+
+ /* When updating in-place, the best possible match is
+ * one with an identical offset, so we prefer that over
+ * the adjacent want_i optimization. */
+ if (updating_basis_file) {
+ /* All the generator's chunks start at blength boundaries. */
+ while (aligned_offset < offset) {
+ aligned_offset += s->blength;
+ aligned_i++;
+ }
+ if ((offset == aligned_offset
+ || (sum == 0 && l == s->blength && aligned_offset + l <= len))
+ && aligned_i < s->count) {
+ if (i != aligned_i) {
+ if (sum != s->sums[aligned_i].sum1
+ || l != s->sums[aligned_i].len
+ || memcmp(sum2, s->sums[aligned_i].sum2, s->s2length) != 0)
+ goto check_want_i;
+ i = aligned_i;
+ }
+ if (offset != aligned_offset) {
+ /* We've matched some zeros in a spot that is also zeros
+ * further along in the basis file, if we find zeros ahead
+ * in the sender's file, we'll output enough literal data
+ * to re-align with the basis file, and get back to seeking
+ * instead of writing. */
+ backup = (int32)(aligned_offset - last_match);
+ if (backup < 0)
+ backup = 0;
+ map = (schar *)map_ptr(buf, aligned_offset - backup, l + backup)
+ + backup;
+ sum = get_checksum1((char *)map, l);
+ if (sum != s->sums[i].sum1)
+ goto check_want_i;
+ get_checksum2((char *)map, l, sum2);
+ if (memcmp(sum2, s->sums[i].sum2, s->s2length) != 0)
+ goto check_want_i;
+ /* OK, we have a re-alignment match. Bump the offset
+ * forward to the new match point. */
+ offset = aligned_offset;
+ }
+ /* This identical chunk is in the same spot in the old and new file. */
+ s->sums[i].flags |= SUMFLG_SAME_OFFSET;
+ want_i = i;
+ }
+ }
+
+ check_want_i:
+ /* we've found a match, but now check to see
+ * if want_i can hint at a better match. */
+ if (i != want_i && want_i < s->count
+ && (!updating_basis_file || s->sums[want_i].offset >= offset
+ || s->sums[want_i].flags & SUMFLG_SAME_OFFSET)
+ && sum == s->sums[want_i].sum1
+ && memcmp(sum2, s->sums[want_i].sum2, s->s2length) == 0) {
+ /* we've found an adjacent match - the RLL coder
+ * will be happy */
+ i = want_i;
+ }
+ want_i = i + 1;
+