+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);
+}
+