1 /* reedsolomon.h 2 * 3 * Global definitions for Reed-Solomon encoder/decoder, 4 * by Phil Karn (karn@ka9q.ampr.org) September 1996 5 * Copyright 1999 Phil Karn, KA9Q 6 * 7 * Wireshark - Network traffic analyzer 8 * By Gerald Combs <gerald@wireshark.org> 9 * Copyright 1998 Gerald Combs 10 * 11 * SPDX-License-Identifier: GPL-2.0-or-later 12 */ 13 14 #ifdef __cplusplus 15 extern "C" { 16 #endif 17 18 /* Set one of these to enable encoder/decoder debugging and error checking, 19 * at the expense of speed */ 20 /* #undef DEBUG 1*/ 21 /* #undef DEBUG 2*/ 22 #undef DEBUG 23 24 /* To select the CCSDS standard (255,223) code, define CCSDS. This 25 * implies standard values for MM, KK, B0 and PRIM. 26 */ 27 /* #undef CCSDS 1*/ 28 #undef CCSDS 29 #ifndef CCSDS 30 31 /* Otherwise, leave CCSDS undefined and set the parameters below: 32 * 33 * Set MM to be the size of each code symbol in bits. The Reed-Solomon 34 * block size will then be NN = 2**M - 1 symbols. Supported values are 35 * defined in rs.c. 36 */ 37 #define MM 8 /* Symbol size in bits */ 38 39 /* 40 * Set KK to be the number of data symbols in each block, which must be 41 * less than the block size. The code will then be able to correct up 42 * to NN-KK erasures or (NN-KK)/2 errors, or combinations thereof with 43 * each error counting as two erasures. 44 */ 45 #define KK 207 /* Number of data symbols per block */ 46 47 /* Set B0 to the first root of the generator polynomial, in alpha form, and 48 * set PRIM to the power of alpha used to generate the roots of the 49 * generator polynomial. The generator polynomial will then be 50 * @**PRIM*B0, @**PRIM*(B0+1), @**PRIM*(B0+2)...@**PRIM*(B0+NN-KK) 51 * where "@" represents a lower case alpha. 52 */ 53 #define B0 1 /* First root of generator polynomial, alpha form */ 54 #define PRIM 1 /* power of alpha used to generate roots of generator poly */ 55 #define STANDARD_ORDER 56 57 /* If you want to select your own field generator polynomial, you'll have 58 * to edit that in rs.c. 59 */ 60 61 #else /* CCSDS */ 62 /* Don't change these, they're CCSDS standard */ 63 #define MM 8 64 #define KK 223 65 #define B0 112 66 #define PRIM 11 67 #endif 68 69 #define NN ((1 << MM) - 1) 70 71 #if MM <= 8 72 typedef unsigned char dtype; 73 #else 74 typedef unsigned int dtype; 75 #endif 76 77 /* Reed-Solomon encoding 78 * data[] is the input block, parity symbols are placed in bb[] 79 * bb[] may lie past the end of the data, e.g., for (255,223): 80 * encode_rs(&data[0],&data[223]); 81 */ 82 int encode_rs(dtype data[], dtype bb[]); 83 84 /* Reed-Solomon erasures-and-errors decoding 85 * The received block goes into data[], and a list of zero-origin 86 * erasure positions, if any, goes in eras_pos[] with a count in no_eras. 87 * 88 * The decoder corrects the symbols in place, if possible and returns 89 * the number of corrected symbols. If the codeword is illegal or 90 * uncorrectible, the data array is unchanged and -1 is returned 91 */ 92 int eras_dec_rs(dtype data[], int eras_pos[], int no_eras); 93 94 #ifdef __cplusplus 95 } 96 #endif 97