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#include "nxonce.h"
#include "foundation/error.h"
#if 0 && _WIN32_WINNT >= 0x600
void NXOnce(nx_once_t once, int (NX_ONCE_API *init_fn)(nx_once_t, void *, void **), void *param)
{
InitOnceExecuteOnce(once, (PINIT_ONCE_FN)init_fn, param, 0);
}
void NXOnceInit(nx_once_t once)
{
InitOnceInitialize(once);
}
#else
/* this ONLY works because of the strict(ish) memory ordering of the AMD64/x86 processors.
Don't use this implementation for a processor that has loose memory ordering restriction (e.g. ARM, PowerPC)
see http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf
*/
void NXOnce(nx_once_t once, int (NX_ONCE_API *init_fn)(nx_once_t, void *, void **), void *param)
{
if (once->status)
return;
EnterCriticalSection(&once->critical_section);
if (once->status)
{
LeaveCriticalSection(&once->critical_section);
return;
}
init_fn(once, param, 0);
// benski> not important for the x86, but on processors with weak memory-order on stores, once->status might set to 1 BEFORE all stores from init_fn complete!
once->status = 1;
LeaveCriticalSection(&once->critical_section);
}
void NXOnceInit(nx_once_t once)
{
once->status=0;
InitializeCriticalSection(&once->critical_section);
}
#endif
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