/*

 * Checksum functions

 *

 * Copyright (C) 2011-2026, Joachim Metz <joachim.metz@gmail.com>

 *

 * Refer to AUTHORS for acknowledgements.

 *

 * This program 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 3 of the License, or

 * (at your option) any later version.

 *

 * This program 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 General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>.

 */

#include <common.h>

#include <types.h>

#include "libevtx_libcerror.h"

/* Table of CRC-32 values of 8-bit values

 */

uint32_t libevtx_checksum_crc32_table[ 256 ];

/* Value to indicate the CRC-32 table been computed

 */

int libevtx_checksum_crc32_table_computed = 0;

/* Initializes the internal CRC-32 table

 * The table speeds up the CRC-32 calculation

 */

void libevtx_checksum_initialize_crc32_table(

      void )

{

  uint32_t crc32             = 0;

  uint32_t crc32_table_index = 0;

  uint8_t bit_iterator       = 0;

  for( crc32_table_index = 0;

       crc32_table_index < 256;

       crc32_table_index++ )

  {

    crc32 = (uint32_t) crc32_table_index;

    for( bit_iterator = 0;

         bit_iterator < 8;

         bit_iterator++ )

    {

      if( crc32 & 1 )

      {

        crc32 = (uint32_t) 0xedb88320UL ^ ( crc32 >> 1 );

      }

      else

      {

        crc32 = crc32 >> 1;

      }

    }

    libevtx_checksum_crc32_table[ crc32_table_index ] = crc32;

  }

  libevtx_checksum_crc32_table_computed = 1;

}

/* Calculates the CRC-32 of a buffer

 * Based on RFC 1952

 * Returns 1 if successful or -1 on error

 */

int libevtx_checksum_calculate_little_endian_crc32(

     uint32_t *crc32,

     uint8_t *buffer,

     size_t size,

     uint32_t initial_value,

     libcerror_error_t **error )

{

  static char *function      = "libevtx_checksum_calculate_little_endian_crc32";

  size_t buffer_offset       = 0;

  uint32_t crc32_table_index = 0;

  if( crc32 == NULL )

  {

    libcerror_error_set(

     error,

     LIBCERROR_ERROR_DOMAIN_ARGUMENTS,

     LIBCERROR_ARGUMENT_ERROR_INVALID_VALUE,

     "%s: invalid CRC-32.",

     function );

    return( -1 );

  }

  if( buffer == NULL )

  {

    libcerror_error_set(

     error,

     LIBCERROR_ERROR_DOMAIN_ARGUMENTS,

     LIBCERROR_ARGUMENT_ERROR_INVALID_VALUE,

     "%s: invalid buffer.",

     function );

    return( -1 );

  }

  if( size > (size_t) SSIZE_MAX )

  {

    libcerror_error_set(

     error,

     LIBCERROR_ERROR_DOMAIN_ARGUMENTS,

     LIBCERROR_ARGUMENT_ERROR_VALUE_EXCEEDS_MAXIMUM,

     "%s: invalid size value exceeds maximum.",

     function );

    return( -1 );

  }

  *crc32 = initial_value ^ (uint32_t) 0xffffffffUL;

        if( libevtx_checksum_crc32_table_computed == 0 )

  {

    libevtx_checksum_initialize_crc32_table();

  }

        for( buffer_offset = 0;

       buffer_offset < size;

       buffer_offset++ )

  {

    crc32_table_index = ( *crc32 ^ buffer[ buffer_offset ] ) & 0x000000ffUL;

    *crc32 = libevtx_checksum_crc32_table[ crc32_table_index ] ^ ( *crc32 >> 8 );

        }

        *crc32 ^= 0xffffffffUL;

  return( 1 );

}

/* Calculates the weak CRC-32 of a buffer

 * Based on RFC 1952, without initial and final XOR operation

 * Returns 1 if successful or -1 on error

 */

int libevtx_checksum_calculate_little_endian_weak_crc32(

     uint32_t *crc32,

     uint8_t *buffer,

     size_t size,

     uint32_t initial_value,

     libcerror_error_t **error )

{

  static char *function      = "libevtx_checksum_calculate_little_endian_weak_crc32";

  size_t buffer_offset       = 0;

  uint32_t crc32_table_index = 0;

  if( crc32 == NULL )

  {

    libcerror_error_set(

     error,

     LIBCERROR_ERROR_DOMAIN_ARGUMENTS,

     LIBCERROR_ARGUMENT_ERROR_INVALID_VALUE,

     "%s: invalid CRC-32.",

     function );

    return( -1 );

  }

  if( buffer == NULL )

  {

    libcerror_error_set(

     error,

     LIBCERROR_ERROR_DOMAIN_ARGUMENTS,

     LIBCERROR_ARGUMENT_ERROR_INVALID_VALUE,

     "%s: invalid buffer.",

     function );

    return( -1 );

  }

  if( size > (size_t) SSIZE_MAX )

  {

    libcerror_error_set(

     error,

     LIBCERROR_ERROR_DOMAIN_ARGUMENTS,

     LIBCERROR_ARGUMENT_ERROR_VALUE_EXCEEDS_MAXIMUM,

     "%s: invalid size value exceeds maximum.",

     function );

    return( -1 );

  }

  *crc32 = initial_value;

        if( libevtx_checksum_crc32_table_computed == 0 )

  {

    libevtx_checksum_initialize_crc32_table();

  }

        for( buffer_offset = 0;

       buffer_offset < size;

       buffer_offset++ )

  {

    crc32_table_index = ( *crc32 ^ buffer[ buffer_offset ] ) & 0x000000ffUL;

    *crc32 = libevtx_checksum_crc32_table[ crc32_table_index ] ^ ( *crc32 >> 8 );

        }

        return( 1 );

}