fix: avoid u32 overflow in statistics for full bitmaps

roaring/src/bitmap/statistics.rs

@@ -20,7 +20,7 @@ pub struct Statistics {
     /// Number of values stored in array containers
     pub n_values_array_containers: u32,
     /// Number of values stored in run containers
-    pub n_values_run_containers: u32,
+    pub n_values_run_containers: u64,
     /// Number of values stored in bitset containers
     pub n_values_bitset_containers: u64,
     /// Number of bytes used by array containers
@@ -89,7 +89,7 @@ impl RoaringBitmap {
                 }
                 Store::Run(runs) => {
                     cardinality += runs.len();
-                    n_values_run_containers += runs.len() as u32;
+                    n_values_run_containers += runs.len();
                     n_bytes_run_containers += runs.byte_size() as u64;
                     n_run_containers += 1;
                 }

roaring/tests/lib.rs

@@ -150,3 +150,20 @@ fn optimize_run() {
     // Calling optimize a second time should return false as no changes will be made
     assert!(!bitmap.optimize());
 }
+
+#[test]
+fn statistics_array_count_remains_u32() {
+    let bitmap = RoaringBitmap::from_iter([1, 2, 65_536]);
+    let stats = bitmap.statistics();
+    let count: u32 = stats.n_values_array_containers;
+    assert_eq!(stats.n_array_containers, 2);
+    assert_eq!(count, 3);
+}
+
+#[test]
+fn statistics_full_run() {
+    let stats = RoaringBitmap::full().statistics();
+    let expected: u64 = 1 << 32;
+    assert_eq!(stats.cardinality, expected);
+    assert_eq!(stats.n_values_run_containers, expected);
+}