Simple String Class

Environment: VC6, NT4 SP5, Windows 95b/98

Background

Although both MFC and STL provide the CString and the string class to manipulate strings, In my recent project I have to develop a simple string class for my particular use. The future includes formatting string, similar to MFC format; searching string with the given wildcards; and numeric conversion with the desired data type.

Class Definition

class CStr
{
public:
 // constructors and destructor
 CStr(const CStr& str);
 CStr(const char* str);
 CStr(const double var)				
  { VarToString(var); }

 CStr()
  { m_nLength = 0; m_pString = 0; }

 virtual ~CStr()						
  { if (m_pString) delete m_pString; }

 // operator overloading helper
 template <class T> friend CStr _cdecl operator +(T var, const CStr& str);

 // operator overloading
 CStr& operator  =(const char* str);
 CStr& operator  =(const CStr& str);

 CStr& operator  =(const double var)	
 { VarToString(var); return *this; }

 template<class T>
 CStr  operator  +(T var)			
 { CStr tstr = *this; return tstr += var; }

 CStr& operator +=(double str)		
 { return *this += (CStr)str; }

 CStr& operator +=(const char* str)	
 { return *this += (CStr)str; }

 CStr& operator +=(const CStr& str);

 // add more logic comparison operators as following,
 // for example, although not efficient
 virtual bool operator !=(char* str)	
  { return strcmp(str, m_pString) != 0; }

 // c type string conversion
 operator char* ()
  { return m_pString; }

 operator const char* () const		
  { return m_pString; }

 char* GetChar()
  { return m_pString; }

 // numeric conversion
 template <class T> GetValue(T& var)
  { return GetVar(var); }

 // search the match string : 
 // WildCards can be '?' and '*' combination
 // return value : true (pattern matchs string), false (no match)
 bool Search(const char* WildCards)	
  { return Match((char*)WildCards, m_pString); }

 // format string
 int Format(const char* format, ...);

protected:
 // can use faster algorithm for search ?
 virtual bool Match(char*, char*);

 virtual bool Scan(char*&, char*&);

 // have any good conversion method ?
 virtual void VarToString(const double var);

 // numeric conversion helpers
 bool NumericParse(void* pvar, char flag);
 
 bool GetVar(bool& var)				
  { return NumericParse((void*)&var, 'b'); }

 bool GetVar(char& var)				
  { return NumericParse((void*)&var, 'c'); }

 bool GetVar(short& var)				
  { return NumericParse((void*)&var, 's'); }

 bool GetVar(int& var)				
  { return NumericParse((void*)&var, 'i'); }

 bool GetVar(long& var)				
  { return NumericParse((void*)&var, 'l'); }

 bool GetVar(float& var)				
  { return NumericParse((void*)&var, 'f'); }

 bool GetVar(double& var)			
  { return NumericParse((void*)&var, 'd'); }

 bool GetVar(unsigned char& var)		
  { return NumericParse((void*)&var, 'C'); }

 bool GetVar(unsigned short& var)	
  { return NumericParse((void*)&var, 'S'); }

 bool GetVar(unsigned int& var)		
  { return NumericParse((void*)&var, 'I'); }

 bool GetVar(unsigned long& var)		
  { return NumericParse((void*)&var, 'L'); }
    

// data block
 int   m_nLength;
 char* m_pString;
};

template <class T>
CStr operator +(T var, const CStr& str) 
{ 
 CStr svar = var;
 return svar += str; 
}

Source Code

The implemented file Str.cpp is independent on MFC and STL string class. Hope this simple string class can be used in most platform. Note that some UNIX C++ compilers do not support snprintf.

Demo Project

StrDemo.cpp demonstrates how to use string numeric conversion, format, and search. Note that the numeric type plus CStr is legal, such as 6.456 + (CStr)"hyt" will produce "6.456hyt" and (CStr)"hyt" + '1' will produce "hyt49". If you do not like that, please modify binary operator CStr operator +(T var, const CStr& str) and corresponding member functions.

Downloads

Download demo project - 6 Kb
Download source - 3 Kb