CString的高效版本

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#pragma once#include <string>template<class T>void SwapFun(T& left, T& right){ T temp = left; left = right; right = temp;}class CShString{public: CShString(char* pStr)  :m_iLen(strlen(pStr))  , m_iMaxSize(CalcuMax(m_iLen))  , px(new char[m_iMaxSize])  , pn(new int(1)) {  memcpy(px, pStr, m_iLen + 1); } CShString(char* pStr, int iLength)  :m_iLen(iLength)  , m_iMaxSize(CalcuMax(iLength))  , px(new char[m_iMaxSize])  , pn(new int(1)) {  ASSERT(iLength == strlen(pStr));  memcpy(px, pStr, m_iLen);  px[m_iLen] = '\0'; } CShString(const CShString& strOther)  : px (strOther.px), pn(strOther.pn); {  ++*pn; } CShString& Assign(const CShString& other) {  Swap(CShString(other.Data(), other.GetLength()));  return *this; } CShString& Assign(const char* pStr) {  Swap(CShString(pStr));  return *this; } CShString& Assign(const char* pStr, int ilength) {  Swap(CShString(pStr, ilength));  return *this; } CShString& Append(const CShString& other) {  int nSize = GetLength() + other.GetLength() + 1;  char* pStr = new char[nSize];  memcpy(pStr, Data(), GetLength());  memcpy(pStr + GetLength(), other,Data(), other.GetLength() + 1);  ResetAs(pStr, nSize); } CShString& Append(const char* pOther) {  int nLen = strlen(pOther);  int nSize = GetLength() + nLen + 1;  char* pStr = new char[nSize];  memcpy(pStr, Data(), GetLength());  memcpy(pStr + GetLength(), pOther, nLen + 1);  ResetAs(pStr, nSize); } CShString& Append(const char* pStr, int ilength) {  int nSize = GetLength() + ilength + 1;  char* pStr = new char[nSize];  memcpy(pStr, Data(), GetLength());  memcpy(pStr + GetLength(), pStr, ilength + 1);  ResetAs(pStr, nSize); } ~CShString(void) {  if (--*pn == 0)  {   delete pn;   delete px;  } } const char* Data() const {  return px; } int GetLength() {  return m_iLen; }private: void ResetAs(char* pStr, int iSize) {  if (--*pn == 0)  {   delete pn;   delete px;  }  m_iMaxSize = CalcuMax(iSize);  m_iLen = iSize - 1;  px = pStr;  pn = new int(1); } void Swap(CShString& other) {  SwapFun(m_iLen, other.m_iLen);  SwapFun(m_iMaxSize, other.m_iMaxSize);  SwapFun(px, other.px);  SwapFun(pn, other.pn); } static int CalcuMax(int iLen) {  int i = 0;  while (INIT_MAX_LEN + (i++) * DELTA_LEN < iLen + 1){}  return INIT_MAX_LEN + (i - 1) * DELTA_LEN; }  static const int INIT_MAX_LEN = 100; static const int DELTA_LEN = 20; int m_iLen; int m_iMaxSize; char* px; int* pn;};
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