Introduce a new API call ast_channel_search_locked, which iterates through the

channel list calling a caller-defined callback.  The callback returns non-zero
if a match is found.  This should speed up some of the code that I committed
earlier today in chan_sip (which is also updated by this commit).

Reviewed by russellb and kpfleming via ReviewBoard:
	http://reviewboard.digium.com/r/28/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@154429 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -10037,19 +10037,21 @@ static int transmit_state_notify(struct sip_pvt *p, int state, int full, int tim
 			   callee must be dialing the same extension that is being monitored.  Simply dialing
 			   the hint'd device is not sufficient. */
 			if (global_notifycid) {
-				struct ast_channel *caller = NULL;
+				auto int find_calling_channel(struct ast_channel *c);
+				int find_calling_channel(struct ast_channel *c) {
+					return (c->pbx &&
+							(!strcasecmp(c->macroexten, p->exten) || !strcasecmp(c->exten, p->exten)) &&
+							!strcasecmp(c->context, p->context));
+				}
 
-				while ((caller = ast_channel_walk_locked(caller))) {
-					if (caller->pbx &&
-						(!strcasecmp(caller->macroexten, p->exten) || !strcasecmp(caller->exten, p->exten)) &&
-						!strcasecmp(caller->context, p->context)) {
-						local_display = ast_strdupa(caller->cid.cid_name);
-						local_target = ast_strdupa(caller->cid.cid_num);
-						ast_channel_unlock(caller);
-						break;
-					}
+				struct ast_channel *caller = ast_channel_search_locked(find_calling_channel);
+
+				if (caller) {
+					local_display = ast_strdupa(caller->cid.cid_name);
+					local_target = ast_strdupa(caller->cid.cid_num);
 					ast_channel_unlock(caller);
-				}				
+					caller = NULL;
+				}
 			}
 
 			/* We create a fake call-id which the phone will send back in an INVITE

include/asterisk/channel.h

@@ -1177,6 +1177,17 @@ struct ast_channel *ast_get_channel_by_exten_locked(const char *exten, const cha
 struct ast_channel *ast_walk_channel_by_exten_locked(const struct ast_channel *chan, const char *exten,
 						     const char *context);
 
+/*! \brief Search for a channel based on the passed channel matching callback
+ * Search for a channel based on the specified is_match callback, and return the
+ * first channel that we match.  When returned, the channel will be locked.  Note
+ * that the is_match callback is called with the passed channel locked, and should
+ * return 0 if there is no match, and non-zero if there is.
+ * \param is_match callback executed on each channel until non-zero is returned, or we
+ *        run out of channels to search.
+ * \return Returns the matched channel, or NULL if no channel was matched.
+ */
+struct ast_channel *ast_channel_search_locked(int (*is_match)(struct ast_channel *));
+
 /*! ! \brief Waits for a digit
  * \param c channel to wait for a digit on
  * \param ms how many milliseconds to wait

main/channel.c

@@ -1226,6 +1226,24 @@ struct ast_channel *ast_walk_channel_by_exten_locked(const struct ast_channel *c
 	return channel_find_locked(chan, NULL, 0, context, exten);
 }
 
+/*! \brief Search for a channel based on the passed channel matching callback (first match) and return it, locked */
+struct ast_channel *ast_channel_search_locked(int (*is_match)(struct ast_channel *))
+{
+	struct ast_channel *c = NULL;
+
+	AST_RWLIST_RDLOCK(&channels);
+	AST_RWLIST_TRAVERSE(&channels, c, chan_list) {
+		ast_channel_lock(c);
+		if (is_match(c)) {
+			break;
+		}
+		ast_channel_unlock(c);
+	}
+	AST_RWLIST_UNLOCK(&channels);
+
+	return c;
+}
+
 /*! \brief Wait, look for hangups and condition arg */
 int ast_safe_sleep_conditional(struct ast_channel *chan, int ms, int (*cond)(void*), void *data)
 {