Add CountingOutputStream

Reviewed By: mdvacca

Differential Revision: D6932872

fbshipit-source-id: 226f30833a786d0c03564f25ec8c4f43d94c48f4

ReactAndroid/src/main/java/com/facebook/react/modules/network/CountingOutputStream.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2007 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.facebook.react.modules.network;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * An OutputStream that counts the number of bytes written.
+ *
+ * @author Chris Nokleberg
+ * @since 1.0
+ */
+public class CountingOutputStream extends FilterOutputStream {
+
+  private long mCount;
+
+  /**
+   * Constructs a new {@code FilterOutputStream} with {@code out} as its
+   * target stream.
+   *
+   * @param out the target stream that this stream writes to.
+   */
+  public CountingOutputStream(OutputStream out) {
+    super(out);
+    mCount = 0;
+  }
+
+  /**
+   * Returns the number of bytes written.
+   */
+  public long getCount() {
+    return mCount;
+  }
+
+  @Override
+  public void write(byte[] b, int off, int len) throws IOException {
+    out.write(b, off, len);
+    mCount += len;
+  }
+
+  @Override
+  public void write(int b) throws IOException {
+    out.write(b);
+    mCount++;
+  }
+
+  // Overriding close() because FilterOutputStream's close() method pre-JDK8 has bad behavior:
+  // it silently ignores any exception thrown by flush(). Instead, just close the delegate stream.
+  // It should flush itself if necessary.
+  @Override
+  public void close() throws IOException {
+    out.close();
+  }
+}