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/* crc.c - crc function */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2008 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/types.h>
#include <grub/lib/crc.h>
static grub_uint32_t crc32c_table [256];
/* Helper for init_crc32c_table. */
static grub_uint32_t
reflect (grub_uint32_t ref, int len)
{
grub_uint32_t result = 0;
int i;
for (i = 1; i <= len; i++)
{
if (ref & 1)
result |= 1 << (len - i);
ref >>= 1;
}
return result;
}
static void
init_crc32c_table (void)
{
grub_uint32_t polynomial = 0x1edc6f41;
int i, j;
for(i = 0; i < 256; i++)
{
crc32c_table[i] = reflect(i, 8) << 24;
for (j = 0; j < 8; j++)
crc32c_table[i] = (crc32c_table[i] << 1) ^
(crc32c_table[i] & (1 << 31) ? polynomial : 0);
crc32c_table[i] = reflect(crc32c_table[i], 32);
}
}
grub_uint32_t
grub_getcrc32c (grub_uint32_t crc, const void *buf, int size)
{
int i;
const grub_uint8_t *data = buf;
if (! crc32c_table[1])
init_crc32c_table ();
crc^= 0xffffffff;
for (i = 0; i < size; i++)
{
crc = (crc >> 8) ^ crc32c_table[(crc & 0xFF) ^ *data];
data++;
}
return crc ^ 0xffffffff;
}
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