/*
 * Copyright (c) 1995, 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.io;

import java.io.*;

/**
 * A piped output stream can be connected to a piped input stream
 * to create a communications pipe. The piped output stream is the
 * sending end of the pipe. Typically, data is written to a
 * <code>PipedOutputStream</code> object by one thread and data is
 * read from the connected <code>PipedInputStream</code> by some
 * other thread. Attempting to use both objects from a single thread
 * is not recommended as it may deadlock the thread.
 * The pipe is said to be <a id=BROKEN> <i>broken</i> </a> if a
 * thread that was reading data bytes from the connected piped input
 * stream is no longer alive.
 *
 * @author James Gosling
 * @see java.io.PipedInputStream
 * @since 1.0
 */
public
class PipedOutputStream extends OutputStream {

 /* REMIND: identification of the read and write sides needs to be
 more sophisticated. Either using thread groups (but what about
 pipes within a thread?) or using finalization (but it may be a
 long time until the next GC). */
 private PipedInputStream sink;

 /**
 * Creates a piped output stream connected to the specified piped
 * input stream. Data bytes written to this stream will then be
 * available as input from <code>snk</code>.
 *
 * @param snk The piped input stream to connect to.
 * @exception IOException if an I/O error occurs.
 */
 public PipedOutputStream(PipedInputStream snk) throws IOException {
 connect(snk);
 }

 /**
 * Creates a piped output stream that is not yet connected to a
 * piped input stream. It must be connected to a piped input stream,
 * either by the receiver or the sender, before being used.
 *
 * @see java.io.PipedInputStream#connect(java.io.PipedOutputStream)
 * @see java.io.PipedOutputStream#connect(java.io.PipedInputStream)
 */
 public PipedOutputStream() {
 }

 /**
 * Connects this piped output stream to a receiver. If this object
 * is already connected to some other piped input stream, an
 * <code>IOException</code> is thrown.
 * <p>
 * If <code>snk</code> is an unconnected piped input stream and
 * <code>src</code> is an unconnected piped output stream, they may
 * be connected by either the call:
 * <blockquote><pre>
 * src.connect(snk)</pre></blockquote>
 * or the call:
 * <blockquote><pre>
 * snk.connect(src)</pre></blockquote>
 * The two calls have the same effect.
 *
 * @param snk the piped input stream to connect to.
 * @exception IOException if an I/O error occurs.
 */
 public synchronized void connect(PipedInputStream snk) throws IOException {
 if (snk == null) {
 throw new NullPointerException();
 } else if (sink != null || snk.connected) {
 throw new IOException("Already connected");
 }
 sink = snk;
 snk.in = -1;
 snk.out = 0;
 snk.connected = true;
 }

 /**
 * Writes the specified <code>byte</code> to the piped output stream.
 * <p>
 * Implements the <code>write</code> method of <code>OutputStream</code>.
 *
 * @param b the <code>byte</code> to be written.
 * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
 * {@link #connect(java.io.PipedInputStream) unconnected},
 * closed, or if an I/O error occurs.
 */
 public void write(int b) throws IOException {
 if (sink == null) {
 throw new IOException("Pipe not connected");
 }
 sink.receive(b);
 }

 /**
 * Writes <code>len</code> bytes from the specified byte array
 * starting at offset <code>off</code> to this piped output stream.
 * This method blocks until all the bytes are written to the output
 * stream.
 *
 * @param b the data.
 * @param off the start offset in the data.
 * @param len the number of bytes to write.
 * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
 * {@link #connect(java.io.PipedInputStream) unconnected},
 * closed, or if an I/O error occurs.
 */
 public void write(byte b[], int off, int len) throws IOException {
 if (sink == null) {
 throw new IOException("Pipe not connected");
 } else if (b == null) {
 throw new NullPointerException();
 } else if ((off < 0) || (off > b.length) || (len < 0) ||
 ((off + len) > b.length) || ((off + len) < 0)) {
 throw new IndexOutOfBoundsException();
 } else if (len == 0) {
 return;
 }
 sink.receive(b, off, len);
 }

 /**
 * Flushes this output stream and forces any buffered output bytes
 * to be written out.
 * This will notify any readers that bytes are waiting in the pipe.
 *
 * @exception IOException if an I/O error occurs.
 */
 public synchronized void flush() throws IOException {
 if (sink != null) {
 synchronized (sink) {
 sink.notifyAll();
 }
 }
 }

 /**
 * Closes this piped output stream and releases any system resources
 * associated with this stream. This stream may no longer be used for
 * writing bytes.
 *
 * @exception IOException if an I/O error occurs.
 */
 public void close() throws IOException {
 if (sink != null) {
 sink.receivedLast();
 }
 }
}