memory: add sanitizing_allocator and sanitizing_blob

Signed-off-by: Simon Rozman <simon@rozman.si>

include/stdex/memory.hpp

@@ -50,4 +50,88 @@ namespace stdex
 	{
 		return std::shared_ptr<T>(p, no_delete<T>{});
 	}
+
+	// sanitizing_allocator::destroy() member generates p parameter not used warning for primitive datatypes T.
+	#pragma warning(push)
+	#pragma warning(disable: 4100)
+
+	///
+	/// An allocator template that sanitizes each memory block before it is destroyed or reallocated
+	///
+	/// \note
+	/// `sanitizing_allocator` introduces a performance penalty. However, it provides an additional level of security.
+	/// Use for security sensitive data memory storage only.
+	///
+	template <class T>
+	class sanitizing_allocator : public std::allocator<T>
+	{
+	public:
+		///
+		/// Convert this type to sanitizing_allocator<T2>
+		///
+		template <class T2>
+		struct rebind
+		{
+			typedef sanitizing_allocator<T2> other; ///< Other type
+		};
+
+		///
+		/// Construct default allocator
+		///
+		sanitizing_allocator() noexcept : std::allocator<T>()
+		{}
+
+		///
+		/// Construct by copying
+		///
+		sanitizing_allocator(_In_ const sanitizing_allocator<T> &other) : std::allocator<T>(other)
+		{}
+
+		///
+		/// Construct from a related allocator
+		///
+		template <class T2>
+		sanitizing_allocator(_In_ const sanitizing_allocator<T2> &other) noexcept : std::allocator<T>(other)
+		{}
+
+		///
+		/// Deallocate object at p sanitizing its content first
+		///
+		void deallocate(_In_ T* const p, _In_ const std::size_t n)
+		{
+#ifdef _WIN32
+			SecureZeroMemory(p, sizeof(T) * n);
+#else
+			memset(p, 0, sizeof(T) * n);
+#endif
+			std::allocator<T>::deallocate(p, n);
+		}
+	};
+
+	#pragma warning(pop)
+
+	///
+	/// Sanitizing BLOB
+	///
+	template <size_t N>
+	class sanitizing_blob
+	{
+	public:
+		sanitizing_blob()
+		{
+			memset(m_data, 0, N);
+		}
+
+		~sanitizing_blob()
+		{
+#ifdef _WIN32
+			SecureZeroMemory(m_data, N);
+#else
+			memset(m_data, 0, N);
+#endif
+		}
+
+	public:
+		unsigned char m_data[N]; ///< BLOB data
+	};
 }