audio/dsound: fix invalid parameters error

Windows (unlike wine) bails out when IDirectSoundBuffer8::Lock is called
with zero length.  Also, hw->pos_emul handling was incorrect when
calling this function for the first time.

Signed-off-by: Kővágó, Zoltán <DirtY.iCE.hu@gmail.com>
Reported-by: KJ Liew <liewkj@yahoo.com>
Tested-by: Howard Spoelstra <hsp.cat7@gmail.com>
Message-id: fe9744216d9d421a2dbb09bcf5fa0dbd18f77ac5.1580684275.git.DirtY.iCE.hu@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

audio/audio.c

@@ -1076,10 +1076,8 @@ static size_t audio_pcm_hw_run_out(HWVoiceOut *hw, size_t live)
     while (live) {
         size_t size, decr, proc;
         void *buf = hw->pcm_ops->get_buffer_out(hw, &size);
-        if (!buf) {
-            /* retrying will likely won't help, drop everything. */
-            hw->mix_buf->pos = (hw->mix_buf->pos + live) % hw->mix_buf->size;
-            return clipped + live;
+        if (!buf || size == 0) {
+            break;
         }
 
         decr = MIN(size / hw->info.bytes_per_frame, live);

audio/dsound_template.h

@@ -244,6 +244,7 @@ static int dsound_init_out(HWVoiceOut *hw, struct audsettings *as,
         goto fail0;
     }
 
+    ds->first_time = true;
     obt_as.endianness = 0;
     audio_pcm_init_info (&hw->info, &obt_as);
 

audio/dsoundaudio.c

@@ -53,12 +53,14 @@ typedef struct {
 typedef struct {
     HWVoiceOut hw;
     LPDIRECTSOUNDBUFFER dsound_buffer;
+    bool first_time;
     dsound *s;
 } DSoundVoiceOut;
 
 typedef struct {
     HWVoiceIn hw;
     LPDIRECTSOUNDCAPTUREBUFFER dsound_capture_buffer;
+    bool first_time;
     dsound *s;
 } DSoundVoiceIn;
 
@@ -414,21 +416,32 @@ static void *dsound_get_buffer_out(HWVoiceOut *hw, size_t *size)
     DSoundVoiceOut *ds = (DSoundVoiceOut *) hw;
     LPDIRECTSOUNDBUFFER dsb = ds->dsound_buffer;
     HRESULT hr;
-    DWORD ppos, act_size;
+    DWORD ppos, wpos, act_size;
     size_t req_size;
     int err;
     void *ret;
 
-    hr = IDirectSoundBuffer_GetCurrentPosition(dsb, &ppos, NULL);
+    hr = IDirectSoundBuffer_GetCurrentPosition(
+        dsb, &ppos, ds->first_time ? &wpos : NULL);
     if (FAILED(hr)) {
         dsound_logerr(hr, "Could not get playback buffer position\n");
         *size = 0;
         return NULL;
     }
 
+    if (ds->first_time) {
+        hw->pos_emul = wpos;
+        ds->first_time = false;
+    }
+
     req_size = audio_ring_dist(ppos, hw->pos_emul, hw->size_emul);
     req_size = MIN(req_size, hw->size_emul - hw->pos_emul);
 
+    if (req_size == 0) {
+        *size = 0;
+        return NULL;
+    }
+
     err = dsound_lock_out(dsb, &hw->info, hw->pos_emul, req_size, &ret, NULL,
                           &act_size, NULL, false, ds->s);
     if (err) {
@@ -508,18 +521,24 @@ static void *dsound_get_buffer_in(HWVoiceIn *hw, size_t *size)
     DSoundVoiceIn *ds = (DSoundVoiceIn *) hw;
     LPDIRECTSOUNDCAPTUREBUFFER dscb = ds->dsound_capture_buffer;
     HRESULT hr;
-    DWORD cpos, act_size;
+    DWORD cpos, rpos, act_size;
     size_t req_size;
     int err;
     void *ret;
 
-    hr = IDirectSoundCaptureBuffer_GetCurrentPosition(dscb, &cpos, NULL);
+    hr = IDirectSoundCaptureBuffer_GetCurrentPosition(
+        dscb, &cpos, ds->first_time ? &rpos : NULL);
     if (FAILED(hr)) {
         dsound_logerr(hr, "Could not get capture buffer position\n");
         *size = 0;
         return NULL;
     }
 
+    if (ds->first_time) {
+        hw->pos_emul = rpos;
+        ds->first_time = false;
+    }
+
     req_size = audio_ring_dist(cpos, hw->pos_emul, hw->size_emul);
     req_size = MIN(req_size, hw->size_emul - hw->pos_emul);