https://openjdk.java.net/ 
/*
 * Copyright (c) 1995, 2006, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

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
PipedOutputStream object by one thread and data is
read from the connected PipedInputStream 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  broken  if a
thread that was reading data bytes from the connected piped input
stream is no longer alive.

Author: James Gosling
See Also:
Since:  1.0
/**
 * 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 snk.

Params:
  • snk –   The piped input stream to connect to.
Throws:
/**
     * 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 Also:
/**
     * 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
IOException is thrown.


If snk is an unconnected piped input stream and
src is an unconnected piped output stream, they may
be connected by either the call:

src.connect(snk)

or the call:

snk.connect(src)

The two calls have the same effect.

Params:
  • snk –   the piped input stream to connect to.
Throws:
/**
     * 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 byte to the piped output stream.


Implements the write method of OutputStream.

Params:
  • b –   the byte to be written.
Throws:
/**
     * 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 len bytes from the specified byte array
starting at offset off to this piped output stream.
This method blocks until all the bytes are written to the output
stream.

Params:
  • b –     the data.
  • off –   the start offset in the data.
  • len –   the number of bytes to write.
Throws:
/**
     * 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.

Throws:
  • IOException – if an I/O error occurs.
/**
     * 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.

Throws:
  • IOException –  if an I/O error occurs.
/**
     * 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();
        }
    }
}