/* Global definitions for Reed-Solomon encoder/decoder * Phil Karn KA9Q, September 1996 * * The parameters MM and KK specify the Reed-Solomon code parameters. * * Set MM to be the size of each code symbol in bits. The Reed-Solomon * block size will then be NN = 2**M - 1 symbols. Supported values are * defined in rs.c. * * Set KK to be the number of data symbols in each block, which must be * less than the block size. The code will then be able to correct up * to NN-KK erasures or (NN-KK)/2 errors, or combinations thereof with * each error counting as two erasures. */ #ifdef MSDOS #define inline /* broken MSC 5.0 */ #endif #define MM 8 /* RS code over GF(2**MM) - change to suit */ #define KK 192 /* 223 */ /* KK = number of information symbols */ #define NN ((1 << MM) - 1) #if (MM <= 8) typedef unsigned char dtype; #else typedef unsigned int dtype; #endif /* Initialization function */ void init_rs(void); /* These two functions *must* be called in this order (e.g., * by init_rs()) before any encoding/decoding */ void generate_gf(void); /* Generate Galois Field */ void gen_poly(void); /* Generate generator polynomial */ /* Reed-Solomon encoding * data is the input block, parity symbols are placed in bb * bb may lie past the end of the data, e.g., for (255,223): * encode_rs(&data,&data); */ int encode_rs(dtype data, dtype bb); /* Reed-Solomon erasures-and-errors decoding * The received block goes into data, and a list of zero-origin * erasure positions, if any, goes in eras_pos with a count in no_eras. * * The decoder corrects the symbols in place, if possible and returns * the number of corrected symbols. If the codeword is illegal or * uncorrectible, the data array is unchanged and -1 is returned */ int eras_dec_rs(dtype data, int eras_pos, int no_eras);
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