C++ 使用 UTF8 BOM 替换 UTF8 文件

void Utf8ToUtf8Bom(const wchar_t* filename) {
  std::ifstream infile;
  std::string strline;
  std::string strresult;
  // BOM HEADER
  char c1 = (char)0xEF;
  char c2 = (char)0xBB;
  char c3 = (char)0xBF;
  infile.open(filename);
  if (infile) {
    getline(infile, strline);
    strresult += strline + "\n";
    if (strresult[0] == c1 && strresult[1] == c2 && strresult[2] == c3) {
      return;
    }
    while (!infile.eof()) {
      getline(infile, strline);
      strresult += strline + "\n";
    }
    // delete "\n"
    strresult.pop_back();
  }

  infile.close();
  // delete old debug.log
  ::_wremove(filename);

  std::ofstream outfile(filename);
  outfile << c1 << c2 << c3;
  outfile << strresult;
  outfile.close();
}