crc32.h

   1 /*
   2  * Copyright (C) 2016 Felix Fietkau <nbd@nbd.name>
   3  *
   4  * Based on busybox code:
   5  *   CRC32 table fill function
   6  *   Copyright (C) 2006 by Rob Sullivan <cogito.ergo.cogito@gmail.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2
  10  * as published by the Free Software Foundation
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  */
  17 #ifndef __BB_CRC32_H
  18 #define __BB_CRC32_H
  19
  20 #include <stdint.h>
  21
  22 static inline void
  23 crc32_filltable(uint32_t *crc_table)
  24 {
  25         uint32_t polynomial = 0xedb88320;
  26         uint32_t c;
  27         int i, j;
  28
  29         for (i = 0; i < 256; i++) {
  30                 c = i;
  31                 for (j = 8; j; j--)
  32                         c = (c&1) ? ((c >> 1) ^ polynomial) : (c >> 1);
  33
  34                 *crc_table++ = c;
  35         }
  36 }
  37
  38 static inline uint32_t
  39 crc32_block(uint32_t val, const void *buf, unsigned len, uint32_t *crc_table)
  40 {
  41         const void *end = (uint8_t*)buf + len;
  42
  43         while (buf != end) {
  44                 val = crc_table[(uint8_t)val ^ *(uint8_t*)buf] ^ (val >> 8);
  45                 buf = (uint8_t*)buf + 1;
  46         }
  47         return val;
  48 }
  49
  50 #endif