mirror of
https://github.com/id-Software/DOOM-3-BFG.git
synced 2024-12-03 09:22:45 +00:00
178 lines
6.4 KiB
C++
178 lines
6.4 KiB
C++
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#pragma hdrstop
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#include "../precompiled.h"
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/*
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CRC-32
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Copyright (C) 1995-1998 Mark Adler
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*/
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#define CRC32_INIT_VALUE 0xffffffffL
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#define CRC32_XOR_VALUE 0xffffffffL
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#ifdef CREATE_CRC_TABLE
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static unsigned long crctable[256];
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/*
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Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
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x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0.
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Polynomials over GF(2) are represented in binary, one bit per coefficient,
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with the lowest powers in the most significant bit. Then adding polynomials
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is just exclusive-or, and multiplying a polynomial by x is a right shift by
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one. If we call the above polynomial p, and represent a byte as the
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polynomial q, also with the lowest power in the most significant bit (so the
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byte 0xb1 is the polynomial x^7+x^3+x^1+x^0), then the CRC is (q*x^32) mod p,
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where a mod b means the remainder after dividing a by b.
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This calculation is done using the shift-register method of multiplying and
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taking the remainder. The register is initialized to zero, and for each
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incoming bit, x^32 is added mod p to the register if the bit is a one (where
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x^32 mod p is p+x^32 = x^26+...+x^0), and the register is multiplied mod p by
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x (which is shifting right by one and adding x^32 mod p if the bit shifted
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out is a one). We start with the highest power (least significant bit) of
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q and repeat for all eight bits of q.
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The table is simply the CRC of all possible eight bit values. This is all
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the information needed to generate CRC's on data a byte at a time for all
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combinations of CRC register values and incoming bytes.
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*/
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void make_crc_table( void )
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{
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int i, j;
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unsigned long c, poly;
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/* terms of polynomial defining this crc (except x^32): */
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static const byte p[] = {0, 1, 2, 4, 5, 7, 8, 10, 11, 12, 16, 22, 23, 26};
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/* make exclusive-or pattern from polynomial (0xedb88320L) */
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poly = 0L;
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for( i = 0; i < sizeof( p ) / sizeof( byte ); i++ )
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{
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poly |= 1L << ( 31 - p[i] );
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}
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for( i = 0; i < 256; i++ )
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{
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c = ( unsigned long )i;
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for( j = 0; j < 8; j++ )
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{
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c = ( c & 1 ) ? poly ^ ( c >> 1 ) : ( c >> 1 );
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}
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crctable[i] = c;
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}
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}
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#else
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/*
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Table of CRC-32's of all single-byte values (made by make_crc_table)
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*/
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static unsigned long crctable[256] =
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{
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0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL,
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0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L,
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0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L,
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0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L,
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0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
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0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L,
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0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL,
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0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L,
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0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 0xa2677172L,
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0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
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0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L,
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0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L,
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0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L,
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0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 0xb8bda50fL,
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0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
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0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL,
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0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL,
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0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L,
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0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 0xe10e9818L,
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0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
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0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL,
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0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L,
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0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL,
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0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L,
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0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
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0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL,
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0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L,
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0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L,
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0x5005713cL, 0x270241aaL, 0xbe0b1010L, 0xc90c2086L,
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0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
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0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L,
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0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL,
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0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL,
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0xead54739L, 0x9dd277afL, 0x04db2615L, 0x73dc1683L,
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0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
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0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L,
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0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL,
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0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L,
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0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 0x67dd4accL,
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0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
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0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L,
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0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL,
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0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L,
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0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 0x4669be79L,
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0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
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0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL,
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0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L,
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0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL,
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0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 0x026d930aL,
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0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
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0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L,
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0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L,
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0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL,
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0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 0x18b74777L,
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0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
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0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L,
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0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L,
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0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL,
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0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L,
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0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
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0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L,
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0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL,
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0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L,
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0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL
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};
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#endif
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void CRC32_InitChecksum( unsigned long& crcvalue )
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{
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crcvalue = CRC32_INIT_VALUE;
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}
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void CRC32_Update( unsigned long& crcvalue, const byte data )
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{
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crcvalue = crctable[( crcvalue ^ data ) & 0xff ] ^ ( crcvalue >> 8 );
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}
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void CRC32_UpdateChecksum( unsigned long& crcvalue, const void* data, int length )
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{
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unsigned long crc;
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const unsigned char* buf = ( const unsigned char* ) data;
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crc = crcvalue;
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while( length-- )
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{
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crc = crctable[( crc ^ ( *buf++ ) ) & 0xff ] ^ ( crc >> 8 );
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}
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crcvalue = crc;
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}
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void CRC32_FinishChecksum( unsigned long& crcvalue )
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{
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crcvalue ^= CRC32_XOR_VALUE;
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}
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unsigned long CRC32_BlockChecksum( const void* data, int length )
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{
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unsigned long crc;
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CRC32_InitChecksum( crc );
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CRC32_UpdateChecksum( crc, data, length );
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CRC32_FinishChecksum( crc );
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return crc;
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}
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