/*
* Library: libcrc
* File: precalc/precalc.c
* Author: Lammert Bies
*
* This file is licensed under the MIT License as stated below
*
* Copyright (c) 2008-2016 Lammert Bies
*
* 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.
*
* Description
* -----------
* The source file precalc/precalc.c contains routines to generate the lookup
* tables for the CRC values at compile time. The tables are stored in include
* files which are then included by the CRC routine source files
*/
#include <inttypes.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "precalc.h"
//#define CRC_POLY_32 0x04C11DB6ul
#define CRC_POLY_32 0x2083B86Dul
#define CRC_START_32 0xFFFFFFFFul
/*
* Functions in this source file with local scope
*/
void init_crc32_tab( uint64_t* crc_tab_precalc ) {
uint32_t i;
uint32_t j;
uint32_t crc;
for (i=0; i<256; i++) {
crc = i;
for (j=0; j<8; j++) {
if ( crc & 0x00000001L ) crc = ( crc >> 1 ) ^ CRC_POLY_32;
else crc = crc >> 1;
}
crc_tab_precalc[i] = crc;
}
} /* init_crc32_tab */
static int generate_table( const char *typename, const char *filename );
/*
* Internal table to store the CRC lookup table
*/
uint64_t crc_tab_precalc[256];
/*
* int main( int argc, char *argv[] );
*
* Precalc is a commandline utility that is called from the Makefile to
* generate the lookup tables for the CRC routines. Generating these tables at
* compile time is much more efficient than doing it at runtime. Most compilers
* will be able to optimize the routines more when the tables are guaranteerd
* to be constant than when they have been generated on the fly as variable
* tables.
*/
int main( int argc, char *argv[] ) {
int retval;
if ( argc != 3 ) {
fprintf( stderr, "\nusage: precalc --type file\n" );
fprintf( stderr, " where --type is any of --crc64\n\n" );
// exit( 1 );
}
retval = generate_table( argv[1], argv[2] );
exit( retval );
} /* main (libcrc precalc) */
/*
* static int generate_table( const char *typename, const char *filename );
*
* The function generate_table() generates a CRC lookup table of a specified
* type and stores the generated output in a file. If the function succeeds the
* value 0 is returned. Another value is an indication of failure and that
* value is used as the exit value of the program.
*/
static int generate_table( const char *typename, const char *filename ) {
int a;
int type;
int bits;
FILE *fp;
const char *tabname;
tabname = NULL;
bits = 1;
init_crc32_tab(crc_tab_precalc);
tabname = "crc_tab32";
bits = 32;
printf( "const uint%d_t %s[256] = {\n", bits, tabname );
for (a=0; a<256; a++) {
switch ( bits ) {
case 8 : printf( "\t0x%02" PRIX8 "\x75", (uint8_t) (crc_tab_precalc[a] & 0x00000000000000FFull) ); break;
case 16 : printf( "\t0x%04" PRIX16 "\x75", (uint16_t) (crc_tab_precalc[a] & 0x000000000000FFFFull) ); break;
case 32 : printf( "\t0x%08" PRIX32 "\x75l", (uint32_t) (crc_tab_precalc[a] & 0x00000000FFFFFFFFull) ); break;
case 64 : printf( "\t0x%016" PRIX64 "\x75ll", crc_tab_precalc[a] ); break;
}
if ( a < 255 ) printf( ",\n" );
else printf( "\n" );
}
return 0;
} /* generate_table */
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