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 * FIDOGATE --- Gateway UNIX Mail/News <-> FIDO NetMail/EchoMail
 * $Id: crc32.c,v 4.7 2003/02/16 15:38:55 n0ll Exp $
 * Compute 32 bit CRC value
 * Copyright (C) 1990-2003
 *  _____ _____
 * |   |___  |   Martin Junius           
 * | | | |   | |   Radiumstr. 18         Internet:    mj@fidogate.org
 * |_|_|_|@home|   D-51069 Koeln, Germany
 * This file is part of FIDOGATE.
 * FIDOGATE 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, or (at your option) any
 * later version.
 * FIDOGATE is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with FIDOGATE; see the file COPYING.  If not, write to the Free
 * Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 * This function was taken from UNZIP 4.1, misc.c. Modified to return 32 bit
 * CRC value for a buffer. Value is initialized with 0xffffffff
 * Copyright, applying to UpdateCRC() and crc_32_tab[]:
 *   COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or code
 *   or tables extracted from it, as desired without restriction.

#include "fidogate.h"

/***** compute_crc32() --- Compute 32 bit CRC value of buffer ****************/


   First, the polynomial itself and its table of feedback terms.  The
   polynomial is

   Note that we take it "backwards" and put the highest-order term in
   the lowest-order bit.  The X^32 term is "implied"; the LSB is the
   X^31 term, etc.  The X^0 term (usually shown as "+1") results in
   the MSB being 1.

   Note that the usual hardware shift register implementation, which
   is what we're using (we're merely optimizing it by doing eight-bit
   chunks at a time) shifts bits into the lowest-order term.  In our
   implementation, that means shifting towards the right.  Why do we
   do it this way?  Because the calculated CRC must be transmitted in
   order from highest-order term to lowest-order term.      UARTs transmit
   characters in order from LSB to MSB.    By storing the CRC this way,
   we hand it to the UART in the order low-byte to high-byte; the UART
   sends each low-bit to hight-bit; and the result is transmission bit
   by bit from highest- to lowest-order term without requiring any bit
   shuffling on our part.  Reception works similarly.

   The feedback terms table consists of 256, 32-bit entries.  Notes:

       The table can be generated at runtime if desired; code to do so
       is shown later.  It might not be obvious, but the feedback
       terms simply represent the results of eight shift/xor opera-
       tions for all combinations of data and CRC register values.

       The values must be right-shifted by eight bits by the "updcrc"
       logic; the shift must be unsigned (bring in zeroes).  On some
       hardware you could probably optimize the shift in assembler by
       using byte-swap instructions.
       polynomial $edb88320


static unsigned long crc_32_tab[] =
    0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
    0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
    0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
    0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
    0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
    0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
    0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
    0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
    0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
    0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
    0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
    0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
    0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
    0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
    0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
    0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
    0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
    0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
    0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
    0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
    0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
    0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
    0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
    0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
    0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
    0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
    0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
    0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
    0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
    0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
    0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
    0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
    0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
    0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
    0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
    0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
    0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
    0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
    0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
    0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
    0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
    0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
    0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
    0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
    0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
    0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
    0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
    0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
    0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
    0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
    0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,

unsigned long compute_crc32(unsigned char *s, int len)
/* Compute CRC value for buffer s, length len */
    register unsigned long crcval = 0xffffffff;

    while (len--)
      crcval = crc_32_tab[((unsigned char) crcval ^ (*s++)) & 0xff]
             ^ (crcval >> 8);
    return ~crcval & 0xffffffff;

 * Compute CRC32

static unsigned long crcval;

void crc32_init(void)
    crcval = 0xffffffff;

void crc32_compute(unsigned char *s, int len)
    while (len--)
      crcval = crc_32_tab[((unsigned char) crcval ^ (*s++)) & 0xff]
                ^ (crcval >> 8);

void crc32_update(int c)
    crcval = crc_32_tab[((unsigned char) crcval ^ c) & 0xff]
      ^ (crcval >> 8);

unsigned long crc32_value(void)
    return ~crcval & 0xffffffff;

 * Compute CRC32 for entire file
unsigned long crc32_file(char *name)
    FILE *fp;
    int c;
    if((fp = fopen(name, R_MODE)) == NULL)
      log("$crc32_file(): can't open %s", name);
      return 0;
    while((c = getc(fp)) != EOF)
    return crc32_value();

#ifdef TEST
/***** Test ******************************************************************/

main(int argc, char *argv[])
    char buffer[1024];

    buffer[0] = 0;
    while(--argc) {
      crc32_compute(*argv, strlen(*argv));
    printf("CRC=%08lx\n", crc32_value());
#endif /**TEST**/

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