vmthreadqueueentry.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 95 行

/*
 * $Id: VmThreadQueueEntry.java,v 1.1 2003/11/25 11:41:17 epr Exp $
 */
package org.jnode.vm;

/**
 * Queue entry for VmThread's.
 * 
 * This class is not synchronized, but protected by PragmaUninterruptible's,
 * since it is used by the scheduler itself.
 * 
 * @author Ewout Prangsma ([e-mail])
 */
final class VmThreadQueueEntry extends VmSystemObject {
	
	protected VmThreadQueueEntry next;
	private VmThreadQueue inUseByQueue;
	protected final VmThread thread;
	private String lastCaller;
	
	/**
	 * Initialize this instance
	 * @param thread
	 */
	public VmThreadQueueEntry(VmThread thread) {
		this.thread = thread;
	}
	
	/**
	 * Gets the next entry
	 * @return next entry
	 * @throws PragmaUninterruptible
	 */
	final VmThreadQueueEntry getNext() 
	throws PragmaUninterruptible {
		return next;
	}

	/**
	 * Is this entry used on any queue.
	 * @return boolean
	 * @throws PragmaUninterruptible
	 */
	final boolean isInUse() 
	throws PragmaUninterruptible {
		return (inUseByQueue != null);
	}
	
	/**
	 * @param q
	 * @param caller
	 * @throws PragmaUninterruptible
	 */
	final void setInUse(VmThreadQueue q, String caller) 
	throws PragmaUninterruptible {
		if (this.inUseByQueue != null) {
			// currently in use
			if (q == null) {
				this.inUseByQueue = null;
			} else if (q == this.inUseByQueue) {
				throw new RuntimeException("Thread (" + thread + ") is already on the " + this.inUseByQueue.name + " queue by " + lastCaller);		
			} else {
				throw new RuntimeException("Thread (" + thread + ") is already in use in another queue: " + this.inUseByQueue.name + "by " + lastCaller + ", cannot add to " + q.name);		
			}
		} else {
			// currently NOT in use
			if (q == null) {
				throw new RuntimeException("Thread (" + thread + ") is not in use");		
			} else {
				this.inUseByQueue = q;
				this.lastCaller = caller;
			}
		}
	}

	/**
	 * @param entry
	 * @throws PragmaUninterruptible
	 */
	final void setNext(VmThreadQueueEntry entry) 
	throws PragmaUninterruptible {
		this.next = entry;
	}
	
	/**
	 * Gets the thread of this entry
	 * @return The thread
	 * @throws PragmaUninterruptible
	 */
	final VmThread getThread() 
	throws PragmaUninterruptible {
		return thread;
	}
}