/*
 * Generic binary BCH encoding/decoding library
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Copyright © 2011 Parrot S.A.
 *
 * Author: Ivan Djelic <ivan.djelic@parrot.com>
 *
 * Description:
 *
 * This library provides runtime configurable encoding/decoding of binary
 * Bose-Chaudhuri-Hocquenghem (BCH) codes.
*/
#ifndef _BCH_H
#define _BCH_H

#include <stdint.h>

#if defined(CONFIG_BCH_CONST_PARAMS)
#define GF_M(_p)               (CONFIG_BCH_CONST_M)
#define GF_T(_p)               (CONFIG_BCH_CONST_T)
#define GF_N(_p)               ((1 << (CONFIG_BCH_CONST_M))-1)
#else
#define GF_M(_p)               ((_p)->m)
#define GF_T(_p)               ((_p)->t)
#define GF_N(_p)               ((_p)->n)
#endif

#define BCH_ECC_WORDS(_p)      DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 32)
#define BCH_ECC_BYTES(_p)      DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 8)

#ifndef dbg
#define dbg(_fmt, args...)     do {} while (0)
#endif

/*
 * represent a polynomial over GF(2^m)
 */
struct gf_poly {
	unsigned int deg;    /* polynomial degree */
	unsigned int c[0];   /* polynomial terms */
};

/* given its degree, compute a polynomial size in bytes */
#define GF_POLY_SZ(_d) (sizeof(struct gf_poly)+((_d)+1)*sizeof(unsigned int))

/* polynomial of degree 1 */
struct gf_poly_deg1 {
	struct gf_poly poly;
	unsigned int   c[2];
};

/**
 * struct bch_control - BCH control structure
 * @m:          Galois field order
 * @n:          maximum codeword size in bits (= 2^m-1)
 * @t:          error correction capability in bits
 * @ecc_bits:   ecc exact size in bits, i.e. generator polynomial degree (<=m*t)
 * @ecc_bytes:  ecc max size (m*t bits) in bytes
 * @a_pow_tab:  Galois field GF(2^m) exponentiation lookup table
 * @a_log_tab:  Galois field GF(2^m) log lookup table
 * @mod8_tab:   remainder generator polynomial lookup tables
 * @ecc_buf:    ecc parity words buffer
 * @ecc_buf2:   ecc parity words buffer
 * @xi_tab:     GF(2^m) base for solving degree 2 polynomial roots
 * @syn:        syndrome buffer
 * @cache:      log-based polynomial representation buffer
 * @elp:        error locator polynomial
 * @poly_2t:    temporary polynomials of degree 2t
 */
struct bch_control {
	unsigned int    m;
	unsigned int    n;
	unsigned int    t;
	unsigned int    ecc_bits;
	unsigned int    ecc_bytes;
/* private: */
	uint16_t       *a_pow_tab;
	uint16_t       *a_log_tab;
	uint32_t       *mod8_tab;
	uint32_t       *ecc_buf;
	uint32_t       *ecc_buf2;
	unsigned int   *xi_tab;
	unsigned int   *syn;
	int            *cache;
	struct gf_poly *elp;
	struct gf_poly *poly_2t[4];
};

struct bch_control *init_bch(int m, int t, unsigned int prim_poly);

void free_bch(struct bch_control *bch);

void encode_bch(struct bch_control *bch, const uint8_t *data,
		unsigned int len, uint8_t *ecc);

int decode_bch(struct bch_control *bch, const uint8_t *data, unsigned int len,
	       const uint8_t *recv_ecc, const uint8_t *calc_ecc,
	       const unsigned int *syn, unsigned int *errloc);

#endif /* _BCH_H */