unique_resource, The General RAII Wrapper for Exclusive Ownership Resource Management.

This is an unique_resource implementation with Boost Software License 1.0. This implementation is based on example implementation in the C++ Standards Committee Paper N4189.

What is unique_resource

unique_resource is a generalization of std::unique_ptr. std::unique_ptr can be instantiated only by pointer like types. unique_resource does not have such limitation and, normally, works with a user's customized deleter.

Installation

Put unique_resource.hpp into your including directory.

Sample Usage

#include <iostream>
#include "unique_resource.hpp"

// some dummy resource functions
using handle_t = int;
decltype(auto) GenHandle(handle_t i) { return i; }
decltype(auto) ReleaseHandle(handle_t handle) {
	std::cout << "release handle " << handle << std::endl;
}

decltype(auto) make_unique_handle(handle_t i) {
	return std_experimental::make_unique_resource(
		GenHandle(i), &ReleaseHandle);
}
int main() {
	auto handle1 = make_unique_handle(1);
	{
		auto handle2 = make_unique_handle(2);
		std::cout << handle2.get() << std::endl; // raw handle access by get()
		// here, handle2 is released.
	}
	auto handle3 = make_unique_handle(3);
	handle3.reset(); // release handle explicitly
	{
		auto handle4 = make_unique_handle(4);
		auto raw_handle4 = handle4.release(); // strip RAII wrapper
		ReleaseHandle(raw_handle4); // now, we should release handle by hand.
	}
	{
		auto handle5 = make_unique_handle(5);
		auto handle6 = std::move(handle5); // move construct
		handle6.reset(GenHandle(6)); // reset raw handle
	}

	std::cout << "Bye!" << std::endl;
}

output

2
release handle 2
release handle 3
release handle 4
release handle 5
release handle 6
Bye!
release handle 1

The detailed documentation is on 7.4.1 of N4189.

Testing

cd test
make

This tests using both C++11 and C++14. Note that not all tests can run on C++11.

What is different from the example implementation in N4189

• License The original codes have no license to use. This implementation has Boost Software License 1.0 (thanks Sandval and Sommerlad for the consent).

• Namespace The original codes are included in namespace "std::experimental", but adding any user codes into namespace "std" or nested namespaces of it cause undefined behavior. So in this implementation, the namespace is changed from "std::experimental" to "std_experimental".

• Some codes for C++11 Using features of C++14, the original codes do not work under C++11. This implementation works under C++11 (and, of course, under C++14 or later).

• Workaround for GCC Because of the bug of GCC, the original codes cause compilation error with GCC. This implementation contains the workaround about the bug and works fine with GCC.

• Test codes The original implementation has test codes but they uses external libraries except standard libraries. This implementation also has test codes but they do not use such libraries except standard ones.