| Код |
// strimem.cpp
// memory-saving String class
// overloaded assignment and copy constructor
#include <iostream>
#include <cstring> //for strcpy(), etc.
using namespace std;
class String;
////////////////////////////////////////////////////////////////
class strCount //keep track of number
{ //of unique strings
private:
int count; //number of instances
char* str; //pointer to string
friend class String; //make ourselves available
//member functions are private
strCount(char* s) //one-arg constructor
{
int length = strlen(s); //length of string argument
str = new char[length+1]; //get memory for string
strcpy(str, s); //copy argument to it
count=1; //start count at 1
}
~strCount() //destructor
{ delete[] str; } //delete the string
};
////////////////////////////////////////////////////////////////
class String //String class
{
private:
strCount* psc; //pointer to strCount
public:
String() //no-arg constructor
{ psc = new strCount("NULL"); }
String(char* s) //1-arg constructor
{ psc = new strCount(s); }
String(String& S) //copy constructor
{
psc = S.psc;
(psc->count)++;
}
~String() //destructor
{
if(psc->count==1) //if we are its last user,
delete psc; // delete our strCount
else // otherwise,
(psc->count)--; // decrement its count
}
void display() //display the String
{
cout << psc->str; //print string
cout << " (addr=" << psc << ")"; //print address
}
void operator = (String& S) //assign the string
{
if(psc->count==1) //if we are its last user,
delete psc; // delete our strCount
else // otherwise,
(psc->count)--; // decrement its count
psc = S.psc; //use argument's strCount
(psc->count)++; //increment its count
}
};
////////////////////////////////////////////////////////////////
int main()
{
String s3 = "When the fox preaches, look to your geese.";
cout << "\ns3="; s3.display(); //display s3
String s1; //define String
s1 = s3; //assign it another String
cout << "\ns1="; s1.display(); //display it
String s2(s3); //initialize with String
cout << "\ns2="; s2.display(); //display it
cout << endl;
return 0;
}
|
|