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78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
/******************************************************************************
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* crc32.c ----
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*
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* Copyright (c) 2022, longpanda <admin@ventoy.net>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 3 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include "vlnk.h"
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static uint32_t crc32c_table [256];
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/* Helper for init_crc32c_table. */
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static uint32_t reflect (uint32_t ref, int len)
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{
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uint32_t result = 0;
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int i;
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for (i = 1; i <= len; i++)
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{
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if (ref & 1)
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result |= 1 << (len - i);
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ref >>= 1;
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}
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return result;
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}
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static void init_crc32c_table (void)
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{
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uint32_t polynomial = 0x1edc6f41;
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int i, j;
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for(i = 0; i < 256; i++)
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{
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crc32c_table[i] = reflect(i, 8) << 24;
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for (j = 0; j < 8; j++)
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crc32c_table[i] = (crc32c_table[i] << 1) ^
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(crc32c_table[i] & (1 << 31) ? polynomial : 0);
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crc32c_table[i] = reflect(crc32c_table[i], 32);
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}
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}
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uint32_t ventoy_getcrc32c (uint32_t crc, const void *buf, int size)
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{
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int i;
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const uint8_t *data = buf;
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if (! crc32c_table[1])
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init_crc32c_table ();
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crc^= 0xffffffff;
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for (i = 0; i < size; i++)
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{
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crc = (crc >> 8) ^ crc32c_table[(crc & 0xFF) ^ *data];
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data++;
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}
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return crc ^ 0xffffffff;
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}
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