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Extension for usb4java which implements javax.usb (JSR-80).
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/*
 * Copyright (C) 2011 Klaus Reimer 
 * See LICENSE.md for licensing information.
 */

package org.usb4java.javax;

import java.nio.ByteBuffer;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

import javax.usb.UsbControlIrp;
import javax.usb.UsbException;
import javax.usb.UsbIrp;
import javax.usb.UsbShortPacketException;

import org.usb4java.DeviceHandle;
import org.usb4java.LibUsb;


/**
 * Abstract base class for IRP queues.
 * 
 * @author Klaus Reimer ([email protected])
 * @param 
 *            The type of IRPs this queue holds.
 */
abstract class AbstractIrpQueue
{
    /** The queued packets. */
    private final Queue irps = new ConcurrentLinkedQueue();

    /** The queue processor thread. */
    private volatile Thread processor;
    
    /** If queue is currently aborting. */
    private volatile boolean aborting;

    /** The USB device. */
    private final AbstractDevice device;

    /**
     * Constructor.
     * 
     * @param device
     *            The USB device. Must not be null.
     */
    AbstractIrpQueue(final AbstractDevice device)
    {
        if (device == null)
            throw new IllegalArgumentException("device must be set");
        this.device = device;
    }

    /**
     * Queues the specified control IRP for processing.
     * 
     * @param irp
     *            The control IRP to queue.
     */
    public final void add(final T irp)
    {
        this.irps.add(irp);

        // Start the queue processor if not already running.
        if (this.processor == null)
        {
            this.processor = new Thread(new Runnable()
            {
                @Override
                public void run()
                {
                    process();
                }
            });
            this.processor.setDaemon(true);
            this.processor.setName("usb4java IRP Queue Processor");
            this.processor.start();
        }
    }

    /**
     * Processes the queue. Methods returns when the queue is empty.
     */
    final void process()
    {
        // Get the next IRP
        T irp = this.irps.poll();
        
        // If there are no IRPs to process then mark the thread as closing
        // right away. Otherwise process the IRP (and more IRPs from the queue
        // if present).
        if (irp == null)
        {
            this.processor = null;
        }
        else
        {
            while (irp != null)
            {
                // Process the IRP
                try
                {
                    processIrp(irp);
                }
                catch (final UsbException e)
                {
                    irp.setUsbException(e);
                }
    
                // Get next IRP and mark the thread as closing before sending
                // the events for the previous IRP
                final T nextIrp = this.irps.poll();
                if (nextIrp == null) this.processor = null;
    
                // Finish the previous IRP
                irp.complete();
                finishIrp(irp);
    
                // Process next IRP (if present)
                irp = nextIrp;
            }
        }

        // No more IRPs are present in the queue so terminate the thread.
        synchronized (this.irps)
        {
            this.irps.notifyAll();
        }
    }

    /**
     * Processes the IRP.
     * 
     * @param irp
     *            The IRP to process.
     * @throws UsbException
     *             When processing the IRP fails.
     */
    protected abstract void processIrp(final T irp) throws UsbException;

    /**
     * Called after IRP has finished. This can be implemented to send events for
     * example.
     * 
     * @param irp
     *            The IRP which has been finished.
     */
    protected abstract void finishIrp(final UsbIrp irp);

    /**
     * Aborts all queued IRPs. The IRP which is currently processed can't be
     * aborted. This method returns as soon as no more IRPs are in the queue and
     * no more are processed.
     */
    public final void abort()
    {
        this.aborting = true;
        this.irps.clear();
        while (isBusy())
        {
            try
            {
                synchronized (this.irps)
                {
                    if (isBusy()) this.irps.wait();
                }
            }
            catch (final InterruptedException e)
            {
                Thread.currentThread().interrupt();
            }
        }
        this.aborting = false;
    }

    /**
     * Checks if queue is busy. A busy queue is a queue which is currently
     * processing IRPs or which still has IRPs in the queue.
     * 
     * @return True if queue is busy, false if not.
     */
    public final boolean isBusy()
    {
        return !this.irps.isEmpty() || this.processor != null;
    }

    /**
     * Returns the configuration.
     * 
     * @return The configuration.
     */
    protected final Config getConfig()
    {
        return Services.getInstance().getConfig();
    }

    /**
     * Returns the USB device.
     * 
     * @return The USB device. Never null.
     */
    protected final AbstractDevice getDevice()
    {
        return this.device;
    }
    
    /**
     * Processes the control IRP.
     * 
     * @param irp
     *            The IRP to process.
     * @throws UsbException
     *             When processing the IRP fails.
     */
    protected final void processControlIrp(final UsbControlIrp irp)
        throws UsbException
    {
        final ByteBuffer buffer =
            ByteBuffer.allocateDirect(irp.getLength());
        buffer.put(irp.getData(), irp.getOffset(), irp.getLength());
        buffer.rewind();
        final DeviceHandle handle = getDevice().open();
        final int result = LibUsb.controlTransfer(handle, irp.bmRequestType(),
            irp.bRequest(), irp.wValue(), irp.wIndex(), buffer,
            getConfig().getTimeout());
        if (result < 0)
        {
            throw ExceptionUtils.createPlatformException(
                "Unable to submit control message", result);
        }
        buffer.rewind();
        buffer.get(irp.getData(), irp.getOffset(), result);
        irp.setActualLength(result);
        if (irp.getActualLength() != irp.getLength()
            && !irp.getAcceptShortPacket())
        {
            throw new UsbShortPacketException();
        }
    }
    
    /**
     * Checks if this queue is currently aborting.
     * 
     * @return True if queue is aborting, false if not.
     */
    protected final boolean isAborting()
    {
        return this.aborting;
    }
}