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PipedOutputStream.java
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179 lines (168 loc) · 5.65 KB
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/*
* 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 name=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 JDK1.0
*/
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();
}
}
}