pbx.c

	if (!chan)
		return -2;

	goto_func = (async) ? ast_async_goto : ast_explicit_goto;
	if (ast_exists_extension(chan, context ? context : chan->context,
				 exten ? exten : chan->exten, priority,
				 chan->cid.cid_num))
		return goto_func(chan, context ? context : chan->context,
				 exten ? exten : chan->exten, priority);
	else 
		return -3;
}

int ast_goto_if_exists(struct ast_channel *chan, const char* context, const char *exten, int priority) {
	return __ast_goto_if_exists(chan, context, exten, priority, 0);
}

int ast_async_goto_if_exists(struct ast_channel *chan, const char * context, const char *exten, int priority) {
	return __ast_goto_if_exists(chan, context, exten, priority, 1);
}

int ast_parseable_goto(struct ast_channel *chan, const char *goto_string) 
{
	char *s;
	char *exten, *pri, *context;
	char *stringp=NULL;
	int ipri;
	int mode = 0;

	if (ast_strlen_zero(goto_string)) {
		ast_log(LOG_WARNING, "Goto requires an argument (optional context|optional extension|priority)\n");
		return -1;
	}
	s = ast_strdupa(goto_string);
	stringp=s;
	context = strsep(&stringp, "|");
	exten = strsep(&stringp, "|");
	if (!exten) {
		/* Only a priority in this one */
		pri = context;
		exten = NULL;
		context = NULL;
	} else {
		pri = strsep(&stringp, "|");
		if (!pri) {
			/* Only an extension and priority in this one */
			pri = exten;
			exten = context;
			context = NULL;
		}
	}
	if (*pri == '+') {
		mode = 1;
		pri++;
	} else if (*pri == '-') {
		mode = -1;
		pri++;
	}
	if (sscanf(pri, "%d", &ipri) != 1) {
		if ((ipri = ast_findlabel_extension(chan, context ? context : chan->context, (exten && strcasecmp(exten, "BYEXTENSION")) ? exten : chan->exten, 
			pri, chan->cid.cid_num)) < 1) {
			ast_log(LOG_WARNING, "Priority '%s' must be a number > 0, or valid label\n", pri);
			return -1;
		} else
			mode = 0;
	} 
	/* At this point we have a priority and maybe an extension and a context */

	if (exten && !strcasecmp(exten, "BYEXTENSION"))
		exten = NULL;

	if (mode) 
		ipri = chan->priority + (ipri * mode);

	ast_explicit_goto(chan, context, exten, ipri);
	ast_cdr_update(chan);
	return 0;

}