www.pudn.com > Reed_Solomon.rar > gen_ccsds_tal.c, change:2002-02-13,size:1485b

```/* Conversion lookup tables from conventional alpha to Berlekamp's
* dual-basis representation. Used in the CCSDS version only.
* taltab[] -- convert conventional to dual basis
* tal1tab[] -- convert dual basis to conventional

* Note: the actual RS encoder/decoder works with the conventional basis.
* So data is converted from dual to conventional basis before either
* encoding or decoding and then converted back.
*
* Copyright 2002 Phil Karn, KA9Q
* May be used under the terms of the GNU General Public License (GPL)
*/
#include <stdio.h>
#define DTYPE unsigned char
DTYPE Taltab[256],Tal1tab[256];

static DTYPE tal[] = { 0x8d, 0xef, 0xec, 0x86, 0xfa, 0x99, 0xaf, 0x7b };

/* Generate conversion lookup tables between conventional alpha representation
* (@**7, @**6, ...@**0)
*  and Berlekamp's dual basis representation
* (l0, l1, ...l7)
*/
int main(){
int i,j,k;

for(i=0;i<256;i++){/* For each value of input */
Taltab[i] = 0;
for(j=0;j<8;j++) /* for each column of matrix */
for(k=0;k<8;k++){ /* for each row of matrix */
if(i & (1<<k))
Taltab[i] ^= tal[7-k] & (1<<j);
}
Tal1tab[Taltab[i]] = i;
}
printf("unsigned char Taltab[] = {\n");
for(i=0;i<256;i++){
if((i % 16) == 0)
printf("\n");
printf("0x%02x,",Taltab[i]);
}
printf("\n};\n\nunsigned char Tal1tab[] = {");
for(i=0;i<256;i++){
if((i % 16) == 0)
printf("\n");
printf("0x%02x,",Tal1tab[i]);
}
printf("\n};\n");
exit(0);
}

```