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/* PipedOutputStream.java -- Write portion of piped streams.

   Copyright (C) 1998, 2000, 2001, 2003 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath 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

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package java.io;

// NOTE: This implementation is very similar to that of PipedWriter.  If you

// fix a bug in here, chances are you should make a similar change to the

// PipedWriter code.

/**

  * This class writes its bytes to a <code>PipedInputStream</code> to

  * which it is connected.

  * <p>

  * It is highly recommended that a <code>PipedOutputStream</code> and its

  * connected <code>PipedInputStream</code> be in different threads.  If

  * they are in the same thread, read and write operations could deadlock

  * the thread.

  *

  * @author Aaron M. Renn (arenn@urbanophile.com)

  */

public class PipedOutputStream extends OutputStream

{

  /** Target PipedInputStream to which this is connected. Null only if this

    * OutputStream hasn't been connected yet. */

  PipedInputStream sink;

  /** Set to true if close() has been called on this OutputStream. */

  boolean closed;

  /**

    * Create an unconnected PipedOutputStream.  It must be connected

    * to a <code>PipedInputStream</code> using the <code>connect</code>

    * method prior to writing any data or an exception will be thrown.

    */

  public PipedOutputStream()

  {

  }

  /**

     * Create a new <code>PipedOutputStream</code> instance

    * to write to the specified <code>PipedInputStream</code>.  This stream

    * is then ready for writing.

    *

    * @param sink The <code>PipedInputStream</code> to connect this stream to.

    *

    * @exception IOException If <code>sink</code> has already been connected

    *                        to a different PipedOutputStream.

    */

  public PipedOutputStream(PipedInputStream sink) throws IOException

  {

    sink.connect(this);

  }

  /**

    * Connects this object to the specified <code>PipedInputStream</code>

    * object.  This stream will then be ready for writing.

    *

    * @param sink The <code>PipedInputStream</code> to connect this stream to

    *

    * @exception IOException If the stream has not been connected or has

    *                        been closed.

    */

  public void connect(PipedInputStream sink) throws IOException

  {

    if (this.sink != null || sink.source != null)

      throw new IOException ("Already connected");

    sink.connect(this);

  }

  /**

    * Write a single byte of date to the stream.  Note that this method will

    * block if the <code>PipedInputStream</code> to which this object is

    * connected has a full buffer.

    *

    * @param b The byte of data to be written, passed as an <code>int</code>.

    *

    * @exception IOException If the stream has not been connected or has

    *                        been closed.

    */

  public void write(int b) throws IOException

  {

    if (sink == null)

      throw new IOException ("Not connected");

    if (closed)

      throw new IOException ("Pipe closed");

    sink.receive (b);

  }

  /**

    * This method writes <code>len</code> bytes of data from the byte array

    * <code>buf</code> starting at index <code>offset</code> in the array

    * to the stream.  Note that this method will block if the

    * <code>PipedInputStream</code> to which this object is connected has

    * a buffer that cannot hold all of the bytes to be written.

    *

    * @param buffer The array containing bytes to write to the stream.

    * @param offset The index into the array to start writing bytes from.

    * @param len The number of bytes to write.

    *

    * @exception IOException If the stream has not been connected or has

    *                        been closed.

    */

  public void write(byte[] buffer, int offset, int len) throws IOException

  {

    if (sink == null)

      throw new IOException ("Not connected");

    if (closed)

      throw new IOException ("Pipe closed");

    sink.receive(buffer, offset, len);

  }

  /**

    * This method does nothing.

    *

    * @exception IOException If the stream is closed.

    * @specnote You'd think that this method would block until the sink

    *           had read all available data. Thats not the case - this method

    *           appears to be a no-op?

    */

  public void flush() throws IOException

  {

  }

  /**

    * This method closes this stream so that no more data can be written

    * to it. Any further attempts to write to this stream may throw an

    * exception

    *

    * @exception IOException If an error occurs

    */

  public void close() throws IOException

  {

    // A close call on an unconnected PipedOutputStream has no effect.

    if (sink != null)

      {

        closed = true;

        // Notify any waiting readers that the stream is now closed.

        synchronized (sink)

        {

          sink.notifyAll();

        }

      }

  }

}