data/val/jesusbmx/HttpCli/src/httpcli/io/PoolingByteArrayOutputStream.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * 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 httpcli.io;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

/**
 * A variation of {@link java.io.ByteArrayOutputStream} that uses a pool of
 * byte[] buffers instead of always allocating them fresh, saving on heap churn.
 */
public class PoolingByteArrayOutputStream extends ByteArrayOutputStream {

  /**
   * If the {@link #PoolingByteArrayOutputStream(ByteArrayPool)} constructor is
   * called, this is the default size to which the underlying byte array is
   * initialized.
   */
  private static final int DEFAULT_SIZE = 256;
  private final ByteArrayPool mPool;

  /**
   * Constructs a new PoolingByteArrayOutputStream with a default size. If more
   * bytes are written to this instance, the underlying byte array will expand.
   */
  public PoolingByteArrayOutputStream(ByteArrayPool pool) {
    this(pool, DEFAULT_SIZE);
  }

  /**
   * Constructs a new {@code ByteArrayOutputStream} with a default size of
   * {@code size} bytes. If more than {@code size} bytes are written to this
   * instance, the underlying byte array will expand.
   *
   * @param size initial size for the underlying byte array. The value will be
   * pinned to a default minimum size.
   */
  public PoolingByteArrayOutputStream(ByteArrayPool pool, int size) {
    mPool = pool;
    buf = mPool.getBuf(Math.max(size, DEFAULT_SIZE));
  }

  @Override
  public void close() throws IOException {
    mPool.returnBuf(buf);
    buf = null;
    super.close();
  }

  @Override
  public void finalize() {
    mPool.returnBuf(buf);
  }

  /**
   * Ensures there is enough space in the buffer for the given number of
   * additional bytes.
   */
  private void expand(int i) {
    /* Can the buffer handle @i more bytes, if not expand it */
    if (count + i <= buf.length) {
      return;
    }
    byte[] newbuf = mPool.getBuf((count + i) * 2);
    System.arraycopy(buf, 0, newbuf, 0, count);
    mPool.returnBuf(buf);
    buf = newbuf;
  }

  @Override
  public synchronized void write(byte[] buffer, int offset, int len) {
    expand(len);
    super.write(buffer, offset, len);
  }

  @Override
  public synchronized void write(int oneByte) {
    expand(1);
    super.write(oneByte);
  }
}