/* * Copyright (C) 2001, 2002, and 2003 Roy Keene * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * email: dact@rkeene.org */ #include "dact.h" #include "crc.h" uint32_t elfcrc(const uint32_t start, const unsigned char *name, const uint32_t n) { uint32_t i, h, g=0; h = start; for (i=0;i<n;i++) { h = (h << 4) + (*name++); g = h & 0xf0000000; if (g) h ^= (g >> ((sizeof(g)*8)-8)); h &= ~g; } return(h); } /* Adler-32 is composed of two sums accumulated per byte: s1 is the sum of all bytes, s2 is the sum of all s1 values. Both sums are done modulo 65521. s1 is initialised to 1, s2 to zero. */ uint32_t crc(const uint32_t prev, unsigned char *val, const uint32_t n) { uint32_t ret=prev, i; uint16_t s1, s2; unsigned char *s=val; if (ret==0) ret=1; s1=ret&0xffff; s2=(ret>>16)&0xffff; for (i=0; i<n; i++) { s1 = (s1 + *s) % 65521; s2 = (s1 + s2) % 65521; *s++; } ret=(s2<<16)|s1; return(ret); }

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