114 lines
3.5 KiB
C
114 lines
3.5 KiB
C
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/*
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* Generic binary BCH encoding/decoding library
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright © 2011 Parrot S.A.
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*
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* Author: Ivan Djelic <ivan.djelic@parrot.com>
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*
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* Description:
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*
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* This library provides runtime configurable encoding/decoding of binary
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* Bose-Chaudhuri-Hocquenghem (BCH) codes.
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*/
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#ifndef _BCH_H
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#define _BCH_H
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#include <stdint.h>
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#if defined(CONFIG_BCH_CONST_PARAMS)
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#define GF_M(_p) (CONFIG_BCH_CONST_M)
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#define GF_T(_p) (CONFIG_BCH_CONST_T)
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#define GF_N(_p) ((1 << (CONFIG_BCH_CONST_M))-1)
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#else
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#define GF_M(_p) ((_p)->m)
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#define GF_T(_p) ((_p)->t)
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#define GF_N(_p) ((_p)->n)
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#endif
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#define BCH_ECC_WORDS(_p) DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 32)
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#define BCH_ECC_BYTES(_p) DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 8)
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#ifndef dbg
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#define dbg(_fmt, args...) do {} while (0)
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#endif
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/*
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* represent a polynomial over GF(2^m)
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*/
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struct gf_poly {
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unsigned int deg; /* polynomial degree */
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unsigned int c[0]; /* polynomial terms */
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};
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/* given its degree, compute a polynomial size in bytes */
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#define GF_POLY_SZ(_d) (sizeof(struct gf_poly)+((_d)+1)*sizeof(unsigned int))
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/* polynomial of degree 1 */
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struct gf_poly_deg1 {
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struct gf_poly poly;
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unsigned int c[2];
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};
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/**
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* struct bch_control - BCH control structure
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* @m: Galois field order
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* @n: maximum codeword size in bits (= 2^m-1)
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* @t: error correction capability in bits
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* @ecc_bits: ecc exact size in bits, i.e. generator polynomial degree (<=m*t)
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* @ecc_bytes: ecc max size (m*t bits) in bytes
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* @a_pow_tab: Galois field GF(2^m) exponentiation lookup table
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* @a_log_tab: Galois field GF(2^m) log lookup table
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* @mod8_tab: remainder generator polynomial lookup tables
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* @ecc_buf: ecc parity words buffer
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* @ecc_buf2: ecc parity words buffer
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* @xi_tab: GF(2^m) base for solving degree 2 polynomial roots
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* @syn: syndrome buffer
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* @cache: log-based polynomial representation buffer
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* @elp: error locator polynomial
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* @poly_2t: temporary polynomials of degree 2t
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*/
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struct bch_control {
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unsigned int m;
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unsigned int n;
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unsigned int t;
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unsigned int ecc_bits;
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unsigned int ecc_bytes;
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/* private: */
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uint16_t *a_pow_tab;
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uint16_t *a_log_tab;
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uint32_t *mod8_tab;
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uint32_t *ecc_buf;
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uint32_t *ecc_buf2;
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unsigned int *xi_tab;
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unsigned int *syn;
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int *cache;
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struct gf_poly *elp;
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struct gf_poly *poly_2t[4];
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};
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struct bch_control *init_bch(int m, int t, unsigned int prim_poly);
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void free_bch(struct bch_control *bch);
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void encode_bch(struct bch_control *bch, const uint8_t *data,
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unsigned int len, uint8_t *ecc);
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int decode_bch(struct bch_control *bch, const uint8_t *data, unsigned int len,
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const uint8_t *recv_ecc, const uint8_t *calc_ecc,
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const unsigned int *syn, unsigned int *errloc);
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#endif /* _BCH_H */
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