AudioBufferProvider comments and cleanup

Add comments about which methods implement the AudioBufferProvider interface.

Simplified the definition of kInvalidPts.  <stdint.h> is very hard to work
with, there seems to be no way to use it reliably to get INT64_MAX without
having a separate source file, which is ugly because it means kInvalidPts
is not a compile-time constant.  So I just deleted AudioBufferProvider.cpp
and used a hard-coded constant instead.

Added a default constructor for Buffer so that the fields aren't random
(especially .raw which is used to determine if the buffer is valid).

Make the pts for getNextBuffer default to kInvalidPTS so code that
doesn't need a pts doesn't have to specify a value.

Rename the parameter to AudioMixer::setBufferProvider to make it clearer.

Change-Id: I87e7290884d4ed975b019f62d1ab6ae2bc5065a5

Author: gkasten

services/audioflinger/Android.mk

@@ -7,7 +7,6 @@ LOCAL_SRC_FILES:=               \
     AudioMixer.cpp.arm          \
     AudioResampler.cpp.arm      \
     AudioPolicyService.cpp      \
-    AudioBufferProvider.cpp     \
     ServiceUtilities.cpp
 #   AudioResamplerSinc.cpp.arm
 #   AudioResamplerCubic.cpp.arm

services/audioflinger/AudioBufferProvider.cpp

@@ -17,8 +17,6 @@
 #ifndef ANDROID_AUDIO_BUFFER_PROVIDER_H
 #define ANDROID_AUDIO_BUFFER_PROVIDER_H
 
-#include <stdint.h>
-#include <sys/types.h>
 #include <utils/Errors.h>
 
 namespace android {
@@ -29,6 +27,7 @@ class AudioBufferProvider
 public:
 
     struct Buffer {
+        Buffer() : raw(NULL), frameCount(0) { }
         union {
             void*       raw;
             short*      i16;
@@ -40,12 +39,12 @@ class AudioBufferProvider
     virtual ~AudioBufferProvider() {}
 
     // value representing an invalid presentation timestamp
-    static const int64_t kInvalidPTS;
+    static const int64_t kInvalidPTS = 0x7FFFFFFFFFFFFFFFLL;    // <stdint.h> is too painful
 
     // pts is the local time when the next sample yielded by getNextBuffer
     // will be rendered.
     // Pass kInvalidPTS if the PTS is unknown or not applicable.
-    virtual status_t getNextBuffer(Buffer* buffer, int64_t pts) = 0;
+    virtual status_t getNextBuffer(Buffer* buffer, int64_t pts = kInvalidPTS) = 0;
 
     virtual void releaseBuffer(Buffer* buffer) = 0;
 };

services/audioflinger/AudioBufferProvider.h

@@ -2891,8 +2891,7 @@ bool AudioFlinger::DirectOutputThread::threadLoop()
             // output audio to hardware
             while (frameCount) {
                 buffer.frameCount = frameCount;
-                activeTrack->getNextBuffer(&buffer,
-                                           AudioBufferProvider::kInvalidPTS);
+                activeTrack->getNextBuffer(&buffer);
                 if (CC_UNLIKELY(buffer.raw == NULL)) {
                     memset(curBuf, 0, frameCount * mFrameSize);
                     break;
@@ -3398,11 +3397,14 @@ AudioFlinger::ThreadBase::TrackBase::~TrackBase()
     }
 }
 
+// AudioBufferProvider interface
+// getNextBuffer() = 0;
+// This implementation of releaseBuffer() is used by Track and RecordTrack, but not TimedTrack
 void AudioFlinger::ThreadBase::TrackBase::releaseBuffer(AudioBufferProvider::Buffer* buffer)
 {
     buffer->raw = NULL;
     mFrameCount = buffer->frameCount;
-    step();
+    (void) step();      // ignore return value of step()
     buffer->frameCount = 0;
 }
 
@@ -3548,6 +3550,7 @@ void AudioFlinger::PlaybackThread::Track::dump(char* buffer, size_t size)
             (int)mAuxBuffer);
 }
 
+// AudioBufferProvider interface
 status_t AudioFlinger::PlaybackThread::Track::getNextBuffer(
     AudioBufferProvider::Buffer* buffer, int64_t pts)
 {
@@ -4096,6 +4099,7 @@ void AudioFlinger::PlaybackThread::TimedTrack::timedYieldSilence(
     mTimedAudioOutputOnTime = false;
 }
 
+// AudioBufferProvider interface
 void AudioFlinger::PlaybackThread::TimedTrack::releaseBuffer(
     AudioBufferProvider::Buffer* buffer) {
 
@@ -4181,6 +4185,7 @@ AudioFlinger::RecordThread::RecordTrack::~RecordTrack()
     }
 }
 
+// AudioBufferProvider interface
 status_t AudioFlinger::RecordThread::RecordTrack::getNextBuffer(AudioBufferProvider::Buffer* buffer, int64_t pts)
 {
     audio_track_cblk_t* cblk = this->cblk();
@@ -4868,8 +4873,7 @@ bool AudioFlinger::RecordThread::threadLoop()
             }
 
             buffer.frameCount = mFrameCount;
-            if (CC_LIKELY(mActiveTrack->getNextBuffer(
-                    &buffer, AudioBufferProvider::kInvalidPTS) == NO_ERROR)) {
+            if (CC_LIKELY(mActiveTrack->getNextBuffer(&buffer) == NO_ERROR)) {
                 size_t framesOut = buffer.frameCount;
                 if (mResampler == NULL) {
                     // no resampling
@@ -5147,6 +5151,7 @@ status_t AudioFlinger::RecordThread::dump(int fd, const Vector<String16>& args)
     return NO_ERROR;
 }
 
+// AudioBufferProvider interface
 status_t AudioFlinger::RecordThread::getNextBuffer(AudioBufferProvider::Buffer* buffer, int64_t pts)
 {
     size_t framesReq = buffer->frameCount;
@@ -5185,6 +5190,7 @@ status_t AudioFlinger::RecordThread::getNextBuffer(AudioBufferProvider::Buffer*
     return NO_ERROR;
 }
 
+// AudioBufferProvider interface
 void AudioFlinger::RecordThread::releaseBuffer(AudioBufferProvider::Buffer* buffer)
 {
     mRsmpInIndex += buffer->frameCount;

services/audioflinger/AudioFlinger.cpp

@@ -346,9 +346,8 @@ class AudioFlinger :
                                 TrackBase(const TrackBase&);
                                 TrackBase& operator = (const TrackBase&);
 
-            virtual status_t getNextBuffer(
-                AudioBufferProvider::Buffer* buffer,
-                int64_t pts) = 0;
+            // AudioBufferProvider interface
+            virtual status_t getNextBuffer(AudioBufferProvider::Buffer* buffer, int64_t pts) = 0;
             virtual void releaseBuffer(AudioBufferProvider::Buffer* buffer);
 
             audio_format_t format() const {
@@ -634,9 +633,10 @@ class AudioFlinger :
                                 Track(const Track&);
                                 Track& operator = (const Track&);
 
-            virtual status_t getNextBuffer(
-                AudioBufferProvider::Buffer* buffer,
-                int64_t pts);
+            // AudioBufferProvider interface
+            virtual status_t getNextBuffer(AudioBufferProvider::Buffer* buffer, int64_t pts = kInvalidPTS);
+            // releaseBuffer() not overridden
+
             virtual uint32_t framesReady() const;
 
             bool isMuted() const { return mMute; }
@@ -703,9 +703,10 @@ class AudioFlinger :
 
             virtual uint32_t framesReady() const;
 
-            virtual status_t getNextBuffer(AudioBufferProvider::Buffer* buffer,
-                                           int64_t pts);
+            // AudioBufferProvider interface
+            virtual status_t getNextBuffer(AudioBufferProvider::Buffer* buffer, int64_t pts);
             virtual void releaseBuffer(AudioBufferProvider::Buffer* buffer);
+
             void timedYieldSamples(AudioBufferProvider::Buffer* buffer);
             void timedYieldSilence(uint32_t numFrames,
                                    AudioBufferProvider::Buffer* buffer);
@@ -1067,9 +1068,9 @@ class AudioFlinger :
                                 RecordTrack(const RecordTrack&);
                                 RecordTrack& operator = (const RecordTrack&);
 
-            virtual status_t getNextBuffer(
-                AudioBufferProvider::Buffer* buffer,
-                int64_t pts);
+            // AudioBufferProvider interface
+            virtual status_t getNextBuffer(AudioBufferProvider::Buffer* buffer, int64_t pts = kInvalidPTS);
+            // releaseBuffer() not overridden
 
             bool                mOverflow;
         };
@@ -1106,9 +1107,10 @@ class AudioFlinger :
                 AudioStreamIn* clearInput();
                 virtual audio_stream_t* stream();
 
-        virtual status_t    getNextBuffer(AudioBufferProvider::Buffer* buffer,
-                                          int64_t pts);
+        // AudioBufferProvider interface
+        virtual status_t    getNextBuffer(AudioBufferProvider::Buffer* buffer, int64_t pts);
         virtual void        releaseBuffer(AudioBufferProvider::Buffer* buffer);
+
         virtual bool        checkForNewParameters_l();
         virtual String8     getParameters(const String8& keys);
         virtual void        audioConfigChanged_l(int event, int param = 0);

services/audioflinger/AudioFlinger.h

@@ -332,11 +332,11 @@ size_t AudioMixer::getUnreleasedFrames(int name) const
     return 0;
 }
 
-void AudioMixer::setBufferProvider(int name, AudioBufferProvider* buffer)
+void AudioMixer::setBufferProvider(int name, AudioBufferProvider* bufferProvider)
 {
     name -= TRACK0;
     assert(uint32_t(name) < MAX_NUM_TRACKS);
-    mState.tracks[name].bufferProvider = buffer;
+    mState.tracks[name].bufferProvider = bufferProvider;
 }