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29 
30 // A sample program demonstrating using Google C++ testing framework.
31 
32 #ifndef GOOGLETEST_SAMPLES_SAMPLE3_INL_H_
33 #define GOOGLETEST_SAMPLES_SAMPLE3_INL_H_
34 
35 #include <stddef.h>
36 
37 
38 // Queue is a simple queue implemented as a singled-linked list.
39 //
40 // The element type must support copy constructor.
41 template <typename E>  // E is the element type
42 class Queue;
43 
44 // QueueNode is a node in a Queue, which consists of an element of
45 // type E and a pointer to the next node.
46 template <typename E>  // E is the element type
47 class QueueNode {
48   friend class Queue<E>;
49 
50  public:
51   // Gets the element in this node.
element()52   const E& element() const { return element_; }
53 
54   // Gets the next node in the queue.
next()55   QueueNode* next() { return next_; }
next()56   const QueueNode* next() const { return next_; }
57 
58  private:
59   // Creates a node with a given element value.  The next pointer is
60   // set to NULL.
QueueNode(const E & an_element)61   explicit QueueNode(const E& an_element)
62       : element_(an_element), next_(nullptr) {}
63 
64   // We disable the default assignment operator and copy c'tor.
65   const QueueNode& operator = (const QueueNode&);
66   QueueNode(const QueueNode&);
67 
68   E element_;
69   QueueNode* next_;
70 };
71 
72 template <typename E>  // E is the element type.
73 class Queue {
74  public:
75   // Creates an empty queue.
Queue()76   Queue() : head_(nullptr), last_(nullptr), size_(0) {}
77 
78   // D'tor.  Clears the queue.
~Queue()79   ~Queue() { Clear(); }
80 
81   // Clears the queue.
Clear()82   void Clear() {
83     if (size_ > 0) {
84       // 1. Deletes every node.
85       QueueNode<E>* node = head_;
86       QueueNode<E>* next = node->next();
87       for (; ;) {
88         delete node;
89         node = next;
90         if (node == nullptr) break;
91         next = node->next();
92       }
93 
94       // 2. Resets the member variables.
95       head_ = last_ = nullptr;
96       size_ = 0;
97     }
98   }
99 
100   // Gets the number of elements.
Size()101   size_t Size() const { return size_; }
102 
103   // Gets the first element of the queue, or NULL if the queue is empty.
Head()104   QueueNode<E>* Head() { return head_; }
Head()105   const QueueNode<E>* Head() const { return head_; }
106 
107   // Gets the last element of the queue, or NULL if the queue is empty.
Last()108   QueueNode<E>* Last() { return last_; }
Last()109   const QueueNode<E>* Last() const { return last_; }
110 
111   // Adds an element to the end of the queue.  A copy of the element is
112   // created using the copy constructor, and then stored in the queue.
113   // Changes made to the element in the queue doesn't affect the source
114   // object, and vice versa.
Enqueue(const E & element)115   void Enqueue(const E& element) {
116     QueueNode<E>* new_node = new QueueNode<E>(element);
117 
118     if (size_ == 0) {
119       head_ = last_ = new_node;
120       size_ = 1;
121     } else {
122       last_->next_ = new_node;
123       last_ = new_node;
124       size_++;
125     }
126   }
127 
128   // Removes the head of the queue and returns it.  Returns NULL if
129   // the queue is empty.
Dequeue()130   E* Dequeue() {
131     if (size_ == 0) {
132       return nullptr;
133     }
134 
135     const QueueNode<E>* const old_head = head_;
136     head_ = head_->next_;
137     size_--;
138     if (size_ == 0) {
139       last_ = nullptr;
140     }
141 
142     E* element = new E(old_head->element());
143     delete old_head;
144 
145     return element;
146   }
147 
148   // Applies a function/functor on each element of the queue, and
149   // returns the result in a new queue.  The original queue is not
150   // affected.
151   template <typename F>
Map(F function)152   Queue* Map(F function) const {
153     Queue* new_queue = new Queue();
154     for (const QueueNode<E>* node = head_; node != nullptr;
155          node = node->next_) {
156       new_queue->Enqueue(function(node->element()));
157     }
158 
159     return new_queue;
160   }
161 
162  private:
163   QueueNode<E>* head_;  // The first node of the queue.
164   QueueNode<E>* last_;  // The last node of the queue.
165   size_t size_;  // The number of elements in the queue.
166 
167   // We disallow copying a queue.
168   Queue(const Queue&);
169   const Queue& operator = (const Queue&);
170 };
171 
172 #endif  // GOOGLETEST_SAMPLES_SAMPLE3_INL_H_
173