+ 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(" -> %zd\n", n);
+#endif
+ if (n != nn) {
+ if (n >= 0 && 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, r->pos + pp, pp, nn);
+#ifdef DEBUG
+ printf(" -> %zd\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;
+ else if (n > want) n = want;
+
+end:
+#ifdef DEBUG
+ show_recovery_buffer_map(r, "done; return %zd", n);
+#endif
+ return (n);
+}
+
+static ssize_t recovery_read_multiple(struct recoverybuf *r,
+ secaddr pos, secaddr want)
+{
+ ssize_t n;
+ secaddr skip, want0 = want;
+
+ while (want > r->sz) {
+ skip = want - r->sz;
+ n = recovery_read_buffer(r, pos + skip, r->sz);
+ if (n < r->sz) return (skip + (n >= 0 ? n : 0));
+ want -= r->sz;
+ }
+ n = recovery_read_buffer(r, pos, want);
+ if (n < 0 || n < want) return (n);
+ return (want0);
+}
+
+static ssize_t recovery_read(struct recoverybuf *r,
+ secaddr pos, secaddr want)
+{
+ secaddr lo = pos, hi = pos + want, span;
+ ssize_t n;
+
+ if (hi < r->good_lo || lo > r->good_hi) {
+ n = recovery_read_multiple(r, lo, hi - lo);
+ if (n > 0) { r->good_lo = lo; r->good_hi = lo + n; }
+ return (n);
+ }
+
+ if (hi > r->good_hi) {
+ span = hi - r->good_hi;
+ n = recovery_read_multiple(r, r->good_hi, span);
+ if (n > 0) r->good_hi += n;
+ if (n < 0 || n < span) return (r->good_hi - lo);
+ }
+
+ if (lo < r->good_lo) {
+ span = r->good_lo - lo;
+ n = recovery_read_multiple(r, lo, span);
+ if (n == span) r->good_lo = lo;
+ else return (n);
+ }
+
+ n = r->good_hi - pos; if (n > want) n = want;
+ if (!n) { errno = EIO; n = -1; }