1/*
2 *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11#ifndef WEBRTC_BASE_TEMPLATE_UTIL_H_
12#define WEBRTC_BASE_TEMPLATE_UTIL_H_
13
14#include <stddef.h>  // For size_t.
15
16namespace rtc {
17
18// template definitions from tr1
19
20template<class T, T v>
21struct integral_constant {
22  static const T value = v;
23  typedef T value_type;
24  typedef integral_constant<T, v> type;
25};
26
27template <class T, T v> const T integral_constant<T, v>::value;
28
29typedef integral_constant<bool, true> true_type;
30typedef integral_constant<bool, false> false_type;
31
32template <class T> struct is_pointer : false_type {};
33template <class T> struct is_pointer<T*> : true_type {};
34
35template <class T, class U> struct is_same : public false_type {};
36template <class T> struct is_same<T,T> : true_type {};
37
38template<class> struct is_array : public false_type {};
39template<class T, size_t n> struct is_array<T[n]> : public true_type {};
40template<class T> struct is_array<T[]> : public true_type {};
41
42template <class T> struct is_non_const_reference : false_type {};
43template <class T> struct is_non_const_reference<T&> : true_type {};
44template <class T> struct is_non_const_reference<const T&> : false_type {};
45
46template <class T> struct is_void : false_type {};
47template <> struct is_void<void> : true_type {};
48
49namespace internal {
50
51// Types YesType and NoType are guaranteed such that sizeof(YesType) <
52// sizeof(NoType).
53typedef char YesType;
54
55struct NoType {
56  YesType dummy[2];
57};
58
59// This class is an implementation detail for is_convertible, and you
60// don't need to know how it works to use is_convertible. For those
61// who care: we declare two different functions, one whose argument is
62// of type To and one with a variadic argument list. We give them
63// return types of different size, so we can use sizeof to trick the
64// compiler into telling us which function it would have chosen if we
65// had called it with an argument of type From.  See Alexandrescu's
66// _Modern C++ Design_ for more details on this sort of trick.
67
68struct ConvertHelper {
69  template <typename To>
70  static YesType Test(To);
71
72  template <typename To>
73  static NoType Test(...);
74
75  template <typename From>
76  static From& Create();
77};
78
79// Used to determine if a type is a struct/union/class. Inspired by Boost's
80// is_class type_trait implementation.
81struct IsClassHelper {
82  template <typename C>
83  static YesType Test(void(C::*)(void));
84
85  template <typename C>
86  static NoType Test(...);
87};
88
89}  // namespace internal
90
91// Inherits from true_type if From is convertible to To, false_type otherwise.
92//
93// Note that if the type is convertible, this will be a true_type REGARDLESS
94// of whether or not the conversion would emit a warning.
95template <typename From, typename To>
96struct is_convertible
97    : integral_constant<bool,
98                        sizeof(internal::ConvertHelper::Test<To>(
99                                   internal::ConvertHelper::Create<From>())) ==
100                        sizeof(internal::YesType)> {
101};
102
103template <typename T>
104struct is_class
105    : integral_constant<bool,
106                        sizeof(internal::IsClassHelper::Test<T>(0)) ==
107                            sizeof(internal::YesType)> {
108};
109
110}  // namespace rtc
111
112#endif  // WEBRTC_BASE_TEMPLATE_UTIL_H_
113