WIP: Add cubeb_stream_get_max_request_size API.

This is intended to support mozilla/audioipc#124

include/cubeb/cubeb.h

@@ -607,6 +607,7 @@ cubeb_stream_get_latency(cubeb_stream * stream, uint32_t * latency);
     @retval CUBEB_ERROR */
 CUBEB_EXPORT int
 cubeb_stream_get_input_latency(cubeb_stream * stream, uint32_t * latency);
+
 /** Set the volume for a stream.
     @param stream the stream for which to adjust the volume.
     @param volume a float between 0.0 (muted) and 1.0 (maximum volume)
@@ -637,6 +638,20 @@ CUBEB_EXPORT int
 cubeb_stream_get_current_device(cubeb_stream * stm,
                                 cubeb_device ** const device);
 
+/** Get the maximum request size for this stream in frames.  This is the largest
+    value that will be presented or requested via `data_callback`'s `nframes`
+   parameter. Note: This value may change if the stream is automatically
+   reconfigured due to device changes. Callers of this API should use
+   cubeb_stream_register_device_changed_callback to monitor device changes and
+   requery this API after a device change.
+    @param stream the stream for which to retrieve max request size.
+    @param max_request_size the max request size in frames.
+    @retval CUBEB_OK
+    @retval CUBEB_ERROR_NOT_SUPPORTED */
+CUBEB_EXPORT int
+cubeb_stream_get_max_request_size(cubeb_stream * stream,
+                                  uint32_t * max_request_size);
+
 /** Destroy a cubeb_device structure.
     @param stream the stream passed in cubeb_stream_get_current_device
     @param devices the devices to destroy

src/cubeb-internal.h

@@ -66,6 +66,8 @@ struct cubeb_ops {
   int (*stream_register_device_changed_callback)(
       cubeb_stream * stream,
       cubeb_device_changed_callback device_changed_callback);
+  int (*stream_get_max_request_size)(cubeb_stream * stream,
+                                     uint32_t * max_request_size);
   int (*register_device_collection_changed)(
       cubeb * context, cubeb_device_type devtype,
       cubeb_device_collection_changed_callback callback, void * user_ptr);

src/cubeb.c

@@ -500,6 +500,22 @@ cubeb_stream_get_current_device(cubeb_stream * stream,
   return stream->context->ops->stream_get_current_device(stream, device);
 }
 
+int
+cubeb_stream_get_max_request_size(cubeb_stream * stream,
+                                  uint32_t * max_request_size)
+{
+  if (!stream || !max_request_size) {
+    return CUBEB_ERROR_INVALID_PARAMETER;
+  }
+
+  if (!stream->context->ops->stream_get_max_request_size) {
+    return CUBEB_ERROR_NOT_SUPPORTED;
+  }
+
+  return stream->context->ops->stream_get_max_request_size(stream,
+                                                           max_request_size);
+}
+
 int
 cubeb_stream_device_destroy(cubeb_stream * stream, cubeb_device * device)
 {

src/cubeb_aaudio.cpp

@@ -1460,6 +1460,7 @@ const static struct cubeb_ops aaudio_ops = {
     /*.stream_get_current_device =*/NULL,
     /*.stream_device_destroy =*/NULL,
     /*.stream_register_device_changed_callback =*/NULL,
+    /*.stream_get_max_request_size =*/NULL,
     /*.register_device_collection_changed =*/NULL};
 
 extern "C" /*static*/ int

src/cubeb_alsa.c

@@ -1487,4 +1487,5 @@ static struct cubeb_ops const alsa_ops = {
     .stream_get_current_device = NULL,
     .stream_device_destroy = NULL,
     .stream_register_device_changed_callback = NULL,
+    .stream_get_max_request_size = NULL,
     .register_device_collection_changed = NULL};

src/cubeb_audiounit.cpp

@@ -3666,5 +3666,6 @@ cubeb_ops const audiounit_ops = {
     /*.stream_device_destroy =*/audiounit_stream_device_destroy,
     /*.stream_register_device_changed_callback =*/
     audiounit_stream_register_device_changed_callback,
+    /*.stream_get_max_request_size = */ NULL,
     /*.register_device_collection_changed =*/
     audiounit_register_device_collection_changed};

src/cubeb_jack.cpp

@@ -175,6 +175,7 @@ static struct cubeb_ops const cbjack_ops = {
     .stream_get_current_device = cbjack_stream_get_current_device,
     .stream_device_destroy = cbjack_stream_device_destroy,
     .stream_register_device_changed_callback = NULL,
+    .stream_get_max_request_size = NULL,
     .register_device_collection_changed = NULL};
 
 struct cubeb_stream {

src/cubeb_kai.c

@@ -366,4 +366,5 @@ static struct cubeb_ops const kai_ops = {
     /*.stream_get_current_device =*/NULL,
     /*.stream_device_destroy =*/NULL,
     /*.stream_register_device_changed_callback=*/NULL,
+    /*.stream_get_max_request_size =*/NULL,
     /*.register_device_collection_changed=*/NULL};

src/cubeb_opensl.c

@@ -1792,4 +1792,5 @@ static struct cubeb_ops const opensl_ops = {
     .stream_get_current_device = NULL,
     .stream_device_destroy = NULL,
     .stream_register_device_changed_callback = NULL,
+    .stream_get_max_request_size = NULL,
     .register_device_collection_changed = NULL};

src/cubeb_oss.c

@@ -1326,4 +1326,5 @@ static struct cubeb_ops const oss_ops = {
     .stream_get_current_device = oss_get_current_device,
     .stream_device_destroy = oss_stream_device_destroy,
     .stream_register_device_changed_callback = NULL,
+    .stream_get_max_request_size = NULL,
     .register_device_collection_changed = NULL};

src/cubeb_pulse.c

@@ -1696,5 +1696,6 @@ static struct cubeb_ops const pulse_ops = {
     .stream_get_current_device = pulse_stream_get_current_device,
     .stream_device_destroy = pulse_stream_device_destroy,
     .stream_register_device_changed_callback = NULL,
+    .stream_get_max_request_size = NULL,
     .register_device_collection_changed =
         pulse_register_device_collection_changed};

src/cubeb_sndio.c

@@ -666,4 +666,5 @@ static struct cubeb_ops const sndio_ops = {
     .stream_get_current_device = NULL,
     .stream_device_destroy = NULL,
     .stream_register_device_changed_callback = NULL,
+    .stream_get_max_request_size = NULL,
     .register_device_collection_changed = NULL};

src/cubeb_sun.c

@@ -730,4 +730,5 @@ static struct cubeb_ops const sun_ops = {
     .stream_get_current_device = sun_get_current_device,
     .stream_device_destroy = sun_stream_device_destroy,
     .stream_register_device_changed_callback = NULL,
+    .stream_get_max_request_size = NULL,
     .register_device_collection_changed = NULL};

src/cubeb_wasapi.cpp

@@ -2965,6 +2965,23 @@ wasapi_stream_set_volume(cubeb_stream * stm, float volume)
   return CUBEB_OK;
 }
 
+// TODO: Need to implement stream_register_device_changed_callback.
+int
+wasapi_stream_get_max_request_size(cubeb_stream * stm,
+                                   uint32_t * max_request_size)
+{
+  auto_lock lock(stm->stream_reset_lock);
+
+  if (!stm->output_client && !stm->input_client) {
+    return CUBEB_ERROR;
+  }
+
+  *max_request_size =
+      std::max(stm->output_buffer_frame_count, stm->input_buffer_frame_count);
+
+  return CUBEB_OK;
+}
+
 static char const *
 wstr_to_utf8(LPCWSTR str)
 {
@@ -3382,6 +3399,7 @@ cubeb_ops const wasapi_ops = {
     /*.stream_get_current_device =*/NULL,
     /*.stream_device_destroy =*/NULL,
     /*.stream_register_device_changed_callback =*/NULL,
+    /*.stream_get_max_request_size =*/wasapi_stream_get_max_request_size,
     /*.register_device_collection_changed =*/
     wasapi_register_device_collection_changed,
 };

src/cubeb_winmm.c

@@ -1179,4 +1179,5 @@ static struct cubeb_ops const winmm_ops = {
     /*.stream_get_current_device =*/NULL,
     /*.stream_device_destroy =*/NULL,
     /*.stream_register_device_changed_callback=*/NULL,
+    /*.stream_get_max_request_size = */ NULL,
     /*.register_device_collection_changed =*/NULL};