Coalesce small buffers in net::BidirectionalStream

components/cronet/android/java/src/org/chromium/net/CronetBidirectionalStream.java

Index: components/cronet/android/java/src/org/chromium/net/CronetBidirectionalStream.java
diff --git a/components/cronet/android/java/src/org/chromium/net/CronetBidirectionalStream.java b/components/cronet/android/java/src/org/chromium/net/CronetBidirectionalStream.java
index 4c0fae741dbf49d5534a516ada1703a9e03fb8b0..a5e684653e93b59369da20eb911633fbbda4e019 100644
--- a/components/cronet/android/java/src/org/chromium/net/CronetBidirectionalStream.java
+++ b/components/cronet/android/java/src/org/chromium/net/CronetBidirectionalStream.java
@@ -14,6 +14,7 @@ import java.nio.ByteBuffer;
 import java.util.AbstractMap;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executor;
@@ -56,7 +57,10 @@ class CronetBidirectionalStream extends BidirectionalStream {
         SUCCESS,
         /* Waiting for {@code write()} to be called. */
         WAITING_FOR_WRITE,
-        /* Writing to the remote, {@code onWriteCompleted()} callback will be called when done. */
+        /*
+         * Writing to the remote, {@code onWriteCompleted()} callback will be called when done.
+         * This state is only applicable when {@code mDisableAutoFlush} is false.
+         */
         WRITING,
         /* There is no more data to write and stream is half-closed by the local side. */
         WRITING_DONE,
@@ -69,12 +73,20 @@ class CronetBidirectionalStream extends BidirectionalStream {
     private final int mInitialPriority;
     private final String mInitialMethod;
     private final String mRequestHeaders[];
+    private final boolean mDisableAutoFlush;
 
     /*
      * Synchronizes access to mNativeStream, mReadState and mWriteState.
      */
     private final Object mNativeStreamLock = new Object();
 
+    @GuardedBy("mNativeStreamLock")
+    private final LinkedList<ByteBuffer> mPendingData;
+
+    @GuardedBy("mNativeStreamLock")
+    // Whether an end-of-stream flag is passed in through write().
+    private boolean mEndOfStreamWritten;
+
     /* Native BidirectionalStream object, owned by CronetBidirectionalStream. */
     @GuardedBy("mNativeStreamLock")
     private long mNativeStream;
@@ -91,10 +103,10 @@ class CronetBidirectionalStream extends BidirectionalStream {
 
     /**
      * Write state is tracking writing flow.
-     *                         / <--- WRITING <---  \
-     *                         |                    |
-     *                         \                    /
-     * NOT_STARTED -> STARTED --> WAITING_FOR_WRITE -> WRITING_DONE -> SUCCESS
+     *                         / <--- WRITING (if !mDisableAutoFlush)<--- \
+     *                         |                                          |
+     *                         \                                          /
+     * NOT_STARTED -> STARTED --> -------------WAITING_FOR_WRITE --------> WRITING_DONE -> SUCCESS
      */
     @GuardedBy("mNativeStreamLock")
     private State mWriteState = State.NOT_STARTED;
@@ -107,12 +119,6 @@ class CronetBidirectionalStream extends BidirectionalStream {
      */
     private OnReadCompletedRunnable mOnReadCompletedTask;
 
-    /*
-     * OnWriteCompleted callback is repeatedly invoked when each write is completed, so it
-     * is cached as a member variable.
-     */
-    private OnWriteCompletedRunnable mOnWriteCompletedTask;
-
     private Runnable mOnDestroyedCallbackForTesting;
 
     private final class OnReadCompletedRunnable implements Runnable {
@@ -165,9 +171,8 @@ class CronetBidirectionalStream extends BidirectionalStream {
                     }
                     if (mEndOfStream) {
                         mWriteState = State.WRITING_DONE;
-                        if (maybeSucceedLocked()) {
-                            return;
-                        }
+                        // Maybe post an onSucceeded callback to be executed after run() completes.
+                        maybeSucceedLocked();
                     } else {
                         mWriteState = State.WAITING_FOR_WRITE;
                     }
@@ -181,7 +186,8 @@ class CronetBidirectionalStream extends BidirectionalStream {
 
     CronetBidirectionalStream(CronetUrlRequestContext requestContext, String url,
             @BidirectionalStream.Builder.StreamPriority int priority, Callback callback,
-            Executor executor, String httpMethod, List<Map.Entry<String, String>> requestHeaders) {
+            Executor executor, String httpMethod, List<Map.Entry<String, String>> requestHeaders,
+            boolean disableAutoFlush) {
         mRequestContext = requestContext;
         mInitialUrl = url;
         mInitialPriority = convertStreamPriority(priority);
@@ -189,6 +195,8 @@ class CronetBidirectionalStream extends BidirectionalStream {
         mExecutor = executor;
         mInitialMethod = httpMethod;
         mRequestHeaders = stringsFromHeaderList(requestHeaders);
+        mDisableAutoFlush = disableAutoFlush;
+        mPendingData = new LinkedList<ByteBuffer>();
     }
 
     @Override
@@ -199,7 +207,7 @@ class CronetBidirectionalStream extends BidirectionalStream {
             }
             try {
                 mNativeStream = nativeCreateBidirectionalStream(
-                        mRequestContext.getUrlRequestContextAdapter());
+                        mRequestContext.getUrlRequestContextAdapter(), mDisableAutoFlush);
                 mRequestContext.onRequestStarted();
                 // Non-zero startResult means an argument error.
                 int startResult = nativeStart(mNativeStream, mInitialUrl, mInitialPriority,
@@ -253,24 +261,52 @@ class CronetBidirectionalStream extends BidirectionalStream {
             if (!buffer.hasRemaining() && !endOfStream) {
                 throw new IllegalArgumentException("Empty buffer before end of stream.");
             }
+            if (isDoneLocked()) {
+                return;
+            }
+            if (mEndOfStreamWritten) {

[kapishnikov, 2016/04/12 19:27:39]

We should move it ahead of
if (isDoneLocked()) {
  return;
}
Writing anything after mEndOfStreamWritten is set should be always illegal.

[xunjieli, 2016/04/12 19:59:03]

Done.

+                throw new IllegalArgumentException("Write after writing end of stream.");
+            }
             if (mWriteState != State.WAITING_FOR_WRITE) {
                 throw new IllegalStateException("Unexpected write attempt.");
             }
-            if (isDoneLocked()) {
-                return;
+            mPendingData.add(buffer);
+            if (endOfStream) {
+                mEndOfStreamWritten = true;
             }
-            if (mOnWriteCompletedTask == null) {
-                mOnWriteCompletedTask = new OnWriteCompletedRunnable();
+            if (mDisableAutoFlush) {
+                return;
             }
-            mOnWriteCompletedTask.mEndOfStream = endOfStream;
             mWriteState = State.WRITING;
-            if (!nativeWriteData(
-                        mNativeStream, buffer, buffer.position(), buffer.limit(), endOfStream)) {
-                // Still waiting on write. This is just to have consistent
-                // behavior with the other error cases.
-                mWriteState = State.WAITING_FOR_WRITE;
-                throw new IllegalArgumentException("Unable to call native write");
+            flushLocked();
+        }
+    }
+
+    @Override
+    public void flush() {
+        synchronized (mNativeStreamLock) {
+            if (!mDisableAutoFlush) {
+                throw new IllegalStateException("flush is called when auto flush is not disabled.");

[kapishnikov, 2016/04/12 19:27:39]

Should we allow calling flush even when disableAutoflush is false? It can be
no-op but we should not throw the exception. The reason is that clients may want
to experiment with and without auto-flush enabled. They should not be required
to change the code for that. Also, from the client point of view auto-flushing
means that flush() is called automatically on every write instead of calling it
manually. Calling flush() multiple times should be allowed.

[xunjieli, 2016/04/12 19:59:03]

Removing the check makes me a bit uneasy, but I think the ability to experiment
without code change is worth it. Done.

             }
+            flushLocked();
+        }
+    }
+
+    @SuppressWarnings("GuardedByChecker")
+    private void flushLocked() {
+        int size = mPendingData.size();
+        ByteBuffer[] buffers = new ByteBuffer[size];
+        int[] positions = new int[size];
+        int[] limits = new int[size];
+        for (int i = 0; i < size; i++) {
+            ByteBuffer buffer = mPendingData.poll();
+            buffers[i] = buffer;
+            positions[i] = buffer.position();
+            limits[i] = buffer.limit();
+        }
+        assert mPendingData.isEmpty();
+        if (!nativeWritevData(mNativeStream, buffers, positions, limits, mEndOfStreamWritten)) {
+            throw new IllegalArgumentException("Unable to call native write");
         }
     }
 
@@ -311,7 +347,7 @@ class CronetBidirectionalStream extends BidirectionalStream {
 
     @SuppressWarnings("unused")
     @CalledByNative
-    private void onRequestHeadersSent() {
+    private void onStreamReady() {
         postTaskToExecutor(new Runnable() {
             public void run() {
                 synchronized (mNativeStreamLock) {
@@ -326,7 +362,7 @@ class CronetBidirectionalStream extends BidirectionalStream {
                 }
 
                 try {
-                    mCallback.onRequestHeadersSent(CronetBidirectionalStream.this);
+                    mCallback.onStreamReady(CronetBidirectionalStream.this);
                 } catch (Exception e) {
                     onCallbackException(e);
                 }
@@ -391,18 +427,25 @@ class CronetBidirectionalStream extends BidirectionalStream {
 
     @SuppressWarnings("unused")
     @CalledByNative
-    private void onWriteCompleted(
-            final ByteBuffer byteBuffer, int initialPosition, int initialLimit) {
-        if (byteBuffer.position() != initialPosition || byteBuffer.limit() != initialLimit) {
-            failWithException(
-                    new CronetException("ByteBuffer modified externally during write", null));
-            return;
+    private void onWritevCompleted(final ByteBuffer[] byteBuffers, int[] initialPositions,
+            int[] initialLimits, boolean endOfStream) {
+        assert byteBuffers.length == initialPositions.length;
+        assert byteBuffers.length == initialLimits.length;
+        assert initialPositions.length == initialLimits.length;
+        for (int i = 0; i < byteBuffers.length; i++) {
+            ByteBuffer buffer = byteBuffers[i];
+            if (buffer.position() != initialPositions[i] || buffer.limit() != initialLimits[i]) {
+                failWithException(
+                        new CronetException("ByteBuffer modified externally during write", null));
+                return;
+            }
+            // Current implementation always writes the complete buffer.
+            buffer.position(buffer.limit());
+            OnWriteCompletedRunnable runnable = new OnWriteCompletedRunnable();
+            runnable.mByteBuffer = buffer;
+            runnable.mEndOfStream = endOfStream;
+            postTaskToExecutor(runnable);
         }
-        // Current implementation always writes the complete buffer.
-        byteBuffer.position(byteBuffer.limit());
-        assert mOnWriteCompletedTask.mByteBuffer == null;
-        mOnWriteCompletedTask.mByteBuffer = byteBuffer;
-        postTaskToExecutor(mOnWriteCompletedTask);
     }
 
     @SuppressWarnings("unused")
@@ -618,7 +661,8 @@ class CronetBidirectionalStream extends BidirectionalStream {
     }
 
     // Native methods are implemented in cronet_bidirectional_stream_adapter.cc.
-    private native long nativeCreateBidirectionalStream(long urlRequestContextAdapter);
+    private native long nativeCreateBidirectionalStream(
+            long urlRequestContextAdapter, boolean disableAutoFlush);
 
     @NativeClassQualifiedName("CronetBidirectionalStreamAdapter")
     private native int nativeStart(long nativePtr, String url, int priority, String method,
@@ -629,8 +673,8 @@ class CronetBidirectionalStream extends BidirectionalStream {
             long nativePtr, ByteBuffer byteBuffer, int position, int limit);
 
     @NativeClassQualifiedName("CronetBidirectionalStreamAdapter")
-    private native boolean nativeWriteData(
-            long nativePtr, ByteBuffer byteBuffer, int position, int limit, boolean endOfStream);
+    private native boolean nativeWritevData(long nativePtr, ByteBuffer[] buffers, int[] positions,
+            int[] limits, boolean endOfStream);
 
     @NativeClassQualifiedName("CronetBidirectionalStreamAdapter")
     private native void nativeDestroy(long nativePtr, boolean sendOnCanceled);