75 lines
1.8 KiB
C
75 lines
1.8 KiB
C
/* crc.c - crc function */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2008 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU 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 GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <grub/types.h>
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#include <grub/lib/crc.h>
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static grub_uint32_t crc32_table [256];
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static void
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init_crc32_table (void)
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{
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auto grub_uint32_t reflect (grub_uint32_t ref, int len);
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grub_uint32_t reflect (grub_uint32_t ref, int len)
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{
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grub_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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grub_uint32_t polynomial = 0x04c11db7;
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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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crc32_table[i] = reflect(i, 8) << 24;
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for (j = 0; j < 8; j++)
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crc32_table[i] = (crc32_table[i] << 1) ^
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(crc32_table[i] & (1 << 31) ? polynomial : 0);
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crc32_table[i] = reflect(crc32_table[i], 32);
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}
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}
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grub_uint32_t
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grub_getcrc32 (grub_uint32_t crc, void *buf, int size)
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{
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int i;
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grub_uint8_t *data = buf;
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if (! crc32_table[1])
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init_crc32_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) ^ crc32_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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