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/* This file is part of the Spring engine (GPL v2 or later), see LICENSE.html */
#ifndef ONCE_H
#define ONCE_H
// Adapted/ripped from Boost, original license below:
// once.hpp
//
// (C) Copyright 2005-7 Anthony Williams
// (C) Copyright 2005 John Maddock
// (C) Copyright 2011-2013 Vicente J. Botet Escriba
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#include <cstring>
#include <cstddef>
namespace spring
{
struct once_flag;
namespace once
{
struct once_context;
inline bool enter_once_region(once_flag& flag, once_context& ctx) noexcept;
inline void commit_once_region(once_flag& flag, once_context& ctx) noexcept;
inline void rollback_once_region(once_flag& flag, once_context& ctx) noexcept;
}
struct once_flag
{
constexpr once_flag() noexcept
: status(0), count(0)
{}
long status;
long count;
};
#define SPRING_ONCE_INIT once_flag()
#define SPRING_THREAD_INVOKE_RET_VOID std::bind
#define SPRING_THREAD_INVOKE_RET_VOID_CALL ()
namespace once
{
typedef char once_char_type;
unsigned const once_mutex_name_fixed_length=54;
unsigned const once_mutex_name_length=once_mutex_name_fixed_length+
sizeof(void*)*2+sizeof(unsigned long)*2+1;
template <class I>
void int_to_string(I p, once_char_type* buf)
{
for(unsigned i=0; i < sizeof(I)*2; ++i,++buf)
{
once_char_type const a='A';
*buf = a + static_cast<once_char_type>((p >> (i*4)) & 0x0f);
}
*buf = 0;
}
inline void name_once_mutex(once_char_type* mutex_name,void* flag_address)
{
static const once_char_type fixed_mutex_name[]="Local\\{C15730E2-145C-4c5e-B005-3BC753F42475}-once-flag";
std::memcpy(mutex_name,fixed_mutex_name,sizeof(fixed_mutex_name));
once::int_to_string(reinterpret_cast<std::ptrdiff_t>(flag_address),
mutex_name + once_mutex_name_fixed_length);
once::int_to_string(GetCurrentProcessId(),
mutex_name + once_mutex_name_fixed_length + sizeof(void*)*2);
}
inline HANDLE open_once_event(once_char_type* mutex_name,void* flag_address)
{
if(!*mutex_name)
{
name_once_mutex(mutex_name,flag_address);
}
return OpenEventA(SYNCHRONIZE | EVENT_MODIFY_STATE,
FALSE,
mutex_name);
}
inline HANDLE create_once_event(once_char_type* mutex_name,void* flag_address)
{
if(!*mutex_name)
{
name_once_mutex(mutex_name,flag_address);
}
return CreateEventA(0, TRUE, FALSE, mutex_name);
}
struct once_context {
long const function_complete_flag_value;
long const running_value;
bool counted;
HANDLE event_handle;
once::once_char_type mutex_name[once_mutex_name_length];
once_context() :
function_complete_flag_value(0xc15730e2),
running_value(0x7f0725e3),
counted(false),
event_handle(NULL)
{
mutex_name[0]=0;
}
~once_context() {
CloseHandle(event_handle);
}
};
enum once_action {try_, break_, continue_};
inline bool enter_once_region(once_flag& flag, once_context& ctx) noexcept
{
long status=InterlockedCompareExchange(&flag.status,ctx.running_value,0);
if(!status)
{
if(!ctx.event_handle)
{
ctx.event_handle=once::open_once_event(ctx.mutex_name,&flag);
}
if(ctx.event_handle)
{
ResetEvent(ctx.event_handle);
}
return true;
}
return false;
}
inline void commit_once_region(once_flag& flag, once_context& ctx) noexcept
{
if(!ctx.counted)
{
InterlockedIncrement(&flag.count);
ctx.counted=true;
}
InterlockedExchange(&flag.status,ctx.function_complete_flag_value);
if(!ctx.event_handle &&
(InterlockedCompareExchange(&flag.count,0,0)>1))
{
ctx.event_handle=once::create_once_event(ctx.mutex_name,&flag);
}
if(ctx.event_handle)
{
SetEvent(ctx.event_handle);
}
}
inline void rollback_once_region(once_flag& flag, once_context& ctx) noexcept
{
InterlockedExchange(&flag.status,0);
if(!ctx.event_handle)
{
ctx.event_handle=once::open_once_event(ctx.mutex_name,&flag);
}
if(ctx.event_handle)
{
SetEvent(ctx.event_handle);
}
}
}
inline void call_once(once_flag& flag, void (*f)())
{
// Try for a quick win: if the procedure has already been called
// just skip through:
once::once_context ctx;
while(InterlockedCompareExchange(&flag.status,0,0)
!=ctx.function_complete_flag_value)
{
if(once::enter_once_region(flag, ctx))
{
f();
once::commit_once_region(flag, ctx);
break;
}
if(!ctx.counted)
{
InterlockedIncrement(&flag.count);
ctx.counted=true;
long status=InterlockedCompareExchange(&flag.status,0,0);
if(status==ctx.function_complete_flag_value)
{
break;
}
if(!ctx.event_handle)
{
ctx.event_handle=once::create_once_event(ctx.mutex_name,&flag);
continue;
}
}
WaitForSingleObjectEx(ctx.event_handle, INFINITE, 0);
}
}
//#endif
template<typename Function>
inline void call_once(once_flag& flag, Function&& f)
{
// Try for a quick win: if the procedure has already been called
// just skip through:
once::once_context ctx;
while(InterlockedCompareExchange(&flag.status,0,0)
!=ctx.function_complete_flag_value)
{
if(once::enter_once_region(flag, ctx))
{
f();
once::commit_once_region(flag, ctx);
break;
}
if(!ctx.counted)
{
InterlockedIncrement(&flag.count);
ctx.counted=true;
long status=InterlockedCompareExchange(&flag.status,0,0);
if(status==ctx.function_complete_flag_value)
{
break;
}
if(!ctx.event_handle)
{
ctx.event_handle=once::create_once_event(ctx.mutex_name,&flag);
continue;
}
}
WaitForSingleObjectEx(ctx.event_handle,INFINITE,0);
}
}
template<typename Function, class A, class ...ArgTypes>
inline void call_once(once_flag& flag, Function&& f, A&& a, ArgTypes&&... args)
{
// Try for a quick win: if the procedure has already been called
// just skip through:
once::once_context ctx;
while(InterlockedCompareExchange(&flag.status,0,0)
!=ctx.function_complete_flag_value)
{
if(once::enter_once_region(flag, ctx))
{
std::bind(
std::forward<Function>(f),
std::forward<A>(a),
std::forward<ArgTypes>(args)...
)();
once::commit_once_region(flag, ctx);
break;
}
if(!ctx.counted)
{
InterlockedIncrement(&flag.count);
ctx.counted=true;
long status=InterlockedCompareExchange(&flag.status,0,0);
if(status==ctx.function_complete_flag_value)
{
break;
}
if(!ctx.event_handle)
{
ctx.event_handle=once::create_once_event(ctx.mutex_name,&flag);
continue;
}
}
WaitForSingleObjectEx(ctx.event_handle,INFINITE,0);
}
}
}
#endif
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