/*
 * Copyright (c) 1996, 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 sun.rmi.transport.tcp;

import java.io.*;

MultiplexOutputStream manages sending data over a conection managed by a ConnectionMultiplexer object. Data written is buffered until the internal buffer is full or the flush() method is called, at which point it attempts to push a packet of bytes through to the remote endpoint. This will never push more bytes than the amount already requested by the remote endpoint (to prevent receive buffer from overflowing), so if the write() and flush() methods will block until their operation can complete if enough bytes cannot be pushed immediately.
Author:Peter Jones
/** * MultiplexOutputStream manages sending data over a conection managed * by a ConnectionMultiplexer object. Data written is buffered until the * internal buffer is full or the flush() method is called, at which * point it attempts to push a packet of bytes through to the remote * endpoint. This will never push more bytes than the amount already * requested by the remote endpoint (to prevent receive buffer from * overflowing), so if the write() and flush() methods will block * until their operation can complete if enough bytes cannot be * pushed immediately. * * @author Peter Jones */
final class MultiplexOutputStream extends OutputStream {
object managing multiplexed connection
/** object managing multiplexed connection */
private ConnectionMultiplexer manager;
information about the connection this is the output stream for
/** information about the connection this is the output stream for */
private MultiplexConnectionInfo info;
output buffer
/** output buffer */
private byte buffer[];
current position to write to in output buffer
/** current position to write to in output buffer */
private int pos = 0;
pending number of bytes requested by remote endpoint
/** pending number of bytes requested by remote endpoint */
private int requested = 0;
true if this connection has been disconnected
/** true if this connection has been disconnected */
private boolean disconnected = false;
lock acquired to access shared variables: requested & disconnected WARNING: Any of the methods manager.send*() should not be invoked while this lock is held, since they could potentially block if the underlying connection's transport buffers are full, and the manager may need to acquire this lock to process and consume data coming over the underlying connection.
/** * lock acquired to access shared variables: * requested & disconnected * WARNING: Any of the methods manager.send*() should not be * invoked while this lock is held, since they could potentially * block if the underlying connection's transport buffers are * full, and the manager may need to acquire this lock to process * and consume data coming over the underlying connection. */
private Object lock = new Object();
Create a new MultiplexOutputStream for the given manager.
Params:
  • manager – object that manages this connection
  • info – structure for connection this stream writes to
  • bufferLength – length of output buffer
/** * Create a new MultiplexOutputStream for the given manager. * @param manager object that manages this connection * @param info structure for connection this stream writes to * @param bufferLength length of output buffer */
MultiplexOutputStream( ConnectionMultiplexer manager, MultiplexConnectionInfo info, int bufferLength) { this.manager = manager; this.info = info; buffer = new byte[bufferLength]; pos = 0; }
Write a byte over connection.
Params:
  • b – byte of data to write
/** * Write a byte over connection. * @param b byte of data to write */
public synchronized void write(int b) throws IOException { while (pos >= buffer.length) push(); buffer[pos ++] = (byte) b; }
Write a subarray of bytes over connection.
Params:
  • b – array containing bytes to write
  • off – offset of beginning of bytes to write
  • len – number of bytes to write
/** * Write a subarray of bytes over connection. * @param b array containing bytes to write * @param off offset of beginning of bytes to write * @param len number of bytes to write */
public synchronized void write(byte b[], int off, int len) throws IOException { if (len <= 0) return; // if enough free space in output buffer, just copy into there int freeSpace = buffer.length - pos; if (len <= freeSpace) { System.arraycopy(b, off, buffer, pos, len); pos += len; return; } // else, flush buffer and send rest directly to avoid array copy flush(); int local_requested; while (true) { synchronized (lock) { while ((local_requested = requested) < 1 && !disconnected) { try { lock.wait(); } catch (InterruptedException e) { } } if (disconnected) throw new IOException("Connection closed"); } if (local_requested < len) { manager.sendTransmit(info, b, off, local_requested); off += local_requested; len -= local_requested; synchronized (lock) { requested -= local_requested; } } else { manager.sendTransmit(info, b, off, len); synchronized (lock) { requested -= len; } // len = 0; break; } } }
Guarantee that all data written to this stream has been pushed over and made available to the remote endpoint.
/** * Guarantee that all data written to this stream has been pushed * over and made available to the remote endpoint. */
public synchronized void flush() throws IOException { while (pos > 0) push(); }
Close this connection.
/** * Close this connection. */
public void close() throws IOException { manager.sendClose(info); }
Take note of more bytes requested by conection at remote endpoint.
Params:
  • num – number of additional bytes requested
/** * Take note of more bytes requested by conection at remote endpoint. * @param num number of additional bytes requested */
void request(int num) { synchronized (lock) { requested += num; lock.notifyAll(); } }
Disconnect this stream from all connection activity.
/** * Disconnect this stream from all connection activity. */
void disconnect() { synchronized (lock) { disconnected = true; lock.notifyAll(); } }
Push bytes in output buffer to connection at remote endpoint. This method blocks until at least one byte has been pushed across.
/** * Push bytes in output buffer to connection at remote endpoint. * This method blocks until at least one byte has been pushed across. */
private void push() throws IOException { int local_requested; synchronized (lock) { while ((local_requested = requested) < 1 && !disconnected) { try { lock.wait(); } catch (InterruptedException e) { } } if (disconnected) throw new IOException("Connection closed"); } if (local_requested < pos) { manager.sendTransmit(info, buffer, 0, local_requested); System.arraycopy(buffer, local_requested, buffer, 0, pos - local_requested); pos -= local_requested; synchronized (lock) { requested -= local_requested; } } else { manager.sendTransmit(info, buffer, 0, pos); synchronized (lock) { requested -= pos; } pos = 0; } } }