OW_ThreadOnce.cpp

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#include "OW_config.h"
#include "OW_ThreadOnce.hpp"
#include "OW_Assertion.hpp"

#if defined(OW_WIN32)

#include <stdio.h>

namespace OW_NAMESPACE
{

void callOnce(OnceFlag& flag, void (*func)())
{
   // this is the double-checked locking pattern, but with a bit more strength than normally implemented :-)
    if (InterlockedCompareExchange(&flag, 1, 1) == 0)
    {
      wchar_t mutexName[MAX_PATH];
      _snwprintf(mutexName, MAX_PATH, L"%X-%p-587ccea9-c95a-4e81-ac51-ab0ddc6cef63", GetCurrentProcessId(), &flag);
      mutexName[MAX_PATH - 1] = 0;

        HANDLE mutex = CreateMutexW(NULL, FALSE, mutexName);
        OW_ASSERT(mutex != NULL);

        int res = 0;
        res = WaitForSingleObject(mutex, INFINITE);
        OW_ASSERT(res == WAIT_OBJECT_0);

        if (InterlockedCompareExchange(&flag, 1, 1) == 0)
        {
            try
            {
                func();
            }
            catch (...)
            {
                res = ReleaseMutex(mutex);
                OW_ASSERT(res);
                res = CloseHandle(mutex);
                OW_ASSERT(res);
                throw;
            }
            InterlockedExchange(&flag, 1);
        }

        res = ReleaseMutex(mutex);
        OW_ASSERT(res);
        res = CloseHandle(mutex);
        OW_ASSERT(res);
    }
}


} // end namespace OW_NAMESPACE

#endif

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