audio: add more audio rate control functions

The next patch needs two new rate control functions. The first
one returns the bytes needed at call time to maintain the
selected rate. The second one adjusts the bytes actually sent.

Split the audio_rate_get_bytes() function into these two
functions and reintroduce audio_rate_get_bytes().

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20220923183640.8314-5-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

audio/audio.c

@@ -2251,26 +2251,39 @@ void audio_rate_start(RateCtl *rate)
     rate->start_ticks = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 }
 
-size_t audio_rate_get_bytes(struct audio_pcm_info *info, RateCtl *rate,
-                            size_t bytes_avail)
+size_t audio_rate_peek_bytes(RateCtl *rate, struct audio_pcm_info *info)
 {
     int64_t now;
     int64_t ticks;
     int64_t bytes;
-    int64_t samples;
-    size_t ret;
+    int64_t frames;
 
     now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     ticks = now - rate->start_ticks;
     bytes = muldiv64(ticks, info->bytes_per_second, NANOSECONDS_PER_SECOND);
-    samples = (bytes - rate->bytes_sent) / info->bytes_per_frame;
-    if (samples < 0 || samples > 65536) {
-        AUD_log(NULL, "Resetting rate control (%" PRId64 " samples)\n", samples);
+    frames = (bytes - rate->bytes_sent) / info->bytes_per_frame;
+    if (frames < 0 || frames > 65536) {
+        AUD_log(NULL, "Resetting rate control (%" PRId64 " frames)\n", frames);
         audio_rate_start(rate);
-        samples = 0;
+        frames = 0;
     }
 
-    ret = MIN(samples * info->bytes_per_frame, bytes_avail);
-    rate->bytes_sent += ret;
-    return ret;
+    return frames * info->bytes_per_frame;
+}
+
+void audio_rate_add_bytes(RateCtl *rate, size_t bytes_used)
+{
+    rate->bytes_sent += bytes_used;
+}
+
+size_t audio_rate_get_bytes(struct audio_pcm_info *info, RateCtl *rate,
+                            size_t bytes_avail)
+{
+    size_t bytes;
+
+    bytes = audio_rate_peek_bytes(rate, info);
+    bytes = MIN(bytes, bytes_avail);
+    audio_rate_add_bytes(rate, bytes);
+
+    return bytes;
 }

audio/audio_int.h

@@ -263,6 +263,8 @@ typedef struct RateCtl {
 } RateCtl;
 
 void audio_rate_start(RateCtl *rate);
+size_t audio_rate_peek_bytes(RateCtl *rate, struct audio_pcm_info *info);
+void audio_rate_add_bytes(RateCtl *rate, size_t bytes_used);
 size_t audio_rate_get_bytes(struct audio_pcm_info *info, RateCtl *rate,
                             size_t bytes_avail);