使用c++11的function包装dll

DllHelper.h

#pragma once

#include <string>
#include <map>
#include <functional>

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>


namespace C0xHelper
{
	class DllHelper
	{
	public:
		DllHelper() :dllModule_(nullptr) 
		{}

		~DllHelper()
		{
			Unload();
		}

		bool Load(const std::wstring& dllPath)
		{
			dllModule_ = ::LoadLibraryW(dllPath.c_str());
			return dllModule_ != nullptr;
		}

		bool Unload()
		{
			if (!dllModule_)
			{
				return true;
			}

			if (!::FreeLibrary(dllModule_))
			{
				return false;
			}

			dllModule_ = nullptr;
			return true;
		}

		template<typename T>
		std::function<T> GetFunction(const std::string& funcName)
		{
			auto itFunc = funcMap_.find(funcName);
			if (itFunc != funcMap_.end())
			{
				return std::function<T>(reinterpret_cast<T*>(itFunc->second));
			}

			auto funcAddr = ::GetProcAddress(dllModule_, funcName.c_str());
			if (!funcAddr)
			{
				return nullptr;
			}

			funcMap_.insert(std::make_pair(funcName, funcAddr));

			return std::function<T>(reinterpret_cast<T*>(funcAddr));
		}

		template<typename T, typename... Args>
		typename std::result_of<std::function<T>(Args...)>::type 
			CallFunction(const std::string& funcName, Args&&... args)
		{
			auto func = GetFunction<T>(funcName);
			if (!func)
			{
				throw std::logic_error(funcName.c_str());
			}
			return func(std::forward<Args>(args)...);
		}

	private:
		HMODULE dllModule_;
		std::map<std::string, FARPROC> funcMap_;
	};
}