Use static allocation rather than scratch pointer in reed_solomon.
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.
This commit is contained in:
Vladimir 'phcoder' Serbinenko
parent
2e13ede59e
commit
bb26e4ff16
2 changed files with 87 additions and 173 deletions
23
ChangeLog
23
ChangeLog
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@ -1,3 +1,26 @@
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2012-01-24 Vladimir Serbinenko <phcoder@gmail.com>
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Use static allocation rather than scratch pointer in reed_solomon.
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It decreases its size significantly and avoids a variable in .text.
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* grub-core/lib/reed_solomon.c (scratch): Removed.
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(chosenstat): New const or static array.
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(sigma): Likewise.
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(errpot): Likewise.
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(errpos): Likewise.
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(sy): Likewise.
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(mstat): Likewise.
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(errvals): Likewise.
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(eqstat): Likewise.
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(pol_evaluate): Replace x with log_x argument. All users updated.
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(syndroms): Removed.
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(gauss_solve): Use statically allocated arrays.
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(rs_recover): Likewise.
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Calculate syndroms directly.
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(decode_block): Use statically allocated arrays.
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(grub_reed_solomon_add_redundancy) [TEST]: Fix -DTEST compilation.
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(main) [TEST]: Allow -DTEST -DSTANDALONE.
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2012-01-24 Vladimir Serbinenko <phcoder@gmail.com>
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Eliminate fixed limit on reed solomon decoder length.
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@ -41,6 +41,9 @@ typedef unsigned char grub_uint8_t;
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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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@ -60,19 +63,29 @@ typedef grub_uint8_t gf_single_t;
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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 char *scratch __attribute__ ((section(".text"))) = (void *) 0x100300;
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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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#if defined (STANDALONE)
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static char *scratch;
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#endif
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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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#define SECTOR_SIZE 512
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#define MAX_BLOCK_SIZE (200 * SECTOR_SIZE)
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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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@ -107,14 +120,11 @@ init_powx (void)
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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, gf_single_t x)
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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, log_x;
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if (x == 0)
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return pol[0];
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log_x = gf_powx_inv[x];
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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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@ -164,26 +174,6 @@ rs_encode (gf_single_t *data, grub_size_t s, grub_size_t rs)
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}
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#endif
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static void
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syndroms (gf_single_t *m, grub_size_t s, grub_size_t rs,
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gf_single_t *sy)
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{
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gf_single_t xn = 1;
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unsigned i;
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sy[0] = pol_evaluate (m, s + rs - 1, xn);
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for (i = 1; i < rs; i++)
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{
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if (xn & (1 << (GF_SIZE - 1)))
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{
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xn <<= 1;
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xn ^= GF_POLYNOMIAL;
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}
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else
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xn <<= 1;
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sy[i] = pol_evaluate (m, s + rs - 1, xn);
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}
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}
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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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@ -214,65 +204,34 @@ gauss_eliminate (gf_single_t *eq, int n, int m, int *chosen)
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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 *chosen;
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int i, j;
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#ifndef STANDALONE
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chosen = xmalloc (n * sizeof (int));
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#else
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chosen = (void *) scratch;
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scratch += n * sizeof (int);
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#endif
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for (i = 0; i < n; i++)
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chosen[i] = -1;
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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, chosen);
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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 (chosen[i] == -1)
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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[chosen[i]] = s;
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sol[chosenstat[i]] = s;
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}
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#ifndef STANDALONE
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free (chosen);
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#else
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scratch -= n * sizeof (int);
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#endif
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}
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static void
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rs_recover (gf_single_t *m, grub_size_t s, grub_size_t rs)
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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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gf_single_t *sigma;
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gf_single_t *errpot;
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int *errpos;
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gf_single_t *sy;
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int errnum = 0;
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int i, j;
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#ifndef STANDALONE
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sigma = xmalloc (rs2 * sizeof (gf_single_t));
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errpot = xmalloc (rs2 * sizeof (gf_single_t));
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errpos = xmalloc (rs2 * sizeof (int));
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sy = xmalloc (rs * sizeof (gf_single_t));
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#else
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sigma = (void *) scratch;
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scratch += rs2 * sizeof (gf_single_t);
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errpot = (void *) scratch;
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scratch += rs2 * sizeof (gf_single_t);
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errpos = (void *) scratch;
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scratch += rs2 * sizeof (int);
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sy = (void *) scratch;
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scratch += rs * sizeof (gf_single_t);
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#endif
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syndroms (m, s, rs, sy);
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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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@ -280,109 +239,44 @@ rs_recover (gf_single_t *m, grub_size_t s, grub_size_t rs)
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/* No error detected. */
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if (i == (int) rs)
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{
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#ifndef STANDALONE
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free (sigma);
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free (errpot);
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free (errpos);
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free (sy);
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#else
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scratch -= rs2 * sizeof (gf_single_t);
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scratch -= rs2 * sizeof (gf_single_t);
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scratch -= rs2 * sizeof (int);
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scratch -= rs * sizeof (gf_single_t);
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#endif
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return;
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}
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{
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gf_single_t *eq;
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#ifndef STANDALONE
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eq = xmalloc (rs2 * (rs2 + 1) * sizeof (gf_single_t));
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#else
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eq = (void *) scratch;
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scratch += rs2 * (rs2 + 1) * sizeof (gf_single_t);
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#endif
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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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eq[i * (rs2 + 1) + j] = sy[i+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 (eq, rs2, rs2, sigma);
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#ifndef STANDALONE
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free (eq);
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#else
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scratch -= rs2 * (rs2 + 1) * sizeof (gf_single_t);
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#endif
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gauss_solve (eqstat, rs2, rs2, sigma);
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}
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{
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gf_single_t xn = 1, yn = 1;
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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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gf_single_t ev = (gf_mul (pol_evaluate (sigma, rs2 - 1, xn), xn) ^ 1);
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if (ev == 0)
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{
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errpot[errnum] = yn;
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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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yn = gf_mul (yn, 2);
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xn = gf_mul (xn, GF_INVERT2);
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}
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}
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{
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gf_single_t *errvals;
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gf_single_t *eq;
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#ifndef STANDALONE
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eq = xmalloc (rs * (errnum + 1) * sizeof (gf_single_t));
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errvals = xmalloc (errnum * sizeof (int));
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#else
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eq = (void *) scratch;
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scratch += rs * (errnum + 1) * sizeof (gf_single_t);
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errvals = (void *) scratch;
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scratch += errnum * sizeof (int);
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#endif
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for (j = 0; j < errnum; j++)
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eq[j] = 1;
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eq[errnum] = sy[0];
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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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eq[(errnum + 1) * i + j] = gf_mul (errpot[j],
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eq[(errnum + 1) * (i - 1) + j]);
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eq[(errnum + 1) * i + errnum] = sy[i];
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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 (eq, rs, errnum, errvals);
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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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m[errpos[i]] ^= errvals[i];
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#ifndef STANDALONE
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free (eq);
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free (errvals);
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#else
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scratch -= rs * (errnum + 1) * sizeof (gf_single_t);
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scratch -= errnum * sizeof (int);
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#endif
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mm[errpos[i]] ^= errvals[i];
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}
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#ifndef STANDALONE
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free (sigma);
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free (errpot);
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free (errpos);
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free (sy);
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#else
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scratch -= rs2 * sizeof (gf_single_t);
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scratch -= rs2 * sizeof (gf_single_t);
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scratch -= rs2 * sizeof (int);
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scratch -= rs * sizeof (gf_single_t);
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#endif
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}
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static void
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@ -394,34 +288,20 @@ decode_block (gf_single_t *ptr, grub_size_t s,
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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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/* Nothing to do. */
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if (!ds || !rr)
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continue;
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#ifndef STANDALONE
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m = xmalloc (ds + rr);
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#else
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m = (gf_single_t *) scratch;
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scratch += ds + rr;
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#endif
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for (j = 0; j < (int) ds; j++)
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m[j] = ptr[SECTOR_SIZE * j + i];
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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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m[j + ds] = rptr[SECTOR_SIZE * j + i];
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mstat[j + ds] = rptr[SECTOR_SIZE * j + i];
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rs_recover (m, ds, rr);
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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] = m[j];
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#ifndef STANDALONE
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free (m);
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#else
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scratch -= ds + rr;
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#endif
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ptr[SECTOR_SIZE * j + i] = mstat[j];
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}
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}
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@ -490,7 +370,9 @@ grub_reed_solomon_add_redundancy (void *buffer, grub_size_t data_size,
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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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@ -538,14 +420,11 @@ main (int argc, char **argv)
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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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#ifdef STANDALONE
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scratch = xmalloc (1048576);
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#endif
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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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@ -562,6 +441,18 @@ main (int argc, char **argv)
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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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