ffmpeg/libavutil/crc.h

   1 /*
   2  * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #ifndef AVUTIL_CRC_H
  22 #define AVUTIL_CRC_H
  23
  24 #include <stdint.h>
  25 #include <stddef.h>
  26 #include "attributes.h"
  27
  28 /**
  29  * @defgroup lavu_crc32 CRC32
  30  * @ingroup lavu_crypto
  31  * @{
  32  */
  33
  34 typedef uint32_t AVCRC;
  35
  36 typedef enum {
  37     AV_CRC_8_ATM,
  38     AV_CRC_16_ANSI,
  39     AV_CRC_16_CCITT,
  40     AV_CRC_32_IEEE,
  41     AV_CRC_32_IEEE_LE,  /*< reversed bitorder version of AV_CRC_32_IEEE */
  42     AV_CRC_16_ANSI_LE,  /*< reversed bitorder version of AV_CRC_16_ANSI */
  43     AV_CRC_24_IEEE = 12,
  44     AV_CRC_MAX,         /*< Not part of public API! Do not use outside libavutil. */
  45 }AVCRCId;
  46
  47 /**
  48  * Initialize a CRC table.
  49  * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
  50  * @param le If 1, the lowest bit represents the coefficient for the highest
  51  *           exponent of the corresponding polynomial (both for poly and
  52  *           actual CRC).
  53  *           If 0, you must swap the CRC parameter and the result of av_crc
  54  *           if you need the standard representation (can be simplified in
  55  *           most cases to e.g. bswap16):
  56  *           av_bswap32(crc << (32-bits))
  57  * @param bits number of bits for the CRC
  58  * @param poly generator polynomial without the x**bits coefficient, in the
  59  *             representation as specified by le
  60  * @param ctx_size size of ctx in bytes
  61  * @return <0 on failure
  62  */
  63 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
  64
  65 /**
  66  * Get an initialized standard CRC table.
  67  * @param crc_id ID of a standard CRC
  68  * @return a pointer to the CRC table or NULL on failure
  69  */
  70 const AVCRC *av_crc_get_table(AVCRCId crc_id);
  71
  72 /**
  73  * Calculate the CRC of a block.
  74  * @param crc CRC of previous blocks if any or initial value for CRC
  75  * @return CRC updated with the data from the given block
  76  *
  77  * @see av_crc_init() "le" parameter
  78  */
  79 uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
  80                 const uint8_t *buffer, size_t length) av_pure;
  81
  82 /**
  83  * @}
  84  */
  85
  86 #endif /* AVUTIL_CRC_H */