Reference counted string (example of handle-body idiom)

refstr.cpp

#include <iostream>

class StringRep {
  friend class String;
private:
	StringRep() { *(rep = new char[1]) = '\0'; }
	~StringRep() { delete[] rep; }
	StringRep(const StringRep& s) { ::strcpy((rep = new char[::strlen(s.rep)+1]), s.rep); }
	StringRep& operator=(const StringRep& s) {
		if (rep != s.rep) {
			delete[] rep;
			::strcpy((rep = new char[::strlen(s.rep)+1]), s.rep);
		}
		return *this;
	}
	StringRep(const char* s) { ::strcpy((rep = new char[::strlen(s) + 1]), s); }
	int length() const { return ::strlen(rep); };
	StringRep operator+(const StringRep& s) const;
private:
	char *rep;
	int count;
};

StringRep StringRep::operator+(const StringRep& s) const {
	char *tmp = new char[length() + s.length() + 1];
	::strcpy(tmp, rep);
	::strcat(tmp, s.rep);
	StringRep tmpret(tmp);
	delete[] tmp;
	return tmpret;
}

class String {
public:
	String() { rep = new StringRep; rep->count = 1; }
	String(const String& s) { rep = s.rep; rep->count++; }
	String& operator=(const String& s) {
		s.rep->count++;
		if (--rep->count <= 0) delete rep;
		rep = s.rep;
		return *this;
	}
	~String() { if (--rep->count <= 0) delete rep; }
	String(const char *s) { rep = new StringRep(s); rep->count = 1;}
	int length() const { return rep->length(); }
	String operator+(const String& s) {
		StringRep t = *rep + *s.rep;
		String retval(t.rep);
		return retval;
	}
	const char *c_str() const {
		return rep->rep;
	}
	// for debug
	int count() const { return rep->count; }
private:
	StringRep *rep;
};