C++/CLI implementation of SafeBuffer class that wraps std::unique_ptr<const char*>. This allows for creation of UnmanagedMemoryStream and saves copying of data between the native and managed sides. I still need to figure out how to handle custom deleters.

cpp_safe_buffer.cpp

    ref class CppSafeBuffer : public ::System::Runtime::InteropServices::SafeBuffer
    {
    private:
        // TODO: Figure out how to handle a custom deleter
        //std::unique_ptr<const char*>::deleter_type _deleter;

    public:
        CppSafeBuffer(std::unique_ptr<const char*> && bytes,
                      const std::size_t size)
            : ::System::Runtime::InteropServices::SafeBuffer(true)
        {
            //_deleter = bytes.get_deleter();
            SetHandle( IntPtr(bytes.release()) );
            Initialize(size);
        }

    protected:
        virtual bool ReleaseHandle() override
        {
            const char* ptr = (const char*) handle.ToPointer();
            //TODO: Figure out how to handle deleters: _deleter(ptr);
            delete ptr;

            SetHandleAsInvalid();
            return true;
        }
    };

    void sampleUsage( std::unique_ptr<const char*> && msg, const std::size_t msgSize )
    {
        using namespace ::System;
        using namespace ::System::IO;

        auto memStream = gcnew UnmanagedMemoryStream(
            gcnew CppSafeBuffer(std::move(msg), msgSize),
            0,
            msgSize,
            FileAccess::Read);

        ::System::Console::WriteLine(memStream->Position);
    }