52 lines
1.7 KiB
C
52 lines
1.7 KiB
C
/* Global definitions for Reed-Solomon encoder/decoder
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* Phil Karn KA9Q, September 1996
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*
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* The parameters MM and KK specify the Reed-Solomon code parameters.
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*
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* Set MM to be the size of each code symbol in bits. The Reed-Solomon
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* block size will then be NN = 2**M - 1 symbols. Supported values are
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* defined in rs.c.
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*
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* Set KK to be the number of data symbols in each block, which must be
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* less than the block size. The code will then be able to correct up
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* to NN-KK erasures or (NN-KK)/2 errors, or combinations thereof with
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* each error counting as two erasures.
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*/
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#define MM 8 /* RS code over GF(2**MM) - change to suit */
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#define KK 223 /* KK = number of information symbols */
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#define NN ((1 << MM) - 1)
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#if (MM <= 8)
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typedef unsigned char dtype;
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#else
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typedef unsigned int dtype;
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#endif
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/* Initialization function */
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void init_rs(void);
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/* These two functions *must* be called in this order (e.g.,
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* by init_rs()) before any encoding/decoding
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*/
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void generate_gf(void); /* Generate Galois Field */
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void gen_poly(void); /* Generate generator polynomial */
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/* Reed-Solomon encoding
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* data[] is the input block, parity symbols are placed in bb[]
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* bb[] may lie past the end of the data, e.g., for (255,223):
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* encode_rs(&data[0],&data[223]);
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*/
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int encode_rs(dtype data[], dtype bb[]);
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/* Reed-Solomon erasures-and-errors decoding
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* The received block goes into data[], and a list of zero-origin
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* erasure positions, if any, goes in eras_pos[] with a count in no_eras.
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*
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* The decoder corrects the symbols in place, if possible and returns
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* the number of corrected symbols. If the codeword is illegal or
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* uncorrectible, the data array is unchanged and -1 is returned
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*/
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int eras_dec_rs(dtype data[], int eras_pos[], int no_eras);
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