43 lines
1.2 KiB
C
43 lines
1.2 KiB
C
#include "nxonce.h"
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#include "foundation/error.h"
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#if 0 && _WIN32_WINNT >= 0x600
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void NXOnce(nx_once_t once, int (NX_ONCE_API *init_fn)(nx_once_t, void *, void **), void *param)
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{
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InitOnceExecuteOnce(once, (PINIT_ONCE_FN)init_fn, param, 0);
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}
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void NXOnceInit(nx_once_t once)
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{
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InitOnceInitialize(once);
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}
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#else
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/* this ONLY works because of the strict(ish) memory ordering of the AMD64/x86 processors.
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Don't use this implementation for a processor that has loose memory ordering restriction (e.g. ARM, PowerPC)
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see http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf
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*/
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void NXOnce(nx_once_t once, int (NX_ONCE_API *init_fn)(nx_once_t, void *, void **), void *param)
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{
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if (once->status)
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return;
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EnterCriticalSection(&once->critical_section);
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if (once->status)
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{
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LeaveCriticalSection(&once->critical_section);
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return;
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}
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init_fn(once, param, 0);
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// 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!
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once->status = 1;
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LeaveCriticalSection(&once->critical_section);
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}
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void NXOnceInit(nx_once_t once)
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{
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once->status=0;
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InitializeCriticalSection(&once->critical_section);
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}
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#endif |