1 files changed, 49 insertions, 0 deletions
diff --git a/compat/borrowed-ptr.hpp b/compat/borrowed-ptr.hpp
new file mode 100644
index 00000000..f649cae3
--- /dev/null
+++ b/compat/borrowed-ptr.hpp
@@ -0,0 +1,49 @@
+#pragma once
+
+namespace floormat::detail_borrowed_ptr {
+struct control_block_;
+} // namespace floormat::detail_borrowed_ptr
+
+namespace floormat {
+template<typename T> class bptr;
+template<typename T> bptr<T> static_pointer_cast(const bptr<T>& p);
+
+template<typename T>
+class bptr final // NOLINT(*-special-member-functions)
+{
+    T* ptr; // todo add simple_bptr that doesn't allow casting. should only have the control block element.
+    detail_borrowed_ptr::control_block_* blk;
+
+    friend bptr<T> static_pointer_cast<T>(const bptr<T>& p);
+
+public:
+    template<typename... Ts>
+    requires std::is_constructible_v<T, Ts&&...>
+    explicit bptr(InPlaceInitT, Ts&&... args) noexcept;
+
+    constexpr bptr(std::nullptr_t) noexcept; // NOLINT(*-explicit-conversions)
+    constexpr bptr() noexcept;
+    explicit bptr(T* ptr) noexcept;
+    ~bptr() 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(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& operator=(bptr<Y>&&) noexcept;
+
+    void swap() noexcept;
+    T* get() noexcept;
+    const T* get() const noexcept;
+    T& operator*() const noexcept;
+    T* operator->() const noexcept;
+    uint32_t use_count() const noexcept;
+    explicit operator bool() const noexcept;
+};
+
+template<typename T> constexpr bptr<T>::bptr(std::nullptr_t) noexcept: ptr{nullptr}, blk{nullptr} {}
+template<typename T> constexpr bptr<T>::bptr() noexcept: bptr{nullptr} {}
+
+
+template<typename T> bptr(T* ptr) -> bptr<T>;
+
+} // namespace floormat