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/*******************************************************************************
* Copyright (c) 2000, 2007 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
* EclipseSource - modification after copying to ECF filetransfer provider
*******************************************************************************/
package org.eclipse.ecf.provider.filetransfer.util;
import java.io.*;
import org.eclipse.core.runtime.*;
import org.eclipse.ecf.internal.provider.filetransfer.Activator;
/**
* 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 int numAttempts;
private 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
*/
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.
logError(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("Timeout while closing input stream"); //$NON-NLS-1$
} catch (IOException e) {
// ignore it - see
// https://bugs.eclipse.org/bugs/show_bug.cgi?id=203423#c10
}
}
}
}
private void logError(String message, IOException e) {
Activator.getDefault().log(new Status(IStatus.ERROR, Activator.PLUGIN_ID, IStatus.ERROR, message, e));
}
/**
* 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
*/
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("Timeout while reading input stream"); //$NON-NLS-1$
}
}
}
/**
* 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
*/
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("Timeout while reading input stream"); //$NON-NLS-1$
}
}
}
/**
* 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
*/
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("Timeout while reading input stream"); //$NON-NLS-1$
}
}
}
/**
* 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();
}
return false;
}
}
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