字符编码转换（使用windows api）

static std::wstring Utf8ToWString(const std::string& sText)
  {
   int nLenWideCharStr = MultiByteToWideChar(CP_UTF8, 0, sText.c_str(), -1, NULL, 0);
   PWCHAR pWideCharStr = NULL;
   pWideCharStr =(PWSTR)HeapAlloc(GetProcessHeap(), 0, nLenWideCharStr*sizeof(wchar_t));
   memset(pWideCharStr,0,nLenWideCharStr*sizeof(wchar_t));
   MultiByteToWideChar(CP_UTF8, 0, sText.c_str(), -1, pWideCharStr, nLenWideCharStr);
   std::wstring wideStr = pWideCharStr;
   HeapFree(GetProcessHeap(), 0, pWideCharStr);
   return wideStr;
  }

  static std::string WStringToUtf8(const std::wstring& sText)
  {
   int nLenWideCharStr = WideCharToMultiByte(CP_UTF8, 0, sText.c_str(), -1, NULL, 0 , NULL, NULL);
   PCHAR pCharStr = NULL;
   pCharStr =(PSTR)HeapAlloc(GetProcessHeap(), 0, nLenWideCharStr*sizeof(char));
   memset(pCharStr,0,nLenWideCharStr*sizeof(char));
   WideCharToMultiByte(CP_UTF8, 0, sText.c_str(), -1, pCharStr, nLenWideCharStr, NULL, NULL);
   std::string str = pCharStr;
   HeapFree(GetProcessHeap(), 0, pCharStr);
   return str;
  }

  static std::string WStringToANSI(const std::wstring& sText)
  {
   int nLenWideCharStr = WideCharToMultiByte(CP_ACP, 0, sText.c_str(), -1, NULL, 0 , NULL, NULL);
   PCHAR pCharStr = NULL;
   pCharStr =(PSTR)HeapAlloc(GetProcessHeap(), 0, nLenWideCharStr*sizeof(char));
   memset(pCharStr,0,nLenWideCharStr*sizeof(char));
   WideCharToMultiByte(CP_ACP, 0, sText.c_str(), -1, pCharStr, nLenWideCharStr, NULL, NULL);
   std::string str = pCharStr;
   HeapFree(GetProcessHeap(), 0, pCharStr);
   return str;
  }

  static std::wstring ANSIToWString(const std::string& sText)
  {
   int nLenWideCharStr = MultiByteToWideChar(CP_ACP, 0, sText.c_str(), -1, NULL, 0);
   PWCHAR pWideCharStr = NULL;
   pWideCharStr =(PWSTR)HeapAlloc(GetProcessHeap(), 0, nLenWideCharStr*sizeof(wchar_t));
   memset(pWideCharStr,0,nLenWideCharStr*sizeof(wchar_t));
   MultiByteToWideChar(CP_ACP, 0, sText.c_str(), -1, pWideCharStr, nLenWideCharStr);
   std::wstring wideStr = pWideCharStr;
   HeapFree(GetProcessHeap(), 0, pWideCharStr);
   return wideStr;

  }

  static std::string Utf8ToAnsi(const std::string& sText)
  {
   std::wstring ws = Utf8ToWString(sText);
   return WStringToANSI(ws);
  }

  static std::string AnsiToUtf8(const std::string& sText)
  {
   std::wstring ws = ANSIToWString(sText);
   return WStringToUtf8(ws);
  }