Kea  2.1.7-git
optional.h
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1 // Copyright (C) 2014-2022 Internet Systems Consortium, Inc. ("ISC")
2 //
3 // This Source Code Form is subject to the terms of the Mozilla Public
4 // License, v. 2.0. If a copy of the MPL was not distributed with this
5 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
6 
7 #ifndef OPTIONAL_H
8 #define OPTIONAL_H
9 
10 #include <exceptions/exceptions.h>
11 #include <ostream>
12 #include <string>
13 
14 namespace isc {
15 namespace util {
16 
35 template<typename T>
36 class Optional {
37 public:
38 
40  typedef T ValueType;
41 
47  template<typename A>
48  Optional<T>& operator=(A other) {
49  default_ = other;
50  unspecified_ = false;
51  return (*this);
52  }
53 
60  operator T() const {
61  return (default_);
62  }
63 
67  bool operator==(const T& other) const {
68  return (default_ == other);
69  }
70 
74  bool operator!=(const T& other) const {
75  return (default_ != other);
76  }
77 
95  : default_(T(0)), unspecified_(true) {
96  }
97 
106  template<typename A>
107  Optional(A value, const bool unspecified = false)
108  : default_(value), unspecified_(unspecified) {
109  }
110 
114  T get() const {
115  return (default_);
116  }
117 
124  T valueOr(T const& or_value) const {
125  if (unspecified_) {
126  return or_value;
127  }
128  return default_;
129  }
130 
138  }
139 
143  bool unspecified() const {
144  return (unspecified_);
145  }
146 
153  bool empty() const {
154  isc_throw(isc::InvalidOperation, "call to empty() not supported");
155  }
156 
157 protected:
160 };
161 
166 template<>
168  : default_(), unspecified_(true) {
169 }
170 
174 template<>
175 inline bool Optional<std::string>::empty() const {
176  return (default_.empty());
177 }
178 
190 template<typename T>
191 std::ostream&
192 operator<<(std::ostream& os, const Optional<T>& optional_value) {
193  os << optional_value.get();
194  return (os);
195 }
196 
197 
198 } // end of namespace isc::util
199 } // end of namespace isc
200 
201 #endif // OPTIONAL_VALUE_H
void unspecified(bool unspecified)
Modifies the flag that indicates whether the value is specified or unspecified.
Definition: optional.h:136
bool unspecified() const
Checks if the value has been specified or unspecified.
Definition: optional.h:143
T ValueType
Type of the encapsulated value.
Definition: optional.h:40
T get() const
Retrieves the encapsulated value.
Definition: optional.h:114
T default_
Encapsulated value.
Definition: optional.h:158
#define isc_throw(type, stream)
A shortcut macro to insert known values into exception arguments.
Optional()
Default constructor.
Definition: optional.h:94
bool operator==(const T &other) const
Equality operator.
Definition: optional.h:67
bool unspecified_
Flag which indicates if the value is specified.
Definition: optional.h:159
Defines the logger used by the top-level component of kea-lfc.
T valueOr(T const &or_value) const
Retrieves the encapsulated value if specified, or the given value otherwise.
Definition: optional.h:124
Optional< T > & operator=(A other)
Assigns a new value value and marks it "specified".
Definition: optional.h:48
A generic exception that is thrown if a function is called in a prohibited way.
bool empty() const
Checks if the encapsulated value is empty.
Definition: optional.h:153
A template representing an optional value.
Definition: optional.h:36
Optional(A value, const bool unspecified=false)
Constructor.
Definition: optional.h:107
bool operator!=(const T &other) const
Inequality operator.
Definition: optional.h:74