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/* 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.

 */

#define MM  8           /* RS code over GF(2**MM) - change to suit */

#define KK  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[0],&data[223]);

 */

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);