58 lines
1.6 KiB
C
58 lines
1.6 KiB
C
/* Conversion lookup tables from conventional alpha to Berlekamp's
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* dual-basis representation. Used in the CCSDS version only.
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* taltab[] -- convert conventional to dual basis
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* tal1tab[] -- convert dual basis to conventional
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* Note: the actual RS encoder/decoder works with the conventional basis.
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* So data is converted from dual to conventional basis before either
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* encoding or decoding and then converted back.
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*
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* Copyright 2002 Phil Karn, KA9Q
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* May be used under the terms of the GNU Lesser General Public License (LGPL)
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#define DTYPE unsigned char
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DTYPE Taltab[256], Tal1tab[256];
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static DTYPE tal[] = { 0x8d, 0xef, 0xec, 0x86, 0xfa, 0x99, 0xaf, 0x7b };
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/* Generate conversion lookup tables between conventional alpha representation
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* (@**7, @**6, ...@**0)
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* and Berlekamp's dual basis representation
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* (l0, l1, ...l7)
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*/
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int main()
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{
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int i, j, k;
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for (i = 0; i < 256; i++) { /* For each value of input */
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Taltab[i] = 0;
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for (j = 0; j < 8; j++) /* for each column of matrix */
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for (k = 0; k < 8; k++) { /* for each row of matrix */
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if (i & (1 << k)) {
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Taltab[i] ^= tal[7 - k] & (1 << j);
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}
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}
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Tal1tab[Taltab[i]] = i;
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}
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printf("unsigned char Taltab[] = {\n");
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for (i = 0; i < 256; i++) {
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if ((i % 16) == 0) {
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printf("\n");
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}
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printf("0x%02x,", Taltab[i]);
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}
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printf("\n};\n\nunsigned char Tal1tab[] = {");
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for (i = 0; i < 256; i++) {
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if ((i % 16) == 0) {
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printf("\n");
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}
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printf("0x%02x,", Tal1tab[i]);
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}
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printf("\n};\n");
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exit(0);
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}
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