/*
* @(#)$Id: FastPipedInputStream.java 3619 2008-03-26 07:23:03Z yui $
*
* Copyright 2006-2008 Makoto YUI
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Contributors:
* Makoto YUI - initial implementation
*/
package hudson.remoting;
import java.io.InputStream;
import java.io.IOException;
import java.lang.ref.WeakReference;
/**
* This class is equivalent to <code>java.io.PipedInputStream</code>. In the
* interface it only adds a constructor which allows for specifying the buffer
* size. Its implementation, however, is much simpler and a lot more efficient
* than its equivalent. It doesn't rely on polling. Instead it uses proper
* synchronization with its counterpart {@link FastPipedOutputStream}.
*
* @author WD
* @link http://developer.java.sun.com/developer/bugParade/bugs/4404700.html
* @see FastPipedOutputStream
*/
public class FastPipedInputStream extends InputStream {
final byte[] buffer;
/**
* Once closed, this is set to the stack trace of who closed it.
*/
ClosedBy closed = null;
int readLaps = 0;
int readPosition = 0;
WeakReference<FastPipedOutputStream> source;
int writeLaps = 0;
int writePosition = 0;
private final Throwable allocatedAt = new Throwable();
/**
* Creates an unconnected PipedInputStream with a default buffer size.
*/
public FastPipedInputStream() {
this.buffer = new byte[0x10000];
}
/**
* Creates a PipedInputStream with a default buffer size and connects it to
* <code>source</code>.
* @exception IOException It was already connected.
*/
public FastPipedInputStream(FastPipedOutputStream source) throws IOException {
this(source, 0x10000 /* 65536 */);
}
/**
* Creates a PipedInputStream with buffer size <code>bufferSize</code> and
* connects it to <code>source</code>.
* @exception IOException It was already connected.
*/
public FastPipedInputStream(FastPipedOutputStream source, int bufferSize) throws IOException {
if(source != null) {
connect(source);
}
this.buffer = new byte[bufferSize];
}
private FastPipedOutputStream source() throws IOException {
FastPipedOutputStream s = source.get();
if (s==null) throw (IOException)new IOException("Writer side has already been abandoned").initCause(allocatedAt);
return s;
}
@Override
public int available() throws IOException {
/* The circular buffer is inspected to see where the reader and the writer
* are located.
*/
synchronized (buffer) {
return writePosition > readPosition /* The writer is in the same lap. */? writePosition
- readPosition
: (writePosition < readPosition /* The writer is in the next lap. */? buffer.length
- readPosition + 1 + writePosition
:
/* The writer is at the same position or a complete lap ahead. */
(writeLaps > readLaps ? buffer.length : 0));
}
}
/**
* @exception IOException The pipe is not connected.
*/
@Override
public void close() throws IOException {
if(source == null) {
throw new IOException("Unconnected pipe");
}
synchronized(buffer) {
closed = new ClosedBy();
// Release any pending writers.
buffer.notifyAll();
}
}
/**
* @exception IOException The pipe is already connected.
*/
public void connect(FastPipedOutputStream source) throws IOException {
if(this.source != null) {
throw new IOException("Pipe already connected");
}
this.source = new WeakReference<FastPipedOutputStream>(source);
source.sink = new WeakReference<FastPipedInputStream>(this);
}
@Override
protected void finalize() throws Throwable {
super.finalize();
close();
}
@Override
public void mark(int readLimit) {
}
@Override
public boolean markSupported() {
return false;
}
public int read() throws IOException {
byte[] b = new byte[1];
return read(b, 0, b.length) == -1 ? -1 : (255 & b[0]);
}
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
/**
* @exception IOException The pipe is not connected.
*/
@Override
public int read(byte[] b, int off, int len) throws IOException {
if(source == null) {
throw new IOException("Unconnected pipe");
}
while (true) {
synchronized(buffer) {
if(writePosition == readPosition && writeLaps == readLaps) {
if(closed != null) {
return -1;
}
source(); // make sure the sink is still trying to read, or else fail the write.
// Wait for any writer to put something in the circular buffer.
try {
buffer.wait(FastPipedOutputStream.TIMEOUT);
} catch (InterruptedException e) {
throw new IOException(e.getMessage());
}
// Try again.
continue;
}
// Don't read more than the capacity indicated by len or what's available
// in the circular buffer.
int amount = Math.min(len, (writePosition > readPosition ? writePosition
: buffer.length)
- readPosition);
System.arraycopy(buffer, readPosition, b, off, amount);
readPosition += amount;
if(readPosition == buffer.length) {// A lap was completed, so go back.
readPosition = 0;
++readLaps;
}
buffer.notifyAll();
return amount;
}
}
}
static final class ClosedBy extends Throwable {
ClosedBy() {
super("The pipe was closed at...");
}
}
}