title: utf8 and utf16 conversion
body: <p>I have a wchar_t string, for example, L"hao123--我的上网主页", I can convert it to utf8 </p>
  
  <p>encoding, the output string is "hao123锛嶏紞鎴戠殑涓婄綉涓婚〉", but finally, I must write this</p>
  
  <p>string to a plain text file, its format is utf16 (I know this from others), "hao123\uFF0D\uFF0D\u6211\u7684\u4E0A\u7F51\u4E3B\u9875". </p>
  
  <p>Because I must save it in C++ std string and then write it to a file, How can I convert </p>
  
  <p>"hao123锛嶏紞鎴戠殑涓婄綉涓婚〉" to "hao123\uFF0D\uFF0D\u6211\u7684\u4E0A\u7F51\u4E3B\u9875" in char or C++ std string ?</p>
  
  <p>Can anyone give me some tips?    </p>
  
  <p>Thanks in advance!</p>