From 7494a7fd962287362a496a38c65bf24a8d190479 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arsen=20Arsenovi=C4=87?= <arsen@aarsen.me>
Date: Mon, 10 Apr 2023 18:08:50 +0200
Subject: [PATCH] unique: Add conversion constructors and tests

---
 include/frg/unique.hpp | 40 ++++++++++++++++++--
 tests/tests.cpp        | 86 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 123 insertions(+), 3 deletions(-)

diff --git a/include/frg/unique.hpp b/include/frg/unique.hpp
index 2dd36e6..f93b6cb 100644
--- a/include/frg/unique.hpp
+++ b/include/frg/unique.hpp
@@ -1,7 +1,9 @@
 #ifndef FRG_UNIQUE_HPP
 #define FRG_UNIQUE_HPP
 
+#include <type_traits>
 #include <utility>
+#include <concepts>
 
 namespace frg {
 
@@ -19,9 +21,38 @@ struct unique_ptr {
 	unique_ptr(Allocator allocator, T *ptr)
 	:_ptr{ptr}, _allocator(std::move(allocator)) {}
 
+	/** Converts a unique_ptr of a different type to the type of this
+	    unique_ptr.
+
+	    The allocator is taken from the old unique_ptr.  It must be
+	    convertible to our allocator type.
+
+	    The pointer type also, naturally, has to be convertible to the
+	    current pointer type.
+	 */
+	template<typename U, typename UAlloc>
+	requires (
+		std::is_convertible_v<U*, T*>
+		&& std::is_constructible_v<Allocator, UAlloc&&>
+	)
+	unique_ptr(unique_ptr<U, UAlloc>&& o)
+	: _ptr { nullptr }, _allocator { std::move(o._allocator) } {
+		reset(o.release());
+	}
+
+	/** \sa unique_ptr(unique_ptr<U, UAlloc>&&)  */
+	template<typename U, typename UAlloc>
+	requires std::constructible_from<unique_ptr, unique_ptr<U, UAlloc>&&>
+	unique_ptr& operator=(unique_ptr<U, UAlloc>&& o) {
+		auto optr = o.release();
+		reset(optr);
+		_allocator = std::forward<UAlloc>(o._allocator);
+		return *this;
+	}
+
+
 	~unique_ptr() {
-		if (_ptr)
-			_allocator.free(_ptr);
+		reset();
 	}
 
 	unique_ptr(const unique_ptr &) = delete;
@@ -60,7 +91,7 @@ struct unique_ptr {
 		return _ptr;
 	}
 
-	void reset(T *ptr) {
+	void reset(T *ptr = nullptr) {
 		T *old = _ptr;
 		_ptr = ptr;
 
@@ -71,6 +102,9 @@ struct unique_ptr {
 private:
 	T *_ptr;
 	Allocator _allocator;
+
+	template<typename U, typename UA>
+	friend struct unique_ptr;
 };
 
 template <typename T, typename Allocator, typename ...Args>
diff --git a/tests/tests.cpp b/tests/tests.cpp
index c2b7cf4..c8e403d 100644
--- a/tests/tests.cpp
+++ b/tests/tests.cpp
@@ -3,6 +3,7 @@
 #include <frg/random.hpp>
 
 #include <gtest/gtest.h>
+#include <memory>
 
 using string = frg::string<frg::stl_allocator>;
 
@@ -319,3 +320,88 @@ TEST(bitset, count) {
 	EXPECT_FALSE(a.all());
 	EXPECT_FALSE(a.none());
 }
+
+#include <frg/unique.hpp>
+
+#include <unordered_set>
+
+struct TestAlloc;
+
+struct TestPool {
+	std::unordered_map<void*, std::size_t> _allocated;
+	std::size_t checknum = 0;
+
+	TestPool()
+	: _allocated {} {}
+
+	void do_check() {
+		ASSERT_TRUE (_allocated.empty())
+			<< "Memory leak?!  In " << (checknum++);
+	}
+
+	TestPool& operator=(const TestPool&) = delete;
+	TestPool(const TestPool&) = delete;
+	TestPool& operator=(TestPool&& o) {
+		std::swap(_allocated, o._allocated);
+		return *this;
+	}
+	TestPool(TestPool&& o) {
+		operator=(std::move (o));
+	}
+
+	void* allocate(std::size_t sz) {
+		auto x = operator new(sz);
+		_allocated.emplace(x, sz);
+		std::cerr << "Allocated " << sz << " bytes at " << x
+			  << std::endl;
+		return x;
+	}
+
+	void free(void* x) {
+		std::cerr << "Deallocating " << x << std::endl;
+		auto xi = _allocated.find(x);
+		ASSERT_FALSE(xi == _allocated.cend())
+			<< "Double or invalid free of " << x;
+		_allocated.erase(xi);
+		operator delete(x);
+	}
+
+	TestAlloc get();
+};
+
+struct TestAlloc {
+	TestPool* tp;
+
+	void* allocate(std::size_t sz) {
+		return tp->allocate(sz);
+	}
+
+	void free(void* x) {
+		tp->free(x);
+	}
+};
+
+TestAlloc TestPool::get() {
+	return { this };
+}
+
+struct Base {};
+struct Derived : Base {};
+
+TEST(unique_ptr, construction_destruction) {
+	using namespace frg;
+	TestPool tp;
+
+	{
+		auto a = frg::make_unique<Base>(tp.get());
+		auto b = std::move(a);
+		a = frg::make_unique<Derived>(tp.get());
+		b = frg::make_unique<Derived>(tp.get());
+
+		tp.get().free(b.release());
+		ASSERT_FALSE(b && b.get() == nullptr);
+		a.reset();
+		ASSERT_FALSE(a && a.get() == nullptr);
+	};
+	tp.do_check();
+}