1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4//
5// The original source code is from:
6// https://code.google.com/p/libphonenumber/source/browse/trunk/cpp/src/phonenumbers/base/template_util.h?r=621
7
8#ifndef I18N_ADDRESSINPUT_UTIL_TEMPLATE_UTIL_H_
9#define I18N_ADDRESSINPUT_UTIL_TEMPLATE_UTIL_H_
10
11#include <cstddef>  // For size_t.
12
13namespace i18n {
14namespace addressinput {
15
16// template definitions from tr1
17
18template<class T, T v>
19struct integral_constant {
20  static const T value = v;
21  typedef T value_type;
22  typedef integral_constant<T, v> type;
23};
24
25template <class T, T v> const T integral_constant<T, v>::value;
26
27typedef integral_constant<bool, true> true_type;
28typedef integral_constant<bool, false> false_type;
29
30template <class T> struct is_pointer : false_type {};
31template <class T> struct is_pointer<T*> : true_type {};
32
33template <class T, class U> struct is_same : public false_type {};
34template <class T> struct is_same<T,T> : true_type {};
35
36template<class> struct is_array : public false_type {};
37template<class T, size_t n> struct is_array<T[n]> : public true_type {};
38template<class T> struct is_array<T[]> : public true_type {};
39
40template <class T> struct is_non_const_reference : false_type {};
41template <class T> struct is_non_const_reference<T&> : true_type {};
42template <class T> struct is_non_const_reference<const T&> : false_type {};
43
44template <class T> struct is_void : false_type {};
45template <> struct is_void<void> : true_type {};
46
47namespace internal {
48
49// Types YesType and NoType are guaranteed such that sizeof(YesType) <
50// sizeof(NoType).
51typedef char YesType;
52
53struct NoType {
54  YesType dummy[2];
55};
56
57// This class is an implementation detail for is_convertible, and you
58// don't need to know how it works to use is_convertible. For those
59// who care: we declare two different functions, one whose argument is
60// of type To and one with a variadic argument list. We give them
61// return types of different size, so we can use sizeof to trick the
62// compiler into telling us which function it would have chosen if we
63// had called it with an argument of type From.  See Alexandrescu's
64// _Modern C++ Design_ for more details on this sort of trick.
65
66struct ConvertHelper {
67  template <typename To>
68  static YesType Test(To);
69
70  template <typename To>
71  static NoType Test(...);
72
73  template <typename From>
74  static From& Create();
75};
76
77// Used to determine if a type is a struct/union/class. Inspired by Boost's
78// is_class type_trait implementation.
79struct IsClassHelper {
80  template <typename C>
81  static YesType Test(void(C::*)(void));
82
83  template <typename C>
84  static NoType Test(...);
85};
86
87}  // namespace internal
88
89// Inherits from true_type if From is convertible to To, false_type otherwise.
90//
91// Note that if the type is convertible, this will be a true_type REGARDLESS
92// of whether or not the conversion would emit a warning.
93template <typename From, typename To>
94struct is_convertible
95    : integral_constant<bool,
96                        sizeof(internal::ConvertHelper::Test<To>(
97                                   internal::ConvertHelper::Create<From>())) ==
98                        sizeof(internal::YesType)> {
99};
100
101template <typename T>
102struct is_class
103    : integral_constant<bool,
104                        sizeof(internal::IsClassHelper::Test<T>(0)) ==
105                            sizeof(internal::YesType)> {
106};
107
108}  // namespace addressinput
109}  // namespace i18n
110
111#endif  // I18N_ADDRESSINPUT_UTIL_TEMPLATE_UTIL_H_
112