/** * Copyright 2005 The Apache Software Foundation * * 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 org.apache.hadoop.io;import java.io.*;/** A reusable {@link DataOutput} implementation that writes to an in-memory * buffer. * * <p>This saves memory over creating a new DataOutputStream and * ByteArrayOutputStream each time data is written. * * <p>Typical usage is something like the following:<pre> * * DataOutputBuffer buffer = new DataOutputBuffer(); * while (... loop condition ...) { *   buffer.reset(); *   ... write buffer using DataOutput methods ... *   byte[] data = buffer.getData(); *   int dataLength = buffer.getLength(); *   ... write data to its ultimate destination ... * } * </pre> *   * @author Doug Cutting */public class DataOutputBuffer extends DataOutputStream {  private static class Buffer extends ByteArrayOutputStream {    public byte[] getData() { return buf; }    public int getLength() { return count; }    public void reset() { count = 0; }    public void write(DataInput in, int len) throws IOException {      int newcount = count + len;      if (newcount > buf.length) {        byte newbuf[] = new byte[Math.max(buf.length << 1, newcount)];        System.arraycopy(buf, 0, newbuf, 0, count);        buf = newbuf;      }      in.readFully(buf, count, len);      count = newcount;    }  }  private Buffer buffer;    /** Constructs a new empty buffer. */  public DataOutputBuffer() {    this(new Buffer());  }    private DataOutputBuffer(Buffer buffer) {    super(buffer);    this.buffer = buffer;  }  /** Returns the current contents of the buffer.   *  Data is only valid to {@link #getLength()}.   */  public byte[] getData() { return buffer.getData(); }  /** Returns the length of the valid data currently in the buffer. */  public int getLength() { return buffer.getLength(); }  /** Resets the buffer to empty. */  public DataOutputBuffer reset() {    this.written = 0;    buffer.reset();    return this;  }  /** Writes bytes from a DataInput directly into the buffer. */  public void write(DataInput in, int length) throws IOException {    buffer.write(in, length);  }}