bb26e4ff16
It decreases its size significantly and avoids a variable in .text. * grub-core/lib/reed_solomon.c (scratch): Removed. (chosenstat): New const or static array. (sigma): Likewise. (errpot): Likewise. (errpos): Likewise. (sy): Likewise. (mstat): Likewise. (errvals): Likewise. (eqstat): Likewise. (pol_evaluate): Replace x with log_x argument. All users updated. (syndroms): Removed. (gauss_solve): Use statically allocated arrays. (rs_recover): Likewise. Calculate syndroms directly. (decode_block): Use statically allocated arrays. (grub_reed_solomon_add_redundancy) [TEST]: Fix -DTEST compilation. (main) [TEST]: Allow -DTEST -DSTANDALONE.
471 lines
11 KiB
C
471 lines
11 KiB
C
/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2010 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifdef TEST
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#define xmalloc malloc
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#define grub_memset memset
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#define grub_memcpy memcpy
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#endif
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#ifndef STANDALONE
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#include <assert.h>
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#endif
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#ifndef STANDALONE
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#ifdef TEST
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typedef unsigned int grub_size_t;
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typedef unsigned char grub_uint8_t;
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#else
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#include <grub/types.h>
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#include <grub/reed_solomon.h>
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#include <grub/util/misc.h>
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#include <grub/misc.h>
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#endif
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#endif
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#define SECTOR_SIZE 512
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#define MAX_BLOCK_SIZE (200 * SECTOR_SIZE)
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#ifdef STANDALONE
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#ifdef TEST
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typedef unsigned int grub_size_t;
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typedef unsigned char grub_uint8_t;
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#else
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#include <grub/types.h>
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#include <grub/misc.h>
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#endif
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void
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grub_reed_solomon_recover (void *ptr_, grub_size_t s, grub_size_t rs);
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#endif
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#define GF_SIZE 8
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typedef grub_uint8_t gf_single_t;
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#define GF_POLYNOMIAL 0x1d
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#define GF_INVERT2 0x8e
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#if defined (STANDALONE) && !defined (TEST)
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static gf_single_t * const gf_powx __attribute__ ((section(".text"))) = (void *) 0x100000;
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static gf_single_t * const gf_powx_inv __attribute__ ((section(".text"))) = (void *) 0x100200;
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static int *const chosenstat __attribute__ ((section(".text"))) = (void *) 0x100300;
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static gf_single_t *const sigma __attribute__ ((section(".text"))) = (void *) 0x100700;
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static gf_single_t *const errpot __attribute__ ((section(".text"))) = (void *) 0x100800;
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static int *const errpos __attribute__ ((section(".text"))) = (void *) 0x100900;
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static gf_single_t *const sy __attribute__ ((section(".text"))) = (void *) 0x100d00;
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static gf_single_t *const mstat __attribute__ ((section(".text"))) = (void *) 0x100e00;
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static gf_single_t *const errvals __attribute__ ((section(".text"))) = (void *) 0x100f00;
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static gf_single_t *const eqstat __attribute__ ((section(".text"))) = (void *) 0x101000;
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/* Next available address: (void *) 0x112000. */
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#else
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static gf_single_t gf_powx[255 * 2];
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static gf_single_t gf_powx_inv[256];
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static int chosenstat[256];
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static gf_single_t sigma[256];
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static gf_single_t errpot[256];
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static int errpos[256];
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static gf_single_t sy[256];
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static gf_single_t mstat[256];
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static gf_single_t errvals[256];
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static gf_single_t eqstat[65536 + 256];
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#endif
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static gf_single_t
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gf_mul (gf_single_t a, gf_single_t b)
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{
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if (a == 0 || b == 0)
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return 0;
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return gf_powx[(int) gf_powx_inv[a] + (int) gf_powx_inv[b]];
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}
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static inline gf_single_t
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gf_invert (gf_single_t a)
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{
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return gf_powx[255 - (int) gf_powx_inv[a]];
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}
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static void
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init_powx (void)
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{
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int i;
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grub_uint8_t cur = 1;
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gf_powx_inv[0] = 0;
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for (i = 0; i < 255; i++)
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{
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gf_powx[i] = cur;
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gf_powx[i + 255] = cur;
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gf_powx_inv[cur] = i;
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if (cur & (1ULL << (GF_SIZE - 1)))
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cur = (cur << 1) ^ GF_POLYNOMIAL;
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else
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cur <<= 1;
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}
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}
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static gf_single_t
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pol_evaluate (gf_single_t *pol, grub_size_t degree, int log_x)
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{
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int i;
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gf_single_t s = 0;
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int log_xn = 0;
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for (i = degree; i >= 0; i--)
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{
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if (pol[i])
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s ^= gf_powx[(int) gf_powx_inv[pol[i]] + log_xn];
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log_xn += log_x;
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if (log_xn >= ((1 << GF_SIZE) - 1))
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log_xn -= ((1 << GF_SIZE) - 1);
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}
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return s;
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}
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#if !defined (STANDALONE)
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static void
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rs_encode (gf_single_t *data, grub_size_t s, grub_size_t rs)
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{
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gf_single_t *rs_polynomial;
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int i, j;
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gf_single_t *m;
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m = xmalloc ((s + rs) * sizeof (gf_single_t));
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grub_memcpy (m, data, s * sizeof (gf_single_t));
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grub_memset (m + s, 0, rs * sizeof (gf_single_t));
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rs_polynomial = xmalloc ((rs + 1) * sizeof (gf_single_t));
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grub_memset (rs_polynomial, 0, (rs + 1) * sizeof (gf_single_t));
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rs_polynomial[rs] = 1;
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/* Multiply with X - a^r */
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for (j = 0; j < rs; j++)
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{
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for (i = 0; i < rs; i++)
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if (rs_polynomial[i])
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rs_polynomial[i] = (rs_polynomial[i + 1]
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^ gf_powx[j + (int) gf_powx_inv[rs_polynomial[i]]]);
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else
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rs_polynomial[i] = rs_polynomial[i + 1];
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if (rs_polynomial[rs])
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rs_polynomial[rs] = gf_powx[j + (int) gf_powx_inv[rs_polynomial[rs]]];
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}
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for (j = 0; j < s; j++)
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if (m[j])
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{
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gf_single_t f = m[j];
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for (i = 0; i <= rs; i++)
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m[i+j] ^= gf_mul (rs_polynomial[i], f);
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}
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free (rs_polynomial);
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grub_memcpy (data + s, m + s, rs * sizeof (gf_single_t));
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free (m);
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}
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#endif
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static void
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gauss_eliminate (gf_single_t *eq, int n, int m, int *chosen)
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{
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int i, j;
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for (i = 0 ; i < n; i++)
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{
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int nzidx;
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int k;
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gf_single_t r;
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for (nzidx = 0; nzidx < m && (eq[i * (m + 1) + nzidx] == 0);
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nzidx++);
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if (nzidx == m)
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continue;
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chosen[i] = nzidx;
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r = gf_invert (eq[i * (m + 1) + nzidx]);
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for (j = 0; j < m + 1; j++)
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eq[i * (m + 1) + j] = gf_mul (eq[i * (m + 1) + j], r);
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for (j = i + 1; j < n; j++)
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{
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gf_single_t rr = eq[j * (m + 1) + nzidx];
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for (k = 0; k < m + 1; k++)
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eq[j * (m + 1) + k] ^= gf_mul (eq[i * (m + 1) + k], rr);
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}
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}
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}
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static void
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gauss_solve (gf_single_t *eq, int n, int m, gf_single_t *sol)
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{
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int i, j;
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for (i = 0; i < n; i++)
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chosenstat[i] = -1;
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for (i = 0; i < m; i++)
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sol[i] = 0;
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gauss_eliminate (eq, n, m, chosenstat);
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for (i = n - 1; i >= 0; i--)
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{
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gf_single_t s = 0;
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if (chosenstat[i] == -1)
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continue;
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for (j = 0; j < m; j++)
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s ^= gf_mul (eq[i * (m + 1) + j], sol[j]);
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s ^= eq[i * (m + 1) + m];
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sol[chosenstat[i]] = s;
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}
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}
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static void
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rs_recover (gf_single_t *mm, grub_size_t s, grub_size_t rs)
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{
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grub_size_t rs2 = rs / 2;
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int errnum = 0;
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int i, j;
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for (i = 0; i < (int) rs; i++)
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sy[i] = pol_evaluate (mm, s + rs - 1, i);
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for (i = 0; i < (int) rs; i++)
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if (sy[i] != 0)
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break;
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/* No error detected. */
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if (i == (int) rs)
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return;
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{
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for (i = 0; i < (int) rs2; i++)
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for (j = 0; j < (int) rs2 + 1; j++)
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eqstat[i * (rs2 + 1) + j] = sy[i+j];
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for (i = 0; i < (int) rs2; i++)
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sigma[i] = 0;
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gauss_solve (eqstat, rs2, rs2, sigma);
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}
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for (i = 0; i < (int) (rs + s); i++)
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if (pol_evaluate (sigma, rs2 - 1, 255 - i) == gf_powx[i])
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{
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errpot[errnum] = gf_powx[i];
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errpos[errnum++] = s + rs - i - 1;
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}
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{
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for (j = 0; j < errnum; j++)
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eqstat[j] = 1;
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eqstat[errnum] = sy[0];
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for (i = 1; i < (int) rs; i++)
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{
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for (j = 0; j < (int) errnum; j++)
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eqstat[(errnum + 1) * i + j] = gf_mul (errpot[j],
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eqstat[(errnum + 1) * (i - 1)
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+ j]);
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eqstat[(errnum + 1) * i + errnum] = sy[i];
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}
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gauss_solve (eqstat, rs, errnum, errvals);
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for (i = 0; i < (int) errnum; i++)
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mm[errpos[i]] ^= errvals[i];
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}
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}
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static void
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decode_block (gf_single_t *ptr, grub_size_t s,
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gf_single_t *rptr, grub_size_t rs)
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{
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int i, j;
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for (i = 0; i < SECTOR_SIZE; i++)
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{
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grub_size_t ds = (s + SECTOR_SIZE - 1 - i) / SECTOR_SIZE;
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grub_size_t rr = (rs + SECTOR_SIZE - 1 - i) / SECTOR_SIZE;
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/* Nothing to do. */
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if (!ds || !rr)
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continue;
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for (j = 0; j < (int) ds; j++)
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mstat[j] = ptr[SECTOR_SIZE * j + i];
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for (j = 0; j < (int) rr; j++)
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mstat[j + ds] = rptr[SECTOR_SIZE * j + i];
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rs_recover (mstat, ds, rr);
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for (j = 0; j < (int) ds; j++)
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ptr[SECTOR_SIZE * j + i] = mstat[j];
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}
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}
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#if !defined (STANDALONE)
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static void
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encode_block (gf_single_t *ptr, grub_size_t s,
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gf_single_t *rptr, grub_size_t rs)
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{
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int i, j;
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for (i = 0; i < SECTOR_SIZE; i++)
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{
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grub_size_t ds = (s + SECTOR_SIZE - 1 - i) / SECTOR_SIZE;
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grub_size_t rr = (rs + SECTOR_SIZE - 1 - i) / SECTOR_SIZE;
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gf_single_t *m;
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if (!ds || !rr)
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continue;
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m = xmalloc (ds + rr);
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for (j = 0; j < ds; j++)
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m[j] = ptr[SECTOR_SIZE * j + i];
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rs_encode (m, ds, rr);
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for (j = 0; j < rr; j++)
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rptr[SECTOR_SIZE * j + i] = m[j + ds];
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free (m);
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}
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}
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#endif
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#if !defined (STANDALONE)
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void
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grub_reed_solomon_add_redundancy (void *buffer, grub_size_t data_size,
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grub_size_t redundancy)
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{
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grub_size_t s = data_size;
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grub_size_t rs = redundancy;
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gf_single_t *ptr = buffer;
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gf_single_t *rptr = ptr + s;
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void *tmp;
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tmp = xmalloc (data_size);
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grub_memcpy (tmp, buffer, data_size);
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/* Nothing to do. */
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if (!rs)
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return;
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init_powx ();
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while (s > 0)
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{
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grub_size_t tt;
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grub_size_t cs, crs;
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cs = s;
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crs = rs;
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tt = cs + crs;
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if (tt > MAX_BLOCK_SIZE)
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{
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cs = ((cs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
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crs = ((crs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
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}
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encode_block (ptr, cs, rptr, crs);
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ptr += cs;
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rptr += crs;
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s -= cs;
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rs -= crs;
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}
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#ifndef TEST
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assert (grub_memcmp (tmp, buffer, data_size) == 0);
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#endif
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free (tmp);
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}
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#endif
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void
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grub_reed_solomon_recover (void *ptr_, grub_size_t s, grub_size_t rs)
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{
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gf_single_t *ptr = ptr_;
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gf_single_t *rptr = ptr + s;
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/* Nothing to do. */
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if (!rs)
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return;
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init_powx ();
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while (s > 0)
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{
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grub_size_t tt;
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grub_size_t cs, crs;
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cs = s;
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crs = rs;
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tt = cs + crs;
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if (tt > MAX_BLOCK_SIZE)
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{
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cs = ((cs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
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crs = ((crs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
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}
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decode_block (ptr, cs, rptr, crs);
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ptr += cs;
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rptr += crs;
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s -= cs;
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rs -= crs;
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}
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}
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#ifdef TEST
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int
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main (int argc, char **argv)
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{
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FILE *in, *out;
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grub_size_t s, rs;
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char *buf;
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grub_memset (gf_powx, 0xee, sizeof (gf_powx));
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grub_memset (gf_powx_inv, 0xdd, sizeof (gf_powx_inv));
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#ifndef STANDALONE
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init_powx ();
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#endif
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#ifndef STANDALONE
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in = fopen ("tst.bin", "rb");
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if (!in)
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return 1;
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fseek (in, 0, SEEK_END);
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s = ftell (in);
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fseek (in, 0, SEEK_SET);
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rs = 0x7007;
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buf = xmalloc (s + rs + SECTOR_SIZE);
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fread (buf, 1, s, in);
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fclose (in);
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grub_reed_solomon_add_redundancy (buf, s, rs);
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out = fopen ("tst_rs.bin", "wb");
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fwrite (buf, 1, s + rs, out);
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fclose (out);
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#else
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out = fopen ("tst_rs.bin", "rb");
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fseek (out, 0, SEEK_END);
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s = ftell (out);
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fseek (out, 0, SEEK_SET);
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rs = 0x7007;
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s -= rs;
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buf = xmalloc (s + rs + SECTOR_SIZE);
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fread (buf, 1, s + rs, out);
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fclose (out);
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#endif
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#if 1
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grub_memset (buf + 512 * 15, 0, 512);
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#endif
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out = fopen ("tst_dam.bin", "wb");
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fwrite (buf, 1, s + rs, out);
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fclose (out);
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grub_reed_solomon_recover (buf, s, rs);
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out = fopen ("tst_rec.bin", "wb");
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fwrite (buf, 1, s, out);
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fclose (out);
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return 0;
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}
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#endif
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