lib/crc.h

   1 /* crc.h -- cyclic redundancy checks
   2    Copyright (C) 2005, 2009-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation, either version 3 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Simon Josefsson.  */
  18
  19 #ifndef CRC_H
  20 #define CRC_H 1
  21
  22 #include <stddef.h>
  23 #include <stdint.h>
  24
  25 #ifdef __cplusplus
  26 extern "C" {
  27 #endif
  28
  29
  30 /* Compute CRC-32 value of LEN bytes long BUF, and return it. */
  31 extern uint32_t crc32 (const char *buf, size_t len) _GL_ATTRIBUTE_PURE;
  32
  33 /* Incrementally update CRC-32 value CRC using LEN bytes long BUF.  In
  34    the first call, use 0 as the value for CRC.  Return the updated
  35    CRC-32 value.  */
  36 extern uint32_t crc32_update (uint32_t crc, const char *buf, size_t len)
  37   _GL_ATTRIBUTE_PURE;
  38
  39 /* Compute modified-CRC-32 value of LEN bytes long BUF, and return it.
  40    The "modification" is to avoid the initial and final XOR operation.
  41    Due to historic implementation errors, this variant is sometimes
  42    used (i.e., in RFC 3961). */
  43 extern uint32_t crc32_no_xor (const char *buf, size_t len)
  44   _GL_ATTRIBUTE_PURE;
  45
  46 /* Incrementally update modified-CRC-32 value CRC using LEN bytes long
  47    BUF.  In the first call, use 0 as the value for CRC.  Return the
  48    updated modified-CRC-32 value.  The "modification" is to avoid the
  49    initial and final XOR operation.  Due to historic implementation
  50    errors, this variant is sometimes used (i.e., in RFC 3961).  */
  51 extern uint32_t
  52 crc32_update_no_xor (uint32_t crc, const char *buf, size_t len)
  53   _GL_ATTRIBUTE_PURE;
  54
  55
  56 #ifdef __cplusplus
  57 }
  58 #endif
  59
  60 #endif /* CRC_H */