1 files changed, 149 insertions, 0 deletions
diff --git a/lib/base/functionwrapper.hpp b/lib/base/functionwrapper.hpp
new file mode 100644
index 0000000..57cf1cb
--- /dev/null
+++ b/lib/base/functionwrapper.hpp
@@ -0,0 +1,149 @@
+/* Icinga 2 | (c) 2012 Icinga GmbH | GPLv2+ */
+
+#ifndef FUNCTIONWRAPPER_H
+#define FUNCTIONWRAPPER_H
+
+#include "base/i2-base.hpp"
+#include "base/value.hpp"
+#include <boost/function_types/function_type.hpp>
+#include <boost/function_types/parameter_types.hpp>
+#include <boost/function_types/result_type.hpp>
+#include <boost/function_types/function_arity.hpp>
+#include <vector>
+
+namespace icinga
+{
+
+template<typename FuncType>
+typename std::enable_if<
+    std::is_class<FuncType>::value &&
+    std::is_same<typename boost::function_types::result_type<decltype(&FuncType::operator())>::type, Value>::value &&
+	boost::function_types::function_arity<decltype(&FuncType::operator())>::value == 2,
+    std::function<Value (const std::vector<Value>&)>>::type
+WrapFunction(FuncType function)
+{
+	static_assert(std::is_same<typename boost::mpl::at_c<typename boost::function_types::parameter_types<decltype(&FuncType::operator())>, 1>::type, const std::vector<Value>&>::value, "Argument type must be const std::vector<Value>");
+	return function;
+}
+
+inline std::function<Value (const std::vector<Value>&)> WrapFunction(void (*function)(const std::vector<Value>&))
+{
+	return [function](const std::vector<Value>& arguments) {
+		function(arguments);
+		return Empty;
+	};
+}
+
+template<typename Return>
+std::function<Value (const std::vector<Value>&)> WrapFunction(Return (*function)(const std::vector<Value>&))
+{
+	return [function](const std::vector<Value>& values) -> Value { return function(values); };
+}
+
+template <std::size_t... Indices>
+struct indices {
+	using next = indices<Indices..., sizeof...(Indices)>;
+};
+
+template <std::size_t N>
+struct build_indices {
+	using type = typename build_indices<N-1>::type::next;
+};
+
+template <>
+struct build_indices<0> {
+	using type = indices<>;
+};
+
+template <std::size_t N>
+using BuildIndices = typename build_indices<N>::type;
+
+struct UnpackCaller
+{
+private:
+	template <typename FuncType, size_t... I>
+	auto Invoke(FuncType f, const std::vector<Value>& args, indices<I...>) -> decltype(f(args[I]...))
+	{
+		return f(args[I]...);
+	}
+
+public:
+	template <typename FuncType, int Arity>
+	auto operator() (FuncType f, const std::vector<Value>& args) -> decltype(Invoke(f, args, BuildIndices<Arity>{}))
+	{
+		return Invoke(f, args, BuildIndices<Arity>{});
+	}
+};
+
+template<typename FuncType, int Arity, typename ReturnType>
+struct FunctionWrapper
+{
+	static Value Invoke(FuncType function, const std::vector<Value>& arguments)
+	{
+		return UnpackCaller().operator()<FuncType, Arity>(function, arguments);
+	}
+};
+
+template<typename FuncType, int Arity>
+struct FunctionWrapper<FuncType, Arity, void>
+{
+	static Value Invoke(FuncType function, const std::vector<Value>& arguments)
+	{
+		UnpackCaller().operator()<FuncType, Arity>(function, arguments);
+		return Empty;
+	}
+};
+
+template<typename FuncType>
+typename std::enable_if<
+	std::is_function<typename std::remove_pointer<FuncType>::type>::value && !std::is_same<FuncType, Value(*)(const std::vector<Value>&)>::value,
+	std::function<Value (const std::vector<Value>&)>>::type
+WrapFunction(FuncType function)
+{
+	return [function](const std::vector<Value>& arguments) {
+		constexpr size_t arity = boost::function_types::function_arity<typename std::remove_pointer<FuncType>::type>::value;
+
+		if (arity > 0) {
+			if (arguments.size() < arity)
+				BOOST_THROW_EXCEPTION(std::invalid_argument("Too few arguments for function."));
+			else if (arguments.size() > arity)
+				BOOST_THROW_EXCEPTION(std::invalid_argument("Too many arguments for function."));
+		}
+
+		using ReturnType = decltype(UnpackCaller().operator()<FuncType, arity>(*static_cast<FuncType *>(nullptr), std::vector<Value>()));
+
+		return FunctionWrapper<FuncType, arity, ReturnType>::Invoke(function, arguments);
+	};
+}
+
+template<typename FuncType>
+typename std::enable_if<
+    std::is_class<FuncType>::value &&
+    !(std::is_same<typename boost::function_types::result_type<decltype(&FuncType::operator())>::type, Value>::value &&
+	boost::function_types::function_arity<decltype(&FuncType::operator())>::value == 2),
+    std::function<Value (const std::vector<Value>&)>>::type
+WrapFunction(FuncType function)
+{
+	static_assert(!std::is_same<typename boost::mpl::at_c<typename boost::function_types::parameter_types<decltype(&FuncType::operator())>, 1>::type, const std::vector<Value>&>::value, "Argument type must be const std::vector<Value>");
+
+	using FuncTypeInvoker = decltype(&FuncType::operator());
+
+	return [function](const std::vector<Value>& arguments) {
+		constexpr size_t arity = boost::function_types::function_arity<FuncTypeInvoker>::value - 1;
+
+		if (arity > 0) {
+			if (arguments.size() < arity)
+				BOOST_THROW_EXCEPTION(std::invalid_argument("Too few arguments for function."));
+			else if (arguments.size() > arity)
+				BOOST_THROW_EXCEPTION(std::invalid_argument("Too many arguments for function."));
+		}
+
+		using ReturnType = decltype(UnpackCaller().operator()<FuncType, arity>(*static_cast<FuncType *>(nullptr), std::vector<Value>()));
+
+		return FunctionWrapper<FuncType, arity, ReturnType>::Invoke(function, arguments);
+	};
+}
+
+}
+
+#endif /* FUNCTIONWRAPPER_H */