зеркало из https://github.com/mozilla/pjs.git
163 строки
7.2 KiB
C
163 строки
7.2 KiB
C
/* crc32.c -- compute the CRC-32 of a data stream
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* Copyright (C) 1995-1996 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/* This file was modified since it was taken from the zlib distribution */
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/* $Id: crc32.c,v 1.1 2000-03-31 20:13:09 relyea%netscape.com Exp $ */
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#include "zlib.h"
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#define local static
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#ifdef DYNAMIC_CRC_TABLE
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local int crc_table_empty = 1;
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local uLongf crc_table[256];
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local void make_crc_table OF((void));
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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.
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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), 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+...+1), 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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local void make_crc_table()
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{
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uLong c;
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int n, k;
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uLong poly; /* polynomial exclusive-or pattern */
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/* terms of polynomial defining this crc (except x^32): */
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static 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 (n = 0; n < sizeof(p)/sizeof(Byte); n++)
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poly |= 1L << (31 - p[n]);
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for (n = 0; n < 256; n++)
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{
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c = (uLong)n;
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for (k = 0; k < 8; k++)
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c = c & 1 ? poly ^ (c >> 1) : c >> 1;
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crc_table[n] = c;
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}
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crc_table_empty = 0;
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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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local uLongf crc_table[256] = {
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0x00000000UL, 0x77073096UL, 0xee0e612cUL, 0x990951baUL, 0x076dc419UL,
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0x706af48fUL, 0xe963a535UL, 0x9e6495a3UL, 0x0edb8832UL, 0x79dcb8a4UL,
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0xe0d5e91eUL, 0x97d2d988UL, 0x09b64c2bUL, 0x7eb17cbdUL, 0xe7b82d07UL,
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0x90bf1d91UL, 0x1db71064UL, 0x6ab020f2UL, 0xf3b97148UL, 0x84be41deUL,
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0x1adad47dUL, 0x6ddde4ebUL, 0xf4d4b551UL, 0x83d385c7UL, 0x136c9856UL,
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0x646ba8c0UL, 0xfd62f97aUL, 0x8a65c9ecUL, 0x14015c4fUL, 0x63066cd9UL,
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0xfa0f3d63UL, 0x8d080df5UL, 0x3b6e20c8UL, 0x4c69105eUL, 0xd56041e4UL,
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0xa2677172UL, 0x3c03e4d1UL, 0x4b04d447UL, 0xd20d85fdUL, 0xa50ab56bUL,
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0x35b5a8faUL, 0x42b2986cUL, 0xdbbbc9d6UL, 0xacbcf940UL, 0x32d86ce3UL,
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0x45df5c75UL, 0xdcd60dcfUL, 0xabd13d59UL, 0x26d930acUL, 0x51de003aUL,
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0xc8d75180UL, 0xbfd06116UL, 0x21b4f4b5UL, 0x56b3c423UL, 0xcfba9599UL,
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0xb8bda50fUL, 0x2802b89eUL, 0x5f058808UL, 0xc60cd9b2UL, 0xb10be924UL,
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0x2f6f7c87UL, 0x58684c11UL, 0xc1611dabUL, 0xb6662d3dUL, 0x76dc4190UL,
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0x01db7106UL, 0x98d220bcUL, 0xefd5102aUL, 0x71b18589UL, 0x06b6b51fUL,
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0x9fbfe4a5UL, 0xe8b8d433UL, 0x7807c9a2UL, 0x0f00f934UL, 0x9609a88eUL,
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0xe10e9818UL, 0x7f6a0dbbUL, 0x086d3d2dUL, 0x91646c97UL, 0xe6635c01UL,
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0x6b6b51f4UL, 0x1c6c6162UL, 0x856530d8UL, 0xf262004eUL, 0x6c0695edUL,
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0x1b01a57bUL, 0x8208f4c1UL, 0xf50fc457UL, 0x65b0d9c6UL, 0x12b7e950UL,
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0x8bbeb8eaUL, 0xfcb9887cUL, 0x62dd1ddfUL, 0x15da2d49UL, 0x8cd37cf3UL,
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0xfbd44c65UL, 0x4db26158UL, 0x3ab551ceUL, 0xa3bc0074UL, 0xd4bb30e2UL,
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0x4adfa541UL, 0x3dd895d7UL, 0xa4d1c46dUL, 0xd3d6f4fbUL, 0x4369e96aUL,
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0x346ed9fcUL, 0xad678846UL, 0xda60b8d0UL, 0x44042d73UL, 0x33031de5UL,
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0xaa0a4c5fUL, 0xdd0d7cc9UL, 0x5005713cUL, 0x270241aaUL, 0xbe0b1010UL,
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0xc90c2086UL, 0x5768b525UL, 0x206f85b3UL, 0xb966d409UL, 0xce61e49fUL,
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0x5edef90eUL, 0x29d9c998UL, 0xb0d09822UL, 0xc7d7a8b4UL, 0x59b33d17UL,
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0x2eb40d81UL, 0xb7bd5c3bUL, 0xc0ba6cadUL, 0xedb88320UL, 0x9abfb3b6UL,
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0x03b6e20cUL, 0x74b1d29aUL, 0xead54739UL, 0x9dd277afUL, 0x04db2615UL,
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0x73dc1683UL, 0xe3630b12UL, 0x94643b84UL, 0x0d6d6a3eUL, 0x7a6a5aa8UL,
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0xe40ecf0bUL, 0x9309ff9dUL, 0x0a00ae27UL, 0x7d079eb1UL, 0xf00f9344UL,
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0x8708a3d2UL, 0x1e01f268UL, 0x6906c2feUL, 0xf762575dUL, 0x806567cbUL,
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0x196c3671UL, 0x6e6b06e7UL, 0xfed41b76UL, 0x89d32be0UL, 0x10da7a5aUL,
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0x67dd4accUL, 0xf9b9df6fUL, 0x8ebeeff9UL, 0x17b7be43UL, 0x60b08ed5UL,
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0xd6d6a3e8UL, 0xa1d1937eUL, 0x38d8c2c4UL, 0x4fdff252UL, 0xd1bb67f1UL,
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0xa6bc5767UL, 0x3fb506ddUL, 0x48b2364bUL, 0xd80d2bdaUL, 0xaf0a1b4cUL,
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0x36034af6UL, 0x41047a60UL, 0xdf60efc3UL, 0xa867df55UL, 0x316e8eefUL,
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0x4669be79UL, 0xcb61b38cUL, 0xbc66831aUL, 0x256fd2a0UL, 0x5268e236UL,
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0xcc0c7795UL, 0xbb0b4703UL, 0x220216b9UL, 0x5505262fUL, 0xc5ba3bbeUL,
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0xb2bd0b28UL, 0x2bb45a92UL, 0x5cb36a04UL, 0xc2d7ffa7UL, 0xb5d0cf31UL,
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0x2cd99e8bUL, 0x5bdeae1dUL, 0x9b64c2b0UL, 0xec63f226UL, 0x756aa39cUL,
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0x026d930aUL, 0x9c0906a9UL, 0xeb0e363fUL, 0x72076785UL, 0x05005713UL,
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0x95bf4a82UL, 0xe2b87a14UL, 0x7bb12baeUL, 0x0cb61b38UL, 0x92d28e9bUL,
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0xe5d5be0dUL, 0x7cdcefb7UL, 0x0bdbdf21UL, 0x86d3d2d4UL, 0xf1d4e242UL,
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0x68ddb3f8UL, 0x1fda836eUL, 0x81be16cdUL, 0xf6b9265bUL, 0x6fb077e1UL,
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0x18b74777UL, 0x88085ae6UL, 0xff0f6a70UL, 0x66063bcaUL, 0x11010b5cUL,
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0x8f659effUL, 0xf862ae69UL, 0x616bffd3UL, 0x166ccf45UL, 0xa00ae278UL,
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0xd70dd2eeUL, 0x4e048354UL, 0x3903b3c2UL, 0xa7672661UL, 0xd06016f7UL,
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0x4969474dUL, 0x3e6e77dbUL, 0xaed16a4aUL, 0xd9d65adcUL, 0x40df0b66UL,
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0x37d83bf0UL, 0xa9bcae53UL, 0xdebb9ec5UL, 0x47b2cf7fUL, 0x30b5ffe9UL,
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0xbdbdf21cUL, 0xcabac28aUL, 0x53b39330UL, 0x24b4a3a6UL, 0xbad03605UL,
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0xcdd70693UL, 0x54de5729UL, 0x23d967bfUL, 0xb3667a2eUL, 0xc4614ab8UL,
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0x5d681b02UL, 0x2a6f2b94UL, 0xb40bbe37UL, 0xc30c8ea1UL, 0x5a05df1bUL,
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0x2d02ef8dL
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};
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#endif
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/* =========================================================================
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* This function can be used by asm versions of crc32()
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*/
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uLongf *get_crc_table()
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{
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#ifdef DYNAMIC_CRC_TABLE
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if (crc_table_empty) make_crc_table();
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#endif
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return (uLongf *)crc_table;
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}
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/* ========================================================================= */
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#define DO1(buf) crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
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#define DO2(buf) DO1(buf); DO1(buf);
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#define DO4(buf) DO2(buf); DO2(buf);
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#define DO8(buf) DO4(buf); DO4(buf);
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/* ========================================================================= */
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PR_PUBLIC_API(uLong) crc32(crc, buf, len)
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uLong crc;
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const Bytef *buf;
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uInt len;
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{
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if (buf == Z_NULL) return 0L;
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#ifdef DYNAMIC_CRC_TABLE
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if (crc_table_empty)
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make_crc_table();
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#endif
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crc = crc ^ 0xffffffffUL;
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while (len >= 8)
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{
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DO8(buf);
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len -= 8;
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}
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if (len) do {
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DO1(buf);
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} while (--len);
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return crc ^ 0xffffffffUL;
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}
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