Add API call to determine if format capability structure is "empty".

Empty here means that there are no formats in the format_cap structure
or the only format in it is the "none" format.

I've added calls to check the emptiness of a format_cap in a few places
in order to short-circuit operations that would otherwise be pointless
as well as to prevent some assertions from being triggered in cases
where channels with no formats are used.
........

Merged revisions 423414 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@423415 65c4cc65-6c06-0410-ace0-fbb531ad65f3

3 files changed, 25 insertions, 0 deletions

diff --git a/main/channel.c b/main/channel.c
index 4595b5944..477bc815b 100644
--- a/main/channel.c
+++ b/main/channel.c
@@ -5327,6 +5327,11 @@ static int set_format(struct ast_channel *chan, struct ast_format_cap *cap_set,
 	ast_assert(rawformat != NULL);
 
 	cap_native = ast_channel_nativeformats(chan);
+	if (ast_format_cap_empty(cap_native)) {
+		ast_log(LOG_ERROR, "Unable to set format because channel %s supports no formats\n",
+				ast_channel_name(chan));
+		return -1;
+	}
 
 	/* Find a translation path from the native format to one of the desired formats */
 	if (!direction) {
diff --git a/main/format_cap.c b/main/format_cap.c
index 65e469fc1..364c924bf 100644
--- a/main/format_cap.c
+++ b/main/format_cap.c
@@ -700,3 +700,18 @@ const char *ast_format_cap_get_names(struct ast_format_cap *cap, struct ast_str
 
 	return ast_str_buffer(*buf);
 }
+
+int ast_format_cap_empty(struct ast_format_cap *cap)
+{
+	int count = ast_format_cap_count(cap);
+
+	if (count > 1) {
+		return 0;
+	}
+
+	if (count == 0 || AST_VECTOR_GET(&cap->preference_order, 0)->format == ast_format_none) {
+		return 1;
+	}
+
+	return 0;
+}
diff --git a/main/translate.c b/main/translate.c
index 0696f5d83..2778ebccf 100644
--- a/main/translate.c
+++ b/main/translate.c
@@ -1276,6 +1276,11 @@ int ast_translator_best_choice(struct ast_format_cap *dst_cap,
 	int i;
 	int j;
 
+	if (ast_format_cap_empty(dst_cap) || ast_format_cap_empty(src_cap)) {
+		ast_log(LOG_ERROR, "Cannot determine best translation path since one capability supports no formats\n");
+		return -1;
+	}
+
 	if (!(joint_cap = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT))) {
 		return -1;
 	}