In C++ convert UT8 to UTF16 and vice versa

utf8helpers.cc

wstring UTF8ToUTF16(const string& utf8) {
  wstring utf16;
  utf16.reserve(utf8.size());
  for ( size_t i = 0; i < utf8.size(); ++i ) {
    unsigned char ch0 = utf8[i];
    if ( (ch0 & 0x80) == 0x00 ) {
      utf16 += ((ch0 & 0x7f));
    } else {
      if ((ch0 & 0xe0) == 0xc0) {
        unsigned char ch1 = utf8[++i];
        utf16 += ((ch0 & 0x3f) << 6)|((ch1 & 0x3f));    
      } else {
        unsigned char ch1 = utf8[++i];
        unsigned char ch2 = utf8[++i];
        utf16 += ((ch0 & 0x0f)<<12)|((ch1 & 0x3f)<<6)|((ch2 & 0x3f));
      }
    }
  }
  return utf16;
}

void BreakUTF8(const string& utf8, vector<string>* out) {
  for (size_t i = 0; i < utf8.size(); ++i) {
    unsigned char c = utf8[i];
    stringstream ss;
    ss << c;
    if ((c & 0x80) == 0x00 ) {            
    } else if ((c & 0xe0) == 0xc0) {
      ss << utf8[++i];
    } else if ((c & 0xf0) == 0xe0) {
      ss << utf8[++i];
      ss << utf8[++i];
    } else if ((c & 0xf8) == 0xf0) {
      ss << utf8[++i];
      ss << utf8[++i];
      ss << utf8[++i];
    } else {
      //Handle error here
    }
    out->push_back(ss.str());
  }  
}