Add helper to Decompose a member pointer

4 files changed, 40 insertions, 1 deletions

diff --git a/lib/util.cpp b/lib/util.cpp
deleted file mode 100644
index 408a76a..0000000
--- a/lib/util.cpp
+++ /dev/null
@@ -1 +0,0 @@
-#include "util.h"
diff --git a/lib/util.h b/lib/util.h
index b60b093..093462d 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -35,6 +35,16 @@ inline constexpr auto GetFirst = Nth<0>;
 inline constexpr auto GetSecond = Nth<1>;
 inline constexpr auto GetSwapped = Nth<0, 1>;
 
+template<typename T, typename M> struct Decompose {
+	consteval Decompose(M T::*) { }
+
+	using ValueType = M;
+	using ContainerType = T;
+};
+
+template<auto MbrPtr> using MemberValueType = typename decltype(Decompose {MbrPtr})::ValueType;
+template<auto MbrPtr> using ContainerType = typename decltype(Decompose {MbrPtr})::ContainerType;
+
 template<typename T>
 bool
 createIfRequired(std::shared_ptr<T> & instance, std::weak_ptr<T> & common)
diff --git a/test/Jamfile.jam b/test/Jamfile.jam
index da2a61a..baf0db4 100644
--- a/test/Jamfile.jam
+++ b/test/Jamfile.jam
@@ -79,5 +79,6 @@ run test-environment.cpp : : : <library>test ;
 run test-ui.cpp : : : <library>test ;
 compile test-static-enumDetails.cpp ;
 compile test-static-stream_support.cpp ;
+compile test-static-util.cpp ;
 alias perf : perf-assetFactory perf-persistence perf-geoData perf-instancing perf-terrain ;
 explicit perf ;
diff --git a/test/test-static-util.cpp b/test/test-static-util.cpp
new file mode 100644
index 0000000..2a8aa81
--- /dev/null
+++ b/test/test-static-util.cpp
@@ -0,0 +1,29 @@
+#include "util.h"
+
+namespace {
+	struct Base1 {
+		int a;
+		float b;
+	};
+
+	struct Base2 {
+		int x;
+		float y;
+	};
+
+	struct Sub : Base1, Base2 {
+		double value;
+	};
+
+	static_assert(std::is_same_v<MemberValueType<&Base1::a>, int>);
+	static_assert(std::is_same_v<MemberValueType<&Base2::y>, float>);
+	static_assert(std::is_same_v<MemberValueType<&Sub::a>, int>);
+	static_assert(std::is_same_v<MemberValueType<&Sub::y>, float>);
+	static_assert(std::is_same_v<MemberValueType<&Sub::value>, double>);
+
+	static_assert(std::is_same_v<ContainerType<&Base1::a>, Base1>);
+	static_assert(std::is_same_v<ContainerType<&Base2::y>, Base2>);
+	static_assert(std::is_same_v<ContainerType<&Sub::a>, Base1>);
+	static_assert(std::is_same_v<ContainerType<&Sub::y>, Base2>);
+	static_assert(std::is_same_v<ContainerType<&Sub::value>, Sub>);
+}