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Diffstat (limited to 'boost/container/uses_allocator.hpp')
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diff --git a/boost/container/uses_allocator.hpp b/boost/container/uses_allocator.hpp new file mode 100644 index 0000000000..2bcc465890 --- /dev/null +++ b/boost/container/uses_allocator.hpp @@ -0,0 +1,169 @@ +////////////////////////////////////////////////////////////////////////////// +// +// (C) Copyright Ion Gaztanaga 2011-2013. Distributed under the Boost +// Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) +// +// See http://www.boost.org/libs/container for documentation. +// +////////////////////////////////////////////////////////////////////////////// + +#ifndef BOOST_CONTAINER_USES_ALLOCATOR_HPP +#define BOOST_CONTAINER_USES_ALLOCATOR_HPP + +#include <boost/container/uses_allocator_fwd.hpp> +#include <boost/container/detail/type_traits.hpp> + +namespace boost { +namespace container { + +//! <b>Remark</b>: if a specialization constructible_with_allocator_suffix<X>::value is true, indicates that T may be constructed +//! with an allocator as its last constructor argument. Ideally, all constructors of T (including the +//! copy and move constructors) should have a variant that accepts a final argument of +//! allocator_type. +//! +//! <b>Requires</b>: if a specialization constructible_with_allocator_suffix<X>::value is true, T must have a nested type, +//! allocator_type and at least one constructor for which allocator_type is the last +//! parameter. If not all constructors of T can be called with a final allocator_type argument, +//! and if T is used in a context where a container must call such a constructor, then the program is +//! ill-formed. +//! +//! <code> +//! template <class T, class Allocator = allocator<T> > +//! class Z { +//! public: +//! typedef Allocator allocator_type; +//! +//! // Default constructor with optional allocator suffix +//! Z(const allocator_type& a = allocator_type()); +//! +//! // Copy constructor and allocator-extended copy constructor +//! Z(const Z& zz); +//! Z(const Z& zz, const allocator_type& a); +//! }; +//! +//! // Specialize trait for class template Z +//! template <class T, class Allocator = allocator<T> > +//! struct constructible_with_allocator_suffix<Z<T,Allocator> > +//! { static const bool value = true; }; +//! </code> +//! +//! <b>Note</b>: This trait is a workaround inspired by "N2554: The Scoped A Model (Rev 2)" +//! (Pablo Halpern, 2008-02-29) to backport the scoped allocator model to C++03, as +//! in C++03 there is no mechanism to detect if a type can be constructed from arbitrary arguments. +//! Applications aiming portability with several compilers should always define this trait. +//! +//! In conforming C++11 compilers or compilers supporting SFINAE expressions +//! (when BOOST_NO_SFINAE_EXPR is NOT defined), this trait is ignored and C++11 rules will be used +//! to detect if a type should be constructed with suffix or prefix allocator arguments. +template <class T> +struct constructible_with_allocator_suffix +{ static const bool value = false; }; + +//! <b>Remark</b>: if a specialization constructible_with_allocator_prefix<X>::value is true, indicates that T may be constructed +//! with allocator_arg and T::allocator_type as its first two constructor arguments. +//! Ideally, all constructors of T (including the copy and move constructors) should have a variant +//! that accepts these two initial arguments. +//! +//! <b>Requires</b>: specialization constructible_with_allocator_prefix<X>::value is true, T must have a nested type, +//! allocator_type and at least one constructor for which allocator_arg_t is the first +//! parameter and allocator_type is the second parameter. If not all constructors of T can be +//! called with these initial arguments, and if T is used in a context where a container must call such +//! a constructor, then the program is ill-formed. +//! +//! <code> +//! template <class T, class Allocator = allocator<T> > +//! class Y { +//! public: +//! typedef Allocator allocator_type; +//! +//! // Default constructor with and allocator-extended default constructor +//! Y(); +//! Y(allocator_arg_t, const allocator_type& a); +//! +//! // Copy constructor and allocator-extended copy constructor +//! Y(const Y& yy); +//! Y(allocator_arg_t, const allocator_type& a, const Y& yy); +//! +//! // Variadic constructor and allocator-extended variadic constructor +//! template<class ...Args> Y(Args&& args...); +//! template<class ...Args> +//! Y(allocator_arg_t, const allocator_type& a, BOOST_FWD_REF(Args)... args); +//! }; +//! +//! // Specialize trait for class template Y +//! template <class T, class Allocator = allocator<T> > +//! struct constructible_with_allocator_prefix<Y<T,Allocator> > +//! { static const bool value = true; }; +//! +//! </code> +//! +//! <b>Note</b>: This trait is a workaround inspired by "N2554: The Scoped Allocator Model (Rev 2)" +//! (Pablo Halpern, 2008-02-29) to backport the scoped allocator model to C++03, as +//! in C++03 there is no mechanism to detect if a type can be constructed from arbitrary arguments. +//! Applications aiming portability with several compilers should always define this trait. +//! +//! In conforming C++11 compilers or compilers supporting SFINAE expressions +//! (when BOOST_NO_SFINAE_EXPR is NOT defined), this trait is ignored and C++11 rules will be used +//! to detect if a type should be constructed with suffix or prefix allocator arguments. +template <class T> +struct constructible_with_allocator_prefix +{ static const bool value = false; }; + +#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED + +namespace container_detail { + +template<typename T, typename Allocator> +struct uses_allocator_imp +{ + // Use SFINAE (Substitution Failure Is Not An Error) to detect the + // presence of an 'allocator_type' nested type convertilble from Allocator. + private: + typedef char yes_type; + struct no_type{ char dummy[2]; }; + + // Match this function if T::allocator_type exists and is + // implicitly convertible from Allocator + template <class U> + static yes_type test(typename U::allocator_type); + + // Match this function if T::allocator_type exists and it's type is `erased_type`. + template <class U, class V> + static typename container_detail::enable_if + < container_detail::is_same<typename U::allocator_type, erased_type> + , yes_type + >::type test(const V&); + + // Match this function if TypeT::allocator_type does not exist or is + // not convertible from Allocator. + template <typename U> + static no_type test(...); + static Allocator alloc; // Declared but not defined + + public: + static const bool value = sizeof(test<T>(alloc)) == sizeof(yes_type); +}; + +} //namespace container_detail { + +#endif //#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED + +//! <b>Remark</b>: Automatically detects whether T has a nested allocator_type that is convertible from +//! Allocator. Meets the BinaryTypeTrait requirements ([meta.rqmts] 20.4.1). A program may +//! specialize this type to define uses_allocator<X>::value as true for a T of user-defined type if T does not +//! have a nested allocator_type but is nonetheless constructible using the specified Allocator where either: +//! the first argument of a constructor has type allocator_arg_t and the second argument has type Alloc or +//! the last argument of a constructor has type Alloc. +//! +//! <b>Result</b>: uses_allocator<T, Allocator>::value== true if a type T::allocator_type +//! exists and either is_convertible<Alloc, T::allocator_type>::value != false or T::allocator_type +//! is an alias `erased_type`. False otherwise. +template <typename T, typename Allocator> +struct uses_allocator + : container_detail::uses_allocator_imp<T, Allocator> +{}; + +}} //namespace boost::container + +#endif //BOOST_CONTAINER_USES_ALLOCATOR_HPP |