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