mdw@git.distorted.org.uk Git - mLib/blob - hash/crc32.h

   1 /* -*-c-*-
   2  *
   3  * Calculating cyclic redundancy values (non-cryptographic!)
   4  *
   5  * (c) 1998 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the mLib utilities library.
  11  *
  12  * mLib is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * mLib is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with mLib; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef MLIB_CRC32_H
  29 #define MLIB_CRC32_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #ifndef MLIB_BITS_H
  38 #  include "bits.h"
  39 #endif
  40
  41 /*----- External values ---------------------------------------------------*/
  42
  43 extern const uint32 crc32_table[256];
  44
  45 /*----- Macros ------------------------------------------------------------*/
  46
  47 /* --- @CRC32@ --- *
  48  *
  49  * Arguments:   @uint32 result@ = where to put the result
  50  *              @uint32 crc@ = carryover from previous call, or zero
  51  *              @void *buf@ = pointer to buffer to check
  52  *              @size_t sz@ = size of the buffer
  53  *
  54  * Use:         A restartable CRC calculator wrapped up in a macro.
  55  */
  56
  57 #define CRC32(result, crc, buf, sz) do {                                \
  58   const octet *_p = (const octet *)(buf);                               \
  59   const octet *_l = _p + (sz);                                          \
  60   uint32 _crc = U32(~(crc));                                            \
  61                                                                         \
  62   while (_p < _l)                                                       \
  63     _crc = (_crc >> 8) ^ crc32_table[U8(*_p++ ^ _crc)];                 \
  64   (result) = U32(~_crc);                                                \
  65 } while (0)
  66
  67 /*----- Functions provided ------------------------------------------------*/
  68
  69 /* --- @crc32@ --- *
  70  *
  71  * Arguments:   @uint32 crc@ = carryover from previous call, or zero
  72  *              @const void *buf@ = pointer to buffer to check
  73  *              @size_t sz@ = size of the buffer
  74  *
  75  * Returns:     The CRC updated by the new buffer.
  76  *
  77  * Use:         A restartable CRC calculator.  This is just a function
  78  *              wrapper for the macro version.
  79  */
  80
  81 extern uint32 crc32(uint32 /*crc*/, const void */*buf*/, size_t /*sz*/);
  82
  83 /*----- That's all, folks -------------------------------------------------*/
  84
  85 #ifdef __cplusplus
  86   }
  87 #endif
  88
  89 #endif