media/ffvpx/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 /**
  22  * @file
  23  * @ingroup lavu_crc32
  24  * Public header for CRC hash function implementation.
  25  */
  26
  27 #ifndef AVUTIL_CRC_H
  28 #define AVUTIL_CRC_H
  29
  30 #include <stdint.h>
  31 #include <stddef.h>
  32 #include "attributes.h"
  33
  34 /**
  35  * @defgroup lavu_crc32 CRC
  36  * @ingroup lavu_hash
  37  * CRC (Cyclic Redundancy Check) hash function implementation.
  38  *
  39  * This module supports numerous CRC polynomials, in addition to the most
  40  * widely used CRC-32-IEEE. See @ref AVCRCId for a list of available
  41  * polynomials.
  42  *
  43  * @{
  44  */
  45
  46 typedef uint32_t AVCRC;
  47
  48 typedef enum {
  49     AV_CRC_8_ATM,
  50     AV_CRC_16_ANSI,
  51     AV_CRC_16_CCITT,
  52     AV_CRC_32_IEEE,
  53     AV_CRC_32_IEEE_LE,  /*< reversed bitorder version of AV_CRC_32_IEEE */
  54     AV_CRC_16_ANSI_LE,  /*< reversed bitorder version of AV_CRC_16_ANSI */
  55     AV_CRC_24_IEEE,
  56     AV_CRC_8_EBU,
  57     AV_CRC_MAX,         /*< Not part of public API! Do not use outside libavutil. */
  58 }AVCRCId;
  59
  60 /**
  61  * Initialize a CRC table.
  62  * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
  63  * @param le If 1, the lowest bit represents the coefficient for the highest
  64  *           exponent of the corresponding polynomial (both for poly and
  65  *           actual CRC).
  66  *           If 0, you must swap the CRC parameter and the result of av_crc
  67  *           if you need the standard representation (can be simplified in
  68  *           most cases to e.g. bswap16):
  69  *           av_bswap32(crc << (32-bits))
  70  * @param bits number of bits for the CRC
  71  * @param poly generator polynomial without the x**bits coefficient, in the
  72  *             representation as specified by le
  73  * @param ctx_size size of ctx in bytes
  74  * @return <0 on failure
  75  */
  76 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
  77
  78 /**
  79  * Get an initialized standard CRC table.
  80  * @param crc_id ID of a standard CRC
  81  * @return a pointer to the CRC table or NULL on failure
  82  */
  83 const AVCRC *av_crc_get_table(AVCRCId crc_id);
  84
  85 /**
  86  * Calculate the CRC of a block.
  87  * @param ctx initialized AVCRC array (see av_crc_init())
  88  * @param crc CRC of previous blocks if any or initial value for CRC
  89  * @param buffer buffer whose CRC to calculate
  90  * @param length length of the buffer
  91  * @return CRC updated with the data from the given block
  92  *
  93  * @see av_crc_init() "le" parameter
  94  */
  95 uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
  96                 const uint8_t *buffer, size_t length) av_pure;
  97
  98 /**
  99  * @}
 100  */
 101
 102 #endif /* AVUTIL_CRC_H */