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1 /* Stuff common to all the general-purpose Reed-Solomon codecs
2  * Copyright 2004 Phil Karn, KA9Q
3  * May be used under the terms of the GNU Lesser General Public License (LGPL)
4  */
5 
6 /* Reed-Solomon codec control block */
7 struct rs {
8   int mm;              /* Bits per symbol */
9   int nn;              /* Symbols per block (= (1<<mm)-1) */
10   data_t *alpha_to;     /* log lookup table */
11   data_t *index_of;     /* Antilog lookup table */
12   data_t *genpoly;      /* Generator polynomial */
13   int nroots;     /* Number of generator roots = number of parity symbols */
14   int fcr;        /* First consecutive root, index form */
15   int prim;       /* Primitive element, index form */
16   int iprim;      /* prim-th root of 1, index form */
17   int pad;        /* Padding bytes in shortened block */
18 };
19 
modnn(struct rs * rs,int x)20 static inline int modnn(struct rs *rs,int x){
21   while (x >= rs->nn) {
22     x -= rs->nn;
23     x = (x >> rs->mm) + (x & rs->nn);
24   }
25   return x;
26 }
27