---
jupytext:
  formats: md:myst
  text_representation:
    extension: .md
    format_name: myst
kernelspec:
  display_name: Python 3
  language: python
  name: python3
---

/*********************************************************************

  Filename:  string6.cpp
  Chapter:   6      Object Creation and Destruction
  Section:   6.10   Strings Using Reference Semantics
  Compiler:  Borland C++     Version 5.0       Summer 1996
  Object Oriented Programming Using C++, Edition 2   By Ira Pohl

*********************************************************************/

//Reference counted my_strings
#include  <iostream>
#include  <assert.h>
#include  <cstring>

using namespace std;

class str_obj {
public:
   int    len, ref_cnt;
   char*  s;
   str_obj() : len(0), ref_cnt(1)
      { s = new char[1]; assert(s != 0); s[0] = 0; }
   str_obj(const char* p) : ref_cnt(1)
      { len = strlen(p); s = new char[len + 1];
        assert(s != 0); strcpy(s, p); }
   ~str_obj() { delete []s; }
};

class my_string {
public:
   my_string() { st = new str_obj; assert(st != 0);}
   my_string(const char* p)
      { st = new str_obj(p); assert(st != 0);}
   my_string(const my_string& str)
       { st = str.st; st -> ref_cnt++; }
   ~my_string();
   void  assign(const my_string& str);
   void  print() const { cout << st -> s; }
private:
   str_obj*  st;
};

void my_string::assign(const my_string& str)
{
   if (str.st != st) {
      if (--st -> ref_cnt == 0)
         delete st;
      st = str.st;
      st -> ref_cnt++;
   }
}

my_string:: ~my_string()
{
   if (--st -> ref_cnt == 0)
      delete st;
}

int main()
{
   char*   str = "The wheel that squeaks the loudest\n";
   my_string  a(str), b ;

   b.assign("Is the one that gets the grease\n");
   cout << str << endl;
   a.print();
   b.print();
}