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/**
*
*/
package nokogiri.internals;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedBlockingQueue;
import nokogiri.XmlSaxPushParser;
/**
* A smart input stream that signals the caller when a chunk of data is consumed
* from the stream. The main use of this stream is to synchronize the
* {@link XmlSaxPushParser} and the {@link XmlSaxParser} which runs in a
* different thread.
*
* @author John Shahid <jvshahid@gmail.com>
*/
public class NokogiriBlockingQueueInputStream extends InputStream
{
private final LinkedBlockingQueue<Task> queue;
protected Task currentTask;
protected ByteArrayInputStream currentStream;
protected int position;
protected boolean closed = false;
public static final ByteArrayInputStream END = new ByteArrayInputStream(new byte[0]);
private static class Task extends FutureTask<Void>
{
private final ByteArrayInputStream stream;
public
Task(ByteArrayInputStream stream)
{
super(new Callable<Void>() {
@Override
public Void call() throws Exception {
// TODO Auto-generated method stub
return null;
}
});
this.stream = stream;
}
public ByteArrayInputStream
getStream()
{
return stream;
}
@Override
public void
run()
{
// don't do anything
}
@Override
public boolean
runAndReset()
{
// don't do anything
return true;
}
@Override
public void
set(Void v)
{
super.set(v);
}
}
public
NokogiriBlockingQueueInputStream()
{
queue = new LinkedBlockingQueue<Task>();
}
/**
* This method shouldn't be called unless the parser has finished parsing or
* threw an exception while doing so, otherwise, there'll be the protential
* that the read method will block indefinitely.
*/
@Override
public synchronized void
close()
{
closed = true;
List<Task> tasks = new LinkedList<Task>();
queue.drainTo(tasks);
tasks.add(currentTask);
for (Task task : tasks) {
task.set(null);
}
}
/**
* Add @param stream to the end of the queue of data that will be returned by
* {@link #read()} and its variants. The method will @return a future whose
* {@link Future#get()} will block until the data in @param stream is read.
*
* Passing the special stream {@link #END} to this method, will cause
* {@link #read()} to return an eof indicator (i.e. -1) to the caller, after
* all the data inserted before {@link #END} is processed.
*
* @return
*/
public synchronized Future<Void>
addChunk(ByteArrayInputStream stream) throws ClosedStreamException
{
if (closed) {
throw new ClosedStreamException("Cannot add a chunk to a closed stream");
}
Task task = new Task(stream);
queue.add(task);
return task;
}
/*
* (non-Javadoc)
*
* @see java.io.InputStream#read()
*/
@Override
public int
read() throws IOException
{
if (currentTask == null || currentStream.available() == 0)
if (getNextTask() == -1) {
return -1;
}
return currentStream.read();
}
/*
* (non-Javadoc)
*
* @see java.io.InputStream#read(byte[], int, int)
*/
@Override
public int
read(byte[] bytes, int off, int len)
{
if (currentTask == null || currentStream.available() == 0) {
if (getNextTask() == -1) {
currentTask.set(null);
return -1;
}
}
return currentStream.read(bytes, off, len);
}
protected int
getNextTask()
{
while (true) {
try {
if (currentTask != null) {
currentTask.set(null);
}
currentTask = queue.take();
currentStream = currentTask.getStream();
return currentStream.available() == 0 ? -1 : currentStream.available();
} catch (InterruptedException ex) {
// keep retrying to read
}
}
}
}
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