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/*
* gen_crc32_table.c - a program for CRC-32 table generation
*
* Originally public domain; changes after 2016-09-07 are copyrighted.
*
* Copyright 2016 Eric Biggers
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include <stdint.h>
#include <stdio.h>
static uint32_t crc32_table[0x800];
static uint32_t
crc32_update_bit(uint32_t remainder, uint8_t next_bit)
{
return (remainder >> 1) ^
(((remainder ^ next_bit) & 1) ? 0xEDB88320 : 0);
}
static uint32_t
crc32_update_byte(uint32_t remainder, uint8_t next_byte)
{
for (int j = 0; j < 8; j++, next_byte >>= 1)
remainder = crc32_update_bit(remainder, next_byte & 1);
return remainder;
}
static void
print_256_entries(const uint32_t *entries)
{
for (size_t i = 0; i < 256 / 4; i++) {
printf("\t");
for (size_t j = 0; j < 4; j++) {
printf("0x%08x,", entries[i * 4 + j]);
if (j != 3)
printf(" ");
}
printf("\n");
}
}
int
main(void)
{
/* crc32_table[i] for 0 <= i < 0x100 is the CRC-32 of byte i. */
for (int i = 0; i < 0x100; i++)
crc32_table[i] = crc32_update_byte(0, i);
/* crc32_table[i] for 0x100 <= i < 0x800 is the CRC-32 of byte i % 0x100
* followed by i / 0x100 zero bytes. */
for (int i = 0x100; i < 0x800; i++)
crc32_table[i] = crc32_update_byte(crc32_table[i - 0x100], 0);
printf("/*\n");
printf(" * crc32_table.h - data table to accelerate CRC-32 computation\n");
printf(" *\n");
printf(" * THIS FILE WAS AUTOMATICALLY GENERATED "
"BY gen_crc32_table.c. DO NOT EDIT.\n");
printf(" */\n");
printf("\n");
printf("#include <stdint.h>\n");
printf("\n");
printf("static const uint32_t crc32_table[] = {\n");
print_256_entries(&crc32_table[0x000]);
printf("#if defined(CRC32_SLICE4) || defined(CRC32_SLICE8)\n");
print_256_entries(&crc32_table[0x100]);
print_256_entries(&crc32_table[0x200]);
print_256_entries(&crc32_table[0x300]);
printf("#endif /* CRC32_SLICE4 || CRC32_SLICE8 */\n");
printf("#if defined(CRC32_SLICE8)\n");
print_256_entries(&crc32_table[0x400]);
print_256_entries(&crc32_table[0x500]);
print_256_entries(&crc32_table[0x600]);
print_256_entries(&crc32_table[0x700]);
printf("#endif /* CRC32_SLICE8 */\n");
printf("};\n");
return 0;
}
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