ppapi/cpp/extensions/optional.h

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef PPAPI_CPP_EXTENSIONS_OPTIONAL_H_
   6 #define PPAPI_CPP_EXTENSIONS_OPTIONAL_H_
   7
   8 namespace pp {
   9 namespace ext {
  10
  11 template <class T>
  12 class Optional {
  13  public:
  14   Optional() : value_(NULL) {
  15   }
  16   // Takes ownership of |value|.
  17   explicit Optional(T* value) : value_(value) {
  18   }
  19   Optional(const T& value) : value_(new T(value)) {
  20   }
  21   Optional(const Optional<T>& other)
  22       : value_(other.value_ ? new T(*other.value_) : NULL) {
  23   }
  24
  25   ~Optional() {
  26     Reset();
  27   }
  28
  29   Optional<T>& operator=(const T& other) {
  30     if (value_ == &other)
  31       return *this;
  32
  33     Reset();
  34     value_ = new T(other);
  35
  36     return *this;
  37   }
  38
  39   Optional<T>& operator=(const Optional<T>& other) {
  40     if (value_ == other.value_)
  41       return *this;
  42
  43     Reset();
  44     if (other.value_)
  45       value_ = new T(*other.value_);
  46
  47     return *this;
  48   }
  49
  50   bool IsSet() const {
  51     return !!value_;
  52   }
  53
  54   T* Get() const {
  55     return value_;
  56   }
  57
  58   // Should only be used when IsSet() is true.
  59   T& operator*() const {
  60     return *value_;
  61   }
  62
  63   // Should only be used when IsSet() is true.
  64   T* operator->() const {
  65     PP_DCHECK(value_);
  66     return value_;
  67   }
  68
  69   // Takes ownership of |value|.
  70   void Set(T* value) {
  71     if (value == value_)
  72       return;
  73
  74     Reset();
  75     *value_ = value;
  76   }
  77
  78   void Reset() {
  79     T* value = value_;
  80     value_ = NULL;
  81     delete value;
  82   }
  83
  84   void Swap(Optional<T>* other) {
  85     T* temp = value_;
  86     value_ = other->value_;
  87     other->value_ = temp;
  88   }
  89
  90  private:
  91   T* value_;
  92 };
  93
  94 }  // namespace ext
  95 }  // namespace pp
  96
  97 #endif  // PPAPI_CPP_EXTENSIONS_OPTIONAL_H_