crc.h 2.5 KB

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374
  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. #ifndef AVUTIL_CRC_H
  21. #define AVUTIL_CRC_H
  22. #include <stdint.h>
  23. #include <stddef.h>
  24. #include "attributes.h"
  25. typedef uint32_t AVCRC;
  26. typedef enum {
  27. AV_CRC_8_ATM,
  28. AV_CRC_16_ANSI,
  29. AV_CRC_16_CCITT,
  30. AV_CRC_32_IEEE,
  31. AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */
  32. AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */
  33. }AVCRCId;
  34. /**
  35. * Initialize a CRC table.
  36. * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
  37. * @param le If 1, the lowest bit represents the coefficient for the highest
  38. * exponent of the corresponding polynomial (both for poly and
  39. * actual CRC).
  40. * If 0, you must swap the CRC parameter and the result of av_crc
  41. * if you need the standard representation (can be simplified in
  42. * most cases to e.g. bswap16):
  43. * av_bswap32(crc << (32-bits))
  44. * @param bits number of bits for the CRC
  45. * @param poly generator polynomial without the x**bits coefficient, in the
  46. * representation as specified by le
  47. * @param ctx_size size of ctx in bytes
  48. * @return <0 on failure
  49. */
  50. int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
  51. /**
  52. * Get an initialized standard CRC table.
  53. * @param crc_id ID of a standard CRC
  54. * @return a pointer to the CRC table or NULL on failure
  55. */
  56. const AVCRC *av_crc_get_table(AVCRCId crc_id);
  57. /**
  58. * Calculate the CRC of a block.
  59. * @param crc CRC of previous blocks if any or initial value for CRC
  60. * @return CRC updated with the data from the given block
  61. *
  62. * @see av_crc_init() "le" parameter
  63. */
  64. uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
  65. const uint8_t *buffer, size_t length) av_pure;
  66. #endif /* AVUTIL_CRC_H */