3 * Global definitions for Reed-Solomon encoder/decoder,
4 * by Phil Karn (karn@ka9q.ampr.org) September 1996
5 * Copyright 1999 Phil Karn, KA9Q
7 * Wireshark - Network traffic analyzer
8 * By Gerald Combs <gerald@wireshark.org>
9 * Copyright 1998 Gerald Combs
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version 2
14 * of the License, or (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
30 /* Set one of these to enable encoder/decoder debugging and error checking,
31 * at the expense of speed */
36 /* To select the CCSDS standard (255,223) code, define CCSDS. This
37 * implies standard values for MM, KK, B0 and PRIM.
43 /* Otherwise, leave CCSDS undefined and set the parameters below:
45 * Set MM to be the size of each code symbol in bits. The Reed-Solomon
46 * block size will then be NN = 2**M - 1 symbols. Supported values are
49 #define MM 8 /* Symbol size in bits */
52 * Set KK to be the number of data symbols in each block, which must be
53 * less than the block size. The code will then be able to correct up
54 * to NN-KK erasures or (NN-KK)/2 errors, or combinations thereof with
55 * each error counting as two erasures.
57 #define KK 207 /* Number of data symbols per block */
59 /* Set B0 to the first root of the generator polynomial, in alpha form, and
60 * set PRIM to the power of alpha used to generate the roots of the
61 * generator polynomial. The generator polynomial will then be
62 * @**PRIM*B0, @**PRIM*(B0+1), @**PRIM*(B0+2)...@**PRIM*(B0+NN-KK)
63 * where "@" represents a lower case alpha.
65 #define B0 1 /* First root of generator polynomial, alpha form */
66 #define PRIM 1 /* power of alpha used to generate roots of generator poly */
67 #define STANDARD_ORDER
69 /* If you want to select your own field generator polynomial, you'll have
70 * to edit that in rs.c.
74 /* Don't change these, they're CCSDS standard */
81 #define NN ((1 << MM) - 1)
84 typedef unsigned char dtype;
86 typedef unsigned int dtype;
89 /* Reed-Solomon encoding
90 * data[] is the input block, parity symbols are placed in bb[]
91 * bb[] may lie past the end of the data, e.g., for (255,223):
92 * encode_rs(&data[0],&data[223]);
94 int encode_rs(dtype data[], dtype bb[]);
96 /* Reed-Solomon erasures-and-errors decoding
97 * The received block goes into data[], and a list of zero-origin
98 * erasure positions, if any, goes in eras_pos[] with a count in no_eras.
100 * The decoder corrects the symbols in place, if possible and returns
101 * the number of corrected symbols. If the codeword is illegal or
102 * uncorrectible, the data array is unchanged and -1 is returned
104 int eras_dec_rs(dtype data[], int eras_pos[], int no_eras);