screen5.h

C++ Primer中文第四版所有配套实例

/*
 * 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]
*/ 

#ifndef SCREEN5_H
#define SCREEN5_H
#include <string>
#include <iostream>

class Screen {
public:
// interface member functions
    typedef std::string::size_type index;
    char get() const { return contents[cursor]; }
    inline char get(index ht, index wd) const;
    Screen(index ht = 0, index wd = 0): 
       contents(ht * wd, ' '), cursor(0), height(ht), width(wd), access_ctr(0) { }
    Screen& move(index r, index c) 
              { do_move(r, c); return *this; }
    const Screen& move(index r, index c) const 
              { do_move(r, c); return *this; }
private:
    void do_move(index r, index c) const;
    void do_display(std::ostream &os) const;
public:
    Screen& set(char);
    Screen& set(index, index, char);
    const Screen& display(std::ostream& os) const;
    // as before
private:
    mutable size_t access_ctr; // may change in a const members
    // other data members as before
    std::string contents;
    index cursor;  
    index height, width;
};

void Screen::do_display(std::ostream& os) const
{	
	++access_ctr;    // keep count of calls to any member function
	os << contents;
}

Screen& Screen::set(char c) 
{ 
	contents[cursor] = c; 
	return *this; 
}

Screen& Screen::set(index r, index c, char ch)
{
	index row = r * width; // row location
	contents[row + c] = ch;
	return *this;
}

char Screen::get(index r, index c) const
{
	index row = r * width; // row location
	return contents[row + c];
}
#endif