/*
  File: MutexImpl.java

  Originally written by Doug Lea and released into the public domain.
  This may be used for any purposes whatsoever without acknowledgment.
  Thanks for the assistance and support of Sun Microsystems Labs,
  and everyone contributing, testing, and using this code.

  History:
  Date       Who                What
  11Jun1998  dl               Create public version
*/

public class MutexImpl implements Mutex  {

  /** The lock status **/
  protected boolean inuse_ = false;

  public void acquire() throws InterruptedException {
    if (Thread.interrupted()) throw new InterruptedException();
    synchronized(this) {
      try {
        while (inuse_) wait();
        inuse_ = true;
      }
      catch (InterruptedException ex) {
        notify();
        throw ex;
      }
    }
  }

  public synchronized void release()  {
    inuse_ = false;
    notify(); 
  }


  public boolean attempt(long msecs) throws InterruptedException {
    if (Thread.interrupted()) throw new InterruptedException();
    synchronized(this) {
      if (!inuse_) {
        inuse_ = true;
        return true;
      }
      else if (msecs <= 0)
        return false;
      else {
        long waitTime = msecs;
        long start = System.currentTimeMillis();
        try {
          for (;;) {
            wait(waitTime);
            if (!inuse_) {
              inuse_ = true;
              return true;
            }
            else {
              waitTime = msecs - (System.currentTimeMillis() - start);
              if (waitTime <= 0) 
                return false;
            }
          }
        }
        catch (InterruptedException ex) {
          notify();
          throw ex;
        }
      }
    }  
  }

}