// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This code is compiled directly on many platforms, including client
// platforms like Windows, Mac, and embedded systems. Before making
// any changes here, make sure that you're not breaking any platforms.
//
//
// Define a small subset of tr1 type traits. The traits we define are:
// is_integral
// is_floating_point
// is_pointer
// is_reference
// is_pod
// has_trivial_constructor
// has_trivial_copy
// has_trivial_assign
// has_trivial_destructor
// remove_const
// remove_volatile
// remove_cv
// remove_reference
// remove_pointer
// is_convertible
// We can add more type traits as required.
#ifndef BASE_TYPE_TRAITS_H_
#define BASE_TYPE_TRAITS_H_
#include "base/template_util.h" // For true_type and false_type
#include <utility> // For pair
namespace base {
// is_integral is false except for the built-in integer types.
template <class T> struct is_integral : false_type { };
template<> struct is_integral<bool> : true_type { };
template<> struct is_integral<char> : true_type { };
template<> struct is_integral<unsigned char> : true_type { };
template<> struct is_integral<signed char> : true_type { };
#if defined(_MSC_VER)
// wchar_t is not by default a distinct type from unsigned short in
// Microsoft C.
// See http://msdn2.microsoft.com/en-us/library/dh8che7s(VS.80).aspx
template<> struct is_integral<__wchar_t> : true_type { };
#else
template<> struct is_integral<wchar_t> : true_type { };
#endif
template<> struct is_integral<short> : true_type { };
template<> struct is_integral<unsigned short> : true_type { };
template<> struct is_integral<int> : true_type { };
template<> struct is_integral<unsigned int> : true_type { };
template<> struct is_integral<long> : true_type { };
template<> struct is_integral<unsigned long> : true_type { };
template<> struct is_integral<long long> : true_type { };
template<> struct is_integral<unsigned long long> : true_type { };
// is_floating_point is false except for the built-in floating-point types.
template <class T> struct is_floating_point : false_type { };
template<> struct is_floating_point<float> : true_type { };
template<> struct is_floating_point<double> : true_type { };
template<> struct is_floating_point<long double> : true_type { };
// is_pointer is false except for pointer types.
template <class T> struct is_pointer : false_type { };
template <class T> struct is_pointer<T*> : true_type { };
// is_reference is false except for reference types.
template<typename T> struct is_reference : false_type {};
template<typename T> struct is_reference<T&> : true_type {};
// We can't get is_pod right without compiler help, so fail conservatively.
// We will assume it's false except for arithmetic types and pointers,
// and const versions thereof. Note that std::pair is not a POD.
template <class T> struct is_pod
: integral_constant<bool, (is_integral<T>::value ||
is_floating_point<T>::value ||
is_pointer<T>::value)> { };
template <class T> struct is_pod<const T> : is_pod<T> { };
// We can't get has_trivial_constructor right without compiler help, so
// fail conservatively. We will assume it's false except for: (1) types
// for which is_pod is true. (2) std::pair of types with trivial
// constructors. (3) array of a type with a trivial constructor.
// (4) const versions thereof.
template <class T> struct has_trivial_constructor : is_pod<T> { };
template <class T, class U> struct has_trivial_constructor<std::pair<T, U> >
: integral_constant<bool,
(has_trivial_constructor<T>::value &&
has_trivial_constructor<U>::value)> { };
template <class A, int N> struct has_trivial_constructor<A[N]>
: has_trivial_constructor<A> { };
template <class T> struct has_trivial_constructor<const T>
: has_trivial_constructor<T> { };
// We can't get has_trivial_copy right without compiler help, so fail
// conservatively. We will assume it's false except for: (1) types
// for which is_pod is true. (2) std::pair of types with trivial copy
// constructors. (3) array of a type with a trivial copy constructor.
// (4) const versions thereof.
template <class T> struct has_trivial_copy : is_pod<T> { };
template <class T, class U> struct has_trivial_copy<std::pair<T, U> >
: integral_constant<bool,
(has_trivial_copy<T>::value &&
has_trivial_copy<U>::value)> { };
template <class A, int N> struct has_trivial_copy<A[N]>
: has_trivial_copy<A> { };
template <class T> struct has_trivial_copy<const T> : has_trivial_copy<T> { };
// We can't get has_trivial_assign right without compiler help, so fail
// conservatively. We will assume it's false except for: (1) types
// for which is_pod is true. (2) std::pair of types with trivial copy
// constructors. (3) array of a type with a trivial assign constructor.
template <class T> struct has_trivial_assign : is_pod<T> { };
template <class T, class U> struct has_trivial_assign<std::pair<T, U> >
: integral_constant<bool,
(has_trivial_assign<T>::value &&
has_trivial_assign<U>::value)> { };
template <class A, int N> struct has_trivial_assign<A[N]>
: has_trivial_assign<A> { };
// We can't get has_trivial_destructor right without compiler help, so
// fail conservatively. We will assume it's false except for: (1) types
// for which is_pod is true. (2) std::pair of types with trivial
// destructors. (3) array of a type with a trivial destructor.
// (4) const versions thereof.
template <class T> struct has_trivial_destructor : is_pod<T> { };
template <class T, class U> struct has_trivial_destructor<std::pair<T, U> >
: integral_constant<bool,
(has_trivial_destructor<T>::value &&
has_trivial_destructor<U>::value)> { };
template <class A, int N> struct has_trivial_destructor<A[N]>
: has_trivial_destructor<A> { };
template <class T> struct has_trivial_destructor<const T>
: has_trivial_destructor<T> { };
// Specified by TR1 [4.7.1]
template<typename T> struct remove_const { typedef T type; };
template<typename T> struct remove_const<T const> { typedef T type; };
template<typename T> struct remove_volatile { typedef T type; };
template<typename T> struct remove_volatile<T volatile> { typedef T type; };
template<typename T> struct remove_cv {
typedef typename remove_const<typename remove_volatile<T>::type>::type type;
};
// Specified by TR1 [4.7.2]
template<typename T> struct remove_reference { typedef T type; };
template<typename T> struct remove_reference<T&> { typedef T type; };
// Specified by TR1 [4.7.4] Pointer modifications.
template<typename T> struct remove_pointer { typedef T type; };
template<typename T> struct remove_pointer<T*> { typedef T type; };
template<typename T> struct remove_pointer<T* const> { typedef T type; };
template<typename T> struct remove_pointer<T* volatile> { typedef T type; };
template<typename T> struct remove_pointer<T* const volatile> {
typedef T type; };
// Specified by TR1 [4.6] Relationships between types
#ifndef _MSC_VER
namespace internal {
// This class is an implementation detail for is_convertible, and you
// don't need to know how it works to use is_convertible. For those
// who care: we declare two different functions, one whose argument is
// of type To and one with a variadic argument list. We give them
// return types of different size, so we can use sizeof to trick the
// compiler into telling us which function it would have chosen if we
// had called it with an argument of type From. See Alexandrescu's
// _Modern C++ Design_ for more details on this sort of trick.
template <typename From, typename To>
struct ConvertHelper {
static small_ Test(To);
static big_ Test(...);
static From Create();
};
} // namespace internal
// Inherits from true_type if From is convertible to To, false_type otherwise.
template <typename From, typename To>
struct is_convertible
: integral_constant<bool,
sizeof(internal::ConvertHelper<From, To>::Test(
internal::ConvertHelper<From, To>::Create()))
== sizeof(small_)> {
};
#endif
} // Close namespace base
#endif // BASE_TYPE_TRAITS_H_