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// A sample program demonstrating using Google C++ testing framework.
#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_