audio: SDL_PutAudioStreamPlanarData should take a channel count.

Fixes #12894.

Author: icculus

examples/audio/05-planar-data/planar-data.c

@@ -65,12 +65,12 @@ SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
             const SDL_FPoint point = { event->button.x, event->button.y };
             if (SDL_PointInRectFloat(&point, &rect_left_button)) {  /* clicked left button? */
                 const Uint8 *planes[] = { left, NULL };  /* specify NULL to say "this specific channel is silent" */
-                SDL_PutAudioStreamPlanarData(stream, (const void * const *) planes, SDL_arraysize(left));
+                SDL_PutAudioStreamPlanarData(stream, (const void * const *) planes, -1, SDL_arraysize(left));
                 SDL_FlushAudioStream(stream);  /* that's all we're playing until it completes. */
                 playing_sound = -1;  /* left is playing */
             } else if (SDL_PointInRectFloat(&point, &rect_right_button)) {  /* clicked right button? */
                 const Uint8 *planes[] = { NULL, right };  /* specify NULL to say "this specific channel is silent" */
-                SDL_PutAudioStreamPlanarData(stream, (const void * const *) planes, SDL_arraysize(right));
+                SDL_PutAudioStreamPlanarData(stream, (const void * const *) planes, -1, SDL_arraysize(right));
                 SDL_FlushAudioStream(stream);  /* that's all we're playing until it completes. */
                 playing_sound = 1;  /* right is playing */
             }

include/SDL3/SDL_audio.h

@@ -1431,6 +1431,14 @@ extern SDL_DECLSPEC bool SDLCALL SDL_PutAudioStreamData(SDL_AudioStream *stream,
  * individual array may be NULL; in this case, silence will be interleaved for
  * that channel.
  *
+ * `num_channels` specifies how many arrays are in `channel_buffers`. This can
+ * be used as a safety to prevent overflow, in case the stream format has
+ * changed elsewhere. If more channels are specified than the current input
+ * spec, they are ignored. If less channels are specified, the missing arrays
+ * are treated as if they are NULL (silence is written to those channels). If
+ * the count is -1, SDL will assume the array count matches the current input
+ * spec.
+ *
  * Note that `num_samples` is the number of _samples per array_. This can also
  * be thought of as the number of _sample frames_ to be queued. A value of 1
  * with stereo arrays will queue two samples to the stream. This is different
@@ -1440,6 +1448,7 @@ extern SDL_DECLSPEC bool SDLCALL SDL_PutAudioStreamData(SDL_AudioStream *stream,
  * \param stream the stream the audio data is being added to.
  * \param channel_buffers a pointer to an array of arrays, one array per
  *                        channel.
+ * \param num_channels the number of arrays in `channel_buffers` or -1.
  * \param num_samples the number of _samples_ per array to write to the
  *                    stream.
  * \returns true on success or false on failure; call SDL_GetError() for more
@@ -1456,7 +1465,7 @@ extern SDL_DECLSPEC bool SDLCALL SDL_PutAudioStreamData(SDL_AudioStream *stream,
  * \sa SDL_GetAudioStreamData
  * \sa SDL_GetAudioStreamQueued
  */
-extern SDL_DECLSPEC bool SDLCALL SDL_PutAudioStreamPlanarData(SDL_AudioStream *stream, const void * const *channel_buffers, int num_samples);
+extern SDL_DECLSPEC bool SDLCALL SDL_PutAudioStreamPlanarData(SDL_AudioStream *stream, const void * const *channel_buffers, int num_channels, int num_samples);
 
 /**
  * Get converted/resampled data from the stream.

src/audio/SDL_audiocvt.c

@@ -910,15 +910,29 @@ GENERIC_INTERLEAVE_WITH_NULLS_FUNCTION(32)
 //GENERIC_INTERLEAVE_WITH_NULLS_FUNCTION(64)   (we don't have any 64-bit audio data types at the moment.)
 #undef GENERIC_INTERLEAVE_WITH_NULLS_FUNCTION
 
-static void InterleaveAudioChannels(void *output, const void * const *channel_buffers, int num_samples, const SDL_AudioSpec *spec)
+static void InterleaveAudioChannels(void *output, const void * const *channel_buffers, int channels, int num_samples, const SDL_AudioSpec *spec)
 {
-    const int channels = spec->channels;
-
     bool have_null_channel = false;
-    for (int i = 0; i < channels; i++) {
-        if (channel_buffers[i] == NULL) {
-            have_null_channel = true;
-            break;
+    const void *channels_full[16];
+
+    // if didn't specify enough channels, pad out a channel array with NULLs.
+    if ((channels >= 0) && (channels < spec->channels)) {
+        have_null_channel = true;
+        SDL_assert(SDL_IsSupportedChannelCount(spec->channels));
+        SDL_assert(spec->channels <= SDL_arraysize(channels_full));
+        SDL_memcpy(channels_full, channel_buffers, channels * sizeof (*channel_buffers));
+        SDL_memset(channels_full + channels, 0, (spec->channels - channels) * sizeof (*channel_buffers));
+        channel_buffers = (const void * const *) channels_full;
+    }
+
+    channels = spec->channels;  // it's either < 0, needs to be clamped to spec->channels, or we just padded it out to spec->channels with channels_full.
+
+    if (!have_null_channel) {
+        for (int i = 0; i < channels; i++) {
+            if (channel_buffers[i] == NULL) {
+                have_null_channel = true;
+                break;
+            }
         }
     }
 
@@ -943,7 +957,7 @@ static void InterleaveAudioChannels(void *output, const void * const *channel_bu
     }
 }
 
-bool SDL_PutAudioStreamPlanarData(SDL_AudioStream *stream, const void * const *channel_buffers, int num_samples)
+bool SDL_PutAudioStreamPlanarData(SDL_AudioStream *stream, const void * const *channel_buffers, int num_channels, int num_samples)
 {
     if (!stream) {
         return SDL_InvalidParamError("stream");
@@ -980,7 +994,7 @@ bool SDL_PutAudioStreamPlanarData(SDL_AudioStream *stream, const void * const *c
 
     const int len = SDL_AUDIO_FRAMESIZE(spec) * num_samples;
     #if DEBUG_AUDIOSTREAM
-    SDL_Log("AUDIOSTREAM: wants to put %d bytes of separated data", len);
+    SDL_Log("AUDIOSTREAM: wants to put %d bytes of planar data", len);
     #endif
 
     // Is the data small enough to just interleave it on the stack and put it through the normal interface?
@@ -999,7 +1013,7 @@ bool SDL_PutAudioStreamPlanarData(SDL_AudioStream *stream, const void * const *c
         callback = FreeAllocatedAudioBuffer;
     }
 
-    InterleaveAudioChannels(data, channel_buffers, num_samples, &spec);
+    InterleaveAudioChannels(data, channel_buffers, num_channels, num_samples, &spec);
 
     // it's okay if the stream format changed on another thread while we didn't hold the lock; PutAudioStreamBufferInternal will notice
     //  and set up a new track with the right format, and the next SDL_PutAudioStreamData will notice that stream->src_spec doesn't

src/dynapi/SDL_dynapi_procs.h

@@ -1283,6 +1283,6 @@ SDL_DYNAPI_PROC(bool,SDL_SetRenderTextureAddressMode,(SDL_Renderer *a,SDL_Textur
 SDL_DYNAPI_PROC(bool,SDL_GetRenderTextureAddressMode,(SDL_Renderer *a,SDL_TextureAddressMode *b,SDL_TextureAddressMode *c),(a,b,c),return)
 SDL_DYNAPI_PROC(SDL_PropertiesID,SDL_GetGPUDeviceProperties,(SDL_GPUDevice *a),(a),return)
 SDL_DYNAPI_PROC(SDL_Renderer*,SDL_CreateGPURenderer,(SDL_Window *a,SDL_GPUShaderFormat b,SDL_GPUDevice **c),(a,b,c),return)
-SDL_DYNAPI_PROC(bool,SDL_PutAudioStreamPlanarData,(SDL_AudioStream *a,const void * const*b,int c),(a,b,c),return)
+SDL_DYNAPI_PROC(bool,SDL_PutAudioStreamPlanarData,(SDL_AudioStream *a,const void * const*b,int c,int d),(a,b,c,d),return)
 SDL_DYNAPI_PROC(bool,SDL_SetAudioIterationCallbacks,(SDL_AudioDeviceID a,SDL_AudioIterationCallback b,SDL_AudioIterationCallback c,void *d),(a,b,c,d),return)
 SDL_DYNAPI_PROC(int,SDL_GetEventDescription,(const SDL_Event *a,char *b,int c),(a,b,c),return)