feat: implement roaring64_bitmap_remove_run_compression

Author: Dr-Emann

include/roaring/roaring64.h

@@ -310,6 +310,12 @@ uint64_t roaring64_bitmap_minimum(const roaring64_bitmap_t *r);
  */
 uint64_t roaring64_bitmap_maximum(const roaring64_bitmap_t *r);
 
+/**
+ * Remove run-length encoding even when it is more space efficient.
+ * Return whether a change was applied.
+ */
+bool roaring64_bitmap_remove_run_compression(roaring64_bitmap_t *r);
+
 /**
  * Returns true if the result has at least one run container.
  */

src/roaring64.c

@@ -941,6 +941,26 @@ uint64_t roaring64_bitmap_maximum(const roaring64_bitmap_t *r) {
         it.key, container_maximum(get_container(r, leaf), get_typecode(leaf)));
 }
 
+bool roaring64_bitmap_remove_run_compression(roaring64_bitmap_t *r) {
+    art_iterator_t it = art_init_iterator(&r->art, /*first=*/true);
+    bool removed = false;
+    while (it.value != NULL) {
+        leaf_t *leaf = (leaf_t *)it.value;
+        if (get_typecode(*leaf) == RUN_CONTAINER_TYPE) {
+            run_container_t *run = CAST_run(get_container(r, *leaf));
+            int32_t card = run_container_cardinality(run);
+            uint8_t new_typecode;
+            container_t *new_container =
+                convert_to_bitset_or_array_container(run, card, &new_typecode);
+            run_container_free(run);
+            replace_container(r, leaf, new_container, new_typecode);
+            removed = true;
+        }
+        art_iterator_next(&it);
+    }
+    return removed;
+}
+
 bool roaring64_bitmap_run_optimize(roaring64_bitmap_t *r) {
     art_iterator_t it = art_init_iterator(&r->art, /*first=*/true);
     bool has_run_container = false;

tests/roaring64_unit.cpp

@@ -931,6 +931,27 @@ DEFINE_TEST(test_maximum) {
     roaring64_bitmap_free(r);
 }
 
+DEFINE_TEST(test_remove_run_compression) {
+    roaring64_bitmap_t* r = roaring64_bitmap_create();
+
+    for (uint64_t i = 0; i < 30000; ++i) {
+        roaring64_bitmap_add(r, i);
+    }
+    assert_true(roaring64_bitmap_run_optimize(r));
+    assert_r64_valid(r);
+
+    assert_true(roaring64_bitmap_remove_run_compression(r));
+    assert_r64_valid(r);
+
+    assert_false(roaring64_bitmap_remove_run_compression(r));
+    assert_r64_valid(r);
+
+    assert_true(roaring64_bitmap_run_optimize(r));
+    assert_r64_valid(r);
+
+    roaring64_bitmap_free(r);
+}
+
 DEFINE_TEST(test_run_optimize) {
     roaring64_bitmap_t* r = roaring64_bitmap_create();
 
@@ -2078,6 +2099,7 @@ int main() {
         cmocka_unit_test(test_is_empty),
         cmocka_unit_test(test_minimum),
         cmocka_unit_test(test_maximum),
+        cmocka_unit_test(test_remove_run_compression),
         cmocka_unit_test(test_run_optimize),
         cmocka_unit_test(test_equals),
         cmocka_unit_test(test_is_subset),