fix(roaring64): art_find_at would return the wrong leaf (#553)

If a leaf shared all but the last byte, art_find_at could return the incorrect leaf, rather than returning NULL

Fixes #552

src/art/art.c

@@ -1093,7 +1093,7 @@ static art_val_t *art_find_at(const art_node_t *node,
         depth += inner_node->prefix_size + 1;
     }
     art_leaf_t *leaf = CAST_LEAF(node);
-    if (depth >= ART_KEY_BYTES - 1) {
+    if (depth >= ART_KEY_BYTES) {
         return (art_val_t *)leaf;
     }
     uint8_t common_prefix =

tests/roaring64_unit.cpp

@@ -205,6 +205,7 @@ DEFINE_TEST(test_add_range_closed) {
         // Range spans more than two containers.
         roaring64_bitmap_t* r = roaring64_bitmap_create();
         roaring64_bitmap_add_range_closed(r, 100, 300000);
+        assert_int_equal(roaring64_bitmap_get_cardinality(r), 300000 - 100 + 1);
         roaring64_bulk_context_t context{};
         assert_false(roaring64_bitmap_contains_bulk(r, &context, 99));
         for (uint64_t i = 100; i <= 300000; ++i) {
@@ -223,6 +224,15 @@ DEFINE_TEST(test_add_range_closed) {
         assert_true(roaring64_bitmap_contains(r, 100));
         roaring64_bitmap_free(r);
     }
+    {
+        // Add a range that spans multiple ART levels (end >> 16 == 0x0101)
+        roaring64_bitmap_t* r = roaring64_bitmap_create();
+        uint64_t end = 0x101ffff;
+        uint64_t start = 0;
+        roaring64_bitmap_add_range_closed(r, start, end);
+        assert_int_equal(roaring64_bitmap_get_cardinality(r), end - start + 1);
+        roaring64_bitmap_free(r);
+    }
 }
 
 DEFINE_TEST(test_contains_bulk) {