Function compute_xor_offsets

pack-bitmap-write.c:345–405

}

static void compute_xor_offsets(struct bitmap_writer *writer)
{
	static const int MAX_XOR_OFFSET_SEARCH = 10;

	int i, next = 0;
	int nr = bitmap_writer_nr_selected_commits(writer);

	if (nr > 1) {
		QSORT(writer->selected, nr, bitmapped_commit_date_cmp);

		for (i = 0; i < nr; i++) {
			struct bitmapped_commit *stored = &writer->selected[i];
			khiter_t hash_pos = kh_get_oid_map(writer->bitmaps,
							   stored->commit->object.oid);

			if (hash_pos == kh_end(writer->bitmaps))
				BUG("selected commit missing from bitmap map: %s",
				    oid_to_hex(&stored->commit->object.oid));

			kh_value(writer->bitmaps, hash_pos) = stored;
		}
	}

	while (next < writer->selected_nr) {
		struct bitmapped_commit *stored = &writer->selected[next];
		int best_offset = 0;
		struct ewah_bitmap *best_bitmap = stored->bitmap;
		struct ewah_bitmap *test_xor;

		if (stored->pseudo_merge)
			goto next;

		for (i = 1; i <= MAX_XOR_OFFSET_SEARCH; ++i) {
			int curr = next - i;

			if (curr < 0)
				break;
			if (writer->selected[curr].pseudo_merge)
				continue;

			test_xor = ewah_pool_new();
			ewah_xor(writer->selected[curr].bitmap, stored->bitmap, test_xor);

			if (test_xor->buffer_size < best_bitmap->buffer_size) {
				if (best_bitmap != stored->bitmap)
					ewah_pool_free(best_bitmap);

				best_bitmap = test_xor;
				best_offset = i;
			} else {
				ewah_pool_free(test_xor);
			}
		}

next:
		stored->xor_offset = best_offset;
		stored->write_as = best_bitmap;