audio: handle buf == NULL in put_buffer_out()

With the next patch all audio backends put_buffer_out() functions
have to handle the buf == NULL case, provided the get_buffer_out()
function may return buf = NULL and size > 0.

It turns out that all audio backends get_buffer_out() functions
either can't return buf = NULL or return buf = NULL and size = 0
at the same time. The only exception is the spiceaudio backend
where size may be uninitialized.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20200920171729.15861-1-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/audio/spiceaudio.c b/audio/spiceaudio.c
index b6b5da4812..c8d81ba442 100644
--- a/audio/spiceaudio.c
+++ b/audio/spiceaudio.c
@@ -135,6 +135,7 @@ static void *line_out_get_buffer(HWVoiceOut *hw, size_t *size)
             (out->fsize - out->fpos) * hw->info.bytes_per_frame);
     } else {
         audio_rate_start(&out->rate);
+        *size = LINE_OUT_SAMPLES << 2;
     }
     return out->frame + out->fpos;
 }
@@ -143,12 +144,14 @@ static size_t line_out_put_buffer(HWVoiceOut *hw, void *buf, size_t size)
 {
     SpiceVoiceOut *out = container_of(hw, SpiceVoiceOut, hw);
 
-    assert(buf == out->frame + out->fpos && out->fpos <= out->fsize);
-    out->fpos += size >> 2;
+    if (buf) {
+        assert(buf == out->frame + out->fpos && out->fpos <= out->fsize);
+        out->fpos += size >> 2;
 
-    if (out->fpos == out->fsize) { /* buffer full */
-        spice_server_playback_put_samples(&out->sin, out->frame);
-        out->frame = NULL;
+        if (out->fpos == out->fsize) { /* buffer full */
+            spice_server_playback_put_samples(&out->sin, out->frame);
+            out->frame = NULL;
+        }
     }
 
     return size;