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Add ULONG PointerToID(void*) and IntPtrToID(size_t) that CRC 64bit pointers

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Sometimes pointers are casted to ULONG just to get an ID or tag - this
is fine for 32bit pointers, but 64bit pointers will truncate which might
result in not being so unique after all.
CRC-ing the pointer should yield a more likely to be unique 32bit value.
NULL is a special case that yields 0 instead of the CRC, so code that
handles IDs/Tags with value 0 differently will continue to work.
For 32bit builds, it just returns the pointer as ULONG.
This commit is contained in:
Daniel Gibson 2016-04-20 17:37:37 +02:00
parent e642cbcd20
commit 23b6374e9a
1 changed files with 30 additions and 0 deletions
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30
Sources/Engine/Base/CRC.h
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@ -70,5 +70,35 @@ inline void CRC_AddBlock(ULONG &ulCRC, UBYTE *pubBlock, ULONG ulSize)
// end crc calculation // end crc calculation
inline void CRC_Finish(ULONG &ulCRC) { ulCRC ^= 0xFFFFFFFF; }; inline void CRC_Finish(ULONG &ulCRC) { ulCRC ^= 0xFFFFFFFF; };
// in 32bit mode, it just returns iPtr ULONG,
// in 64bit mode it returns the CRC hash of iPtr (or 0 if ptr == NULL)
// so either way you should get a value that very likely uniquely identifies the pointer
inline ULONG IntPtrToID(size_t iPtr)
{
#if PLATFORM_32BIT
return (ULONG)iPtr;
#else
// in case the code relies on 0 having special meaning because of NULL-pointers...
if(iPtr == 0) return 0;
ULONG ret;
CRC_Start(ret);
CRC_AddLONGLONG(ret, iPtr);
CRC_Finish(ret);
return ret;
#endif
}
// in 32bit mode, it just returns the pointer's address as ULONG,
// in 64bit mode it returns the CRC hash of the pointer's address (or 0 if ptr == NULL)
// so either way you should get a value that very likely uniquely identifies the pointer
inline ULONG PointerToID(void* ptr)
{
#if PLATFORM_32BIT
return (ULONG)(size_t)ptr;
#else
return IntPtrToID((size_t)ptr);
#endif
}
#endif /* include-once check. */ #endif /* include-once check. */