mempool: implement move semantics for MempoolInstance

Currently it uses default implementations that does not set pointers of
moved objects to `NULL` and they are still by moved object. Let's
manually implement move semantics because we will need to move
MempoolInstance as a part of `tnt::Buffer` later.

Along the way, mark other constructors and operators as `noexcept`.

Part of #110

Author: drewdzzz

src/Utils/Mempool.hpp

@@ -34,6 +34,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <utility>
 
 namespace tnt {
 
@@ -44,6 +45,20 @@ class MempoolStats {
 	void statAddBlock() { ++m_BlockCount; }
 	void statDelBlock() { --m_BlockCount; }
 public:
+	MempoolStats() = default;
+	MempoolStats(MempoolStats &&other) noexcept
+	{
+		/* Call move assignment operator. */
+		*this = std::forward<MempoolStats>(other);
+	}
+	MempoolStats &operator=(MempoolStats &&other) noexcept
+	{
+		m_SlabCount = other.m_SlabCount;
+		m_BlockCount = other.m_BlockCount;
+		other.m_SlabCount = 0;
+		other.m_BlockCount = 0;
+	}
+
 	/** Count of allocated (used) blocks. */
 	size_t statBlockCount() const { return m_BlockCount; }
 	/** Count of allocated (total) slabs. */
@@ -60,6 +75,10 @@ class MempoolStats<false> {
 	void statAddBlock() { }
 	void statDelBlock() { }
 public:
+	MempoolStats() = default;
+	MempoolStats(MempoolStats &&other) noexcept = default;
+	MempoolStats &operator=(MempoolStats &&other) noexcept = default;
+
 	/** Disabled. return SIZE_MAX. */
 	size_t statBlockCount() const { return SIZE_MAX; }
 	/** Disabled. return SIZE_MAX. */
@@ -106,6 +125,15 @@ class MempoolInstance : public MempoolStats<ENABLE_STATS> {
 
 	using Stats_t = MempoolStats<ENABLE_STATS>;
 
+	void ReleaseSlabList(void) noexcept
+	{
+		while (m_SlabList != nullptr) {
+			Slab *tmp = m_SlabList;
+			m_SlabList = m_SlabList->next;
+			delete tmp;
+		}
+	}
+
 public:
 	// Constants for stat.
 	static constexpr size_t REAL_SIZE = B;
@@ -114,15 +142,32 @@ class MempoolInstance : public MempoolStats<ENABLE_STATS> {
 	static constexpr size_t BLOCK_ALIGN = BA;
 	static constexpr size_t SLAB_ALIGN = SA;
 
-	MempoolInstance() = default;
-	~MempoolInstance() noexcept
+	MempoolInstance() noexcept = default;
+	MempoolInstance(const MempoolInstance &other) = delete;
+	MempoolInstance &operator=(const MempoolInstance &other) = delete;
+	MempoolInstance(MempoolInstance &&other) noexcept
 	{
-		while (m_SlabList != nullptr) {
-			Slab *tmp = m_SlabList;
-			m_SlabList = m_SlabList->next;
-			delete tmp;
-		}
+		/* Call move assignment operator. */
+		*this = std::forward<MempoolInstance>(other);
+	}
+	MempoolInstance &operator=(MempoolInstance &&other) noexcept
+	{
+		if (this == &other)
+			return *this;
+		/* Move base class. */
+		MempoolStats<ENABLE_STATS>::operator=(std::forward<MempoolInstance>(other));
+		ReleaseSlabList();
+		m_SlabList = other.m_SlabList;
+		m_FreeList = other.m_FreeList;
+		m_SlabDataBeg = other.m_SlabDataBeg;
+		m_SlabDataEnd = other.m_SlabDataEnd;
+		other.m_SlabList = nullptr;
+		other.m_FreeList = nullptr;
+		other.m_SlabDataBeg = nullptr;
+		other.m_SlabDataEnd = nullptr;
+		return *this;
 	}
+	~MempoolInstance() noexcept { ReleaseSlabList(); }
 	static MempoolInstance& defaultInstance()
 	{
 		static MempoolInstance instance;

test/MempoolUnitTest.cpp

@@ -32,6 +32,7 @@
 #include "../src/Utils/Mempool.hpp"
 #include "Utils/Helpers.hpp"
 #include <iostream>
+#include <utility>
 
 template <size_t S>
 struct Allocation {
@@ -247,6 +248,40 @@ test_alignment()
 	}
 }
 
+template <size_t S>
+void
+test_move()
+{
+	TEST_INIT(2, S, 0);
+	constexpr size_t N = 1024;
+	tnt::MempoolInstance<S> mp;
+
+	Allocations<S, N * 6> all;
+	for (size_t i = 0; i < N; i++)
+		all.add(mp.allocate());
+	fail_unless(all.are_valid());
+
+	tnt::MempoolInstance<S> mp_move_constructed(std::move(mp));
+	for (size_t i = 0; i < N; i++) {
+		all.add(mp_move_constructed.allocate());
+		all.add(mp.allocate());
+	}
+	fail_unless(all.are_valid());
+
+	tnt::MempoolInstance<S> mp_move_copied;
+	/* Allocate some memory and let ASAN check if it won't be leaked. */
+	for (size_t i = 0; i < N; i++) {
+		char *ptr = mp_move_copied.allocate();
+		(void)ptr;
+	}
+	mp_move_copied = std::move(mp);
+	for (size_t i = 0; i < N; i++) {
+		all.add(mp_move_copied.allocate());
+		all.add(mp.allocate());
+	}
+	fail_unless(all.are_valid());
+}
+
 int main()
 {
 	test_default<8>();
@@ -275,4 +310,10 @@ int main()
 	test_alignment<120, 2>();
 	test_alignment<120, 13>();
 	test_alignment<120, 64>();
+
+	test_move<8>();
+	test_move<64>();
+	test_move<14>();
+	test_move<72>();
+	test_move<80>();
 }