Update ComPtr and use an out_ptr() function

1 files changed, 69 insertions, 26 deletions

diff --git a/common/comptr.h b/common/comptr.h
index cdc6dec0..5a733ea2 100644
--- a/common/comptr.h
+++ b/common/comptr.h
@@ -2,49 +2,46 @@
 #define COMMON_COMPTR_H
 
 #include <cstddef>
+#include <memory>
+#include <type_traits>
 #include <utility>
-
-#include "opthelpers.h"
-
+#include <variant>
 
 template<typename T>
-class ComPtr {
-    T *mPtr{nullptr};
+struct ComPtr {
+    using element_type = T;
+
+    static constexpr bool RefIsNoexcept{noexcept(std::declval<T&>().AddRef())
+        && noexcept(std::declval<T&>().Release())};
 
-public:
     ComPtr() noexcept = default;
-    ComPtr(const ComPtr &rhs) : mPtr{rhs.mPtr} { if(mPtr) mPtr->AddRef(); }
+    ComPtr(const ComPtr &rhs) noexcept(RefIsNoexcept) : mPtr{rhs.mPtr}
+    { if(mPtr) mPtr->AddRef(); }
     ComPtr(ComPtr&& rhs) noexcept : mPtr{rhs.mPtr} { rhs.mPtr = nullptr; }
     ComPtr(std::nullptr_t) noexcept { }
     explicit ComPtr(T *ptr) noexcept : mPtr{ptr} { }
     ~ComPtr() { if(mPtr) mPtr->Release(); }
 
-    ComPtr& operator=(const ComPtr &rhs)
+    ComPtr& operator=(const ComPtr &rhs) noexcept(RefIsNoexcept)
     {
-        if(!rhs.mPtr)
+        if constexpr(RefIsNoexcept)
         {
-            if(mPtr)
-                mPtr->Release();
-            mPtr = nullptr;
+            if(rhs.mPtr) rhs.mPtr->AddRef();
+            if(mPtr) mPtr->Release();
+            mPtr = rhs.mPtr;
+            return *this;
         }
         else
         {
-            rhs.mPtr->AddRef();
-            try {
-                if(mPtr)
-                    mPtr->Release();
-                mPtr = rhs.mPtr;
-            }
-            catch(...) {
-                rhs.mPtr->Release();
-                throw;
-            }
+            ComPtr tmp{rhs};
+            if(mPtr) mPtr->Release();
+            mPtr = tmp.release();
+            return *this;
         }
-        return *this;
     }
-    ComPtr& operator=(ComPtr&& rhs)
+    ComPtr& operator=(ComPtr&& rhs) noexcept(RefIsNoexcept)
     {
-        if(&rhs != this) LIKELY
+        if(&rhs != this)
         {
             if(mPtr) mPtr->Release();
             mPtr = std::exchange(rhs.mPtr, nullptr);
@@ -52,17 +49,63 @@ public:
         return *this;
     }
 
+    void reset(T *ptr=nullptr) noexcept(RefIsNoexcept)
+    {
+        if(mPtr) mPtr->Release();
+        mPtr = ptr;
+    }
+
     explicit operator bool() const noexcept { return mPtr != nullptr; }
 
     T& operator*() const noexcept { return *mPtr; }
     T* operator->() const noexcept { return mPtr; }
     T* get() const noexcept { return mPtr; }
-    T** getPtr() noexcept { return &mPtr; }
 
     T* release() noexcept { return std::exchange(mPtr, nullptr); }
 
     void swap(ComPtr &rhs) noexcept { std::swap(mPtr, rhs.mPtr); }
     void swap(ComPtr&& rhs) noexcept { std::swap(mPtr, rhs.mPtr); }
+
+private:
+    T *mPtr{nullptr};
 };
 
+
+namespace al {
+
+template<typename SP, typename PT, typename ...Args>
+class out_ptr_t {
+    static_assert(!std::is_same_v<PT,void*>);
+
+    SP &mRes;
+    std::variant<PT,void*> mPtr{};
+
+public:
+    out_ptr_t(SP &res) : mRes{res} { }
+    ~out_ptr_t()
+    {
+        auto set_res = [this](auto &ptr)
+        { mRes.reset(static_cast<PT>(ptr)); };
+        std::visit(set_res, mPtr);
+    }
+    out_ptr_t(const out_ptr_t&) = delete;
+
+    out_ptr_t& operator=(const out_ptr_t&) = delete;
+
+    operator PT*() noexcept
+    { return &std::get<PT>(mPtr); }
+
+    operator void**() noexcept
+    { return &mPtr.template emplace<void*>(); }
+};
+
+template<typename T=void, typename SP, typename ...Args>
+auto out_ptr(SP &res)
+{
+    using ptype = typename SP::element_type*;
+    return out_ptr_t<SP,ptype>{res};
+}
+
+} // namespace al
+
 #endif