/*
 * 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 https://www.aomedia.org/license/software-license. 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 https://www.aomedia.org/license/patent-license.
 */

#include "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 = (uint8_t)((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];
    }
}
static 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 svt_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 svt_av1_get_crc_value(void *crc_calculator, uint8_t *p, int length) {
    CRC_CALCULATOR *p_crc_calculator = (CRC_CALCULATOR *)crc_calculator;
    crc_calculator_reset(p_crc_calculator);
    crc_calculator_process_data(p_crc_calculator, p, length);
    return crc_calculator_get_crc(p_crc_calculator);
}
