+
+ /* 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;
+ if (offset == aligned_offset) {
+ int32 i2;
+ for (i2 = i; i2 >= 0; i2 = s->sums[i2].chain) {
+ if (s->sums[i2].offset != offset)
+ continue;
+ if (i2 != i) {
+ if (sum != s->sums[i2].sum1
+ || memcmp(sum2, s->sums[i2].sum2, s->s2length) != 0)
+ break;
+ i = i2;
+ }
+ /* This chunk remained in the same spot in the old and new file. */
+ s->sums[i].flags |= SUMFLG_SAME_OFFSET;
+ want_i = 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;
+