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/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.hbase.io;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.WritableByteChannel;

import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.hbase.util.Bytes;

/**
 * Not thread safe!
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class ByteBufferOutputStream extends OutputStream {

  protected ByteBuffer buf;

  public ByteBufferOutputStream(int capacity) {
    this(capacity, false);
  }

  public ByteBufferOutputStream(int capacity, boolean useDirectByteBuffer) {
    this(allocate(capacity, useDirectByteBuffer));
  }

  /**
   * @param bb ByteBuffer to use. If too small, will be discarded and a new one allocated in its
   * place; i.e. the passed in BB may NOT BE RETURNED!! Minimally it will be altered. SIDE EFFECT!!
   * If you want to get the newly allocated ByteBuffer, you'll need to pick it up when
   * done with this instance by calling {@link #getByteBuffer()}. All this encapsulation violation
   * is so we can recycle buffers rather than allocate each time; it can get expensive especially
   * if the buffers are big doing allocations each time or having them undergo resizing because
   * initial allocation was small.
   * @see #getByteBuffer()
   */
  public ByteBufferOutputStream(final ByteBuffer bb) {
    this.buf = bb;
    this.buf.clear();
  }

  public int size() {
    return buf.position();
  }

  private static ByteBuffer allocate(final int capacity, final boolean useDirectByteBuffer) {
    return useDirectByteBuffer? ByteBuffer.allocateDirect(capacity): ByteBuffer.allocate(capacity);
  }

  /**
   * This flips the underlying BB so be sure to use it _last_!
   * @return ByteBuffer
   */
  public ByteBuffer getByteBuffer() {
    buf.flip();
    return buf;
  }

  private void checkSizeAndGrow(int extra) {
    if ( (buf.position() + extra) > buf.limit()) {
      // size calculation is complex, because we could overflow negative,
      // and/or not allocate enough space. this fixes that.
      int newSize = (int)Math.min((((long)buf.capacity()) * 2),
          (long)(Integer.MAX_VALUE));
      newSize = Math.max(newSize, buf.position() + extra);
      ByteBuffer newBuf = allocate(newSize, buf.isDirect());
      buf.flip();
      newBuf.put(buf);
      buf = newBuf;
    }
  }

  // OutputStream
  @Override
  public void write(int b) throws IOException {
    checkSizeAndGrow(Bytes.SIZEOF_BYTE);

    buf.put((byte)b);
  }

 /**
  * Writes the complete contents of this byte buffer output stream to
  * the specified output stream argument.
  *
  * @param      out   the output stream to which to write the data.
  * @exception  IOException  if an I/O error occurs.
  */
  public synchronized void writeTo(OutputStream out) throws IOException {
    WritableByteChannel channel = Channels.newChannel(out);
    ByteBuffer bb = buf.duplicate();
    bb.flip();
    channel.write(bb);
  }

  @Override
  public void write(byte[] b) throws IOException {
    checkSizeAndGrow(b.length);

    buf.put(b);
  }

  @Override
  public void write(byte[] b, int off, int len) throws IOException {
    checkSizeAndGrow(len);

    buf.put(b, off, len);
  }

  @Override
  public void flush() throws IOException {
    // noop
  }

  @Override
  public void close() throws IOException {
    // noop again. heh
  }

  public byte[] toByteArray(int offset, int length) {
    ByteBuffer bb = buf.duplicate();
    bb.flip();

    byte[] chunk = new byte[length];

    bb.position(offset);
    bb.get(chunk, 0, length);
    return chunk;
  }
}