gtest/samples/sample3-inl.h

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// A sample program demonstrating using Google C++ testing framework.
//
// Author: wan@google.com (Zhanyong Wan)

#ifndef GTEST_SAMPLES_SAMPLE3_INL_H_
#define GTEST_SAMPLES_SAMPLE3_INL_H_

#include <stddef.h>


// Queue is a simple queue implemented as a singled-linked list.
//
// The element type must support copy constructor.
template <typename E>  // E is the element type
class Queue;

// QueueNode is a node in a Queue, which consists of an element of
// type E and a pointer to the next node.
template <typename E>  // E is the element type
class QueueNode
{
  friend class Queue<E>;

public:
  // Gets the element in this node.
  const E & element() const { return element_; }

  // Gets the next node in the queue.
  QueueNode * next() { return next_; }
  const QueueNode * next() const { return next_; }

private:
  // Creates a node with a given element value.  The next pointer is
  // set to NULL.
  explicit QueueNode(const E & an_element) : element_(an_element), next_(NULL) {}

  // We disable the default assignment operator and copy c'tor.
  const QueueNode & operator = (const QueueNode &);
  QueueNode(const QueueNode &);

  E element_;
  QueueNode * next_;
};

template <typename E>  // E is the element type.
class Queue
{
public:
  // Creates an empty queue.
  Queue() : head_(NULL), last_(NULL), size_(0) {}

  // D'tor.  Clears the queue.
  ~Queue() { Clear(); }

  // Clears the queue.
  void Clear()
  {
    if (size_ > 0)
      {
        // 1. Deletes every node.
        QueueNode<E> * node = head_;
        QueueNode<E> * next = node->next();

        for (; ;)
          {
            delete node;
            node = next;

            if (node == NULL) { break; }

            next = node->next();
          }

        // 2. Resets the member variables.
        head_ = last_ = NULL;
        size_ = 0;
      }
  }

  // Gets the number of elements.
  size_t Size() const { return size_; }

  // Gets the first element of the queue, or NULL if the queue is empty.
  QueueNode<E> * Head() { return head_; }
  const QueueNode<E> * Head() const { return head_; }

  // Gets the last element of the queue, or NULL if the queue is empty.
  QueueNode<E> * Last() { return last_; }
  const QueueNode<E> * Last() const { return last_; }

  // Adds an element to the end of the queue.  A copy of the element is
  // created using the copy constructor, and then stored in the queue.
  // Changes made to the element in the queue doesn't affect the source
  // object, and vice versa.
  void Enqueue(const E & element)
  {
    QueueNode<E> * new_node = new QueueNode<E>(element);

    if (size_ == 0)
      {
        head_ = last_ = new_node;
        size_ = 1;
      }

    else
      {
        last_->next_ = new_node;
        last_ = new_node;
        size_++;
      }
  }

  // Removes the head of the queue and returns it.  Returns NULL if
  // the queue is empty.
  E * Dequeue()
  {
    if (size_ == 0)
      {
        return NULL;
      }

    const QueueNode<E> * const old_head = head_;
    head_ = head_->next_;
    size_--;

    if (size_ == 0)
      {
        last_ = NULL;
      }

    E * element = new E(old_head->element());
    delete old_head;

    return element;
  }

  // Applies a function/functor on each element of the queue, and
  // returns the result in a new queue.  The original queue is not
  // affected.
  template <typename F>
  Queue * Map(F function) const
  {
    Queue * new_queue = new Queue();

    for (const QueueNode<E> * node = head_; node != NULL; node = node->next_)
      {
        new_queue->Enqueue(function(node->element()));
      }

    return new_queue;
  }

private:
  QueueNode<E> * head_; // The first node of the queue.
  QueueNode<E> * last_; // The last node of the queue.
  size_t size_;  // The number of elements in the queue.

  // We disallow copying a queue.
  Queue(const Queue &);
  const Queue & operator = (const Queue &);
};

#endif  // GTEST_SAMPLES_SAMPLE3_INL_H_