StreamPumper.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*
*/
package org.apache.tools.ant.taskdefs;
import org.apache.tools.ant.util.FileUtils;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
/**
* Copies all data from an input stream to an output stream.
*
* @since Ant 1.2
*/
public class StreamPumper implements Runnable {
private static final int SMALL_BUFFER_SIZE = 128;
private final InputStream is;
private final OutputStream os;
private volatile boolean askedToStop;
private volatile boolean finished;
private final boolean closeWhenExhausted;
private boolean autoflush = false;
private Exception exception = null;
private int bufferSize = SMALL_BUFFER_SIZE;
private boolean started = false;
private final boolean useAvailable;
private PostStopHandle postStopHandle;
/**
* Create a new StreamPumper.
*
* @param is input stream to read data from
* @param os output stream to write data to.
* @param closeWhenExhausted if true, the output stream will be closed when
* the input is exhausted.
*/
public StreamPumper(InputStream is, OutputStream os, boolean closeWhenExhausted) {
this(is, os, closeWhenExhausted, false);
}
/**
* Create a new StreamPumper.
* <p><b>Note:</b> If you set useAvailable to true, you must
* explicitly invoke {@link #stop stop} or interrupt the
* corresponding Thread when you are done or the run method will
* never finish on some JVMs (namely those where available returns
* 0 on a closed stream). Setting it to true may also impact
* performance negatively. This flag should only be set to true
* if you intend to stop the pumper before the input stream gets
* closed.</p>
*
* @param is input stream to read data from
* @param os output stream to write data to.
* @param closeWhenExhausted if true, the output stream will be closed when
* the input is exhausted.
* @param useAvailable whether the pumper should use {@link
* java.io.InputStream#available available} to determine
* whether input is ready, thus trying to emulate
* non-blocking behavior.
*
* @since Ant 1.8.0
*/
public StreamPumper(InputStream is, OutputStream os,
boolean closeWhenExhausted,
boolean useAvailable) {
this.is = is;
this.os = os;
this.closeWhenExhausted = closeWhenExhausted;
this.useAvailable = useAvailable;
}
/**
* Create a new StreamPumper.
*
* @param is input stream to read data from
* @param os output stream to write data to.
*/
public StreamPumper(InputStream is, OutputStream os) {
this(is, os, false);
}
/**
* Set whether data should be flushed through to the output stream.
* @param autoflush if true, push through data; if false, let it be buffered
* @since Ant 1.6.3
*/
/*package*/ void setAutoflush(boolean autoflush) {
this.autoflush = autoflush;
}
/**
* Copies data from the input stream to the output stream.
*
* Terminates as soon as the input stream is closed or an error occurs.
*/
@Override
public void run() {
synchronized (this) {
started = true;
}
finished = false;
final byte[] buf = new byte[bufferSize];
try {
int length;
while (!this.askedToStop && !Thread.interrupted()) {
waitForInput(is);
if (askedToStop || Thread.interrupted()) {
break;
}
length = is.read(buf);
if (length < 0) {
// EOF
break;
}
if (length > 0) {
// we did read something, so write it out
os.write(buf, 0, length);
if (autoflush) {
os.flush();
}
}
}
this.doPostStop();
} catch (InterruptedException ie) {
// likely PumpStreamHandler trying to stop us
} catch (Exception e) {
synchronized (this) {
exception = e;
}
} finally {
if (closeWhenExhausted) {
FileUtils.close(os);
}
finished = true;
askedToStop = false;
synchronized (this) {
notifyAll();
}
}
}
/**
* Tells whether the end of the stream has been reached.
* @return true is the stream has been exhausted.
*/
public boolean isFinished() {
return finished;
}
/**
* This method blocks until the StreamPumper finishes.
* @throws InterruptedException if interrupted.
* @see #isFinished()
*/
public synchronized void waitFor() throws InterruptedException {
while (!isFinished()) {
wait();
}
}
/**
* Set the size in bytes of the read buffer.
* @param bufferSize the buffer size to use.
* @throws IllegalStateException if the StreamPumper is already running.
*/
public synchronized void setBufferSize(int bufferSize) {
if (started) {
throw new IllegalStateException("Cannot set buffer size on a running StreamPumper");
}
this.bufferSize = bufferSize;
}
/**
* Get the size in bytes of the read buffer.
*
* @return the int size of the read buffer.
*/
public synchronized int getBufferSize() {
return bufferSize;
}
/**
* Get the exception encountered, if any.
* @return the Exception encountered.
*/
public synchronized Exception getException() {
return exception;
}
/**
* Stop the pumper as soon as possible.
* Note that it may continue to block on the input stream
* but it will really stop the thread as soon as it gets EOF
* or any byte, and it will be marked as finished.
* @return Returns a {@link PostStopHandle} for the callers to
* know if the status of post-stop activities, that happen, before this
* {@link StreamPumper} is actually finished
* @since Ant 1.6.3
* @since Ant 10.2.0 this method returns a {@link PostStopHandle}
*/
/*package*/
synchronized PostStopHandle stop() {
askedToStop = true;
postStopHandle = new PostStopHandle();
notifyAll();
return postStopHandle;
}
private static final long POLL_INTERVAL = 100;
private void waitForInput(InputStream is)
throws IOException, InterruptedException {
if (useAvailable) {
while (!askedToStop && is.available() == 0) {
if (Thread.interrupted()) {
throw new InterruptedException();
}
synchronized (this) {
this.wait(POLL_INTERVAL);
}
}
}
}
private void doPostStop() throws IOException {
try {
final byte[] buf = new byte[bufferSize];
int length;
// We were asked to stop, the contract allows us to do any non-blocking
// final bits of reads, before actually finishing. So we try and drain any (non-blocking) available
// data. We *don't* check the thread interrupt status, anymore, once we start draining this non-blocking
// available data, to allow us to cleanly write out any available data.
if (askedToStop) {
int bytesReadableWithoutBlocking;
while ((bytesReadableWithoutBlocking = is.available()) > 0) {
length = is.read(buf, 0, Math.min(bytesReadableWithoutBlocking, buf.length));
if (length <= 0) {
break;
}
os.write(buf, 0, length);
}
}
// this can potentially be blocking, but that's OK since our post stop activity is allowed to
// cleanup/flush any data and the PostStopHandle let's the caller control over how long they want
// this to go, before actually interrupting the thread
os.flush();
} finally {
if (this.postStopHandle != null) {
this.postStopHandle.latch.countDown();
this.postStopHandle.inPostStopTasks = false;
}
}
}
/**
* A handle that can be used after {@link #stop()} has been invoked to check if the
* {@link StreamPumper} is in the process of do some post-stop tasks (like flushing
* of streams), before finishing.
*/
final class PostStopHandle {
private boolean inPostStopTasks = true;
private final CountDownLatch latch = new CountDownLatch(1);
/**
* Returns true if the {@link StreamPumper} is doing post-stop tasks (like flushing of streams).
* Else returns false.
* @return
*/
boolean isInPostStopTasks() {
return inPostStopTasks;
}
/**
* Waits for a maximum of {@code timeout} time for the post-stop activities to complete.
*
* @param timeout The maximum amount of time to wait for the post-stop activities to complete
* @param timeUnit The unit of {@code timeout}
* @return Returns true if the post-stop activities completed within the specified {@code timeout}.
* Else returns false
* @throws InterruptedException If the current thread was interrupted while waiting
*/
boolean awaitPostStopCompletion(final long timeout, final TimeUnit timeUnit) throws InterruptedException {
return this.latch.await(timeout, timeUnit);
}
}
}