109 lines
3.3 KiB
C
109 lines
3.3 KiB
C
|
// Copyright (c) 2011 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.
|
||
|
|
|
||
|
|
#ifndef BASE_TEMPLATE_UTIL_H_
|
||
|
|
#define BASE_TEMPLATE_UTIL_H_
|
||
|
|
|
||
|
|
#include <cstddef> // For size_t.
|
||
|
|
|
||
|
|
#include "build/build_config.h"
|
||
|
|
|
||
|
|
namespace base {
|
||
|
|
|
||
|
|
// template definitions from tr1
|
||
|
|
|
||
|
|
template<class T, T v>
|
||
|
|
struct integral_constant {
|
||
|
|
static const T value = v;
|
||
|
|
typedef T value_type;
|
||
|
|
typedef integral_constant<T, v> type;
|
||
|
|
};
|
||
|
|
|
||
|
|
template <class T, T v> const T integral_constant<T, v>::value;
|
||
|
|
|
||
|
|
typedef integral_constant<bool, true> true_type;
|
||
|
|
typedef integral_constant<bool, false> false_type;
|
||
|
|
|
||
|
|
template <class T> struct is_pointer : false_type {};
|
||
|
|
template <class T> struct is_pointer<T*> : true_type {};
|
||
|
|
|
||
|
|
template <class T, class U> struct is_same : public false_type {};
|
||
|
|
template <class T> struct is_same<T,T> : true_type {};
|
||
|
|
|
||
|
|
template<class> struct is_array : public false_type {};
|
||
|
|
template<class T, size_t n> struct is_array<T[n]> : public true_type {};
|
||
|
|
template<class T> struct is_array<T[]> : public true_type {};
|
||
|
|
|
||
|
|
template <class T> struct is_non_const_reference : false_type {};
|
||
|
|
template <class T> struct is_non_const_reference<T&> : true_type {};
|
||
|
|
template <class T> struct is_non_const_reference<const T&> : false_type {};
|
||
|
|
|
||
|
|
template <class T> struct is_void : false_type {};
|
||
|
|
template <> struct is_void<void> : true_type {};
|
||
|
|
|
||
|
|
namespace internal {
|
||
|
|
|
||
|
|
// Types YesType and NoType are guaranteed such that sizeof(YesType) <
|
||
|
|
// sizeof(NoType).
|
||
|
|
typedef char YesType;
|
||
|
|
|
||
|
|
struct NoType {
|
||
|
|
YesType dummy[2];
|
||
|
|
};
|
||
|
|
|
||
|
|
// 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.
|
||
|
|
|
||
|
|
struct ConvertHelper {
|
||
|
|
template <typename To>
|
||
|
|
static YesType Test(To);
|
||
|
|
|
||
|
|
template <typename To>
|
||
|
|
static NoType Test(...);
|
||
|
|
|
||
|
|
template <typename From>
|
||
|
|
static From& Create();
|
||
|
|
};
|
||
|
|
|
||
|
|
// Used to determine if a type is a struct/union/class. Inspired by Boost's
|
||
|
|
// is_class type_trait implementation.
|
||
|
|
struct IsClassHelper {
|
||
|
|
template <typename C>
|
||
|
|
static YesType Test(void(C::*)(void));
|
||
|
|
|
||
|
|
template <typename C>
|
||
|
|
static NoType Test(...);
|
||
|
|
};
|
||
|
|
|
||
|
|
} // namespace internal
|
||
|
|
|
||
|
|
// Inherits from true_type if From is convertible to To, false_type otherwise.
|
||
|
|
//
|
||
|
|
// Note that if the type is convertible, this will be a true_type REGARDLESS
|
||
|
|
// of whether or not the conversion would emit a warning.
|
||
|
|
template <typename From, typename To>
|
||
|
|
struct is_convertible
|
||
|
|
: integral_constant<bool,
|
||
|
|
sizeof(internal::ConvertHelper::Test<To>(
|
||
|
|
internal::ConvertHelper::Create<From>())) ==
|
||
|
|
sizeof(internal::YesType)> {
|
||
|
|
};
|
||
|
|
|
||
|
|
template <typename T>
|
||
|
|
struct is_class
|
||
|
|
: integral_constant<bool,
|
||
|
|
sizeof(internal::IsClassHelper::Test<T>(0)) ==
|
||
|
|
sizeof(internal::YesType)> {
|
||
|
|
};
|
||
|
|
|
||
|
|
} // namespace base
|
||
|
|
|
||
|
|
#endif // BASE_TEMPLATE_UTIL_H_
|