Make VideoFrame.Buffer implementations lock-free.

Replaces lock-based implementation with AtomicInteger.

Bug: webrtc:7749
Change-Id: I226093b0af2090c080dfd4f87ed8f33a3f9efbd8
Reviewed-on: https://webrtc-review.googlesource.com/64162
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22798}

sdk/android/BUILD.gn

@@ -725,6 +725,7 @@ dist_jar("libwebrtc") {
 # TODO(sakal): Extract files from this target to releveant subtargets, video, audio etc.
 rtc_android_library("base_java") {
   java_files = [
+    "api/org/webrtc/RefCounted.java",
     "src/java/org/webrtc/CalledByNative.java",
     "src/java/org/webrtc/CalledByNativeUnchecked.java",
     "src/java/org/webrtc/Histogram.java",
@@ -732,6 +733,7 @@ rtc_android_library("base_java") {
     "src/java/org/webrtc/JniHelper.java",
     "src/java/org/webrtc/JNINamespace.java",
     "src/java/org/webrtc/NativeClassQualifiedName.java",
+    "src/java/org/webrtc/RefCountDelegate.java",
     "src/java/org/webrtc/WebRtcClassLoader.java",
   ]
 

sdk/android/api/org/webrtc/JavaI420Buffer.java

@@ -11,6 +11,7 @@
 package org.webrtc;
 
 import java.nio.ByteBuffer;
+import javax.annotation.Nullable;
 import org.webrtc.VideoFrame.I420Buffer;
 
 /** Implementation of VideoFrame.I420Buffer backed by Java direct byte buffers. */
@@ -23,13 +24,10 @@ public class JavaI420Buffer implements VideoFrame.I420Buffer {
   private final int strideY;
   private final int strideU;
   private final int strideV;
-  private final Runnable releaseCallback;
-  private final Object refCountLock = new Object();
-
-  private int refCount;
+  private final RefCountDelegate refCountDelegate;
 
   private JavaI420Buffer(int width, int height, ByteBuffer dataY, int strideY, ByteBuffer dataU,
-      int strideU, ByteBuffer dataV, int strideV, Runnable releaseCallback) {
+      int strideU, ByteBuffer dataV, int strideV, @Nullable Runnable releaseCallback) {
     this.width = width;
     this.height = height;
     this.dataY = dataY;
@@ -38,9 +36,7 @@ public class JavaI420Buffer implements VideoFrame.I420Buffer {
     this.strideY = strideY;
     this.strideU = strideU;
     this.strideV = strideV;
-    this.releaseCallback = releaseCallback;
-
-    this.refCount = 1;
+    this.refCountDelegate = new RefCountDelegate(releaseCallback);
   }
 
   /** Wraps existing ByteBuffers into JavaI420Buffer object without copying the contents. */
@@ -155,18 +151,12 @@ public class JavaI420Buffer implements VideoFrame.I420Buffer {
 
   @Override
   public void retain() {
-    synchronized (refCountLock) {
-      ++refCount;
-    }
+    refCountDelegate.retain();
   }
 
   @Override
   public void release() {
-    synchronized (refCountLock) {
-      if (--refCount == 0 && releaseCallback != null) {
-        releaseCallback.run();
-      }
-    }
+    refCountDelegate.release();
   }
 
   @Override

sdk/android/api/org/webrtc/RefCounted.java

@@ -0,0 +1,28 @@
+/*
+ *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.webrtc;
+
+/**
+ * Interface for ref counted objects in WebRTC. These objects have significant resources that need
+ * to be freed when they are no longer in use. Each objects starts with ref count of one when
+ * created. If a reference is passed as a parameter to a method, the caller has ownesrship of the
+ * object by default - calling release is not necessary unless retain is called.
+ */
+public interface RefCounted {
+  /** Increases ref count by one. */
+  void retain();
+
+  /**
+   * Decreases ref count by one. When the ref count reaches zero, resources related to the object
+   * will be freed.
+   */
+  void release();
+}

sdk/android/api/org/webrtc/VideoFrame.java

@@ -27,8 +27,15 @@ import javax.annotation.Nullable;
  * WebRTC software encoders.
  */
 @JNINamespace("webrtc::jni")
-public class VideoFrame {
-  public interface Buffer {
+public class VideoFrame implements RefCounted {
+  /**
+   * Implements image storage medium. Might be for example an OpenGL texture or a memory region
+   * containing I420-data.
+   *
+   * <p>Reference counting is needed since a video buffer can be shared between multiple VideoSinks,
+   * and the buffer needs to be returned to the VideoSource as soon as all references are gone.
+   */
+  public interface Buffer extends RefCounted {
     /**
      * Resolution of the buffer in pixels.
      */
@@ -42,12 +49,8 @@ public class VideoFrame {
      */
     @CalledByNative("Buffer") I420Buffer toI420();
 
-    /**
-     * Reference counting is needed since a video buffer can be shared between multiple VideoSinks,
-     * and the buffer needs to be returned to the VideoSource as soon as all references are gone.
-     */
-    @CalledByNative("Buffer") void retain();
-    @CalledByNative("Buffer") void release();
+    @Override @CalledByNative("Buffer") void retain();
+    @Override @CalledByNative("Buffer") void release();
 
     /**
      * Crops a region defined by |cropx|, |cropY|, |cropWidth| and |cropHeight|. Scales it to size
@@ -123,6 +126,11 @@ public class VideoFrame {
   private final int rotation;
   private final long timestampNs;
 
+  /**
+   * Constructs a new VideoFrame backed by the given {@code buffer}.
+   *
+   * @note Ownership of the buffer object is tranferred to the new VideoFrame.
+   */
   @CalledByNative
   public VideoFrame(Buffer buffer, int rotation, long timestampNs) {
     if (buffer == null) {
@@ -171,13 +179,12 @@ public class VideoFrame {
     return buffer.getWidth();
   }
 
-  /**
-   * Reference counting of the underlying buffer.
-   */
+  @Override
   public void retain() {
     buffer.retain();
   }
 
+  @Override
   @CalledByNative
   public void release() {
     buffer.release();

sdk/android/src/java/org/webrtc/NV12Buffer.java

@@ -11,6 +11,7 @@
 package org.webrtc;
 
 import java.nio.ByteBuffer;
+import javax.annotation.Nullable;
 
 @JNINamespace("webrtc::jni")
 public class NV12Buffer implements VideoFrame.Buffer {
@@ -19,21 +20,16 @@ public class NV12Buffer implements VideoFrame.Buffer {
   private final int stride;
   private final int sliceHeight;
   private final ByteBuffer buffer;
-  private final Runnable releaseCallback;
-  private final Object refCountLock = new Object();
-
-  private int refCount;
+  private final RefCountDelegate refCountDelegate;
 
   public NV12Buffer(int width, int height, int stride, int sliceHeight, ByteBuffer buffer,
-      Runnable releaseCallback) {
+      @Nullable Runnable releaseCallback) {
     this.width = width;
     this.height = height;
     this.stride = stride;
     this.sliceHeight = sliceHeight;
     this.buffer = buffer;
-    this.releaseCallback = releaseCallback;
-
-    refCount = 1;
+    this.refCountDelegate = new RefCountDelegate(releaseCallback);
   }
 
   @Override
@@ -53,18 +49,12 @@ public class NV12Buffer implements VideoFrame.Buffer {
 
   @Override
   public void retain() {
-    synchronized (refCountLock) {
-      ++refCount;
-    }
+    refCountDelegate.retain();
   }
 
   @Override
   public void release() {
-    synchronized (refCountLock) {
-      if (--refCount == 0 && releaseCallback != null) {
-        releaseCallback.run();
-      }
-    }
+    refCountDelegate.release();
   }
 
   @Override

sdk/android/src/java/org/webrtc/NV21Buffer.java

@@ -11,22 +11,21 @@
 package org.webrtc;
 
 import java.nio.ByteBuffer;
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.annotation.Nullable;
 
 @JNINamespace("webrtc::jni")
 public class NV21Buffer implements VideoFrame.Buffer {
   private final byte[] data;
   private final int width;
   private final int height;
-  private final Runnable releaseCallback;
-  private final Object refCountLock = new Object();
+  private final RefCountDelegate refCountDelegate;
 
-  private int refCount = 1;
-
-  public NV21Buffer(byte[] data, int width, int height, Runnable releaseCallback) {
+  public NV21Buffer(byte[] data, int width, int height, @Nullable Runnable releaseCallback) {
     this.data = data;
     this.width = width;
     this.height = height;
-    this.releaseCallback = releaseCallback;
+    this.refCountDelegate = new RefCountDelegate(releaseCallback);
   }
 
   @Override
@@ -48,18 +47,12 @@ public class NV21Buffer implements VideoFrame.Buffer {
 
   @Override
   public void retain() {
-    synchronized (refCountLock) {
-      ++refCount;
-    }
+    refCountDelegate.retain();
   }
 
   @Override
   public void release() {
-    synchronized (refCountLock) {
-      if (--refCount == 0 && releaseCallback != null) {
-        releaseCallback.run();
-      }
-    }
+    refCountDelegate.release();
   }
 
   @Override

sdk/android/src/java/org/webrtc/RefCountDelegate.java

@@ -0,0 +1,41 @@
+/*
+ *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.webrtc;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.annotation.Nullable;
+
+/**
+ * Implementation of RefCounted that executes a Runnable once the ref count reaches zero.
+ */
+class RefCountDelegate implements RefCounted {
+  private final AtomicInteger refCount = new AtomicInteger(1);
+  private final @Nullable Runnable releaseCallback;
+
+  /**
+   * @param releaseCallback Callback that will be executed once the ref count reaches zero.
+   */
+  public RefCountDelegate(@Nullable Runnable releaseCallback) {
+    this.releaseCallback = releaseCallback;
+  }
+
+  @Override
+  public void retain() {
+    refCount.incrementAndGet();
+  }
+
+  @Override
+  public void release() {
+    if (refCount.decrementAndGet() == 0 && releaseCallback != null) {
+      releaseCallback.run();
+    }
+  }
+}

sdk/android/src/java/org/webrtc/TextureBufferImpl.java

@@ -12,6 +12,8 @@ package org.webrtc;
 
 import android.graphics.Matrix;
 import java.nio.ByteBuffer;
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.annotation.Nullable;
 
 /**
  * Android texture buffer backed by a SurfaceTextureHelper's texture. The buffer calls
@@ -24,20 +26,17 @@ class TextureBufferImpl implements VideoFrame.TextureBuffer {
   private final int id;
   private final Matrix transformMatrix;
   private final SurfaceTextureHelper surfaceTextureHelper;
-  private final Runnable releaseCallback;
-  private final Object refCountLock = new Object();
-  private int refCount;
+  private final RefCountDelegate refCountDelegate;
 
   public TextureBufferImpl(int width, int height, Type type, int id, Matrix transformMatrix,
-      SurfaceTextureHelper surfaceTextureHelper, Runnable releaseCallback) {
+      SurfaceTextureHelper surfaceTextureHelper, @Nullable Runnable releaseCallback) {
     this.width = width;
     this.height = height;
     this.type = type;
     this.id = id;
     this.transformMatrix = transformMatrix;
     this.surfaceTextureHelper = surfaceTextureHelper;
-    this.releaseCallback = releaseCallback;
-    this.refCount = 1; // Creator implicitly holds a reference.
+    this.refCountDelegate = new RefCountDelegate(releaseCallback);
   }
 
   @Override
@@ -72,18 +71,12 @@ class TextureBufferImpl implements VideoFrame.TextureBuffer {
 
   @Override
   public void retain() {
-    synchronized (refCountLock) {
-      ++refCount;
-    }
+    refCountDelegate.retain();
   }
 
   @Override
   public void release() {
-    synchronized (refCountLock) {
-      if (--refCount == 0 && releaseCallback != null) {
-        releaseCallback.run();
-      }
-    }
+    refCountDelegate.release();
   }
 
   @Override