Mir
optional_value.h
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1 /*
2  * Copyright © 2014 Canonical Ltd.
3  *
4  * This program is free software: you can redistribute it and/or modify
5  * it under the terms of the GNU Lesser General Public License version 2 or 3 as
6  * published by the Free Software Foundation.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11  * GNU Lesser General Public License for more details.
12  *
13  * You should have received a copy of the GNU Lesser General Public License
14  * along with this program. If not, see <http://www.gnu.org/licenses/>.
15  *
16  * Authored by: Alberto Aguirre <alberto.aguirre@canonical.com>
17  */
18 
19 #ifndef MIR_OPTIONAL_VALUE_H_
20 #define MIR_OPTIONAL_VALUE_H_
21 
22 #include "mir/fatal.h"
23 #include <utility>
24 
25 namespace mir
26 {
27 template<typename T>
29 {
30 public:
31  optional_value() = default;
32  optional_value(T const& value) : value_(value), is_set_{true} {}
33 
35  {
36  value_ = value;
37  is_set_ = true;
38  return *this;
39  }
40 
41  bool is_set() const { return is_set_; }
42 
43  T const& value() const
44  {
45  die_if_unset();
46  return value_;
47  }
48 
49  T& value()
50  {
51  die_if_unset();
52  return value_;
53  }
54 
55  T&& consume()
56  {
57  die_if_unset();
58  is_set_ = false;
59  return std::move(value_);
60  }
61 
62  operator bool() const
63  {
64  return is_set();
65  }
66 
67 private:
68  void die_if_unset() const
69  {
70  if (!is_set())
71  {
72  (*fatal_error)("Accessing value of unset optional");
73  }
74  }
75 
76  T value_;
77  bool is_set_{false};
78 };
79 
80 
81 template<typename T>
82 inline bool operator == (optional_value<T> const& lhs, optional_value<T> const& rhs)
83 {
84  return lhs.is_set() == rhs.is_set() &&
85  (!lhs.is_set() || lhs.value() == rhs.value());
86 }
87 
88 template<typename T>
89 inline bool operator != (optional_value<T> const& lhs, optional_value<T> const& rhs)
90 {
91  return !(lhs == rhs);
92 }
93 
94 template<typename T>
95 inline bool operator == (optional_value<T> const& lhs, T const& rhs)
96 {
97  return lhs.is_set() && (lhs.value() == rhs);
98 }
99 
100 template<typename T>
101 inline bool operator != (optional_value<T> const& lhs, T const& rhs)
102 {
103  return !(lhs == rhs);
104 }
105 
106 template<typename T>
107 inline bool operator == (T const& lhs, optional_value<T> const& rhs)
108 {
109  return rhs == lhs;
110 }
111 
112 template<typename T>
113 inline bool operator != (T const& lhs, optional_value<T> const& rhs)
114 {
115  return rhs != lhs;
116 }
117 }
118 
119 #endif /* MIR_OPTIONAL_VALUE_H_ */
Definition: optional_value.h:29
optional_value(T const &value)
Definition: optional_value.h:32
optional_value & operator=(T const &value)
Definition: optional_value.h:34
T & value()
Definition: optional_value.h:49
optional_value()=default
bool is_set() const
Definition: optional_value.h:41
T const & value() const
Definition: optional_value.h:43
T && consume()
Definition: optional_value.h:55
Definition: splash_session.h:24
constexpr bool operator!=(IntWrapper< Tag, ValueType > const &lhs, IntWrapper< Tag, ValueType > const &rhs)
Definition: int_wrapper.h:53
constexpr bool operator==(IntWrapper< Tag, ValueType > const &lhs, IntWrapper< Tag, ValueType > const &rhs)
Definition: int_wrapper.h:47

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This documentation is licensed under the GPL version 2 or 3.