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     29 
     30 // A sample program demonstrating using Google C++ testing framework.
     31 //
     32 // Author: wan (at) google.com (Zhanyong Wan)
     33 
     34 #ifndef GTEST_SAMPLES_SAMPLE3_INL_H_
     35 #define GTEST_SAMPLES_SAMPLE3_INL_H_
     36 
     37 #include <stddef.h>
     38 
     39 
     40 // Queue is a simple queue implemented as a singled-linked list.
     41 //
     42 // The element type must support copy constructor.
     43 template <typename E>  // E is the element type
     44 class Queue;
     45 
     46 // QueueNode is a node in a Queue, which consists of an element of
     47 // type E and a pointer to the next node.
     48 template <typename E>  // E is the element type
     49 class QueueNode {
     50   friend class Queue<E>;
     51 
     52  public:
     53   // Gets the element in this node.
     54   const E& element() const { return element_; }
     55 
     56   // Gets the next node in the queue.
     57   QueueNode* next() { return next_; }
     58   const QueueNode* next() const { return next_; }
     59 
     60  private:
     61   // Creates a node with a given element value.  The next pointer is
     62   // set to NULL.
     63   QueueNode(const E& an_element) : element_(an_element), next_(NULL) {}
     64 
     65   // We disable the default assignment operator and copy c'tor.
     66   const QueueNode& operator = (const QueueNode&);
     67   QueueNode(const QueueNode&);
     68 
     69   E element_;
     70   QueueNode* next_;
     71 };
     72 
     73 template <typename E>  // E is the element type.
     74 class Queue {
     75 public:
     76 
     77   // Creates an empty queue.
     78   Queue() : head_(NULL), last_(NULL), size_(0) {}
     79 
     80   // D'tor.  Clears the queue.
     81   ~Queue() { Clear(); }
     82 
     83   // Clears the queue.
     84   void Clear() {
     85     if (size_ > 0) {
     86       // 1. Deletes every node.
     87       QueueNode<E>* node = head_;
     88       QueueNode<E>* next = node->next();
     89       for (; ;) {
     90         delete node;
     91         node = next;
     92         if (node == NULL) break;
     93         next = node->next();
     94       }
     95 
     96       // 2. Resets the member variables.
     97       head_ = last_ = NULL;
     98       size_ = 0;
     99     }
    100   }
    101 
    102   // Gets the number of elements.
    103   size_t Size() const { return size_; }
    104 
    105   // Gets the first element of the queue, or NULL if the queue is empty.
    106   QueueNode<E>* Head() { return head_; }
    107   const QueueNode<E>* Head() const { return head_; }
    108 
    109   // Gets the last element of the queue, or NULL if the queue is empty.
    110   QueueNode<E>* Last() { return last_; }
    111   const QueueNode<E>* Last() const { return last_; }
    112 
    113   // Adds an element to the end of the queue.  A copy of the element is
    114   // created using the copy constructor, and then stored in the queue.
    115   // Changes made to the element in the queue doesn't affect the source
    116   // object, and vice versa.
    117   void Enqueue(const E& element) {
    118     QueueNode<E>* new_node = new QueueNode<E>(element);
    119 
    120     if (size_ == 0) {
    121       head_ = last_ = new_node;
    122       size_ = 1;
    123     } else {
    124       last_->next_ = new_node;
    125       last_ = new_node;
    126       size_++;
    127     }
    128   }
    129 
    130   // Removes the head of the queue and returns it.  Returns NULL if
    131   // the queue is empty.
    132   E* Dequeue() {
    133     if (size_ == 0) {
    134       return NULL;
    135     }
    136 
    137     const QueueNode<E>* const old_head = head_;
    138     head_ = head_->next_;
    139     size_--;
    140     if (size_ == 0) {
    141       last_ = NULL;
    142     }
    143 
    144     E* element = new E(old_head->element());
    145     delete old_head;
    146 
    147     return element;
    148   }
    149 
    150   // Applies a function/functor on each element of the queue, and
    151   // returns the result in a new queue.  The original queue is not
    152   // affected.
    153   template <typename F>
    154   Queue* Map(F function) const {
    155     Queue* new_queue = new Queue();
    156     for (const QueueNode<E>* node = head_; node != NULL; node = node->next_) {
    157       new_queue->Enqueue(function(node->element()));
    158     }
    159 
    160     return new_queue;
    161   }
    162 
    163  private:
    164   QueueNode<E>* head_;  // The first node of the queue.
    165   QueueNode<E>* last_;  // The last node of the queue.
    166   size_t size_;  // The number of elements in the queue.
    167 
    168   // We disallow copying a queue.
    169   Queue(const Queue&);
    170   const Queue& operator = (const Queue&);
    171  };
    172 
    173 #endif  // GTEST_SAMPLES_SAMPLE3_INL_H_
    174