dvd-sector-copy.c: Rewrite the bad-sector recovery machinery.

It's now much more aggressive about skipping good sectors squished
between bad ones.

diff --git a/dvd-sector-copy.c b/dvd-sector-copy.c
index d663c0b..908bbbc 100644 (file)
--- a/dvd-sector-copy.c
+++ b/dvd-sector-copy.c
@@ -489,25 +489,189 @@ static void recovered(secaddr bad_lo, secaddr bad_hi)
   status = 1;
 }
 
+struct recoverybuf {
+  unsigned char *buf;
+  secaddr sz, pos, start, end;
+};
+
+static void rearrange_sectors(struct recoverybuf *r,
+                             secaddr dest, secaddr src, secaddr len)
+{
+  assert(dest + len <= r->sz);
+  assert(src + len <= r->sz);
+  memmove(r->buf + dest*SECTORSZ, r->buf + src*SECTORSZ, len*SECTORSZ);
+}
+
+#ifdef DEBUG
+__attribute__((format(printf, 2, 3)))
+static void show_recovery_buffer_map(const struct recoverybuf *r,
+                                    const char *what, ...)
+{
+  va_list ap;
+
+  va_start(ap, what);
+  clear_progress();
+  printf(";; recovery buffer (");
+  vprintf(what, ap);
+  printf("): "
+        "(%"PRIuSEC") ..%"PRIuSEC".. "
+        "[%"PRIuSEC" ..%"PRIuSEC".. %"PRIuSEC"] "
+        "..%"PRIuSEC".. (%"PRIuSEC")\n",
+        r->pos, r->start,
+        r->pos + r->start, r->end - r->start, r->pos + r->end,
+        r->sz - r->end, r->pos + r->sz);
+  va_end(ap);
+  assert(r->start <= r->end);
+  assert(r->end <= r->sz);
+}
+#endif
+
+static ssize_t recovery_read_sectors(struct recoverybuf *r,
+                                    secaddr pos, secaddr off, secaddr want)
+{
+  ssize_t n;
+
+  assert(off + want <= r->sz);
+  n = read_sectors(pos, r->buf + off*SECTORSZ, want);
+  return (n);
+}
+
+static ssize_t recovery_read(struct recoverybuf *r,
+                            secaddr pos, secaddr want)
+{
+  secaddr diff, pp, nn;
+  ssize_t n;
+
+#ifdef DEBUG
+  clear_progress();
+  show_recovery_buffer_map(r, "begin(%"PRIuSEC", %"PRIuSEC")", pos, want);
+#endif
+
+  if (pos < r->pos) {
+    diff = r->pos - pos;
+    if (r->start + diff >= r->sz) {
+      r->pos = pos; r->start = r->end = 0;
+#ifdef DEBUG
+      show_recovery_buffer_map(r, "cleared; shift up by %"PRIuSEC"", diff);
+#endif
+    } else {
+      if (r->end + diff > r->sz) r->end = r->sz - diff;
+      rearrange_sectors(r, r->start + diff, r->start, r->end - r->start);
+      r->start += diff; r->end += diff;
+#ifdef DEBUG
+      show_recovery_buffer_map(r, "shifted up by %"PRIuSEC"", diff);
+#endif
+    }
+  } else if (pos > r->pos + r->end) {
+      r->pos = pos; r->start = r->end = 0;
+#ifdef DEBUG
+      show_recovery_buffer_map(r, "cleared; beyond previous region");
+#endif
+  } else if (pos + want > r->pos + r->sz) {
+    diff = (pos + want) - (r->pos + r->sz);
+    if (r->end <= diff) {
+      r->pos = pos; r->start = r->end = 0;
+#ifdef DEBUG
+      show_recovery_buffer_map(r, "cleared; shift down by %"PRIuSEC"", diff);
+#endif
+    } else {
+      if (r->start < diff) r->start = diff;
+      rearrange_sectors(r, r->start - diff, r->start, r->end - r->start);
+      r->start -= diff; r->end -= diff;
+#ifdef DEBUG
+      show_recovery_buffer_map(r, "shifted down by %"PRIuSEC"", diff);
+#endif
+    }
+  }
+
+  if (pos < r->pos + r->start) {
+    pp = pos - r->pos; nn = r->start - pp;
+#ifdef DEBUG
+    printf(";; read low (%"PRIuSEC"@%"PRIuSEC", %"PRIuSEC")", pos, pp, nn);
+    fflush(stdout);
+#endif
+    n = recovery_read_sectors(r, pos, pp, nn);
+#ifdef DEBUG
+    printf(" -> %ld\n", n);
+#endif
+    if (n != nn) {
+      if (n > want) n = want;
+      goto end;
+    }
+    r->start = pp;
+#ifdef DEBUG
+    show_recovery_buffer_map(r, "joined new region");
+#endif
+  }
+
+  if (pos + want > r->pos + r->end) {
+    pp = r->end; nn = (pos + want) - (r->pos + r->end);
+#ifdef DEBUG
+    printf(";; read high (%"PRIuSEC"@%"PRIuSEC", %"PRIuSEC")",
+          r->pos + pp, pp, nn);
+fflush(stdout);
+#endif
+    n = recovery_read_sectors(r, pos, pp, nn);
+#ifdef DEBUG
+    printf(" -> %ld\n", n);
+#endif
+    if (n > 0) {
+      r->end += n;
+#ifdef DEBUG
+      show_recovery_buffer_map(r, "joined new region");
+#endif
+    }
+  }
+
+  n = r->pos + r->end - pos;
+  if (!n && want) n = -1;
+
+end:
+#ifdef DEBUG
+  show_recovery_buffer_map(r, "done; return %ld", n);
+#endif
+  return (n);
+}
+
+static secaddr run_length_wanted(secaddr pos, secaddr badlen,
+                                secaddr sz, secaddr end)
+{
+  secaddr want;
+
+  want = 3*badlen/2;
+  if (!want) want = 1;
+  if (want > end - pos) want = end - pos;
+  if (want > sz) want = sz;
+  return (want);
+}
+
 static ssize_t find_good_sector(secaddr *pos_inout, secaddr end,
                                unsigned char *buf, secaddr sz)
 {
   int i;
-  secaddr pos = *pos_inout, bad_lo, bad_hi, good, step;
+  secaddr pos = *pos_inout, bad_lo, bad_hi, good, step, want;
+  struct recoverybuf r;
   ssize_t n;
 
+  r.buf = buf; r.sz = sz; r.pos = r.start = r.end = 0;
   report_bad_blocks_progress(pos, pos, errno);
+
+  want = sz; if (want > end - pos) want = end - pos;
   for (i = 0; i < 4; i++) {
-    n = read_sectors(pos, buf, 1);
+    n = recovery_read(&r, pos, want);
+#ifdef DEBUG
+    clear_progress();
+    printf(";; [retry] try reading %"PRIuSEC" .. %"PRIuSEC" -> %ld\n",
+          pos, pos + want, n);
+#endif
     if (n > 0) {
       clear_progress();
       moan("sector %"PRIuSEC" read ok after retry", pos);
-      bad_lo = bad_hi = pos;
       return (n);
     }
   }
 
-  bad_lo = pos; step = 1; bad_hi = pos + 1;
+  bad_lo = pos; bad_hi = pos + 1;
   for (;;) {
     report_bad_blocks_progress(bad_lo, bad_hi, errno);
     if (bad_hi >= end) {
@@ -515,23 +679,41 @@ static ssize_t find_good_sector(secaddr *pos_inout, secaddr end,
       moan("giving up on this extent");
       recovered(bad_lo, end); *pos_inout = end; return (0);
     }
-    step *= 2;
-    if (step > end - bad_lo) step = end - bad_lo;
+    step = 2*(bad_hi - bad_lo); if (step > end - bad_lo) step = end - bad_lo;
     pos = bad_lo + step - 1;
-    n = read_sectors(pos, buf, 1);
-    if (n > 0) break;
-    bad_hi = pos + 1;
+    want = run_length_wanted(pos, step, sz, end);
+    n = recovery_read(&r, pos, want);
+#ifdef DEBUG
+    clear_progress();
+    printf(";; [bound] try reading %"PRIuSEC" .. %"PRIuSEC" -> %ld\n",
+          pos, pos + want, n);
+#endif
+    if (n == want) break;
+    if (n < 0) n = 0;
+    bad_hi = pos + n + 1;
   }
 
   good = pos;
   while (good > bad_hi) {
     report_bad_blocks_progress(bad_lo, bad_hi, errno);
     pos = bad_hi + (good - bad_hi)/2;
-    n = read_sectors(pos, buf, 1);
-    if (n > 0) good = pos;
-    else bad_hi = pos + 1;
+    step = pos - bad_lo;
+    want = run_length_wanted(pos, step, sz, end);
+    n = recovery_read(&r, pos, want);
+#ifdef DEBUG
+    clear_progress();
+    printf(";; [limit] try reading %"PRIuSEC" .. %"PRIuSEC" -> %ld\n",
+          pos, pos + want, n);
+#endif
+    if (n < 0) n = 0;
+    if (n == want) good = pos;
+    else bad_hi = pos + n + 1;
   }
   recovered(bad_lo, bad_hi); *pos_inout = good;
+  if (r.pos + r.start <= good && good <= r.pos + r.end) {
+    rearrange_sectors(&r, 0, good - r.pos, r.pos + r.end - good);
+  } else
+    n = 0;
   return (n);
 }