59 lines
1.3 KiB
C
59 lines
1.3 KiB
C
/* Reed-Solomon encoder
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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 <string.h>
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#ifdef FIXED
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#include "fixed.h"
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#elif defined(BIGSYM)
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#include "int.h"
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#else
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#include "char.h"
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#endif
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void ENCODE_RS(
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#ifdef FIXED
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data_t *data, data_t *bb, int pad)
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{
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#else
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void *p, data_t *data, data_t *bb)
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{
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struct rs *rs = (struct rs *)p;
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#endif
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int i, j;
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data_t feedback;
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#ifdef FIXED
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/* Check pad parameter for validity */
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if (pad < 0 || pad >= NN) {
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return;
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}
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#endif
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memset(bb, 0, NROOTS * sizeof(data_t));
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for (i = 0; i < NN - NROOTS - PAD; i++) {
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feedback = INDEX_OF[data[i] ^ bb[0]];
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if (feedback != A0) { /* feedback term is non-zero */
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#ifdef UNNORMALIZED
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/* This line is unnecessary when GENPOLY[NROOTS] is unity, as it must
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* always be for the polynomials constructed by init_rs()
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*/
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feedback = MODNN(NN - GENPOLY[NROOTS] + feedback);
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#endif
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for (j = 1; j < NROOTS; j++) {
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bb[j] ^= ALPHA_TO[MODNN(feedback + GENPOLY[NROOTS - j])];
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}
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}
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/* Shift */
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memmove(&bb[0], &bb[1], sizeof(data_t) * (NROOTS - 1));
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if (feedback != A0) {
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bb[NROOTS - 1] = ALPHA_TO[MODNN(feedback + GENPOLY[0])];
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}
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else {
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bb[NROOTS - 1] = 0;
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}
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}
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}
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