1 /* Conversion lookup tables from conventional alpha to Berlekamp's 2 * dual-basis representation. Used in the CCSDS version only. 3 * taltab[] -- convert conventional to dual basis 4 * tal1tab[] -- convert dual basis to conventional 5 6 * Note: the actual RS encoder/decoder works with the conventional basis. 7 * So data is converted from dual to conventional basis before either 8 * encoding or decoding and then converted back. 9 * 10 * Copyright 2002 Phil Karn, KA9Q 11 * May be used under the terms of the GNU Lesser General Public License (LGPL) 12 */ 13 #include <stdio.h> 14 #include <stdlib.h> 15 16 #define DTYPE unsigned char 17 DTYPE Taltab[256],Tal1tab[256]; 18 19 static DTYPE tal[] = { 0x8d, 0xef, 0xec, 0x86, 0xfa, 0x99, 0xaf, 0x7b }; 20 21 /* Generate conversion lookup tables between conventional alpha representation 22 * (@**7, @**6, ...@**0) 23 * and Berlekamp's dual basis representation 24 * (l0, l1, ...l7) 25 */ 26 int main(){ 27 int i,j,k; 28 29 for(i=0;i<256;i++){/* For each value of input */ 30 Taltab[i] = 0; 31 for(j=0;j<8;j++) /* for each column of matrix */ 32 for(k=0;k<8;k++){ /* for each row of matrix */ 33 if(i & (1<<k)) 34 Taltab[i] ^= tal[7-k] & (1<<j); 35 } 36 Tal1tab[Taltab[i]] = i; 37 } 38 printf("unsigned char Taltab[] = {\n"); 39 for(i=0;i<256;i++){ 40 if((i % 16) == 0) 41 printf("\n"); 42 printf("0x%02x,",Taltab[i]); 43 } 44 printf("\n};\n\nunsigned char Tal1tab[] = {"); 45 for(i=0;i<256;i++){ 46 if((i % 16) == 0) 47 printf("\n"); 48 printf("0x%02x,",Tal1tab[i]); 49 } 50 printf("\n};\n"); 51 exit(0); 52 } 53 54
