mirror of
https://github.com/ptitSeb/Serious-Engine
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23b6374e9a
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.
105 lines
2.9 KiB
C
105 lines
2.9 KiB
C
/* Copyright (c) 2002-2012 Croteam Ltd.
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This program is free software; you can redistribute it and/or modify
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it under the terms of version 2 of the GNU General Public License as published by
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the Free Software Foundation
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */
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#ifndef SE_INCL_CRC_H
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#define SE_INCL_CRC_H
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#ifdef PRAGMA_ONCE
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#pragma once
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#endif
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extern ENGINE_API ULONG crc_aulCRCTable[256];
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// begin crc calculation
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inline void CRC_Start(ULONG &ulCRC) { ulCRC = 0xFFFFFFFF; };
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// add data to a crc value
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inline void CRC_AddBYTE( ULONG &ulCRC, UBYTE ub)
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{
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ulCRC = (ulCRC>>8)^crc_aulCRCTable[UBYTE(ulCRC)^ub];
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};
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inline void CRC_AddWORD( ULONG &ulCRC, UWORD uw)
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{
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CRC_AddBYTE(ulCRC, UBYTE(uw>> 8));
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CRC_AddBYTE(ulCRC, UBYTE(uw>> 0));
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};
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inline void CRC_AddLONG( ULONG &ulCRC, ULONG ul)
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{
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CRC_AddBYTE(ulCRC, UBYTE(ul>>24));
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CRC_AddBYTE(ulCRC, UBYTE(ul>>16));
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CRC_AddBYTE(ulCRC, UBYTE(ul>> 8));
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CRC_AddBYTE(ulCRC, UBYTE(ul>> 0));
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};
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inline void CRC_AddLONGLONG( ULONG &ulCRC, __uint64 x)
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{
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CRC_AddBYTE(ulCRC, UBYTE(x>>56));
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CRC_AddBYTE(ulCRC, UBYTE(x>>48));
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CRC_AddBYTE(ulCRC, UBYTE(x>>40));
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CRC_AddBYTE(ulCRC, UBYTE(x>>32));
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CRC_AddBYTE(ulCRC, UBYTE(x>>24));
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CRC_AddBYTE(ulCRC, UBYTE(x>>16));
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CRC_AddBYTE(ulCRC, UBYTE(x>> 8));
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CRC_AddBYTE(ulCRC, UBYTE(x>> 0));
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}
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inline void CRC_AddFLOAT(ULONG &ulCRC, FLOAT f)
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{
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CRC_AddLONG(ulCRC, *(ULONG*)&f);
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};
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// add memory block to a CRC value
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inline void CRC_AddBlock(ULONG &ulCRC, UBYTE *pubBlock, ULONG ulSize)
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{
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for( INDEX i=0; i<ulSize; i++) CRC_AddBYTE( ulCRC, pubBlock[i]);
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};
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// end crc calculation
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inline void CRC_Finish(ULONG &ulCRC) { ulCRC ^= 0xFFFFFFFF; };
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// in 32bit mode, it just returns iPtr ULONG,
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// in 64bit mode it returns the CRC hash of iPtr (or 0 if ptr == NULL)
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// so either way you should get a value that very likely uniquely identifies the pointer
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inline ULONG IntPtrToID(size_t iPtr)
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{
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#if PLATFORM_32BIT
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return (ULONG)iPtr;
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#else
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// in case the code relies on 0 having special meaning because of NULL-pointers...
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if(iPtr == 0) return 0;
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ULONG ret;
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CRC_Start(ret);
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CRC_AddLONGLONG(ret, iPtr);
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CRC_Finish(ret);
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return ret;
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#endif
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}
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// in 32bit mode, it just returns the pointer's address as ULONG,
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// in 64bit mode it returns the CRC hash of the pointer's address (or 0 if ptr == NULL)
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// so either way you should get a value that very likely uniquely identifies the pointer
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inline ULONG PointerToID(void* ptr)
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{
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#if PLATFORM_32BIT
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return (ULONG)(size_t)ptr;
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#else
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return IntPtrToID((size_t)ptr);
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#endif
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}
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#endif /* include-once check. */
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