GNU Radio's SATNOGS Package
encode_rs.h
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1/* The guts of the Reed-Solomon encoder, meant to be #included
2 * into a function body with the following typedefs, macros and variables supplied
3 * according to the code parameters:
4
5 * data_t - a typedef for the data symbol
6 * data_t data[] - array of NN-NROOTS-PAD and type data_t to be encoded
7 * data_t parity[] - an array of NROOTS and type data_t to be written with parity symbols
8 * NROOTS - the number of roots in the RS code generator polynomial,
9 * which is the same as the number of parity symbols in a block.
10 Integer variable or literal.
11 *
12 * NN - the total number of symbols in a RS block. Integer variable or literal.
13 * PAD - the number of pad symbols in a block. Integer variable or literal.
14 * ALPHA_TO - The address of an array of NN elements to convert Galois field
15 * elements in index (log) form to polynomial form. Read only.
16 * INDEX_OF - The address of an array of NN elements to convert Galois field
17 * elements in polynomial form to index (log) form. Read only.
18 * MODNN - a function to reduce its argument modulo NN. May be inline or a macro.
19 * GENPOLY - an array of NROOTS+1 elements containing the generator polynomial in index form
20
21 * The memset() and memmove() functions are used. The appropriate header
22 * file declaring these functions (usually <string.h>) must be included by the calling
23 * program.
24
25 * Copyright 2004, Phil Karn, KA9Q
26 * May be used under the terms of the GNU Lesser General Public License (LGPL)
27 */
28
29
30#undef A0
31#define A0 (NN) /* Special reserved value encoding zero in index form */
32
33{
34 int i, j;
36
37 memset(parity, 0, NROOTS * sizeof(data_t));
38
39 for (i = 0; i < NN - NROOTS - PAD; i++)
40 {
41 feedback = INDEX_OF[data[i] ^ parity[0]];
42 if (feedback != A0) { /* feedback term is non-zero */
43#ifdef UNNORMALIZED
44 /* This line is unnecessary when GENPOLY[NROOTS] is unity, as it must
45 * always be for the polynomials constructed by init_rs()
46 */
48#endif
49 for (j = 1; j < NROOTS; j++) {
51 }
52 }
53 /* Shift */
54 memmove(&parity[0], &parity[1], sizeof(data_t) * (NROOTS - 1));
55 if (feedback != A0) {
57 }
58 else {
59 parity[NROOTS - 1] = 0;
60 }
61 }
62}
#define NN
Definition: ccsds.h:3
#define NROOTS
Definition: ccsds.h:4
unsigned char data_t
Definition: ccsds.h:1
#define PAD
Definition: char.h:19
#define MODNN(x)
Definition: char.h:8
#define INDEX_OF
Definition: char.h:13
#define GENPOLY
Definition: char.h:14
#define ALPHA_TO
Definition: char.h:12
int j
Definition: decode_rs.h:73
int i
Definition: decode_rs.h:73
#define A0
Definition: encode_rs.h:31
data_t feedback
Definition: encode_rs.h:35
memset(parity, 0, NROOTS *sizeof(data_t))
static int parity(int x)
Definition: fec.h:360