/*******************************************************************************
* Copyright (c) 2000, 2011 IBM Corporation 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:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.mylyn.internal.commons.net;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InterruptedIOException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.OperationCanceledException;
import org.eclipse.mylyn.commons.net.Policy;
/**
* Polls a progress monitor periodically and handles timeouts over extended durations. For this class to be effective, a
* high numAttempts should be specified, and the underlying stream should time out frequently on reads (every second or
* so). Supports resuming partially completed operations after an InterruptedIOException if the underlying stream does.
* Check the bytesTransferred field to determine how much of the operation completed; conversely, at what point to
* resume.
*/
public class PollingInputStream extends FilterInputStream {
private static final boolean DEBUG = Policy.DEBUG_STREAMS;
private final int numAttempts;
private final IProgressMonitor monitor;
private boolean cancellable;
/**
* Creates a new polling input stream.
*
* @param in
* the underlying input stream
* @param numAttempts
* the number of attempts before issuing an InterruptedIOException, if 0, retries indefinitely until
* canceled
* @param monitor
* the progress monitor to be polled for cancellation
*/
public PollingInputStream(InputStream in, int numAttempts, IProgressMonitor monitor) {
super(in);
this.numAttempts = numAttempts;
this.monitor = monitor;
this.cancellable = true;
}
/**
* Wraps the underlying stream's method. It may be important to wait for an input stream to be closed because it
* holds an implicit lock on a system resource (such as a file) while it is open. Closing a stream may take time if
* the underlying stream is still servicing a previous request.
*
* @throws OperationCanceledException
* if the progress monitor is canceled
* @throws InterruptedIOException
* if the underlying operation times out numAttempts times
*/
@Override
public void close() throws InterruptedIOException {
int attempts = 0;
try {
readPendingInput();
} catch (IOException e) {
// We shouldn't get an exception when we're getting the available input.
// If we do, just log it so we can close.
CommonsNetPlugin.log(IStatus.ERROR, e.getMessage(), e);
} finally {
boolean stop = false;
while (!stop) {
try {
if (in != null) {
in.close();
}
stop = true;
} catch (InterruptedIOException e) {
if (checkCancellation()) {
throw new OperationCanceledException();
}
if (++attempts == numAttempts) {
throw new InterruptedIOException(Messages.PollingInputStream_closeTimeout);
}
if (DEBUG) {
System.out.println("close retry=" + attempts); //$NON-NLS-1$
}
} catch (IOException e) {
// ignore it - see https://bugs.eclipse.org/bugs/show_bug.cgi?id=203423#c10
}
}
}
}
/**
* Wraps the underlying stream's method.
*
* @return the next byte of data, or -1 if the end of the stream is reached.
* @throws OperationCanceledException
* if the progress monitor is canceled
* @throws InterruptedIOException
* if the underlying operation times out numAttempts times and no data was received, bytesTransferred
* will be zero
* @throws IOException
* if an i/o error occurs
*/
@Override
public int read() throws IOException {
int attempts = 0;
for (;;) {
if (checkCancellation()) {
throw new OperationCanceledException();
}
try {
return in.read();
} catch (InterruptedIOException e) {
if (++attempts == numAttempts) {
throw new InterruptedIOException(Messages.PollingInputStream_readTimeout);
}
if (DEBUG) {
System.out.println("read retry=" + attempts); //$NON-NLS-1$
}
}
}
}
/**
* Wraps the underlying stream's method.
*
* @param buffer
* - the buffer into which the data is read.
* @param off
* - the start offset of the data.
* @param len
* - the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or -1 if there is no more data because the end of the
* stream has been reached.
* @throws OperationCanceledException
* if the progress monitor is canceled
* @throws InterruptedIOException
* if the underlying operation times out numAttempts times and no data was received, bytesTransferred
* will be zero
* @throws IOException
* if an i/o error occurs
*/
@Override
public int read(byte[] buffer, int off, int len) throws IOException {
int attempts = 0;
for (;;) {
if (checkCancellation()) {
throw new OperationCanceledException();
}
try {
return in.read(buffer, off, len);
} catch (InterruptedIOException e) {
if (e.bytesTransferred != 0) {
return e.bytesTransferred; // keep partial transfer
}
if (++attempts == numAttempts) {
throw new InterruptedIOException(Messages.PollingInputStream_readTimeout);
}
if (DEBUG) {
System.out.println("read retry=" + attempts); //$NON-NLS-1$
}
}
}
}
/**
* Wraps the underlying stream's method.
*
* @param count
* - the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @throws OperationCanceledException
* if the progress monitor is canceled
* @throws InterruptedIOException
* if the underlying operation times out numAttempts times and no data was received, bytesTransferred
* will be zero
* @throws IOException
* if an i/o error occurs
*/
@Override
public long skip(long count) throws IOException {
int attempts = 0;
for (;;) {
if (checkCancellation()) {
throw new OperationCanceledException();
}
try {
return in.skip(count);
} catch (InterruptedIOException e) {
if (e.bytesTransferred != 0) {
return e.bytesTransferred; // keep partial transfer
}
if (++attempts == numAttempts) {
throw new InterruptedIOException(Messages.PollingInputStream_readTimeout);
}
if (DEBUG) {
System.out.println("read retry=" + attempts); //$NON-NLS-1$
}
}
}
}
/**
* Reads any pending input from the input stream so that the stream can savely be closed.
*/
protected void readPendingInput() throws IOException {
byte[] buffer = new byte[2048];
while (true) {
int available = in.available();
if (available < 1) {
break;
}
if (available > buffer.length) {
available = buffer.length;
}
if (in.read(buffer, 0, available) < 1) {
break;
}
}
}
/**
* Called to set whether cancellation will be checked by this stream. Turning cancellation checking off can be very
* useful for protecting critical portions of a protocol that shouldn't be interrupted. For example, it is often
* necessary to protect login sequences.
*
* @param cancellable
* a flag controlling whether this stream will check for cancellation.
*/
public void setIsCancellable(boolean cancellable) {
this.cancellable = cancellable;
}
/**
* Checked whether the monitor for this stream has been cancelled. If the cancellable flag is <code>false</code>
* then the monitor is never cancelled.
*
* @return <code>true</code> if the monitor has been cancelled and <code>false</code> otherwise.
*/
private boolean checkCancellation() {
if (cancellable) {
return monitor.isCanceled();
} else {
return false;
}
}
}