crc.h 3.1 KB

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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. * @file
  22. * @ingroup lavu_crc32
  23. * Public header for CRC hash function implementation.
  24. */
  25. #ifndef AVUTIL_CRC_H
  26. #define AVUTIL_CRC_H
  27. #include <stdint.h>
  28. #include <stddef.h>
  29. #include "attributes.h"
  30. #include "version.h"
  31. /**
  32. * @defgroup lavu_crc32 CRC
  33. * @ingroup lavu_hash
  34. * CRC (Cyclic Redundancy Check) hash function implementation.
  35. *
  36. * This module supports numerous CRC polynomials, in addition to the most
  37. * widely used CRC-32-IEEE. See @ref AVCRCId for a list of available
  38. * polynomials.
  39. *
  40. * @{
  41. */
  42. typedef uint32_t AVCRC;
  43. typedef enum {
  44. AV_CRC_8_ATM,
  45. AV_CRC_16_ANSI,
  46. AV_CRC_16_CCITT,
  47. AV_CRC_32_IEEE,
  48. AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */
  49. AV_CRC_16_ANSI_LE, /*< reversed bitorder version of AV_CRC_16_ANSI */
  50. #if FF_API_CRC_BIG_TABLE
  51. AV_CRC_24_IEEE = 12,
  52. #else
  53. AV_CRC_24_IEEE,
  54. #endif /* FF_API_CRC_BIG_TABLE */
  55. AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */
  56. }AVCRCId;
  57. /**
  58. * Initialize a CRC table.
  59. * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
  60. * @param le If 1, the lowest bit represents the coefficient for the highest
  61. * exponent of the corresponding polynomial (both for poly and
  62. * actual CRC).
  63. * If 0, you must swap the CRC parameter and the result of av_crc
  64. * if you need the standard representation (can be simplified in
  65. * most cases to e.g. bswap16):
  66. * av_bswap32(crc << (32-bits))
  67. * @param bits number of bits for the CRC
  68. * @param poly generator polynomial without the x**bits coefficient, in the
  69. * representation as specified by le
  70. * @param ctx_size size of ctx in bytes
  71. * @return <0 on failure
  72. */
  73. int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
  74. /**
  75. * Get an initialized standard CRC table.
  76. * @param crc_id ID of a standard CRC
  77. * @return a pointer to the CRC table or NULL on failure
  78. */
  79. const AVCRC *av_crc_get_table(AVCRCId crc_id);
  80. /**
  81. * Calculate the CRC of a block.
  82. * @param crc CRC of previous blocks if any or initial value for CRC
  83. * @return CRC updated with the data from the given block
  84. *
  85. * @see av_crc_init() "le" parameter
  86. */
  87. uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
  88. const uint8_t *buffer, size_t length) av_pure;
  89. /**
  90. * @}
  91. */
  92. #endif /* AVUTIL_CRC_H */