output_api: play() returns a length

The old API required an output plugin to not return until all data
passed to the play() method is consumed.  Some output plugins have to
loop to fulfill that requirement, and may block during that.  Simplify
these, by letting them consume only part of the buffer: make play()
return the length of the consumed data.

1 files changed, 11 insertions, 20 deletions

diff --git a/src/output/alsa_plugin.c b/src/output/alsa_plugin.c
index bbb03e80b..05e097513 100644
--- a/src/output/alsa_plugin.c
+++ b/src/output/alsa_plugin.c
@@ -441,7 +441,7 @@ alsa_close(void *data)
 	mixer_close(ad->mixer);
 }
 
-static bool
+static size_t
 alsa_play(void *data, const char *chunk, size_t size)
 {
 	struct alsa_data *ad = data;
@@ -449,28 +449,19 @@ alsa_play(void *data, const char *chunk, size_t size)
 
 	size /= ad->frame_size;
 
-	while (size > 0) {
+	while (true) {
 		ret = ad->writei(ad->pcm, chunk, size);
-
-		if (ret == -EAGAIN || ret == -EINTR)
-			continue;
-
-		if (ret < 0) {
-			if (alsa_recover(ad, ret) < 0) {
-				g_warning("closing ALSA device \"%s\" due to write "
-					  "error: %s\n",
-					  alsa_device(ad), snd_strerror(-errno));
-				return false;
-			}
-
-			continue;
+		if (ret > 0)
+			return ret * ad->frame_size;
+
+		if (ret < 0 && ret != -EAGAIN && ret != -EINTR &&
+		    alsa_recover(ad, ret) < 0) {
+			g_warning("closing ALSA device \"%s\" due to write "
+				  "error: %s\n",
+				  alsa_device(ad), snd_strerror(-errno));
+			return 0;
 		}
-
-		chunk += ret * ad->frame_size;
-		size -= ret;
 	}
-
-	return true;
 }
 
 const struct audio_output_plugin alsaPlugin = {