commit fd044f4: [Minor] Enable make_shared like behaviour

[Vsevolod Stakhov]

Author: Vsevolod Stakhov
Date: 2021-07-22 17:08:36 +0100
URL: https://github.com/rspamd/rspamd/commit/fd044f4cf02a5cad4d023af5df375d1f124e31bd

[Minor] Enable make_shared like behaviour

---
 src/libutil/cxx/local_shared_ptr.hxx | 122 +++++++++++++++++++++++++++--------
 test/rspamd_cxx_unit_utils.hxx       |  30 +++++++++
 2 files changed, 124 insertions(+), 28 deletions(-)

diff --git a/src/libutil/cxx/local_shared_ptr.hxx b/src/libutil/cxx/local_shared_ptr.hxx
index 8c8751447..5a9cccb38 100644
--- a/src/libutil/cxx/local_shared_ptr.hxx
+++ b/src/libutil/cxx/local_shared_ptr.hxx
@@ -30,12 +30,79 @@
  */
 namespace rspamd {
 
+namespace detail {
+
+class ref_cnt {
+public:
+	using refcount_t = int;
+
+	constexpr auto add_shared() -> refcount_t {
+		return ++ref_shared;
+	}
+	constexpr auto release_shared() -> refcount_t {
+		return --ref_shared;
+	}
+	constexpr auto release_weak() -> refcount_t {
+		return --ref_weak;
+	}
+	constexpr auto shared_count() const -> refcount_t {
+		return ref_shared;
+	}
+	virtual ~ref_cnt() {}
+	virtual void dispose() = 0;
+private:
+	refcount_t ref_weak = 0;
+	refcount_t ref_shared = 1;
+};
+
 template <class T>
-class local_weak_ptr {
-	typedef T element_type;
+class obj_and_refcnt : public ref_cnt {
+private:
+	typedef typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type storage_type;
+	storage_type storage;
+	bool initialized;
+	virtual void dispose() override {
+		if (initialized) {
+			T *p = reinterpret_cast<T *>(&storage);
+			p->~T();
+			initialized = false;
+		}
+	}
+public:
+	template <typename... Args>
+	explicit obj_and_refcnt(Args&&... args) : initialized(true)
+	{
+		new(&storage) T(std::forward<Args>(args)...);
+	}
+	auto get(void) -> T* {
+		if (initialized) {
+			return reinterpret_cast<T *>(&storage);
+		}
+
+		return nullptr;
+	}
+	virtual ~obj_and_refcnt() = default;
+};
 
+template <class T, class D = typename std::default_delete<T>>
+class ptr_and_refcnt : public ref_cnt {
+private:
+	T* ptr;
+	D deleter;
+	virtual void dispose() override {
+		deleter(ptr);
+		ptr = nullptr;
+	}
+public:
+	explicit ptr_and_refcnt(T *_ptr, D d = std::default_delete<T>()) : ptr(_ptr),
+			deleter(std::move(d)) {}
+	virtual ~ptr_and_refcnt() = default;
 };
 
+}
+
+template <class T> class local_weak_ptr;
+
 template <class T>
 class local_shared_ptr {
 public:
@@ -48,8 +115,15 @@ public:
 
 	template<class Y, typename std::enable_if<
 	        std::is_convertible<Y*, element_type*>::value, bool>::type = true>
-	explicit local_shared_ptr(Y* p) : px(p), cnt(new local_shared_ptr::control) {
-		cnt->add_shared();
+	explicit local_shared_ptr(Y* p) : px(p), cnt(new detail::ptr_and_refcnt(p))
+	{
+	}
+
+	// custom deleter
+	template<class Y, class D, typename std::enable_if<
+			std::is_convertible<Y*, element_type*>::value, bool>::type = true>
+	explicit local_shared_ptr(Y* p, D d) : px(p), cnt(new detail::ptr_and_refcnt(p, std::move(d)))
+	{
 	}
 
 	local_shared_ptr(const local_shared_ptr& r) noexcept : px(r.px), cnt(r.cnt) {
@@ -67,8 +141,7 @@ public:
 	~local_shared_ptr() {
 		if (cnt) {
 			if (cnt->release_shared() <= 0) {
-				delete px;
-				px = nullptr;
+				cnt->dispose();
 
 				if (cnt->release_weak() <= 0) {
 					delete cnt;
@@ -135,31 +208,24 @@ public:
 	}
 
 private:
-	class control {
-	public:
-		using refcount_t = int;
-
-		constexpr auto add_shared() -> refcount_t {
-			return ++ref_shared;
-		}
-		constexpr auto release_shared() -> refcount_t {
-			return --ref_shared;
-		}
-		constexpr auto release_weak() -> refcount_t {
-			return --ref_weak;
-		}
-		constexpr auto shared_count() const -> refcount_t {
-			return ref_shared;
-		}
-	private:
-		refcount_t ref_weak = 0;
-		refcount_t ref_shared = 0;
-	};
-
 	T *px; // contained pointer
-	control *cnt;
+	detail::ref_cnt *cnt;
+
+	template<class _T, class ... Args>
+	friend local_shared_ptr<_T> local_make_shared(Args && ... args);
 };
 
+template<class T, class ... Args>
+local_shared_ptr<T> local_make_shared(Args && ... args)
+{
+	local_shared_ptr<T> ptr;
+	auto tmp_object = new detail::obj_and_refcnt<T>(std::forward<Args>(args)...);
+	ptr.px = tmp_object->get();
+	ptr.cnt = tmp_object;
+
+	return ptr;
+}
+
 }
 
 #endif //RSPAMD_LOCAL_SHARED_PTR_HXX
diff --git a/test/rspamd_cxx_unit_utils.hxx b/test/rspamd_cxx_unit_utils.hxx
index a6cbc3a32..be5d193f4 100644
--- a/test/rspamd_cxx_unit_utils.hxx
+++ b/test/rspamd_cxx_unit_utils.hxx
@@ -206,6 +206,36 @@ TEST_CASE("shared_ptr dtor") {
 	CHECK(t == true);
 }
 
+TEST_CASE("make_shared dtor") {
+	bool t;
+
+	{
+		auto pi = rspamd::local_make_shared<deleter_test>(t);
+
+		CHECK((!pi ? false : true));
+		CHECK(!!pi);
+		CHECK(pi.get() != nullptr);
+		CHECK(pi.use_count() == 1);
+		CHECK(pi.unique());
+		CHECK(t == false);
+
+		rspamd::local_shared_ptr<deleter_test> pi2(pi);
+		CHECK(pi2 == pi);
+		CHECK(pi.use_count() == 2);
+		pi.reset();
+		CHECK(!(pi2 == pi));
+		CHECK(pi2.use_count() == 1);
+		CHECK(t == false);
+
+		pi = pi2;
+		CHECK(pi2 == pi);
+		CHECK(pi.use_count() == 2);
+		CHECK(t == false);
+	}
+
+	CHECK(t == true);
+}
+
 }
 
 #endif