historical/toontown-classic.git/panda/include/conditionVarWin32Impl.h

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/**
* PANDA 3D SOFTWARE
* Copyright (c) Carnegie Mellon University. All rights reserved.
*
* All use of this software is subject to the terms of the revised BSD
* license. You should have received a copy of this license along
* with this source code in a file named "LICENSE."
*
* @file conditionVarWin32Impl.h
* @author drose
* @date 2006-02-07
*/
#ifndef CONDITIONVARWIN32IMPL_H
#define CONDITIONVARWIN32IMPL_H
#include "pandabase.h"
#include "selectThreadImpl.h"
#if defined(WIN32_VC)
#include "mutexWin32Impl.h"
#include "pnotify.h"
class MutexWin32Impl;
/**
* Uses Windows native calls to implement a ConditionVar.
*
* On Windows Vista and above, we use the system's native condition variables.
*
* On Windows XP, we follow the "SetEvent" implementation suggested by
* http://www.cs.wustl.edu/~schmidt/win32-cv-1.html . This allows us to
* implement both notify() and notify_all().
*
* As described by the above reference, this implementation suffers from a few
* weaknesses; in particular, it does not necessarily wake up all threads
* fairly; and it may sometimes incorrectly wake up a thread that was not
* waiting at the time notify() was called. But we figure it's good enough
* for our purposes.
*/
class EXPCL_PANDA_PIPELINE ConditionVarWin32Impl {
public:
INLINE ConditionVarWin32Impl(MutexWin32Impl &mutex);
INLINE ~ConditionVarWin32Impl();
INLINE void wait();
INLINE void wait(double timeout);
INLINE void notify();
INLINE void notify_all();
private:
MutexWin32Impl &_mutex;
// On Windows XP, the first field contains a Signal (auto-reset) event,
// the second field a broadcast (manual reset) event, third a waiter count.
// On Windows Vista and above, the first contains a PCONDITION_VARIABLE.
volatile PVOID _cvar[3] = {nullptr, nullptr, nullptr};
};
#include "conditionVarWin32Impl.I"
#endif // WIN32_VC
#endif