fname2.cpp

来自「Think in C++文中代码实现」· C++ 代码 · 共 69 行

// File from page 516 in "Thinking in C++" by Bruce Eckel
//////////////////////////////////////////////////
// From the compressed package ECKELT02.ZIP 4/11/95
// (Original ECKELT01.ZIP dated 2/21/95)
// Copyright (c) Bruce Eckel, 1995 
// Source code file from the book "Thinking in C++", 
// Prentice Hall, 1995, ISBN: 0-13-917709-4
// All rights reserved EXCEPT as allowed by the following 
// statements: You may freely use this file for your own 
// work, including modifications and distribution in 
// executable form only. You may copy and distribute this 
// file, as long as it is only distributed in the complete 
// (compressed) package with the other files from this 
// book and you do not remove this copyright and notice. 
// You may not distribute modified versions of the source 
// code in this package. This package may be freely placed 
// on bulletin boards, internet nodes, shareware disks and 
// product vendor disks. You may not use this file in 
// printed media without the express permission of the 
// author. Bruce Eckel makes no 
// representation about the suitability of this software 
// for any purpose. It is provided "as is" without express 
// or implied warranty of any kind. The entire risk as to 
// the quality and performance of the software is with 
// you. Should the software prove defective, you assume 
// the cost of all necessary servicing, repair, or 
// correction. 
// If you think you've found an error, please 
// email all modified files with loudly commented changes 
// to: [e-mail] (please use the same 
// address for non-code errors found in the book).
//////////////////////////////////////////////////

//: FNAME2.CPP -- Subtyping solves the problem
#include <fstream.h>
#include <strstrea.h>
#include "..\allege.h"

class fname2 : public ifstream {
  enum { bsize = 100 };
  char buf[bsize];
  ostrstream Name;
  int nameset;
public:
  fname2() : Name(buf, bsize), nameset(0) {}
  fname2(const char* filename)
    : ifstream(filename), Name(buf, bsize) {
      Name << filename << ends;
      nameset = 1;
  }
  const char* name() const { return buf; }
  void name(const char* newname) {
    if(nameset) return; // Don't overwrite
    Name << newname << ends;
    nameset = 1;
  }
};

main() {
  fname2 file("fname2.cpp");
  allegefile(file);
  cout << "name: " << file.name() << endl;
  const bsize = 100;
  char buf[bsize];
  file.getline(buf, bsize); // This works too!
  file.seekg(-200, ios::end);
  cout << file.rdbuf() << endl;
}