queue_push_char.cpp

C++Primer 第四版 包括windows 平台下各章的例子程序

/*
 * This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
 * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
 * copyright and warranty notices given in that book:
 * 
 * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
 * 
 * 
 * "The authors and publisher have taken care in the preparation of this book,
 * but make no expressed or implied warranty of any kind and assume no
 * responsibility for errors or omissions. No liability is assumed for
 * incidental or consequential damages in connection with or arising out of the
 * use of the information or programs contained herein."
 * 
 * Permission is granted for this code to be used for educational purposes in
 * association with the book, given proper citation if and when posted or
 * reproduced.Any commercial use of this code requires the explicit written
 * permission of the publisher, Addison-Wesley Professional, a division of
 * Pearson Education, Inc. Send your request for permission, stating clearly
 * what code you would like to use, and in what specific way, to the following
 * address: 
 * 
 * 	Pearson Education, Inc.
 * 	Rights and Contracts Department
 * 	75 Arlington Street, Suite 300
 * 	Boston, MA 02216
 * 	Fax: [phone]
*/ 

#include "MS_Queue.h"

#include <stdexcept>
using std::out_of_range;
#include <iostream>
using std::ostream; 
#include <cstring>
using std::strlen; using std::strncpy;

void Queue<const char*>::push(const char *const &val)
{
    // allocate a new character array and copy characters from val
    char* new_item = new char[strlen(val) + 1];
    strncpy(new_item, val, strlen(val) + 1);

    // store pointer to newly allocated and initialized element
    QueueItem<const char*> *pt =
        new QueueItem<const char*>(new_item); 

    // put item onto existing queue
    if (empty())
        head = tail = pt;   // queue has only one element
    else {
        tail->next = pt;    // add new element to end of queue
        tail = pt;
    }
}

void Queue<const char*>::pop()
{
    // remember head so we can delete it
    QueueItem<const char*> *p = head; 
    delete head->item;    // delete the array allocated in push
    head = head->next;    // head now points to next element
    delete p;             // delete old head element
}