);