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Location: FeatherHAB/wsprhab/lib/jtencode/init_rs_int.c
2fa25ca2db21
3.0 KiB
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Don't zero out everything in position, because we need some of that data; fix timer clocking
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 | /* Initialize a RS codec
*
* Copyright 2002 Phil Karn, KA9Q
* May be used under the terms of the GNU Lesser General Public License (LGPL)
*
* Slightly modified by Jason Milldrum NT7S, 2015 to fit into the Arduino framework
*/
#include <string.h>
#include <stdlib.h>
#include "jtencode.h"
#include "rs_common.h"
void free_rs_int(void * p)
{
struct rs *rs = (struct rs *)p;
free(rs->alpha_to);
free(rs->index_of);
free(rs->genpoly);
free(rs);
}
void * init_rs_int(int symsize, int gfpoly, int fcr, int prim,
int nroots, int pad)
{
struct rs *rs;
int i, j, sr,root,iprim;
rs = ((struct rs *)0);
/* Check parameter ranges */
if(symsize < 0 || symsize > 8*sizeof(data_t)){
goto done;
}
if(fcr < 0 || fcr >= (1<<symsize))
goto done;
if(prim <= 0 || prim >= (1<<symsize))
goto done;
if(nroots < 0 || nroots >= (1<<symsize))
goto done; /* Can't have more roots than symbol values! */
if(pad < 0 || pad >= ((1<<symsize) -1 - nroots))
goto done; /* Too much padding */
rs = (struct rs *)calloc(1,sizeof(struct rs));
if(rs == ((struct rs *)0))
goto done;
rs->mm = symsize;
rs->nn = (1<<symsize)-1;
rs->pad = pad;
rs->alpha_to = (data_t *)malloc(sizeof(data_t)*(rs->nn+1));
if(rs->alpha_to == NULL){
free(rs);
rs = ((struct rs *)0);
goto done;
}
rs->index_of = (data_t *)malloc(sizeof(data_t)*(rs->nn+1));
if(rs->index_of == NULL){
free(rs->alpha_to);
free(rs);
rs = ((struct rs *)0);
goto done;
}
/* Generate Galois field lookup tables */
rs->index_of[0] = A_0; /* log(zero) = -inf */
rs->alpha_to[A_0] = 0; /* alpha**-inf = 0 */
sr = 1;
for(i=0;i<rs->nn;i++){
rs->index_of[sr] = i;
rs->alpha_to[i] = sr;
sr <<= 1;
if(sr & (1<<symsize))
sr ^= gfpoly;
sr &= rs->nn;
}
if(sr != 1){
/* field generator polynomial is not primitive! */
free(rs->alpha_to);
free(rs->index_of);
free(rs);
rs = ((struct rs *)0);
goto done;
}
/* Form RS code generator polynomial from its roots */
rs->genpoly = (data_t *)malloc(sizeof(data_t)*(nroots+1));
if(rs->genpoly == NULL){
free(rs->alpha_to);
free(rs->index_of);
free(rs);
rs = ((struct rs *)0);
goto done;
}
rs->fcr = fcr;
rs->prim = prim;
rs->nroots = nroots;
/* Find prim-th root of 1, used in decoding */
for(iprim=1;(iprim % prim) != 0;iprim += rs->nn)
;
rs->iprim = iprim / prim;
rs->genpoly[0] = 1;
for (i = 0,root=fcr*prim; i < nroots; i++,root += prim) {
rs->genpoly[i+1] = 1;
/* Multiply rs->genpoly[] by @**(root + x) */
for (j = i; j > 0; j--){
if (rs->genpoly[j] != 0)
rs->genpoly[j] = rs->genpoly[j-1] ^ rs->alpha_to[modnn(rs,rs->index_of[rs->genpoly[j]] + root)];
else
rs->genpoly[j] = rs->genpoly[j-1];
}
/* rs->genpoly[0] can never be zero */
rs->genpoly[0] = rs->alpha_to[modnn(rs,rs->index_of[rs->genpoly[0]] + root)];
}
/* convert rs->genpoly[] to index form for quicker encoding */
for (i = 0; i <= nroots; i++)
rs->genpoly[i] = rs->index_of[rs->genpoly[i]];
done:;
return rs;
}
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