queuehead.java

来自「纯java操作系统jnode,安装简单和操作简单的个人使用的Java操作系统」· Java 代码 · 共 177 行

/*
 * $Id: QueueHead.java,v 1.1 2003/11/25 11:42:17 epr Exp $
 */
package org.jnode.driver.usb.uhci;

import org.jnode.system.ResourceManager;
import org.jnode.util.NumberUtils;

/**
 * @author Ewout Prangsma ([e-mail])
 */
public class QueueHead extends AbstractTreeStructure {

	/** Horizontal link */
	private AbstractTreeStructure linkPointer;
	/** Vertical link is updated by HC, so don't keep here */
	
	/**
	 * Create a new instance
	 * @param rm
	 */
	public QueueHead(ResourceManager rm) {
		super(rm, 32, 16);
		// Set Linkpointer to invalid
		setInt(0, 1);
		// Set Element Linkpointer to invalid
		setInt(4, 1);
	}
	
	/**
	 * Set the link pointer to the given transfer descriptor.
	 * @param td
	 */
	public final void setLink(TransferDescriptor td) {
		final int ptr = td.getDescriptorAddress() & 0xFFFFFFF0;
		this.linkPointer = td;
		setInt(0, ptr);
	}
	
	/**
	 * Set the link pointer to the given queue head.
	 * @param qh
	 */
	public final void setLink(QueueHead qh) {
		final int ptr = (qh.getDescriptorAddress() & 0xFFFFFFF0) | 0x2;
		this.linkPointer = qh;
		setInt(0, ptr);
	}
	
	/**
	 * Insert the link pointer to the given queue head.
	 * @param qh
	 */
	public final void insertLink(QueueHead qh) {
		if (qh.getLink() != null) {
			throw new IllegalArgumentException("qh.link must be null");
		}
		qh.setInt(0, this.getInt(0));
		qh.linkPointer = this.linkPointer;
		setLink(qh);
	}
	
	/**
	 * Set the link pointer as invalid
	 */
	public final void removeLink() {
		setInt(0, 1);
		this.linkPointer = null;
	}
	
	/**
	 * Remove a given queue from the linked list starting at this queue.
	 */
	public final void removeLink(QueueHead qh) {
		QueueHead p = this;
		while (p.linkPointer != qh) {
			if (p.linkPointer instanceof QueueHead) {
				p = (QueueHead)p.linkPointer;
			} else {
				// qh not found in linked list
				return;
			}
		}
		this.linkPointer = qh.linkPointer;
		this.setInt(0, qh.getInt(0));
	}
	
	/**
	 * @return Returns the linkPointer.
	 */
	public final AbstractStructure getLink() {
		return this.linkPointer;
	}
	
	/**
	 * Add a request to this queue.
	 * @param request
	 */
	public final void add(UHCIRequest request) {
		if (isEmpty()) {
			//log.debug("execute request");
			setElement(request.getFirstTD());
		} else {
			throw new IllegalStateException("Cannot add to non-empty queue");
		}
	}
	
	/**
	 * Remove a request from this queue.
	 * @param request
	 */
	public final void remove(UHCIRequest request) {
		TransferDescriptor td = request.getFirstTD();
		while (td != null) {
			if (isElement(td)) {
				removeElement();
				// Break the loop, we're done
				td = null;
			} else {
				td = td.getNextTD();
			}
		}
	}
	
	/**
	 * Set the element link pointer to the given transfer descriptor.
	 * @param td
	 */
	final void setElement(TransferDescriptor td) {
		final int ptr = td.getDescriptorAddress() & 0xFFFFFFF0;
		setInt(4, ptr);
	}
	
	/**
	 * Is the element link pointer pointing to the given transfer descriptor.
	 * @param td
	 */
	private final boolean isElement(TransferDescriptor td) {
		final int cur = getInt(4);
		final int ptr = td.getDescriptorAddress() & 0xFFFFFFF0;
		return ((cur & 1) == 0) && ((cur & 0xFFFFFFF0) == ptr);
	}
	
	/**
	 * Set the element link pointer to the given queue head.
	 * @param qh
	 */
	/*private final void setElement(QueueHead qh) {
		final int ptr = (qh.getDescriptorAddress() & 0xFFFFFFF0) | 0x2;
		setInt(4, ptr);
	}*/
	
	/**
	 * Set the element link pointer as invalid
	 */
	private final void removeElement() {
		setInt(4, 1);
	}
	
	/**
	 * Does this queue have no elements.
	 * @return True if this queue has not elements (T-bit=1), false otherwise.
	 */
	public final boolean isEmpty() {
		final int v = getInt(4);
		return ((v & 1) == 1);
	}
	
	/**
	 * Convert to a String representation
	 * @see java.lang.Object#toString()
	 */
	public String toString() {
		return "QH[" + NumberUtils.hex(getInt(0)) + ", " + NumberUtils.hex(getInt(4)) + "]"; 
	}
}