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.

Part of #110

Author: drewdzzz

src/Utils/Mempool.hpp

@@ -115,6 +115,19 @@ class MempoolInstance : public MempoolStats<ENABLE_STATS> {
 	static constexpr size_t SLAB_ALIGN = SA;
 
 	MempoolInstance() = default;
+	MempoolInstance(const MempoolInstance& other) = default;
+	MempoolInstance &operator=(const MempoolInstance& other) = default;
+	MempoolInstance(MempoolInstance&& other) noexcept
+	{
+		memcpy(this, &other, sizeof(*this));
+		memset(&other, 0, sizeof(*this));
+	}
+	MempoolInstance &operator=(MempoolInstance&& other) noexcept
+	{
+		memcpy(this, &other, sizeof(*this));
+		memset(&other, 0, sizeof(*this));
+		return *this;
+	}
 	~MempoolInstance() noexcept
 	{
 		while (m_SlabList != nullptr) {

test/MempoolUnitTest.cpp

@@ -247,6 +247,35 @@ 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;
+	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 +304,10 @@ 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>();
 }