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authorJordan K. Hubbard <jkh@FreeBSD.org>1994-06-22 04:49:04 +0000
committerJordan K. Hubbard <jkh@FreeBSD.org>1994-06-22 04:49:04 +0000
commit7fd50c04dea0225e6cb0d9966353dfae47f4ad56 (patch)
treee1a1aefbbf783ac527d97a51beaff60ac9653ac8 /sbin/ft/ftecc.c
parent8ffbd12df25addd769ebbe562b3b950f30c1d3c5 (diff)
downloadsrc-7fd50c04dea0225e6cb0d9966353dfae47f4ad56.tar.gz
src-7fd50c04dea0225e6cb0d9966353dfae47f4ad56.zip
Update this to the latest version from Steve Gerakines. This is an easy
drop-in for me and looks substantailly neater than the previous version, so I'll give the floppy tape users a break (but just this once :).
Notes
Notes: svn path=/head/; revision=1765
Diffstat (limited to 'sbin/ft/ftecc.c')
-rw-r--r--sbin/ft/ftecc.c128
1 files changed, 93 insertions, 35 deletions
diff --git a/sbin/ft/ftecc.c b/sbin/ft/ftecc.c
index e49964459c3f..fbba10f07fa5 100644
--- a/sbin/ft/ftecc.c
+++ b/sbin/ft/ftecc.c
@@ -17,6 +17,11 @@
* POSSIBILITY OF SUCH DAMAGE.
*
* ftecc.c - QIC-40/80 Reed-Solomon error correction
+ * 05/30/94 v1.0 ++sg
+ * Did some minor optimization. The multiply by 0xc0 was a dog so it
+ * was replaced with a table lookup. Fixed a couple of places where
+ * bad sectors could go unnoticed. Moved to release.
+ *
* 03/22/94 v0.4
* Major re-write. It can handle everything required by QIC now.
*
@@ -112,6 +117,45 @@ static UCHAR alpha_log[] = {
/*
+ * Multiplication table for 0xc0.
+ */
+static UCHAR mult_c0[] = {
+ 0x00, 0xc0, 0x07, 0xc7, 0x0e, 0xce, 0x09, 0xc9,
+ 0x1c, 0xdc, 0x1b, 0xdb, 0x12, 0xd2, 0x15, 0xd5,
+ 0x38, 0xf8, 0x3f, 0xff, 0x36, 0xf6, 0x31, 0xf1,
+ 0x24, 0xe4, 0x23, 0xe3, 0x2a, 0xea, 0x2d, 0xed,
+ 0x70, 0xb0, 0x77, 0xb7, 0x7e, 0xbe, 0x79, 0xb9,
+ 0x6c, 0xac, 0x6b, 0xab, 0x62, 0xa2, 0x65, 0xa5,
+ 0x48, 0x88, 0x4f, 0x8f, 0x46, 0x86, 0x41, 0x81,
+ 0x54, 0x94, 0x53, 0x93, 0x5a, 0x9a, 0x5d, 0x9d,
+ 0xe0, 0x20, 0xe7, 0x27, 0xee, 0x2e, 0xe9, 0x29,
+ 0xfc, 0x3c, 0xfb, 0x3b, 0xf2, 0x32, 0xf5, 0x35,
+ 0xd8, 0x18, 0xdf, 0x1f, 0xd6, 0x16, 0xd1, 0x11,
+ 0xc4, 0x04, 0xc3, 0x03, 0xca, 0x0a, 0xcd, 0x0d,
+ 0x90, 0x50, 0x97, 0x57, 0x9e, 0x5e, 0x99, 0x59,
+ 0x8c, 0x4c, 0x8b, 0x4b, 0x82, 0x42, 0x85, 0x45,
+ 0xa8, 0x68, 0xaf, 0x6f, 0xa6, 0x66, 0xa1, 0x61,
+ 0xb4, 0x74, 0xb3, 0x73, 0xba, 0x7a, 0xbd, 0x7d,
+ 0x47, 0x87, 0x40, 0x80, 0x49, 0x89, 0x4e, 0x8e,
+ 0x5b, 0x9b, 0x5c, 0x9c, 0x55, 0x95, 0x52, 0x92,
+ 0x7f, 0xbf, 0x78, 0xb8, 0x71, 0xb1, 0x76, 0xb6,
+ 0x63, 0xa3, 0x64, 0xa4, 0x6d, 0xad, 0x6a, 0xaa,
+ 0x37, 0xf7, 0x30, 0xf0, 0x39, 0xf9, 0x3e, 0xfe,
+ 0x2b, 0xeb, 0x2c, 0xec, 0x25, 0xe5, 0x22, 0xe2,
+ 0x0f, 0xcf, 0x08, 0xc8, 0x01, 0xc1, 0x06, 0xc6,
+ 0x13, 0xd3, 0x14, 0xd4, 0x1d, 0xdd, 0x1a, 0xda,
+ 0xa7, 0x67, 0xa0, 0x60, 0xa9, 0x69, 0xae, 0x6e,
+ 0xbb, 0x7b, 0xbc, 0x7c, 0xb5, 0x75, 0xb2, 0x72,
+ 0x9f, 0x5f, 0x98, 0x58, 0x91, 0x51, 0x96, 0x56,
+ 0x83, 0x43, 0x84, 0x44, 0x8d, 0x4d, 0x8a, 0x4a,
+ 0xd7, 0x17, 0xd0, 0x10, 0xd9, 0x19, 0xde, 0x1e,
+ 0xcb, 0x0b, 0xcc, 0x0c, 0xc5, 0x05, 0xc2, 0x02,
+ 0xef, 0x2f, 0xe8, 0x28, 0xe1, 0x21, 0xe6, 0x26,
+ 0xf3, 0x33, 0xf4, 0x34, 0xfd, 0x3d, 0xfa, 0x3a
+};
+
+
+/*
* Return number of sectors available in a segment.
*/
int
@@ -142,29 +186,37 @@ sect_bytes(ULONG badmap)
/*
* Multiply two numbers in the field.
*/
-static UCHAR
+static inline UCHAR
multiply(UCHAR a, UCHAR b)
{
+ int tmp;
+
if (!a || !b) return(0);
- return(alpha_power[(alpha_log[a] + alpha_log[b]) % 255]);
+ tmp = alpha_log[a] + alpha_log[b];
+ if (tmp > 254) tmp -= 255;
+ return(alpha_power[tmp]);
}
/*
* Multiply by an exponent.
*/
-static UCHAR
+static inline UCHAR
multiply_out(UCHAR a, int b)
{
+ int tmp;
+
if (!a) return(0);
- return(alpha_power[(alpha_log[a] + b) % 255]);
+ tmp = alpha_log[a] + b;
+ if (tmp > 254) tmp -= 255;
+ return(alpha_power[tmp]);
}
/*
* Divide two numbers.
*/
-static UCHAR
+static inline UCHAR
divide(UCHAR a, UCHAR b)
{
int tmp;
@@ -179,7 +231,7 @@ divide(UCHAR a, UCHAR b)
/*
* Divide using exponent.
*/
-static UCHAR
+static inline UCHAR
divide_out(UCHAR a, UCHAR b)
{
int tmp;
@@ -194,13 +246,13 @@ divide_out(UCHAR a, UCHAR b)
/*
* This returns the value z^{a-b}.
*/
-static UCHAR
+static inline UCHAR
z_of_ab(UCHAR a, UCHAR b)
{
int tmp = a - b;
if (tmp < 0) tmp += 255;
- return(alpha_power[tmp % 255]);
+ return(alpha_power[tmp]);
}
@@ -208,12 +260,13 @@ z_of_ab(UCHAR a, UCHAR b)
* Calculate the inverse matrix for two or three errors. Returns 0
* if there is no inverse or 1 if successful.
*/
-static int
+static inline int
calculate_inverse(int nerrs, int *pblk, struct inv_mat *inv)
{
/* First some variables to remember some of the results. */
UCHAR z20, z10, z21, z12, z01, z02;
UCHAR i0, i1, i2;
+ UCHAR iv0, iv1, iv2;
if (nerrs < 2) return(1);
if (nerrs > 3) return(0);
@@ -243,21 +296,21 @@ calculate_inverse(int nerrs, int *pblk, struct inv_mat *inv)
if (!inv->log_denom) return(0);
inv->log_denom = 255 - alpha_log[inv->log_denom];
- inv->zs[0][0] = multiply_out(alpha_power[i1] ^ alpha_power[i2],
- inv->log_denom);
+ iv0 = alpha_power[255 - i0];
+ iv1 = alpha_power[255 - i1];
+ iv2 = alpha_power[255 - i2];
+ i0 = alpha_power[i0];
+ i1 = alpha_power[i1];
+ i2 = alpha_power[i2];
+ inv->zs[0][0] = multiply_out(i1 ^ i2, inv->log_denom);
inv->zs[0][1] = multiply_out(z21 ^ z12, inv->log_denom);
- inv->zs[0][2] = multiply_out(alpha_power[255-i1] ^ alpha_power[255-i2],
- inv->log_denom);
- inv->zs[1][0] = multiply_out(alpha_power[i0] ^ alpha_power[i2],
- inv->log_denom);
+ inv->zs[0][2] = multiply_out(iv1 ^ iv2, inv->log_denom);
+ inv->zs[1][0] = multiply_out(i0 ^ i2, inv->log_denom);
inv->zs[1][1] = multiply_out(z20 ^ z02, inv->log_denom);
- inv->zs[1][2] = multiply_out(alpha_power[255-i0] ^ alpha_power[255-i2],
- inv->log_denom);
- inv->zs[2][0] = multiply_out(alpha_power[i0] ^ alpha_power[i1],
- inv->log_denom);
+ inv->zs[1][2] = multiply_out(iv0 ^ iv2, inv->log_denom);
+ inv->zs[2][0] = multiply_out(i0 ^ i1, inv->log_denom);
inv->zs[2][1] = multiply_out(z10 ^ z01, inv->log_denom);
- inv->zs[2][2] = multiply_out(alpha_power[255-i0] ^ alpha_power[255-i1],
- inv->log_denom);
+ inv->zs[2][2] = multiply_out(iv0 ^ iv1, inv->log_denom);
}
return(1);
}
@@ -266,7 +319,7 @@ calculate_inverse(int nerrs, int *pblk, struct inv_mat *inv)
/*
* Determine the error magnitudes for a given matrix and syndromes.
*/
-static void
+static inline void
determine(int nerrs, struct inv_mat *inv, UCHAR *ss, UCHAR *es)
{
UCHAR tmp;
@@ -283,21 +336,22 @@ determine(int nerrs, struct inv_mat *inv, UCHAR *ss, UCHAR *es)
/*
* Compute the 3 syndrome values.
*/
-static int
+static inline int
compute_syndromes(UCHAR *data, int nblks, int col, UCHAR *ss)
{
UCHAR r0, r1, r2, t1, t2;
UCHAR *rptr;
- int row;
- rptr = &data[col];
+ rptr = data + col;
+ data += nblks << 10;
r0 = r1 = r2 = 0;
- for (row = 0; row < nblks; row++, rptr += QCV_BLKSIZE) {
+ while (rptr < data) {
t1 = *rptr ^ r0;
- t2 = multiply(0xc0, t1);
+ t2 = mult_c0[t1];
r0 = t2 ^ r1;
r1 = t2 ^ r2;
r2 = t1;
+ rptr += QCV_BLKSIZE;
}
if (r0 || r1 || r2) {
ss[0] = divide_out(r0 ^ divide_out(r1 ^ divide_out(r2, 1), 1), nblks);
@@ -315,24 +369,28 @@ compute_syndromes(UCHAR *data, int nblks, int col, UCHAR *ss)
int
set_parity (UCHAR *data, ULONG badmap)
{
- int col, row, max;
UCHAR r0, r1, r2, t1, t2;
UCHAR *rptr;
+ int max, row, col;
max = sect_count(badmap) - 3;
- for (col = 0; col < QCV_BLKSIZE; col++, data++) {
+ col = QCV_BLKSIZE;
+ while (col--) {
rptr = data;
r0 = r1 = r2 = 0;
- for (row = 0; row < max; row++, rptr += QCV_BLKSIZE) {
+ row = max;
+ while (row--) {
t1 = *rptr ^ r0;
- t2 = multiply(0xc0, t1);
+ t2 = mult_c0[t1];
r0 = t2 ^ r1;
r1 = t2 ^ r2;
r2 = t1;
+ rptr += QCV_BLKSIZE;
}
*rptr = r0; rptr += QCV_BLKSIZE;
*rptr = r1; rptr += QCV_BLKSIZE;
*rptr = r2;
+ data++;
}
return(0);
}
@@ -359,8 +417,8 @@ check_parity(UCHAR *data, ULONG badmap, ULONG crcmap)
if (crcmap) {
for (i = 0; i < nblks; i++) {
if (crcmap & (1 << i)) {
+ if (crcerrs == 3) return(1);
eblk[crcerrs++] = i;
- if (crcerrs >= 3) break;
}
}
}
@@ -380,7 +438,7 @@ check_parity(UCHAR *data, ULONG badmap, ULONG crcmap)
eblk[crcerrs] = alpha_log[divide(ss[1], ss[0])];
if (eblk[crcerrs] >= nblks) return(1);
es[0] = ss[1];
- crcerrs++;
+ if (++crcerrs > 3) return(1);
break;
case 1: /* 1 error (+ possible failures) */
@@ -394,7 +452,7 @@ check_parity(UCHAR *data, ULONG badmap, ULONG crcmap)
} else { /* add failure */
eblk[crcerrs] = alpha_log[divide(i1, i2)];
if (eblk[crcerrs] >= nblks) return(1);
- crcerrs++;
+ if (++crcerrs > 3) return(1);
if (!calculate_inverse(crcerrs, eblk, &inv)) return(1);
}
determine(crcerrs, &inv, ss, es);
@@ -411,7 +469,7 @@ check_parity(UCHAR *data, ULONG badmap, ULONG crcmap)
/* Make corrections. */
for (i = 0; i < crcerrs; i++) {
- data[eblk[i] * QCV_BLKSIZE+col] ^= es[i];
+ data[(eblk[i] << 10) | col] ^= es[i];
ss[0] ^= divide_out(es[i], eblk[i]);
ss[1] ^= es[i];
ss[2] ^= multiply_out(es[i], eblk[i]);