Memory Byte Array OutputStream : OutputStream « File « Java Tutorial






/**
 * 
 * JFreeReport : a free Java reporting library
 * 
 *
 * Project Info:  http://reporting.pentaho.org/
 *
 * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * ------------
 * MemoryByteArrayOutputStream.java
 * ------------
 * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
 */

import java.io.IOException;
import java.io.OutputStream;

/**
 * A string writer that is able to write large amounts of data. The original
 * StringWriter contained in Java doubles its buffersize everytime the buffer
 * overflows. This is nice with small amounts of data, but awfull for huge
 * buffers.
 * 
 * @author Thomas Morgner
 */
public class MemoryByteArrayOutputStream extends OutputStream {
  private int maximumBufferIncrement;

  private int cursor;

  private byte[] buffer;

  private byte[] singleIntArray;

  /**
   * Create a new character-stream writer whose critical sections will
   * synchronize on the writer itself.
   */
  public MemoryByteArrayOutputStream() {
    this(4096, 65536);
  }

  /**
   * Create a new character-stream writer whose critical sections will
   * synchronize on the writer itself.
   */
  public MemoryByteArrayOutputStream(final int bufferSize, final int maximumBufferIncrement) {
    this.maximumBufferIncrement = maximumBufferIncrement;
    this.buffer = new byte[bufferSize];
    this.singleIntArray = new byte[1];
  }

  /**
   * Write a portion of an array of characters.
   * 
   * @param cbuf
   *          Array of characters
   * @param off
   *          Offset from which to start writing characters
   * @param len
   *          Number of characters to write
   * @throws java.io.IOException
   *           If an I/O error occurs
   */
  public synchronized void write(final byte[] cbuf, final int off, final int len)
      throws IOException {
    if (len < 0) {
      throw new IllegalArgumentException();
    }
    if (off < 0) {
      throw new IndexOutOfBoundsException();
    }
    if (cbuf == null) {
      throw new NullPointerException();
    }
    if ((len + off) > cbuf.length) {
      throw new IndexOutOfBoundsException();
    }

    ensureSize(cursor + len);

    System.arraycopy(cbuf, off, this.buffer, cursor, len);
    cursor += len;
  }

  /**
   * Writes <code>b.length</code> bytes from the specified byte array to this
   * output stream. The general contract for <code>write(b)</code> is that it
   * should have exactly the same effect as the call <code>write(b, 0,
   * b.length)</code>.
   * 
   * @param b
   *          the data.
   * @throws java.io.IOException
   *           if an I/O error occurs.
   * @see java.io.OutputStream#write(byte[], int, int)
   */
  public void write(final byte[] b) throws IOException {
    write(b, 0, b.length);
  }

  /**
   * Writes the specified byte to this output stream. The general contract for
   * <code>write</code> is that one byte is written to the output stream. The
   * byte to be written is the eight low-order bits of the argument
   * <code>b</code>. The 24 high-order bits of <code>b</code> are ignored.
   * <p/> Subclasses of <code>OutputStream</code> must provide an
   * implementation for this method.
   * 
   * @param b
   *          the <code>byte</code>.
   * @throws java.io.IOException
   *           if an I/O error occurs. In particular, an
   *           <code>IOException</code> may be thrown if the output stream has
   *           been closed.
   */
  public synchronized void write(final int b) throws IOException {
    this.singleIntArray[0] = (byte) (0xFF & b);
    write(singleIntArray, 0, 1);
  }

  private void ensureSize(final int size) {
    if (this.buffer.length >= size) {
      return;
    }

    final int computedSize = (int) Math.min((this.buffer.length + 1) * 1.5, this.buffer.length
        + maximumBufferIncrement);
    final int newSize = Math.max(size, computedSize);
    final byte[] newBuffer = new byte[newSize];
    System.arraycopy(this.buffer, 0, newBuffer, 0, cursor);
    this.buffer = newBuffer;
  }

  /**
   * Flush the stream. If the stream has saved any characters from the various
   * write() methods in a buffer, write them immediately to their intended
   * destination. Then, if that destination is another character or byte stream,
   * flush it. Thus one flush() invocation will flush all the buffers in a chain
   * of Writers and OutputStreams. <p/> If the intended destination of this
   * stream is an abstraction provided by the underlying operating system, for
   * example a file, then flushing the stream guarantees only that bytes
   * previously written to the stream are passed to the operating system for
   * writing; it does not guarantee that they are actually written to a physical
   * device such as a disk drive.
   * 
   * @throws java.io.IOException
   *           If an I/O error occurs
   */
  public void flush() throws IOException {
    if ((buffer.length - cursor) > 50000) {
      System.out.println("WASTED: " + (buffer.length - cursor));
    }
  }

  /**
   * Close the stream, flushing it first. Once a stream has been closed, further
   * write() or flush() invocations will cause an IOException to be thrown.
   * Closing a previously-closed stream, however, has no effect.
   * 
   * @throws java.io.IOException
   *           If an I/O error occurs
   */
  public void close() throws IOException {
  }

  public synchronized byte[] toByteArray() {
    final byte[] retval = new byte[cursor];
    System.arraycopy(buffer, 0, retval, 0, cursor);
    return retval;
  }

  public int getLength() {
    return cursor;
  }

  public byte[] getRaw() {
    if ((buffer.length - cursor) > 50000) {
      System.out.println("WASTED: " + (buffer.length - cursor) + " Length: " + buffer.length);
    }
    return buffer;
  }
}








11.13.OutputStream
11.13.1.Byte Counting OutputStream
11.13.2.Memory Byte Array OutputStream
11.13.3.A null output stream. All data written to this stream is ignored.
11.13.4.Provides true Closable semantics ordinarily missing in a {@link java.io.ByteArrayOutputStream}.
11.13.5.Write the entire contents of the supplied string to the given stream. This method always flushes and closes the stream when finished.
11.13.6.Transfers all bytes that can be read from one stream to another stream.