1 /* Copyright 2006-2008 Joaquin M Lopez Munoz.
2  * Distributed under the Boost Software License, Version 1.0.
3  * (See accompanying file LICENSE_1_0.txt or copy at
4  * http://www.boost.org/LICENSE_1_0.txt)
5  *
6  * See http://www.boost.org/libs/flyweight for library home page.
7  */
8 
9 #ifndef BOOST_FLYWEIGHT_LOCKING_TAG_HPP
10 #define BOOST_FLYWEIGHT_LOCKING_TAG_HPP
11 
12 #if defined(_MSC_VER)&&(_MSC_VER>=1200)
13 #pragma once
14 #endif
15 
16 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
17 #include <boost/parameter/parameters.hpp>
18 #include <boost/type_traits/is_base_and_derived.hpp>
19 
20 namespace boost{
21 
22 namespace flyweights{
23 
24 /* Three ways to indicate that a given class T is a locking policy:
25  *   1. Make it derived from locking_marker.
26  *   2. Specialize is_locking to evaluate to boost::mpl::true_.
27  *   3. Pass it as locking<T> when defining a flyweight type.
28  */
29 
30 struct locking_marker{};
31 
32 template<typename T>
33 struct is_locking:is_base_and_derived<locking_marker,T>
34 {};
35 
36 template<typename T=parameter::void_>
37 struct locking:parameter::template_keyword<locking<>,T>
38 {};
39 
40 } /* namespace flyweights */
41 
42 } /* namespace boost */
43 
44 #endif
45