标准C++实现字符串类CString(5)

void CString::AssignNewSpace(int iNewTotalSize, int iNeedMove)
 {
  char *pNewSpace = NULL;        //新的字符串指针，初始化NULL
 
 if (iNewTotalSize <= m_nSize)          //确保新的内存空间大于原来的内存空间
  return ;
 
 // allocate new space
  pNewSpace = new char [iNewTotalSize];    //pNewSpace动态申请内存空间
  if (pNewSpace == NULL)
  return ;
 
 if (iNeedMove)               
  {
  memcpy(pNewSpace, m_pDataStart, m_nLength + 1); //将原有字符串复制给新申请内存
  }
  SAFEDELETE(m_pBuffer);              //安全删除原有的字符串m_pBuffer
  m_pBuffer    = pNewSpace; 
  m_pDataStart = m_pBuffer;
  m_pDataEnd  = &(m_pDataStart[m_nLength]);      //重置m_pBuffer，m_pDataStart，m_pDataEnd
 
 // adjust new size
  m_nSize = iNewTotalSize;
 }
 
//////////////////////////////////////////////////////////////////////////////
 // concatenation
 
// NOTE: "operator+" is done as friend functions for simplicity
 //      There are three variants:
 //          CString + CString
 // and for ? = TCHAR, LPCTSTR
 //          CString + ?
 //          ? + CString
 void CString::ConcatCopy(const char *str1, int nSrc1Len, const char *str2, int nSrc2Len)
 {
  int nNewLen = nSrc1Len + nSrc2Len;
 
 AssignNewSpace(nNewLen + 1, 0);
 
 // append two string
  Append(str1, nSrc1Len);
  Append(str2, nSrc2Len);
 }
 
// friend methods
 // Class + Class
 CString operator+(const CString& string1, const CString& string2)
 {
  CString s;
 
 s.ConcatCopy(string1.GetData(), string1.GetLength(), string2.GetData(), string2.GetLength());
  return s;
 }
 
// Class + char
 CString operator+(const CString& string, char ch)
 {
  CString s;
  char str[2];
 
 str[0] = ch;
  str[1] = 0;
  s.ConcatCopy(string.GetData(), string.GetLength(), str, 1);
 
 return s;
 }
 
// char + Class
 CString operator+(char ch, const CString& string)
 {
  CString s;
  char str[2];
 
 str[0] = ch;
  str[1] = 0;
  s.ConcatCopy(string.GetData(), string.GetLength(), str, 1);
 
 return s;
 }
 
// Class + char *
 CString operator+(const CString& string, const char *lpsz)
 {
  CString s;
 
 s.ConcatCopy(string.GetData(), string.GetLength(), lpsz, strlen(lpsz));
 
 return s;
 }
 
// char * + Class
 CString operator+(const char *lpsz, const CString& string)
 {
  CString s;
 
 s.ConcatCopy(string.GetData(), string.GetLength(), lpsz, strlen(lpsz));
 
 return s;
 }
 
// Compare operators
 bool operator==(const CString& s1, const CString& s2)
 {
  return (s1.Compare(s2.GetData()) == 0);
 }
 bool operator==(const CString& s1, const char* s2)
 {
  return (s1.Compare(s2) == 0);
 }
 bool operator==(const char* s1, const CString& s2)
 {
  return (s2.Compare(s1) == 0);
 }
 
bool operator!=(const CString& s1, const CString& s2)
 {
  return (s1.Compare(s2.GetData()) != 0);
 }
 bool operator!=(const CString& s1, const char* s2)
 {
  return (s1.Compare(s2) != 0);
 }
 bool operator!=(const char* s1, const CString& s2)
 {
  return (s2.Compare(s1) != 0);
 }
 
bool operator>(const CString& s1, const CString& s2)
 {
  return (s1.Compare(s2.GetData()) > 0);
 }
 bool operator>(const CString& s1, const char* s2)
 {
  return (s1.Compare(s2) > 0);
 }
 bool operator>(const char* s1, const CString& s2)
 {
  return (s2.Compare(s1) < 0);
 }
 
bool operator<(const CString& s1, const CString& s2)
 {
  return (s1.Compare(s2.GetData()) < 0);
 }
 bool operator<(const CString& s1, const char* s2)
 {
  return (s1.Compare(s2) < 0);
 }
 bool operator<(const char* s1, const CString& s2)
 {
  return (s2.Compare(s1) > 0);
 }
 
bool operator>=(const CString& s1, const CString& s2)
 {
  return (s1.Compare(s2.GetData()) >= 0);
 }
 bool operator>=(const CString& s1, const char* s2)
 {
  return (s1.Compare(s2) >= 0);
 }
 bool operator>=(const char* s1, const CString& s2)
 {
  return (s2.Compare(s1) <= 0);
 }
 
bool operator<=(const CString& s1, const CString& s2)
 {
  return (s1.Compare(s2.GetData()) <= 0);
 }
 bool operator<=(const CString& s1, const char* s2)
 {
  return (s1.Compare(s2) <= 0);
 }
 bool operator<=(const char* s1, const CString& s2)
 {
  return (s2.Compare(s1) >= 0);
 }