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/*******************************************************************************
* Copyright (c) 2007, 2008 Wind River Systems, Inc. and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Wind River Systems - initial API and implementation
*******************************************************************************/
package org.eclipse.tm.tcf.core;
import java.io.IOException;
import org.eclipse.tm.tcf.protocol.IPeer;
/**
* Abstract implementation of IChannel interface for stream oriented transport protocols.
*
* StreamChannel implements communication link connecting two end points (peers).
* The channel asynchronously transmits messages: commands, results and events.
*
* StreamChannel uses escape sequences to represent End-Of-Message and End-Of-Stream markers.
*
* Clients can subclass StreamChannel to support particular stream oriented transport (wire) protocol.
* Also, see ChannelTCP for a concrete IChannel implementation that works on top of TCP sockets as a transport.
*/
public abstract class StreamChannel extends AbstractChannel {
public static final int ESC = 3;
private int bin_data_size;
public StreamChannel(IPeer remote_peer) {
super(remote_peer);
}
public StreamChannel(IPeer local_peer, IPeer remote_peer) {
super(local_peer, remote_peer);
}
protected abstract int get() throws IOException;
protected abstract void put(int n) throws IOException;
protected void put(byte[] buf) throws IOException {
for (byte b : buf) put(b & 0xff);
}
@Override
protected final int read() throws IOException {
for (;;) {
int res = get();
if (res < 0) return EOS;
assert res >= 0 && res <= 0xff;
if (bin_data_size > 0) {
bin_data_size--;
return res;
}
if (res != ESC) return res;
int n = get();
switch (n) {
case 0: return ESC;
case 1: return EOM;
case 2: return EOS;
case 3:
for (int i = 0;; i += 7) {
res = get();
bin_data_size |= (res & 0x7f) << i;
if ((res & 0x80) == 0) break;
}
break;
default:
if (n < 0) return EOS;
assert false;
}
}
}
@Override
protected final void write(int n) throws IOException {
switch (n) {
case ESC: put(ESC); put(0); break;
case EOM: put(ESC); put(1); break;
case EOS: put(ESC); put(2); break;
default:
assert n >= 0 && n <= 0xff;
put(n);
}
}
@Override
protected void write(byte[] buf) throws IOException {
if (buf.length > 32 && isZeroCopySupported()) {
put(ESC); put(3);
int n = buf.length;
for (;;) {
if (n <= 0x7f) {
put(n);
break;
}
put((n & 0x7f) | 0x80);
n = n >> 7;
}
put(buf);
}
else {
for (byte b : buf) {
int n = b & 0xff;
put(n);
if (n == ESC) put(0);
}
}
}
}
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