MongoDB C++ Driver  mongocxx-3.1.0
view_or_value.hpp
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2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
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7 // http://www.apache.org/licenses/LICENSE-2.0
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9 // Unless required by applicable law or agreed to in writing, software
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12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 #pragma once
16 
17 #include <type_traits>
18 
19 #include <bsoncxx/stdx/optional.hpp>
20 
21 #include <bsoncxx/config/prelude.hpp>
22 
23 namespace bsoncxx {
24 BSONCXX_INLINE_NAMESPACE_BEGIN
25 
29 template <typename View, typename Value>
31  public:
32  using view_type = View;
33  using value_type = Value;
34 
38  static_assert(std::is_constructible<View, Value>::value,
39  "View type must be constructible from a Value");
40 
44  static_assert(std::is_default_constructible<View>::value,
45  "View type must be default constructible");
46 
51  BSONCXX_INLINE view_or_value() = default;
52 
60  BSONCXX_INLINE view_or_value(View view) : _view{view} {
61  }
62 
69  BSONCXX_INLINE view_or_value(Value&& value) : _value(std::move(value)), _view(*_value) {
70  }
71 
75  BSONCXX_INLINE view_or_value(const view_or_value& other)
76  : _value(other._value), _view(_value ? *_value : other._view) {
77  }
78 
82  BSONCXX_INLINE view_or_value& operator=(const view_or_value& other) {
83  _value = other._value;
84  _view = _value ? *_value : other._view;
85  return *this;
86  }
87 
91 
93  BSONCXX_INLINE view_or_value(view_or_value&& other) noexcept
94  : _value{std::move(other._value)},
95  _view(_value ? *_value : std::move(other._view)) {
96  other._view = View();
97  other._value = stdx::nullopt;
98  }
99 
104  BSONCXX_INLINE view_or_value& operator=(view_or_value&& other) noexcept {
105  _value = std::move(other._value);
106  _view = _value ? *_value : std::move(other._view);
107  other._view = View();
108  other._value = stdx::nullopt;
109  return *this;
110  }
111 
117  BSONCXX_INLINE bool is_owning() const noexcept {
118  return static_cast<bool>(_value);
119  }
120 
126  BSONCXX_INLINE operator View() const {
127  return _view;
128  }
129 
135  BSONCXX_INLINE const View& view() const {
136  return _view;
137  }
138 
139  private:
140  stdx::optional<Value> _value;
141  View _view;
142 };
143 
151 template <typename View, typename Value>
152 BSONCXX_INLINE bool operator==(const view_or_value<View, Value>& lhs,
153  const view_or_value<View, Value>& rhs) {
154  return lhs.view() == rhs.view();
155 }
156 
157 template <typename View, typename Value>
158 BSONCXX_INLINE bool operator!=(const view_or_value<View, Value>& lhs,
159  const view_or_value<View, Value>& rhs) {
160  return !(lhs == rhs);
161 }
165 
173 template <typename View, typename Value>
174 BSONCXX_INLINE bool operator==(const view_or_value<View, Value>& lhs, View rhs) {
175  return lhs.view() == rhs;
176 }
177 
178 template <typename View, typename Value>
179 BSONCXX_INLINE bool operator==(View lhs, const view_or_value<View, Value>& rhs) {
180  return rhs == lhs;
181 }
182 
183 template <typename View, typename Value>
184 BSONCXX_INLINE bool operator!=(const view_or_value<View, Value>& lhs, View rhs) {
185  return !(lhs == rhs);
186 }
187 
188 template <typename View, typename Value>
189 BSONCXX_INLINE bool operator!=(View lhs, const view_or_value<View, Value>& rhs) {
190  return !(rhs == lhs);
191 }
192 
193 template <typename View, typename Value>
194 BSONCXX_INLINE bool operator==(const view_or_value<View, Value>& lhs, const Value& rhs) {
195  return lhs.view() == View(rhs);
196 }
197 
198 template <typename View, typename Value>
199 BSONCXX_INLINE bool operator==(const Value& lhs, const view_or_value<View, Value>& rhs) {
200  return rhs == lhs;
201 }
202 
203 template <typename View, typename Value>
204 BSONCXX_INLINE bool operator!=(const view_or_value<View, Value>& lhs, const Value& rhs) {
205  return !(lhs == rhs);
206 }
207 
208 template <typename View, typename Value>
209 BSONCXX_INLINE bool operator!=(const Value& lhs, const view_or_value<View, Value>& rhs) {
210  return !(rhs == lhs);
211 }
215 
216 BSONCXX_INLINE_NAMESPACE_END
217 } // namespace bsoncxx
218 
219 #include <bsoncxx/config/postlude.hpp>
view_or_value(Value &&value)
Constructs a view_or_value from a Value type.
Definition: view_or_value.hpp:69
Definition: error_code.hpp:72
view_or_value()=default
Class View must be constructible from an instance of class Value.
view_or_value(View view)
Construct a view_or_value from a View.
Definition: view_or_value.hpp:60
Class representing a view-or-value variant type.
Definition: view_or_value.hpp:30
bool is_owning() const noexcept
Return whether or not this view_or_value owns an underlying Value.
Definition: view_or_value.hpp:117
const View & view() const
Get a View for the type.
Definition: view_or_value.hpp:135
bool operator==(const view_or_value< View, Value > &lhs, const view_or_value< View, Value > &rhs)
Compare view_or_value objects for (in)-equality.
Definition: view_or_value.hpp:152
bool operator==(const view_or_value< View, Value > &lhs, View rhs)
Mixed (in)-equality operators for view_or_value against View or Value types.
Definition: view_or_value.hpp:174
view_or_value(view_or_value &&other) noexcept
Construct a view_or_value from a moved-in view_or_value.
Definition: view_or_value.hpp:93
view_or_value & operator=(view_or_value &&other) noexcept
Assign to this view_or_value from a moved-in view_or_value.
Definition: view_or_value.hpp:104
view_or_value & operator=(const view_or_value &other)
Assign to this view_or_value from a copied view_or_value.
Definition: view_or_value.hpp:82
view_or_value(const view_or_value &other)
Construct a view_or_value from a copied view_or_value.
Definition: view_or_value.hpp:75
Definition: element.hpp:24