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/*
* Copyright (c) 2016, Alliance for Open Media. All rights reserved
*
* This source code is subject to the terms of the BSD 2 Clause License and
* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
* was not distributed with this source code in the LICENSE file, you can
* obtain it at www.aomedia.org/license/software. If the Alliance for Open
* Media Patent License 1.0 was not distributed with this source code in the
* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
*/
#include "av1/encoder/hash.h"
static void crc_calculator_process_data(CRC_CALCULATOR *p_crc_calculator,
uint8_t *pData, uint32_t dataLength) {
for (uint32_t i = 0; i < dataLength; i++) {
const uint8_t index =
(p_crc_calculator->remainder >> (p_crc_calculator->bits - 8)) ^
pData[i];
p_crc_calculator->remainder <<= 8;
p_crc_calculator->remainder ^= p_crc_calculator->table[index];
}
}
void crc_calculator_reset(CRC_CALCULATOR *p_crc_calculator) {
p_crc_calculator->remainder = 0;
}
static uint32_t crc_calculator_get_crc(CRC_CALCULATOR *p_crc_calculator) {
return p_crc_calculator->remainder & p_crc_calculator->final_result_mask;
}
static void crc_calculator_init_table(CRC_CALCULATOR *p_crc_calculator) {
const uint32_t high_bit = 1 << (p_crc_calculator->bits - 1);
const uint32_t byte_high_bit = 1 << (8 - 1);
for (uint32_t value = 0; value < 256; value++) {
uint32_t remainder = 0;
for (uint8_t mask = byte_high_bit; mask != 0; mask >>= 1) {
if (value & mask) {
remainder ^= high_bit;
}
if (remainder & high_bit) {
remainder <<= 1;
remainder ^= p_crc_calculator->trunc_poly;
} else {
remainder <<= 1;
}
}
p_crc_calculator->table[value] = remainder;
}
}
void av1_crc_calculator_init(CRC_CALCULATOR *p_crc_calculator, uint32_t bits,
uint32_t truncPoly) {
p_crc_calculator->remainder = 0;
p_crc_calculator->bits = bits;
p_crc_calculator->trunc_poly = truncPoly;
p_crc_calculator->final_result_mask = (1 << bits) - 1;
crc_calculator_init_table(p_crc_calculator);
}
uint32_t av1_get_crc_value(CRC_CALCULATOR *p_crc_calculator, uint8_t *p,
int length) {
crc_calculator_reset(p_crc_calculator);
crc_calculator_process_data(p_crc_calculator, p, length);
return crc_calculator_get_crc(p_crc_calculator);
}
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