From e0a53d4747bcffa094130dfc6edf1ec6e06c0575 Mon Sep 17 00:00:00 2001
From: Max Kellermann <mk@cm4all.com>
Date: Wed, 10 Apr 2024 09:39:36 +0200
Subject: [PATCH] util/IntrusiveTreeSet: add debug method Check()
Only for the unit test.
---
src/util/IntrusiveTreeSet.hxx | 10 ++++++++++
src/util/RedBlackTree.hxx | 30 ++++++++++++++++++++++++++++++
test/util/TestIntrusiveTreeSet.cxx | 4 ++++
3 files changed, 44 insertions(+)
diff --git a/src/util/IntrusiveTreeSet.hxx b/src/util/IntrusiveTreeSet.hxx
index 8320529a3..3b788a60a 100644
--- a/src/util/IntrusiveTreeSet.hxx
+++ b/src/util/IntrusiveTreeSet.hxx
@@ -176,6 +176,16 @@ public:
[[nodiscard]]
IntrusiveTreeSet() noexcept = default;
+#ifndef NDEBUG
+ /**
+ * For debugging only: check the integrity of the red-black
+ * tree.
+ */
+ void Check() noexcept {
+ RedBlackTreeNode::BlackHeight(GetRoot());
+ }
+#endif
+
[[nodiscard]]
constexpr bool empty() const noexcept {
return GetRoot() == nullptr;
diff --git a/src/util/RedBlackTree.hxx b/src/util/RedBlackTree.hxx
index 8cb205a5a..07012cede 100644
--- a/src/util/RedBlackTree.hxx
+++ b/src/util/RedBlackTree.hxx
@@ -173,6 +173,36 @@ struct RedBlackTreeNode {
return GetLeftMost(this);
}
+#ifndef NDEBUG
+ /**
+ * Determine the "black height" (the number of black nodes in
+ * any path from the root to the leaves). This is for
+ * debugging only. It walks the whole tree and aborts if the
+ * black height is not consistent.
+ */
+ static unsigned BlackHeight(const RedBlackTreeNode *node) noexcept {
+ if (node == nullptr)
+ /* leaf nodes (NIL / nullptr) count as
+ black */
+ return 1;
+
+ assert(node->parent != nullptr);
+ assert(node->color != Color::HEAD);
+ assert(node->color != Color::RED || node->parent->color != Color::RED);
+
+ assert(node->children[0] == nullptr || node->children[0]->parent == node);
+ assert(node->children[1] == nullptr || node->children[1]->parent == node);
+
+ const unsigned left_height = BlackHeight(node->children[0]);
+ const unsigned right_height = BlackHeight(node->children[1]);
+
+ /* the black height must be equal in all paths */
+ assert(left_height == right_height);
+
+ return left_height + (node->color == Color::BLACK);
+ }
+#endif
+
private:
[[nodiscard]]
constexpr static RedBlackTreeNode *GetLeftHandedParent(RedBlackTreeNode *node) noexcept {
diff --git a/test/util/TestIntrusiveTreeSet.cxx b/test/util/TestIntrusiveTreeSet.cxx
index e2fca6ca7..71e3fab88 100644
--- a/test/util/TestIntrusiveTreeSet.cxx
+++ b/test/util/TestIntrusiveTreeSet.cxx
@@ -182,6 +182,10 @@ TEST(IntrusiveTreeSet, RandomOrder)
set.pop_front();
EXPECT_FALSE(items[remove].is_linked());
+#ifndef NDEBUG
+ set.Check();
+#endif
+
expected = remove + 1;
for (const auto &i : set) {
EXPECT_EQ(i.value, expected++);