/* -*-c++-*- OpenThreads library, Copyright (C) 2002 - 2007  The Open Thread Group
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#ifndef _WIN32CONDITION_H_
#define _WIN32CONDITION_H_

#include "Mutex.h"

namespace OpenThreads {

class Win32ConditionImpl
{
public:
    /// number of waiters.
    long waiters_;

    Condition(long max = 0L)
    {
        waiters_ = 0;
        sema_ = CreateSemaphore(NULL,0,0x7fffffff,NULL);
        waiters_done_ = CreateEvent(NULL,FALSE,FALSE,NULL);
    }

    ~Condition()
    {
    //    CloseHandle(sema_);
    //    CloseHandle(waiters_done_);
    }

    inline int broadcast ()
    {
         waiters_lock_.lock();
         int have_waiters = 0;

        if (waiters_ > 0)
        {
          // We are broadcasting, even if there is just one waiter...
          // Record the fact that we are broadcasting.  This helps the
          // wait() method know how to optimize itself.  Be sure to
          // set this with the <waiters_lock_> held.
          was_broadcast_ = 1;
          have_waiters = 1;
        }
        waiters_lock_.unlock();
        
        int result = 0;
        if (have_waiters)
        {
            // Wake up all the waiters.
            ReleaseSemaphore(sema_,waiters_,NULL);
            WaitForSingleObject(waiters_done_,INFINITE) ;
            // This is okay, even without the <waiters_lock_> held because
            // no other waiter threads can wake up to access it.
            was_broadcast_ = 0;
        }
        return result;
    }

    inline int wait (Mutex& external_mutex)
    {
        // Prevent race conditions on the <waiters_> count.
        waiters_lock_.lock();
        waiters_++;
        waiters_lock_.unlock();
        
        int result = 0;
        
        external_mutex.unlock();
        
        DWORD dwResult = WaitForSingleObject(sema_,INFINITE);
        if(dwResult != WAIT_OBJECT_0)
            result = (int)dwResult;
        
        // Reacquire lock to avoid race conditions on the <waiters_> count.
        waiters_lock_.lock();
        
        // We're ready to return, so there's one less waiter.
        waiters_--;
        
        int last_waiter = was_broadcast_ && waiters_ == 0;
        
        // Release the lock so that other collaborating threads can make
        // progress.
        waiters_lock_.unlock();
        
        if (result != -1 && last_waiter)
            SetEvent(waiters_done_);
        
        external_mutex.lock();
        
        return result;
    }


protected:

  /// Serialize access to the waiters count.
  Mutex waiters_lock_;

  /// Queue up threads waiting for the condition to become signaled.
  HANDLE sema_;
  /**
   * An auto reset event used by the broadcast/signal thread to wait
   * for the waiting thread(s) to wake up and get a chance at the
   * semaphore.
   */
  HANDLE waiters_done_;

  /// Keeps track of whether we were broadcasting or just signaling.
  size_t was_broadcast_;

};

}
#endif
