hash.c (2541B)
1 /* 2 * Copyright (c) 2016, Alliance for Open Media. All rights reserved. 3 * 4 * This source code is subject to the terms of the BSD 2 Clause License and 5 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License 6 * was not distributed with this source code in the LICENSE file, you can 7 * obtain it at www.aomedia.org/license/software. If the Alliance for Open 8 * Media Patent License 1.0 was not distributed with this source code in the 9 * PATENTS file, you can obtain it at www.aomedia.org/license/patent. 10 */ 11 12 #include "av1/encoder/hash.h" 13 14 #include <stddef.h> 15 16 #include "config/av1_rtcd.h" 17 18 /* CRC-32C (iSCSI) polynomial in reversed bit order. */ 19 #define POLY 0x82f63b78 20 21 /* Construct table for software CRC-32C calculation. */ 22 void av1_crc32c_calculator_init(CRC32C *p_crc32c) { 23 uint32_t crc; 24 25 for (int n = 0; n < 256; n++) { 26 crc = n; 27 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 28 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 29 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 30 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 31 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 32 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 33 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 34 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1; 35 p_crc32c->table[0][n] = crc; 36 } 37 for (int n = 0; n < 256; n++) { 38 crc = p_crc32c->table[0][n]; 39 for (int k = 1; k < 8; k++) { 40 crc = p_crc32c->table[0][crc & 0xff] ^ (crc >> 8); 41 p_crc32c->table[k][n] = crc; 42 } 43 } 44 } 45 46 /* Table-driven software version as a fall-back. This is about 15 times slower 47 than using the hardware instructions. This assumes little-endian integers, 48 as is the case on Intel processors that the assembler code here is for. */ 49 uint32_t av1_get_crc32c_value_c(void *c, const uint8_t *buf, size_t len) { 50 const uint8_t *next = buf; 51 uint64_t crc; 52 CRC32C *p = (CRC32C *)c; 53 crc = 0 ^ 0xffffffff; 54 while (len && ((uintptr_t)next & 7) != 0) { 55 crc = p->table[0][(crc ^ *next++) & 0xff] ^ (crc >> 8); 56 len--; 57 } 58 while (len >= 8) { 59 crc ^= *(uint64_t *)next; 60 crc = p->table[7][crc & 0xff] ^ p->table[6][(crc >> 8) & 0xff] ^ 61 p->table[5][(crc >> 16) & 0xff] ^ p->table[4][(crc >> 24) & 0xff] ^ 62 p->table[3][(crc >> 32) & 0xff] ^ p->table[2][(crc >> 40) & 0xff] ^ 63 p->table[1][(crc >> 48) & 0xff] ^ p->table[0][crc >> 56]; 64 next += 8; 65 len -= 8; 66 } 67 while (len) { 68 crc = p->table[0][(crc ^ *next++) & 0xff] ^ (crc >> 8); 69 len--; 70 } 71 return (uint32_t)crc ^ 0xffffffff; 72 }