src/helper/crc32.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 /***************************************************************************
   4  *   Copyright (C) 2013-2014 by Franck Jullien                             *
   5  *   elec4fun@gmail.com                                                    *
   6  *                                                                         *
   7  *   Copyright (C) 2022 Otto-von-Guericke-Universität Magdeburg            *
   8  *   marian.buschsieweke@ovgu.de                                           *
   9  ***************************************************************************/
  10
  11 #ifdef HAVE_CONFIG_H
  12 #include "config.h"
  13 #endif
  14
  15 #include "crc32.h"
  16 #include <stdint.h>
  17 #include <stddef.h>
  18
  19 static uint32_t crc_le_step(uint32_t poly, uint32_t crc, uint32_t data_in,
  20                 unsigned int data_bits)
  21 {
  22         for (unsigned int i = 0; i < data_bits; i++) {
  23                 uint32_t d, c;
  24                 d = ((data_in >> i) & 0x1) ? 0xffffffff : 0;
  25                 c = (crc & 0x1) ? 0xffffffff : 0;
  26                 crc = crc >> 1;
  27                 crc = crc ^ ((d ^ c) & poly);
  28         }
  29
  30         return crc;
  31 }
  32
  33 uint32_t crc32_le(uint32_t poly, uint32_t seed, const void *_data,
  34                 size_t data_len)
  35 {
  36         if (((uintptr_t)_data & 0x3) || (data_len & 0x3)) {
  37                 /* data is unaligned, processing data one byte at a time */
  38                 const uint8_t *data = _data;
  39                 for (size_t i = 0; i < data_len; i++)
  40                         seed = crc_le_step(poly, seed, data[i], 8);
  41         } else {
  42                 /* data is aligned, processing 32 bit at a time */
  43                 data_len >>= 2;
  44                 const uint32_t *data = _data;
  45                 for (size_t i = 0; i < data_len; i++)
  46                         seed = crc_le_step(poly, seed, data[i], 32);
  47         }
  48
  49         return seed;
  50 }