From 92d60403f3de094dc2d040a7fce869a5bb60695a Mon Sep 17 00:00:00 2001
From: Stanislaw Halik <sthalik@misaki.pl>
Date: Sat, 4 May 2024 22:57:32 +0200
Subject: a

---
 compat/borrowed-ptr-fwd.hpp | 42 +++++++++++++++++------
 compat/borrowed-ptr.cpp     |  2 +-
 compat/borrowed-ptr.inl     | 84 ++++++++++++++++++++++++++++-----------------
 test/bptr.cpp               | 52 ++++++++++++++++++++++++++++
 4 files changed, 137 insertions(+), 43 deletions(-)

diff --git a/compat/borrowed-ptr-fwd.hpp b/compat/borrowed-ptr-fwd.hpp
index 465e9bf4..01dd20f7 100644
--- a/compat/borrowed-ptr-fwd.hpp
+++ b/compat/borrowed-ptr-fwd.hpp
@@ -1,6 +1,15 @@
 #pragma once
 
-namespace floormat::detail_borrowed_ptr { struct control_block_; }
+namespace floormat::detail_borrowed_ptr {
+
+struct control_block;
+template<typename From, typename To>
+concept DerivedFrom = requires(From* x) {
+    requires !std::is_same_v<From, To>;
+    requires std::is_nothrow_convertible_v<From*, To*>;
+};
+
+} // namespace floormat::detail_borrowed_ptr
 
 namespace floormat {
 
@@ -11,26 +20,39 @@ template<typename T>
 class bptr final // NOLINT(*-special-member-functions)
 {
     mutable T* casted_ptr;
-    detail_borrowed_ptr::control_block_* blk;
+    detail_borrowed_ptr::control_block* blk;
 
-    explicit bptr(DirectInitT, T* casted_ptr, detail_borrowed_ptr::control_block_* blk) noexcept;
-    //explicit bptr(NoInitT) noexcept;
+    explicit bptr(DirectInitT, T* casted_ptr, detail_borrowed_ptr::control_block* blk) noexcept;
+
+    struct private_tag_t final {};
+    static constexpr private_tag_t private_tag{};
+
+    template<typename Y> bptr(const bptr<Y>& other, private_tag_t) noexcept;
+    template<typename Y> bptr& _copy_assign(const bptr<Y>& other) noexcept;
+    template<typename Y> bptr(bptr<Y>&& other, private_tag_t) noexcept;
+    template<typename Y> bptr& _move_assign(bptr<Y>&& other) noexcept;
 
 public:
     template<typename... Ts>
     requires std::is_constructible_v<T, Ts&&...>
     explicit bptr(InPlaceInitT, Ts&&... args) noexcept;
 
-    bptr(std::nullptr_t) noexcept; // NOLINT(*-explicit-conversions)
-    bptr() noexcept;
     explicit bptr(T* ptr) noexcept;
+    bptr() noexcept;
     ~bptr() noexcept;
 
+    bptr(std::nullptr_t) noexcept; // NOLINT(*-explicit-conversions)
     bptr& operator=(std::nullptr_t) noexcept;
-    template<typename Y> requires std::is_convertible_v<Y*, T*> bptr(const bptr<Y>&) noexcept;
-    template<typename Y> requires std::is_convertible_v<Y*, T*> bptr& operator=(const bptr<Y>&) noexcept;
-    template<typename Y> requires std::is_convertible_v<Y*, T*> bptr(bptr<Y>&&) noexcept;
-    template<typename Y> requires std::is_convertible_v<Y*, T*> bptr& operator=(bptr<Y>&&) noexcept;
+
+    bptr(const bptr&) noexcept;
+    bptr& operator=(const bptr&) noexcept;
+    template<detail_borrowed_ptr::DerivedFrom<T> Y> bptr(const bptr<Y>&) noexcept;
+    template<detail_borrowed_ptr::DerivedFrom<T> Y> bptr& operator=(const bptr<Y>&) noexcept;
+
+    bptr(bptr&&) noexcept;
+    bptr& operator=(bptr&&) noexcept;
+    template<detail_borrowed_ptr::DerivedFrom<T> Y> bptr(bptr<Y>&&) noexcept;
+    template<detail_borrowed_ptr::DerivedFrom<T> Y> bptr& operator=(bptr<Y>&&) noexcept;
 
     friend bool operator==<T>(const bptr<T>& a, const bptr<T>& b) noexcept;
     explicit operator bool() const noexcept;
diff --git a/compat/borrowed-ptr.cpp b/compat/borrowed-ptr.cpp
index 413527cb..a73b869f 100644
--- a/compat/borrowed-ptr.cpp
+++ b/compat/borrowed-ptr.cpp
@@ -13,7 +13,7 @@ namespace floormat::detail_borrowed_ptr {
 #pragma warning(push)
 #pragma warning(disable : 5205)
 #endif
-void control_block_::decrement(control_block_*& blk) noexcept
+void control_block::decrement(control_block*& blk) noexcept
 {
     fm_bptr_assert(blk);
     auto c = --blk->_count;
diff --git a/compat/borrowed-ptr.inl b/compat/borrowed-ptr.inl
index fd2d25d2..98e0fec5 100644
--- a/compat/borrowed-ptr.inl
+++ b/compat/borrowed-ptr.inl
@@ -1,6 +1,7 @@
 #pragma once
 #include "borrowed-ptr.hpp"
 #include "compat/assert.hpp"
+#include <utility>
 
 #define FM_BPTR_DEBUG
 
@@ -21,22 +22,22 @@ namespace floormat::detail_borrowed_ptr {
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
 #endif
-struct control_block_
+struct control_block
 {
     void* _ptr; // todo maybe add directly embeddable objects?
     uint32_t _count;
     virtual void free_ptr() noexcept = 0;
-    static void decrement(control_block_*& blk) noexcept;
+    static void decrement(control_block*& blk) noexcept;
 };
 #ifdef __GNUG__
 #pragma GCC diagnostic pop
 #endif
 
 template<typename T>
-struct control_block_impl final: control_block_
+struct control_block_impl final: control_block
 {
     void free_ptr() noexcept override;
-    [[nodiscard]] static control_block_* create(T* ptr) noexcept;
+    [[nodiscard]] static control_block* create(T* ptr) noexcept;
 protected:
     explicit control_block_impl(T* ptr) noexcept;
 };
@@ -56,7 +57,7 @@ void control_block_impl<T>::free_ptr() noexcept
 }
 
 template <typename T>
-control_block_* control_block_impl<T>::create(T* ptr) noexcept
+control_block* control_block_impl<T>::create(T* ptr) noexcept
 {
     if (ptr)
     {
@@ -71,12 +72,10 @@ control_block_* control_block_impl<T>::create(T* ptr) noexcept
 
 namespace floormat {
 
-template<typename T> bptr<T>::bptr(DirectInitT, T* casted_ptr, detail_borrowed_ptr::control_block_* blk) noexcept:
+template<typename T> bptr<T>::bptr(DirectInitT, T* casted_ptr, detail_borrowed_ptr::control_block* blk) noexcept:
     casted_ptr{casted_ptr}, blk{blk}
 {}
 
-//template<typename T> bptr<T>::bptr(NoInitT) noexcept {}
-
 template<typename T>
 template<typename... Ts>
 requires std::is_constructible_v<T, Ts&&...>
@@ -103,28 +102,29 @@ bptr<T>::~bptr() noexcept
         blk->decrement(blk);
 }
 
+template<typename T> bptr<T>::bptr(const bptr& other) noexcept: bptr{other, private_tag} {}
+template<typename T> bptr<T>& bptr<T>::operator=(const bptr& other) noexcept { return _copy_assign(other); }
+
 template<typename T>
-template<typename Y>
-requires std::is_convertible_v<Y*, T*>
-bptr<T>::bptr(const bptr<Y>& other) noexcept:
-    casted_ptr{other.casted_ptr}, blk{other.blk}
-{
-    if (blk)
-    {
-        ++blk->_count;
-        fm_bptr_assert(blk->_count > 1);
-    }
-}
+template<detail_borrowed_ptr::DerivedFrom<T> Y>
+bptr<T>::bptr(const bptr<Y>& other) noexcept: bptr{other, private_tag} {}
 
 template<typename T>
-template<typename Y>
-requires std::is_convertible_v<Y*, T*>
-bptr<T>::bptr(bptr<Y>&& other) noexcept:
-    casted_ptr{other.casted_ptr}, blk{other.blk}
-{
-    other.casted_ptr = nullptr;
-    other.blk = nullptr;
-}
+template<detail_borrowed_ptr::DerivedFrom<T> Y>
+bptr<T>& bptr<T>::operator=(const bptr<Y>& other) noexcept
+{ return _copy_assign(other); }
+
+template<typename T> bptr<T>& bptr<T>::operator=(bptr&& other) noexcept { return _move_assign(move(other)); }
+template<typename T> bptr<T>::bptr(bptr&& other) noexcept: bptr{move(other), private_tag} {}
+
+template<typename T>
+template<detail_borrowed_ptr::DerivedFrom<T> Y>
+bptr<T>::bptr(bptr<Y>&& other) noexcept: bptr{move(other), private_tag} {}
+
+template<typename T>
+template<detail_borrowed_ptr::DerivedFrom<T> Y>
+bptr<T>& bptr<T>::operator=(bptr<Y>&& other) noexcept
+{ return _move_assign(move(other)); }
 
 template<typename T>
 void bptr<T>::reset() noexcept
@@ -153,8 +153,19 @@ template<typename T> bptr<T>& bptr<T>::operator=(std::nullptr_t) noexcept { rese
 
 template<typename T>
 template<typename Y>
-requires std::is_convertible_v<Y*, T*>
-bptr<T>& bptr<T>::operator=(const bptr<Y>& other) noexcept
+bptr<T>::bptr(const bptr<Y>& other, private_tag_t) noexcept:
+    casted_ptr{other.casted_ptr}, blk{other.blk}
+{
+    if (blk)
+    {
+        ++blk->_count;
+        fm_bptr_assert(blk->_count > 1);
+    }
+}
+
+template<typename T>
+template<typename Y>
+bptr<T>& bptr<T>::_copy_assign(const bptr<Y>& other) noexcept
 {
     if (blk != other.blk)
     {
@@ -170,10 +181,19 @@ bptr<T>& bptr<T>::operator=(const bptr<Y>& other) noexcept
 
 template<typename T>
 template<typename Y>
-requires std::is_convertible_v<Y*, T*>
-bptr<T>& bptr<T>::operator=(bptr<Y>&& other) noexcept
+bptr<T>::bptr(bptr<Y>&& other, private_tag_t) noexcept:
+    casted_ptr{other.casted_ptr}, blk{other.blk}
 {
-    blk->decrement(blk);
+    other.casted_ptr = nullptr;
+    other.blk = nullptr;
+}
+
+template<typename T>
+template<typename Y>
+bptr<T>& bptr<T>::_move_assign(bptr<Y>&& other) noexcept
+{
+    if (blk)
+        blk->decrement(blk);
     casted_ptr = other.casted_ptr;
     blk = other.blk;
     other.casted_ptr = nullptr;
diff --git a/test/bptr.cpp b/test/bptr.cpp
index 99d6cd2c..6f823344 100644
--- a/test/bptr.cpp
+++ b/test/bptr.cpp
@@ -39,8 +39,59 @@ template bptr<Foo> static_pointer_cast(const bptr<Bar>&) noexcept;
 
 namespace {
 
+int A_total = 0, A_alive = 0; // NOLINT
+
+struct A
+{
+    int val, serial;
+    explicit A(int val) : val{val}, serial{++A_total} { ++A_alive; }
+    ~A() noexcept { --A_alive; fm_assert(A_alive >= 0); }
+};
+
 void test1()
 {
+    A_total = 0; A_alive = 0;
+
+    auto p1 = bptr<A>{InPlace, 1};
+    fm_assert(p1.use_count() == 1);
+    fm_assert(p1.get());
+    fm_assert(A_total == 1);
+    fm_assert(A_alive == 1);
+
+    p1 = nullptr;
+    fm_assert(p1.use_count() == 0);
+    fm_assert(!p1.get());
+    fm_assert(A_total == 1);
+    fm_assert(A_alive == 0);
+}
+
+void test2()
+{
+    A_total = 0; A_alive = 0;
+
+    auto p1 = bptr<A>{InPlace, 2};
+    auto p2 = p1;
+
+    fm_assert(p1.get());
+    fm_assert(p1.get() == p2.get());
+    fm_assert(p1->val == 2);
+    fm_assert(p1->serial == 1);
+    fm_assert(A_total == 1);
+    fm_assert(A_alive == 1);
+
+    p1 = nullptr;
+    fm_assert(!p1.get());
+    fm_assert(p2.get());
+    fm_assert(p2->val == 2);
+    fm_assert(p2->serial == 1);
+    fm_assert(A_total == 1);
+    fm_assert(A_alive == 1);
+
+    p2 = nullptr;
+    fm_assert(!p1.get());
+    fm_assert(!p2.get());
+    fm_assert(A_total == 1);
+    fm_assert(A_alive == 0);
 }
 
 } // namespace
@@ -48,6 +99,7 @@ void test1()
 void test_app::test_bptr()
 {
     test1();
+    test2();
 }
 
 } // namespace floormat
-- 
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