86 lines
2.1 KiB
C
86 lines
2.1 KiB
C
/* Dhara - NAND flash management layer
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* Copyright (C) 2013 Daniel Beer <dlbeer@gmail.com>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#ifndef ECC_GF13_H_
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#define ECC_GF13_H_
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#include <stdint.h>
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/* Galois field tables of order 2^13-1 */
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#define GF13_ORDER 8191
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typedef uint16_t gf13_elem_t;
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/* If you need to reduce the code size, you can define GF13_NO_TABLES.
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*
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* This results in much smaller (but also much slower) code.
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*/
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#ifdef GF13_NO_TABLES
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gf13_elem_t gf13_mul(gf13_elem_t a, gf13_elem_t b);
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gf13_elem_t gf13_div(gf13_elem_t a, gf13_elem_t b);
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static inline gf13_elem_t gf13_divx(gf13_elem_t a)
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{
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return gf13_mul(a, 0x100d);
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}
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static inline gf13_elem_t gf13_mulx(gf13_elem_t a)
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{
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gf13_elem_t r = a << 1;
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if (r & 8192)
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r ^= 0x201b;
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return r;
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}
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#else
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extern const gf13_elem_t gf13_exp[8192];
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extern const gf13_elem_t gf13_log[8192];
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/* Wrappers for field arithmetic */
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static inline gf13_elem_t gf13_wrap(gf13_elem_t s)
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{
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return (s >= GF13_ORDER) ? (s - GF13_ORDER) : s;
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}
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static inline gf13_elem_t gf13_mul(gf13_elem_t a, gf13_elem_t b)
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{
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return gf13_exp[gf13_wrap(gf13_log[a] + gf13_log[b])];
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}
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static inline gf13_elem_t gf13_div(gf13_elem_t a, gf13_elem_t b)
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{
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return gf13_exp[gf13_wrap(gf13_log[a] + GF13_ORDER - gf13_log[b])];
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}
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static inline gf13_elem_t gf13_divx(gf13_elem_t a)
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{
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return gf13_exp[gf13_wrap(gf13_log[a] + GF13_ORDER - 1)];
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}
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static inline gf13_elem_t gf13_mulx(gf13_elem_t a)
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{
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return gf13_exp[gf13_wrap(gf13_log[a] + 1)];
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}
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#endif
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#endif
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