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authorAndrew Moore <alm@FreeBSD.org>1994-02-07 04:36:09 +0000
committerAndrew Moore <alm@FreeBSD.org>1994-02-07 04:36:09 +0000
commit6dac698341e5e6e13058ce4af7e6e2de052d501f (patch)
treeed5064ba2c1fd27250dbbafb9b717df3aac9a3ed /sbin/ft/ftecc.c
parent97acce82ca89bbcf42bdbb73f61fb328ec3224ca (diff)
downloadsrc-6dac698341e5e6e13058ce4af7e6e2de052d501f.tar.gz
src-6dac698341e5e6e13058ce4af7e6e2de052d501f.zip
import floppy tape controller
Notes
Notes: svn path=/cvs2svn/branches/unlabeled-1.1.1/; revision=1112
Diffstat (limited to 'sbin/ft/ftecc.c')
-rw-r--r--sbin/ft/ftecc.c316
1 files changed, 316 insertions, 0 deletions
diff --git a/sbin/ft/ftecc.c b/sbin/ft/ftecc.c
new file mode 100644
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--- /dev/null
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+/*
+ * ftecc.c 10/30/93 v0.3
+ * Handle error correction for floppy tape drives.
+ *
+ * File contents are copyrighted by David L. Brown and falls under the
+ * terms of the GPL version 2 or greater. See his original release for
+ * the specific terms.
+ *
+ * Steve Gerakines
+ * steve2@genesis.nred.ma.us
+ * Modified slightly to fit with my tape driver. I'm not at all happy
+ * with this module and will have it replaced with a more functional one
+ * in the next release(/RSN). I am close, but progress will continue to
+ * be slow until I can find a book on the subject where the translator
+ * understands both the to and from languages. :-( For now it will
+ * suffice.
+ */
+#include <sys/ftape.h>
+
+/*
+ * In order to speed up the correction and adjustment, we can compute
+ * a matrix of coefficients for the multiplication.
+ */
+struct inv_mat {
+ UCHAR log_denom; /* The log z of the denominator. */
+ UCHAR zs[3][3]; /* The coefficients for the adjustment matrix. */
+};
+
+/* This array is a table of powers of x, from 0 to 254. */
+static UCHAR alpha_power[] = {
+ 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
+ 0x87, 0x89, 0x95, 0xad, 0xdd, 0x3d, 0x7a, 0xf4,
+ 0x6f, 0xde, 0x3b, 0x76, 0xec, 0x5f, 0xbe, 0xfb,
+ 0x71, 0xe2, 0x43, 0x86, 0x8b, 0x91, 0xa5, 0xcd,
+ 0x1d, 0x3a, 0x74, 0xe8, 0x57, 0xae, 0xdb, 0x31,
+ 0x62, 0xc4, 0x0f, 0x1e, 0x3c, 0x78, 0xf0, 0x67,
+ 0xce, 0x1b, 0x36, 0x6c, 0xd8, 0x37, 0x6e, 0xdc,
+ 0x3f, 0x7e, 0xfc, 0x7f, 0xfe, 0x7b, 0xf6, 0x6b,
+ 0xd6, 0x2b, 0x56, 0xac, 0xdf, 0x39, 0x72, 0xe4,
+ 0x4f, 0x9e, 0xbb, 0xf1, 0x65, 0xca, 0x13, 0x26,
+ 0x4c, 0x98, 0xb7, 0xe9, 0x55, 0xaa, 0xd3, 0x21,
+ 0x42, 0x84, 0x8f, 0x99, 0xb5, 0xed, 0x5d, 0xba,
+ 0xf3, 0x61, 0xc2, 0x03, 0x06, 0x0c, 0x18, 0x30,
+ 0x60, 0xc0, 0x07, 0x0e, 0x1c, 0x38, 0x70, 0xe0,
+ 0x47, 0x8e, 0x9b, 0xb1, 0xe5, 0x4d, 0x9a, 0xb3,
+ 0xe1, 0x45, 0x8a, 0x93, 0xa1, 0xc5, 0x0d, 0x1a,
+ 0x34, 0x68, 0xd0, 0x27, 0x4e, 0x9c, 0xbf, 0xf9,
+ 0x75, 0xea, 0x53, 0xa6, 0xcb, 0x11, 0x22, 0x44,
+ 0x88, 0x97, 0xa9, 0xd5, 0x2d, 0x5a, 0xb4, 0xef,
+ 0x59, 0xb2, 0xe3, 0x41, 0x82, 0x83, 0x81, 0x85,
+ 0x8d, 0x9d, 0xbd, 0xfd, 0x7d, 0xfa, 0x73, 0xe6,
+ 0x4b, 0x96, 0xab, 0xd1, 0x25, 0x4a, 0x94, 0xaf,
+ 0xd9, 0x35, 0x6a, 0xd4, 0x2f, 0x5e, 0xbc, 0xff,
+ 0x79, 0xf2, 0x63, 0xc6, 0x0b, 0x16, 0x2c, 0x58,
+ 0xb0, 0xe7, 0x49, 0x92, 0xa3, 0xc1, 0x05, 0x0a,
+ 0x14, 0x28, 0x50, 0xa0, 0xc7, 0x09, 0x12, 0x24,
+ 0x48, 0x90, 0xa7, 0xc9, 0x15, 0x2a, 0x54, 0xa8,
+ 0xd7, 0x29, 0x52, 0xa4, 0xcf, 0x19, 0x32, 0x64,
+ 0xc8, 0x17, 0x2e, 0x5c, 0xb8, 0xf7, 0x69, 0xd2,
+ 0x23, 0x46, 0x8c, 0x9f, 0xb9, 0xf5, 0x6d, 0xda,
+ 0x33, 0x66, 0xcc, 0x1f, 0x3e, 0x7c, 0xf8, 0x77,
+ 0xee, 0x5b, 0xb6, 0xeb, 0x51, 0xa2, 0xc3
+};
+
+/*
+ * This is the reverse lookup table. There is no log of 0, so the
+ * first element is not valid.
+ */
+static UCHAR alpha_log[] = {
+ 0xff, 0x00, 0x01, 0x63, 0x02, 0xc6, 0x64, 0x6a,
+ 0x03, 0xcd, 0xc7, 0xbc, 0x65, 0x7e, 0x6b, 0x2a,
+ 0x04, 0x8d, 0xce, 0x4e, 0xc8, 0xd4, 0xbd, 0xe1,
+ 0x66, 0xdd, 0x7f, 0x31, 0x6c, 0x20, 0x2b, 0xf3,
+ 0x05, 0x57, 0x8e, 0xe8, 0xcf, 0xac, 0x4f, 0x83,
+ 0xc9, 0xd9, 0xd5, 0x41, 0xbe, 0x94, 0xe2, 0xb4,
+ 0x67, 0x27, 0xde, 0xf0, 0x80, 0xb1, 0x32, 0x35,
+ 0x6d, 0x45, 0x21, 0x12, 0x2c, 0x0d, 0xf4, 0x38,
+ 0x06, 0x9b, 0x58, 0x1a, 0x8f, 0x79, 0xe9, 0x70,
+ 0xd0, 0xc2, 0xad, 0xa8, 0x50, 0x75, 0x84, 0x48,
+ 0xca, 0xfc, 0xda, 0x8a, 0xd6, 0x54, 0x42, 0x24,
+ 0xbf, 0x98, 0x95, 0xf9, 0xe3, 0x5e, 0xb5, 0x15,
+ 0x68, 0x61, 0x28, 0xba, 0xdf, 0x4c, 0xf1, 0x2f,
+ 0x81, 0xe6, 0xb2, 0x3f, 0x33, 0xee, 0x36, 0x10,
+ 0x6e, 0x18, 0x46, 0xa6, 0x22, 0x88, 0x13, 0xf7,
+ 0x2d, 0xb8, 0x0e, 0x3d, 0xf5, 0xa4, 0x39, 0x3b,
+ 0x07, 0x9e, 0x9c, 0x9d, 0x59, 0x9f, 0x1b, 0x08,
+ 0x90, 0x09, 0x7a, 0x1c, 0xea, 0xa0, 0x71, 0x5a,
+ 0xd1, 0x1d, 0xc3, 0x7b, 0xae, 0x0a, 0xa9, 0x91,
+ 0x51, 0x5b, 0x76, 0x72, 0x85, 0xa1, 0x49, 0xeb,
+ 0xcb, 0x7c, 0xfd, 0xc4, 0xdb, 0x1e, 0x8b, 0xd2,
+ 0xd7, 0x92, 0x55, 0xaa, 0x43, 0x0b, 0x25, 0xaf,
+ 0xc0, 0x73, 0x99, 0x77, 0x96, 0x5c, 0xfa, 0x52,
+ 0xe4, 0xec, 0x5f, 0x4a, 0xb6, 0xa2, 0x16, 0x86,
+ 0x69, 0xc5, 0x62, 0xfe, 0x29, 0x7d, 0xbb, 0xcc,
+ 0xe0, 0xd3, 0x4d, 0x8c, 0xf2, 0x1f, 0x30, 0xdc,
+ 0x82, 0xab, 0xe7, 0x56, 0xb3, 0x93, 0x40, 0xd8,
+ 0x34, 0xb0, 0xef, 0x26, 0x37, 0x0c, 0x11, 0x44,
+ 0x6f, 0x78, 0x19, 0x9a, 0x47, 0x74, 0xa7, 0xc1,
+ 0x23, 0x53, 0x89, 0xfb, 0x14, 0x5d, 0xf8, 0x97,
+ 0x2e, 0x4b, 0xb9, 0x60, 0x0f, 0xed, 0x3e, 0xe5,
+ 0xf6, 0x87, 0xa5, 0x17, 0x3a, 0xa3, 0x3c, 0xb7
+};
+
+/* Return number of sectors available in a segment. */
+int sect_count(ULONG badmap)
+{
+ int i, amt;
+
+ for (amt = QCV_BLKSEG, i = 0; i < QCV_BLKSEG; i++)
+ if (badmap & (1 << i)) amt--;
+ return(amt);
+}
+
+/* Return number of bytes available in a segment. */
+int sect_bytes(ULONG badmap)
+{
+ int i, amt;
+
+ for (amt = QCV_SEGSIZE, i = 0; i < QCV_BLKSEG; i++)
+ if (badmap & (1 << i)) amt -= QCV_BLKSIZE;
+ return(amt);
+}
+
+/* Multiply two numbers in the field. */
+static UCHAR multiply(UCHAR a, UCHAR b)
+{
+ int tmp;
+
+ if (a == 0 || b == 0) return(0);
+ tmp = (alpha_log[a] + alpha_log[b]);
+ if (tmp > 254) tmp -= 255;
+ return (alpha_power[tmp]);
+}
+
+static UCHAR divide(UCHAR a, UCHAR b)
+{
+ int tmp;
+
+ if (a == 0 || b == 0) return(0);
+ tmp = (alpha_log[a] - alpha_log[b]);
+ if (tmp < 0) tmp += 255;
+ return (alpha_power[tmp]);
+}
+
+/*
+ * This is just like divide, except we have already looked up the log
+ * of the second number.
+ */
+static UCHAR divide_out(UCHAR a, UCHAR b)
+{
+ int tmp;
+
+ if (a == 0) return 0;
+ tmp = alpha_log[a] - b;
+ if (tmp < 0) tmp += 255;
+ return (alpha_power[tmp]);
+}
+
+/* This returns the value z^{a-b}. */
+static UCHAR z_of_ab(UCHAR a, UCHAR b)
+{
+ int tmp = (int)a - (int)b;
+
+ if (tmp < 0)
+ tmp += 255;
+ else if (tmp >= 255)
+ tmp -= 255;
+ return(alpha_power[tmp]);
+}
+
+/* Calculate the inverse matrix. Returns 1 if the matrix is valid, or
+ * zero if there is no inverse. The i's are the indices of the bytes
+ * to be corrected.
+ */
+static int calculate_inverse (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;
+
+ i0 = pblk[0]; i1 = pblk[1]; i2 = pblk[2];
+
+ z20 = z_of_ab (i2, i0); z10 = z_of_ab (i1, i0);
+ z21 = z_of_ab (i2, i1); z12 = z_of_ab (i1, i2);
+ z01 = z_of_ab (i0, i1); z02 = z_of_ab (i0, i2);
+ inv->log_denom = (z20 ^ z10 ^ z21 ^ z12 ^ z01 ^ z02);
+ if (inv->log_denom == 0) return 0;
+ inv->log_denom = alpha_log[inv->log_denom];
+
+ /* Calculate all of the coefficients on the top. */
+ inv->zs[0][0] = alpha_power[i1] ^ alpha_power[i2];
+ inv->zs[0][1] = z21 ^ z12;
+ inv->zs[0][2] = alpha_power[255-i1] ^ alpha_power[255-i2];
+
+ inv->zs[1][0] = alpha_power[i0] ^ alpha_power[i2];
+ inv->zs[1][1] = z20 ^ z02;
+ inv->zs[1][2] = alpha_power[255-i0] ^ alpha_power[255-i2];
+
+ inv->zs[2][0] = alpha_power[i0] ^ alpha_power[i1];
+ inv->zs[2][1] = z10 ^ z01;
+ inv->zs[2][2] = alpha_power[255-i0] ^ alpha_power[255-i1];
+ return(1);
+}
+
+/*
+ * Determine the error values for a given inverse matrix and syndromes.
+ */
+static void determine3(struct inv_mat *inv, UCHAR *es, UCHAR *ss)
+{
+ UCHAR tmp;
+ int i, j;
+
+ for (i = 0; i < 3; i++) {
+ tmp = 0;
+ for (j = 0; j < 3; j++) tmp ^= multiply (ss[j], inv->zs[i][j]);
+ es[i] = divide_out(tmp, inv->log_denom);
+ }
+}
+
+
+/*
+ * Compute the 3 syndrome values. The data pointer should point to
+ * the offset within the first block of the column to calculate. The
+ * count of blocks is in blocks. The three bytes will be placed in
+ * ss[0], ss[1], and ss[2].
+ */
+static void compute_syndromes(UCHAR *data, int nblks, int col, UCHAR *ss)
+{
+ int i;
+ UCHAR v;
+
+ ss[0] = 0; ss[1] = 0; ss[2] = 0;
+ for (i = (nblks-1)*QCV_BLKSIZE; i >= 0; i -= QCV_BLKSIZE) {
+ v = data[i+col];
+ if (ss[0] & 0x01) { ss[0] >>= 1; ss[0] ^= 0xc3; } else ss[0] >>= 1;
+ ss[0] ^= v;
+ ss[1] ^= v;
+ if (ss[2] & 0x80) { ss[2] <<= 1; ss[2] ^= 0x87; } else ss[2] <<= 1;
+ ss[2] ^= v;
+ }
+}
+
+/*
+ * Calculate the parity bytes for a segment. Returns 0 on success.
+ */
+int set_parity (UCHAR *data, ULONG badmap)
+{
+ int col;
+ struct inv_mat inv;
+ UCHAR ss[3], es[3];
+ int nblks, pblk[3];
+
+ nblks = sect_count(badmap);
+ pblk[0] = nblks-3; pblk[1] = nblks-2; pblk[2] = nblks-1;
+ if (!calculate_inverse(pblk, &inv)) return(1);
+
+ pblk[0] *= QCV_BLKSIZE; pblk[1] *= QCV_BLKSIZE; pblk[2] *= QCV_BLKSIZE;
+ for (col = 0; col < QCV_BLKSIZE; col++) {
+ compute_syndromes (data, nblks-3, col, ss);
+ determine3(&inv, es, ss);
+ data[pblk[0]+col] = es[0];
+ data[pblk[1]+col] = es[1];
+ data[pblk[2]+col] = es[2];
+ }
+ return(0);
+}
+
+
+/*
+ * Check and correct errors in a block. Returns 0 on success,
+ * 1 if failed.
+ */
+int check_parity(UCHAR *data, ULONG badmap, ULONG crcmap)
+{
+ int i, j, col, crcerrs, r, tries, nblks;
+ struct inv_mat inv;
+ UCHAR ss[3], es[3];
+ int i1, i2, eblk[3];
+
+ nblks = sect_count(badmap);
+ crcerrs = 0;
+ for (i = 0; crcerrs < 3 && i < nblks; i++)
+ if (crcmap & (1 << i)) eblk[crcerrs++] = i;
+
+ for (i = 1, j = crcerrs; j < 3 && i < nblks; i++)
+ if ((crcmap & (1 << i)) == 0) eblk[j++] = i;
+
+ if (!calculate_inverse (eblk, &inv)) return(1);
+
+ eblk[0] *= QCV_BLKSIZE; eblk[1] *= QCV_BLKSIZE; eblk[2] *= QCV_BLKSIZE;
+ r = 0;
+ for (col = 0; col < QCV_BLKSIZE; col++) {
+ compute_syndromes (data, nblks, col, ss);
+
+ if (!ss[0] && !ss[1] && !ss[2]) continue;
+ if (crcerrs) {
+ determine3 (&inv, es, ss);
+ for (j = 0; j < crcerrs; j++)
+ data[eblk[j] + col] ^= es[j];
+ compute_syndromes (data, nblks, col, ss);
+ if (!ss[0] && !ss[1] && !ss[2]) {
+ r = 1;
+ continue;
+ }
+ }
+ determine3 (&inv, es, ss);
+ i1 = alpha_log[divide(ss[2], ss[1])];
+ i2 = alpha_log[divide(ss[1], ss[0])];
+ if (i1 != i2 || ((QCV_BLKSIZE * i1) + col) > QCV_SEGSIZE)
+ r = 1;
+ else
+ data[QCV_BLKSIZE * i1 + col] ^= ss[1];
+ }
+
+ return(r);
+}