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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"
#include "config/av1_rtcd.h"
/* 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, const uint8_t *buf, size_t len) {
const uint8_t *next = 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;
}