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

   1 /* -*-c-*-
   2  *
   3  * $Id: crc32.h,v 1.6 2000/07/02 22:20:42 mdw Exp $
   4  *
   5  * Calculating cyclic redundancy values (non-cryptographic!)
   6  *
   7  * (c) 1998 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of the mLib utilities library.
  13  *
  14  * mLib is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * mLib is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with mLib; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: crc32.h,v $
  33  * Revision 1.6  2000/07/02 22:20:42  mdw
  34  * Fix constant name.
  35  *
  36  * Revision 1.5  1999/12/10 23:42:04  mdw
  37  * Change header file guard names.
  38  *
  39  * Revision 1.4  1999/06/01 09:47:22  mdw
  40  * Make the return type of `crc32' a `uint32' now that we have `bits.h'.
  41  *
  42  * Revision 1.3  1999/05/06 19:51:35  mdw
  43  * Reformatted the LGPL notice a little bit.
  44  *
  45  * Revision 1.2  1999/05/05 18:50:31  mdw
  46  * Change licensing conditions to LGPL.
  47  *
  48  * Revision 1.1.1.1  1998/06/17 23:44:42  mdw
  49  * Initial version of mLib
  50  *
  51  */
  52
  53 #ifndef MLIB_CRC32_H
  54 #define MLIB_CRC32_H
  55
  56 #ifdef __cplusplus
  57   extern "C" {
  58 #endif
  59
  60 /*----- Header files ------------------------------------------------------*/
  61
  62 #ifndef MLIB_BITS_H
  63 #  include "bits.h"
  64 #endif
  65
  66 /*----- External values ---------------------------------------------------*/
  67
  68 extern uint32 crc32_table[256];
  69
  70 /*----- Macros ------------------------------------------------------------*/
  71
  72 /* --- @CRC32@ --- *
  73  *
  74  * Arguments:   @uint32 result@ = where to put the result
  75  *              @uint32 crc@ = carryover from previous call, or zero
  76  *              @void *buf@ = pointer to buffer to check
  77  *              @size_t sz@ = size of the buffer
  78  *
  79  * Use:         A restartable CRC calculator wrapped up in a macro.
  80  */
  81
  82 #define CRC32(result, crc, buf, sz) do {                                \
  83   const octet *_p = (const octet *)(buf);                               \
  84   const octet *_l = _p + (sz);                                          \
  85   uint32 _crc = U32(~(crc));                                            \
  86                                                                         \
  87   while (_p < _l)                                                       \
  88     _crc = (_crc >> 8) ^ crc32_table[U8(*_p++ ^ _crc)];                 \
  89   (result) = U32(~_crc);                                                \
  90 } while (0)
  91
  92 /*----- Functions provided ------------------------------------------------*/
  93
  94 /* --- @crc32@ --- *
  95  *
  96  * Arguments:   @uint32 crc@ = carryover from previous call, or zero
  97  *              @const void *buf@ = pointer to buffer to check
  98  *              @size_t sz@ = size of the buffer
  99  *
 100  * Returns:     The CRC updated by the new buffer.
 101  *
 102  * Use:         A restartable CRC calculator.  This is just a function
 103  *              wrapper for the macro version.
 104  */
 105
 106 extern uint32 crc32(uint32 /*crc*/, const void */*buf*/, size_t /*sz*/);
 107
 108 /*----- That's all, folks -------------------------------------------------*/
 109
 110 #ifdef __cplusplus
 111   }
 112 #endif
 113
 114 #endif