/*

 * 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 = (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 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);

}

/* CRC-32C (iSCSI) polynomial in reversed bit order. */

#define POLY 0x82f63b78

/* Construct table for software CRC-32C calculation. */

void av1_crc32c_calculator_init(CRC32C *p_crc32c) {

  uint32_t crc;

  for (int n = 0; n < 256; n++) {

    crc = n;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;

    p_crc32c->table[0][n] = crc;

  }

  for (int n = 0; n < 256; n++) {

    crc = p_crc32c->table[0][n];

    for (int k = 1; k < 8; k++) {

      crc = p_crc32c->table[0][crc & 0xff] ^ (crc >> 8);

      p_crc32c->table[k][n] = crc;

    }

  }

}

/* Table-driven software version as a fall-back.  This is about 15 times slower

 than using the hardware instructions.  This assumes little-endian integers,

 as is the case on Intel processors that the assembler code here is for. */

uint32_t av1_get_crc32c_value_c(void *c, uint8_t *buf, size_t len) {

  const uint8_t *next = (const uint8_t *)(buf);

  uint64_t crc;

  CRC32C *p = (CRC32C *)c;

  crc = 0 ^ 0xffffffff;

  while (len && ((uintptr_t)next & 7) != 0) {

    crc = p->table[0][(crc ^ *next++) & 0xff] ^ (crc >> 8);

    len--;

  }

  while (len >= 8) {

    crc ^= *(uint64_t *)next;

    crc = p->table[7][crc & 0xff] ^ p->table[6][(crc >> 8) & 0xff] ^

          p->table[5][(crc >> 16) & 0xff] ^ p->table[4][(crc >> 24) & 0xff] ^

          p->table[3][(crc >> 32) & 0xff] ^ p->table[2][(crc >> 40) & 0xff] ^

          p->table[1][(crc >> 48) & 0xff] ^ p->table[0][crc >> 56];

    next += 8;

    len -= 8;

  }

  while (len) {

    crc = p->table[0][(crc ^ *next++) & 0xff] ^ (crc >> 8);

    len--;

  }

  return (uint32_t)crc ^ 0xffffffff;

}