Sams Teach Yourself C++ in 21 Days

What’s Next 765

21

21: typedef int BOOL;

22:

23:

24: class String

25: {

26: public:

27: // constructors

28: String();

29: String(const char *const);

30: String(const String &);

31: ~String();

32:

33: char & operator[](int offset);

34: char operator[](int offset) const;

35:

36: String & operator= (const String &);

37: int GetLen()const { return itsLen; }

38: const char * GetString() const { return itsString; }

39: BOOL Invariants() const;

40:

41: private:

42: String (int); // private constructor

43: char * itsString;

44: // unsigned short itsLen;

45: int itsLen;

46: };

47:

48: // default constructor creates string of 0 bytes

49: String::String()

50: {

51: itsString = new char[1];

52: itsString[0] = ‘\0’;

53: itsLen=0;

54: ASSERT(Invariants());

55: }

56:

57: // private (helper) constructor, used only by

58: // class methods for creating a new string of

59: // required size. Null filled.

60: String::String(int len)

61: {

62: itsString = new char[len+1];

63: for (int i = 0; i <= len; i++)

64: itsString[i] = ‘\0’;

65: itsLen=len;

66: ASSERT(Invariants());

67: }

68:

LISTING21.4 continued