third_party/protobuf: Update to HEAD (83d681ee2c)

third_party/protobuf/java/core/src/main/java/com/google/protobuf/ByteBufferWriter.java

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
 // https://developers.google.com/protocol-buffers/
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
@@ skipping 15 matching lines @@
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 package com.google.protobuf;
 
 import static java.lang.Math.max;
 import static java.lang.Math.min;
 
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.lang.ref.SoftReference;
+import java.lang.reflect.Field;
 import java.nio.ByteBuffer;
+import java.nio.channels.WritableByteChannel;
 
 /**
  * Utility class to provide efficient writing of {@link ByteBuffer}s to {@link OutputStream}s.
  */
 final class ByteBufferWriter {
   private ByteBufferWriter() {}
 
   /**
    * Minimum size for a cached buffer. This prevents us from allocating buffers that are too
    * small to be easily reused.
@@ skipping 17 matching lines @@
   /**
    * Keeping a soft reference to a thread-local buffer. This buffer is used for writing a
    * {@link ByteBuffer} to an {@link OutputStream} when no zero-copy alternative was available.
    * Using a "soft" reference since VMs may keep this reference around longer than "weak"
    * (e.g. HotSpot will maintain soft references until memory pressure warrants collection).
    */
   private static final ThreadLocal<SoftReference<byte[]>> BUFFER =
       new ThreadLocal<SoftReference<byte[]>>();
 
   /**
+   * This is a hack for GAE, where {@code FileOutputStream} is unavailable.
+   */
+  private static final Class<?> FILE_OUTPUT_STREAM_CLASS = safeGetClass("java.io.FileOutputStream");
+  private static final long CHANNEL_FIELD_OFFSET = getChannelFieldOffset(FILE_OUTPUT_STREAM_CLASS);
+
+  /**
    * For testing purposes only. Clears the cached buffer to force a new allocation on the next
    * invocation.
    */
   static void clearCachedBuffer() {
     BUFFER.set(null);
   }
 
   /**
    * Writes the remaining content of the buffer to the given stream. The buffer {@code position}
    * will remain unchanged by this method.
    */
   static void write(ByteBuffer buffer, OutputStream output) throws IOException {
     final int initialPos = buffer.position();
     try {
       if (buffer.hasArray()) {
         // Optimized write for array-backed buffers.
         // Note that we're taking the risk that a malicious OutputStream could modify the array.
         output.write(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining());
-      } else if (output instanceof FileOutputStream) {
-        // Use a channel to write out the ByteBuffer. This will automatically empty the buffer.
-        ((FileOutputStream) output).getChannel().write(buffer);
-      } else {
+      } else if (!writeToChannel(buffer, output)){
         // Read all of the data from the buffer to an array.
         // TODO(nathanmittler): Consider performance improvements for other "known" stream types.
         final byte[] array = getOrCreateBuffer(buffer.remaining());
         while (buffer.hasRemaining()) {
           int length = min(buffer.remaining(), array.length);
           buffer.get(array, 0, length);
           output.write(array, 0, length);
         }
       }
     } finally {
@@ skipping 25 matching lines @@
   }
 
   private static byte[] getBuffer() {
     SoftReference<byte[]> sr = BUFFER.get();
     return sr == null ? null : sr.get();
   }
 
   private static void setBuffer(byte[] value) {
     BUFFER.set(new SoftReference<byte[]>(value));
   }
+
+  private static boolean writeToChannel(ByteBuffer buffer, OutputStream output) throws IOException {
+    if (CHANNEL_FIELD_OFFSET >= 0 && FILE_OUTPUT_STREAM_CLASS.isInstance(output)) {
+      // Use a channel to write out the ByteBuffer. This will automatically empty the buffer.
+      WritableByteChannel channel = null;
+      try {
+        channel = (WritableByteChannel) UnsafeUtil.getObject(output, CHANNEL_FIELD_OFFSET);
+      } catch (ClassCastException e) {
+        // Absorb.
+      }
+      if (channel != null) {
+        channel.write(buffer);
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private static Class<?> safeGetClass(String className) {
+    try {
+      return Class.forName(className);
+    } catch (ClassNotFoundException e) {
+      return null;
+    }
+  }
+  private static long getChannelFieldOffset(Class<?> clazz) {
+    try {
+      if (clazz != null && UnsafeUtil.hasUnsafeArrayOperations()) {
+        Field field = clazz.getDeclaredField("channel");
+        return UnsafeUtil.objectFieldOffset(field);
+      }
+    } catch (Throwable e) {
+      // Absorb
+    }
+    return -1;
+  }
 }