text: /*
   * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  /**
   * @file
   * @ingroup lavu_crc32
   * Public header for CRC hash function implementation.
   */
  
  #ifndef AVUTIL_CRC_H
  #define AVUTIL_CRC_H
  
  #include <stdint.h>
  #include <stddef.h>
  #include "attributes.h"
  #include "libavutilVersion.h"
  
  /**
   * @defgroup lavu_crc32 CRC
   * @ingroup lavu_hash
   * CRC (Cyclic Redundancy Check) hash function implementation.
   *
   * This module supports numerous CRC polynomials, in addition to the most
   * widely used CRC-32-IEEE. See @ref AVCRCId for a list of available
   * polynomials.
   *
   * @{
   */
  
  typedef uint32_t AVCRC;
  
  typedef enum {
      AV_CRC_8_ATM,
      AV_CRC_16_ANSI,
      AV_CRC_16_CCITT,
      AV_CRC_32_IEEE,
      AV_CRC_32_IEEE_LE,  /*< reversed bitorder version of AV_CRC_32_IEEE */
      AV_CRC_16_ANSI_LE,  /*< reversed bitorder version of AV_CRC_16_ANSI */
  #if FF_API_CRC_BIG_TABLE
      AV_CRC_24_IEEE = 12,
  #else
      AV_CRC_24_IEEE,
  #endif /* FF_API_CRC_BIG_TABLE */
      AV_CRC_MAX,         /*< Not part of public API! Do not use outside libavutil. */
  }AVCRCId;
  
  /**
   * Initialize a CRC table.
   * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
   * @param le If 1, the lowest bit represents the coefficient for the highest
   *           exponent of the corresponding polynomial (both for poly and
   *           actual CRC).
   *           If 0, you must swap the CRC parameter and the result of av_crc
   *           if you need the standard representation (can be simplified in
   *           most cases to e.g. bswap16):
   *           av_bswap32(crc << (32-bits))
   * @param bits number of bits for the CRC
   * @param poly generator polynomial without the x**bits coefficient, in the
   *             representation as specified by le
   * @param ctx_size size of ctx in bytes
   * @return <0 on failure
   */
  int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
  
  /**
   * Get an initialized standard CRC table.
   * @param crc_id ID of a standard CRC
   * @return a pointer to the CRC table or NULL on failure
   */
  const AVCRC *av_crc_get_table(AVCRCId crc_id);
  
  /**
   * Calculate the CRC of a block.
   * @param crc CRC of previous blocks if any or initial value for CRC
   * @return CRC updated with the data from the given block
   *
   * @see av_crc_init() "le" parameter
   */
  uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
                  const uint8_t *buffer, size_t length) av_pure;
  
  /**
   * @}
   */
  
  #endif /* AVUTIL_CRC_H */
  