深入分析 Java I/O 的工作机制

[java]代码库

class AsyncResult implements IAsyncResult{ 
    private byte[] result_; 
    private AtomicBoolean done_ = new AtomicBoolean(false); 
    private Lock lock_ = new ReentrantLock(); 
    private Condition condition_; 
    private long startTime_; 
    public AsyncResult(){        
        condition_ = lock_.newCondition();// 创建一个锁
        startTime_ = System.currentTimeMillis(); 
    }    
 /*** 检查需要的数据是否已经返回，如果没有返回阻塞 */ 
 public byte[] get(){ 
        lock_.lock(); 
        try{ 
            if (!done_.get()){condition_.await();} 
        }catch (InterruptedException ex){ 
            throw new AssertionError(ex); 
        }finally{lock_.unlock();} 
        return result_; 
 } 
 /*** 检查需要的数据是否已经返回 */ 
    public boolean isDone(){return done_.get();} 
 /*** 检查在指定的时间内需要的数据是否已经返回，如果没有返回抛出超时异常 */ 
    public byte[] get(long timeout, TimeUnit tu) throws TimeoutException{ 
        lock_.lock(); 
        try{            boolean bVal = true; 
            try{ 
                if ( !done_.get() ){ 
           long overall_timeout = timeout - (System.currentTimeMillis() - startTime_); 
                    if(overall_timeout > 0)// 设置等待超时的时间
                        bVal = condition_.await(overall_timeout, TimeUnit.MILLISECONDS); 
                    else bVal = false; 
                } 
            }catch (InterruptedException ex){ 
                throw new AssertionError(ex); 
            } 
            if ( !bVal && !done_.get() ){// 抛出超时异常
                throw new TimeoutException("Operation timed out."); 
            } 
        }finally{lock_.unlock();      } 
        return result_; 
 } 
 /*** 该函数拱另外一个线程设置要返回的数据，并唤醒在阻塞的线程 */ 
    public void result(Message response){        
        try{ 
            lock_.lock(); 
            if ( !done_.get() ){                
                result_ = response.getMessageBody();// 设置返回的数据
                done_.set(true); 
                condition_.signal();// 唤醒阻塞的线程
            } 
        }finally{lock_.unlock();}        
    }    
 }//源代码片段来自云代码http://yuncode.net