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  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_24_IEEE = 12,
  43.     AV_CRC_MAX,         /*< Not part of public API! Do not use outside libavutil. */
  44. }AVCRCId;
  45.  
  46. /**
  47.  * Initialize a CRC table.
  48.  * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
  49.  * @param le If 1, the lowest bit represents the coefficient for the highest
  50.  *           exponent of the corresponding polynomial (both for poly and
  51.  *           actual CRC).
  52.  *           If 0, you must swap the CRC parameter and the result of av_crc
  53.  *           if you need the standard representation (can be simplified in
  54.  *           most cases to e.g. bswap16):
  55.  *           av_bswap32(crc << (32-bits))
  56.  * @param bits number of bits for the CRC
  57.  * @param poly generator polynomial without the x**bits coefficient, in the
  58.  *             representation as specified by le
  59.  * @param ctx_size size of ctx in bytes
  60.  * @return <0 on failure
  61.  */
  62. int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
  63.  
  64. /**
  65.  * Get an initialized standard CRC table.
  66.  * @param crc_id ID of a standard CRC
  67.  * @return a pointer to the CRC table or NULL on failure
  68.  */
  69. const AVCRC *av_crc_get_table(AVCRCId crc_id);
  70.  
  71. /**
  72.  * Calculate the CRC of a block.
  73.  * @param crc CRC of previous blocks if any or initial value for CRC
  74.  * @return CRC updated with the data from the given block
  75.  *
  76.  * @see av_crc_init() "le" parameter
  77.  */
  78. uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
  79.                 const uint8_t *buffer, size_t length) av_pure;
  80.  
  81. /**
  82.  * @}
  83.  */
  84.  
  85. #endif /* AVUTIL_CRC_H */
  86.