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-rw-r--r--common/docecc.c100
1 files changed, 50 insertions, 50 deletions
diff --git a/common/docecc.c b/common/docecc.c
index 74ac7411a..cf45e0f6d 100644
--- a/common/docecc.c
+++ b/common/docecc.c
@@ -98,30 +98,30 @@ for(ci=(n)-1;ci >=0;ci--)\
/* generate GF(2**m) from the irreducible polynomial p(X) in Pp[0]..Pp[m]
lookup tables: index->polynomial form alpha_to[] contains j=alpha**i;
- polynomial form -> index form index_of[j=alpha**i] = i
+ polynomial form -> index form index_of[j=alpha**i] = i
alpha=2 is the primitive element of GF(2**m)
HARI's COMMENT: (4/13/94) alpha_to[] can be used as follows:
- Let @ represent the primitive element commonly called "alpha" that
+ Let @ represent the primitive element commonly called "alpha" that
is the root of the primitive polynomial p(x). Then in GF(2^m), for any
0 <= i <= 2^m-2,
- @^i = a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
+ @^i = a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
where the binary vector (a(0),a(1),a(2),...,a(m-1)) is the representation
of the integer "alpha_to[i]" with a(0) being the LSB and a(m-1) the MSB. Thus for
example the polynomial representation of @^5 would be given by the binary
representation of the integer "alpha_to[5]".
- Similarily, index_of[] can be used as follows:
- As above, let @ represent the primitive element of GF(2^m) that is
+ Similarily, index_of[] can be used as follows:
+ As above, let @ represent the primitive element of GF(2^m) that is
the root of the primitive polynomial p(x). In order to find the power
of @ (alpha) that has the polynomial representation
- a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
+ a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
we consider the integer "i" whose binary representation with a(0) being LSB
and a(m-1) MSB is (a(0),a(1),...,a(m-1)) and locate the entry
"index_of[i]". Now, @^index_of[i] is that element whose polynomial
representation is (a(0),a(1),a(2),...,a(m-1)).
NOTE:
- The element alpha_to[2^m-1] = 0 always signifying that the
+ The element alpha_to[2^m-1] = 0 always signifying that the
representation of "@^infinity" = 0 is (0,0,0,...,0).
- Similarily, the element index_of[0] = A0 always signifying
+ Similarily, the element index_of[0] = A0 always signifying
that the power of alpha which has the polynomial representation
(0,0,...,0) is "infinity".
@@ -183,8 +183,8 @@ generate_gf(dtype Alpha_to[NN + 1], dtype Index_of[NN + 1])
* */
static int
eras_dec_rs(dtype Alpha_to[NN + 1], dtype Index_of[NN + 1],
- gf bb[NN - KK + 1], gf eras_val[NN-KK], int eras_pos[NN-KK],
- int no_eras)
+ gf bb[NN - KK + 1], gf eras_val[NN-KK], int eras_pos[NN-KK],
+ int no_eras)
{
int deg_lambda, el, deg_omega;
int i, j, r,k;
@@ -225,7 +225,7 @@ eras_dec_rs(dtype Alpha_to[NN + 1], dtype Index_of[NN + 1],
for(i=1;i<=NN-KK;i++) {
tmp = Index_of[s[i]];
if (tmp != A0)
- tmp = modnn(tmp + 2 * KK * (B0+i-1)*PRIM);
+ tmp = modnn(tmp + 2 * KK * (B0+i-1)*PRIM);
s[i] = tmp;
}
@@ -412,9 +412,9 @@ eras_dec_rs(dtype Alpha_to[NN + 1], dtype Index_of[NN + 1],
}
/* Apply error to data */
if (num1 != 0) {
- eras_val[j] = Alpha_to[modnn(Index_of[num1] + Index_of[num2] + NN - Index_of[den])];
+ eras_val[j] = Alpha_to[modnn(Index_of[num1] + Index_of[num2] + NN - Index_of[den])];
} else {
- eras_val[j] = 0;
+ eras_val[j] = 0;
}
}
finish:
@@ -447,12 +447,12 @@ int doc_decode_ecc(unsigned char sector[SECTOR_SIZE], unsigned char ecc1[6])
/* init log and exp tables here to save memory. However, it is slower */
Alpha_to = malloc((NN + 1) * sizeof(dtype));
if (!Alpha_to)
- return -1;
+ return -1;
Index_of = malloc((NN + 1) * sizeof(dtype));
if (!Index_of) {
- free(Alpha_to);
- return -1;
+ free(Alpha_to);
+ return -1;
}
generate_gf(Alpha_to, Index_of);
@@ -465,48 +465,48 @@ int doc_decode_ecc(unsigned char sector[SECTOR_SIZE], unsigned char ecc1[6])
bb[3] = ((ecc1[3] & 0xc0) >> 6) | ((ecc1[0] & 0xff) << 2);
nb_errors = eras_dec_rs(Alpha_to, Index_of, bb,
- error_val, error_pos, 0);
+ error_val, error_pos, 0);
if (nb_errors <= 0)
- goto the_end;
+ goto the_end;
/* correct the errors */
for(i=0;i<nb_errors;i++) {
- pos = error_pos[i];
- if (pos >= NB_DATA && pos < KK) {
- nb_errors = -1;
- goto the_end;
- }
- if (pos < NB_DATA) {
- /* extract bit position (MSB first) */
- pos = 10 * (NB_DATA - 1 - pos) - 6;
- /* now correct the following 10 bits. At most two bytes
- can be modified since pos is even */
- index = (pos >> 3) ^ 1;
- bitpos = pos & 7;
- if ((index >= 0 && index < SECTOR_SIZE) ||
- index == (SECTOR_SIZE + 1)) {
- val = error_val[i] >> (2 + bitpos);
- parity ^= val;
- if (index < SECTOR_SIZE)
- sector[index] ^= val;
- }
- index = ((pos >> 3) + 1) ^ 1;
- bitpos = (bitpos + 10) & 7;
- if (bitpos == 0)
- bitpos = 8;
- if ((index >= 0 && index < SECTOR_SIZE) ||
- index == (SECTOR_SIZE + 1)) {
- val = error_val[i] << (8 - bitpos);
- parity ^= val;
- if (index < SECTOR_SIZE)
- sector[index] ^= val;
- }
- }
+ pos = error_pos[i];
+ if (pos >= NB_DATA && pos < KK) {
+ nb_errors = -1;
+ goto the_end;
+ }
+ if (pos < NB_DATA) {
+ /* extract bit position (MSB first) */
+ pos = 10 * (NB_DATA - 1 - pos) - 6;
+ /* now correct the following 10 bits. At most two bytes
+ can be modified since pos is even */
+ index = (pos >> 3) ^ 1;
+ bitpos = pos & 7;
+ if ((index >= 0 && index < SECTOR_SIZE) ||
+ index == (SECTOR_SIZE + 1)) {
+ val = error_val[i] >> (2 + bitpos);
+ parity ^= val;
+ if (index < SECTOR_SIZE)
+ sector[index] ^= val;
+ }
+ index = ((pos >> 3) + 1) ^ 1;
+ bitpos = (bitpos + 10) & 7;
+ if (bitpos == 0)
+ bitpos = 8;
+ if ((index >= 0 && index < SECTOR_SIZE) ||
+ index == (SECTOR_SIZE + 1)) {
+ val = error_val[i] << (8 - bitpos);
+ parity ^= val;
+ if (index < SECTOR_SIZE)
+ sector[index] ^= val;
+ }
+ }
}
/* use parity to test extra errors */
if ((parity & 0xff) != 0)
- nb_errors = -1;
+ nb_errors = -1;
the_end:
free(Alpha_to);
generated by cgit v1.2.3-70-g09d2 (git 2.51.2) at 2025-10-31 06:44:08 +0000