AudioTrackShared: Move framesReadySafe to ServerProxy

Allows common use for latency computation.
Implementation for AudioRecordServerProxy added.

Test: audio sanity, subsequent latency tests
Bug: 80447764
Change-Id: Ib53181cdced16606bf268769a04bd52c689d89d3

include/private/media/AudioTrackShared.h

@@ -555,6 +555,9 @@ public:
     // Total count of the number of flushed frames since creation (never reset).
     virtual int64_t     framesFlushed() const { return mFlushed; }
 
+    // Safe frames ready query with no side effects.
+    virtual size_t      framesReadySafe() const = 0;
+
     // Get dynamic buffer size from the shared control block.
     uint32_t            getBufferSizeInFrames() const {
         return android_atomic_acquire_load((int32_t *)&mCblk->mBufferSizeInFrames);
@@ -592,8 +595,7 @@ public:
     // which may include non-contiguous frames
     virtual size_t      framesReady();
 
-    // Safe frames ready query used by dump() - this has no side effects.
-    virtual size_t      framesReadySafe() const;
+    size_t              framesReadySafe() const override; // frames available to read by server.
 
     // Currently AudioFlinger will call framesReady() for a fast track from two threads:
     // FastMixer thread, and normal mixer thread.  This is dangerous, as the proxy is intended
@@ -697,6 +699,8 @@ public:
         return mCblk->u.mStreaming.mRear; // For completeness only; mRear written by server.
     }
 
+    size_t framesReadySafe() const override; // frames available to read by client.
+
 protected:
     virtual ~AudioRecordServerProxy() { }
 };

media/libaudioclient/AudioTrackShared.cpp

@@ -1231,6 +1231,21 @@ int32_t StaticAudioTrackServerProxy::getRear() const
     return 0;
 }
 
+__attribute__((no_sanitize("integer")))
+size_t AudioRecordServerProxy::framesReadySafe() const
+{
+    if (mIsShutdown) {
+        return 0;
+    }
+    const int32_t front = android_atomic_acquire_load(&mCblk->u.mStreaming.mFront);
+    const int32_t rear = mCblk->u.mStreaming.mRear;
+    const ssize_t filled = rear - front;
+    if (!(0 <= filled && (size_t) filled <= mFrameCount)) {
+        return 0; // error condition, silently return 0.
+    }
+    return filled;
+}
+
 // ---------------------------------------------------------------------------
 
 }   // namespace android