1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
|
// Copyright 2005 Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ----
// Author: lar@google.com (Laramie Leavitt)
//
// Template metaprogramming utility functions.
//
// 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.
//
//
// The names chosen here reflect those used in tr1 and the boost::mpl
// library, there are similar operations used in the Loki library as
// well. I prefer the boost names for 2 reasons:
// 1. I think that portions of the Boost libraries are more likely to
// be included in the c++ standard.
// 2. It is not impossible that some of the boost libraries will be
// included in our own build in the future.
// Both of these outcomes means that we may be able to directly replace
// some of these with boost equivalents.
//
#ifndef GOOGLE_PROTOBUF_TEMPLATE_UTIL_H_
#define GOOGLE_PROTOBUF_TEMPLATE_UTIL_H_
namespace google {
namespace protobuf {
namespace internal {
// Types small_ and big_ are guaranteed such that sizeof(small_) <
// sizeof(big_)
typedef char small_;
struct big_ {
char dummy[2];
};
// Identity metafunction.
template <class T>
struct identity_ {
typedef T type;
};
// integral_constant, defined in tr1, is a wrapper for an integer
// value. We don't really need this generality; we could get away
// with hardcoding the integer type to bool. We use the fully
// general integer_constant for compatibility with 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;
// Abbreviations: true_type and false_type are structs that represent boolean
// true and false values. Also define the boost::mpl versions of those names,
// true_ and false_.
typedef integral_constant<bool, true> true_type;
typedef integral_constant<bool, false> false_type;
typedef true_type true_;
typedef false_type false_;
// if_ is a templatized conditional statement.
// if_<cond, A, B> is a compile time evaluation of cond.
// if_<>::type contains A if cond is true, B otherwise.
template<bool cond, typename A, typename B>
struct if_{
typedef A type;
};
template<typename A, typename B>
struct if_<false, A, B> {
typedef B type;
};
// type_equals_ is a template type comparator, similar to Loki IsSameType.
// type_equals_<A, B>::value is true iff "A" is the same type as "B".
//
// New code should prefer base::is_same, defined in base/type_traits.h.
// It is functionally identical, but is_same is the standard spelling.
template<typename A, typename B>
struct type_equals_ : public false_ {
};
template<typename A>
struct type_equals_<A, A> : public true_ {
};
// and_ is a template && operator.
// and_<A, B>::value evaluates "A::value && B::value".
template<typename A, typename B>
struct and_ : public integral_constant<bool, (A::value && B::value)> {
};
// or_ is a template || operator.
// or_<A, B>::value evaluates "A::value || B::value".
template<typename A, typename B>
struct or_ : public integral_constant<bool, (A::value || B::value)> {
};
} // namespace internal
} // namespace protobuf
} // namespace google
#endif // GOOGLE_PROTOBUF_TEMPLATE_UTIL_H_
|
