broadcast: Added option to replace a specific index

We are wasting way too much time looking for announcements and updates
in the broadcast. We can just hint where to find the message to be
evicted and safe the traversal.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

gossipd/broadcast.c

@@ -22,6 +22,28 @@ static struct queued_message *new_queued_message(tal_t *ctx,
 	return msg;
 }
 
+bool replace_broadcast(struct broadcast_state *bstate, u64 *index,
+		       const int type, const u8 *tag, const u8 *payload)
+{
+	struct queued_message *msg;
+	bool evicted = false;
+
+	msg = uintmap_get(&bstate->broadcasts, *index);
+	if (msg && msg->type == type &&
+	    memeq(msg->tag, tal_len(msg->tag), tag, tal_len(tag))) {
+		uintmap_del(&bstate->broadcasts, *index);
+		tal_free(msg);
+		evicted = true;
+	}
+
+	*index = bstate->next_index;
+	/* Now add the message to the queue */
+	msg = new_queued_message(bstate, type, tag, payload);
+	uintmap_add(&bstate->broadcasts, *index, msg);
+	bstate->next_index++;
+	return evicted;
+}
+
 bool queue_broadcast(struct broadcast_state *bstate,
 		     const int type,
 		     const u8 *tag,
@@ -37,7 +59,8 @@ bool queue_broadcast(struct broadcast_state *bstate,
 	for (msg = uintmap_first(&bstate->broadcasts, &index);
 	     msg;
 	     msg = uintmap_after(&bstate->broadcasts, &index)) {
-		if (msg->type == type && memcmp(msg->tag, tag, tal_len(tag)) == 0) {
+		if (msg->type == type &&
+		    memeq(msg->tag, tal_len(msg->tag), tag, tal_len(tag))) {
 			uintmap_del(&bstate->broadcasts, index);
 			tal_free(msg);
 			evicted = true;

gossipd/broadcast.h

@@ -36,6 +36,17 @@ bool queue_broadcast(struct broadcast_state *bstate,
 			     const u8 *tag,
 			     const u8 *payload);
 
+/* Replace a queued message with @index, if it matches the type and
+ * tag for the new message. The new message will be queued with the
+ * next highest index. @index is updated to hold the index of the
+ * newly queued message*/
+bool replace_broadcast(struct broadcast_state *bstate,
+		       u64 *index,
+		       const int type,
+		       const u8 *tag,
+		       const u8 *payload);
+
+
 struct queued_message *next_broadcast_message(struct broadcast_state *bstate, u64 last_index);
 
 #endif /* LIGHTNING_LIGHTNINGD_GOSSIP_BROADCAST_H */