特殊字符转义

void String::print(String *str)
{
  char *st= (char*)Ptr, *end= st+str_length;
  for (; st < end; st++)
  {
    uchar c= *st;
    switch (c)
    {
    case '\\':
      str->append(STRING_WITH_LEN("\\\\"));
      break;
    case '\0':
      str->append(STRING_WITH_LEN("\\0"));
      break;
    case '\'':
      str->append(STRING_WITH_LEN("\\'"));
      break;
    case '\n':
      str->append(STRING_WITH_LEN("\\n"));
      break;
    case '\r':
      str->append(STRING_WITH_LEN("\\r"));
      break;
    case '\032': // Ctrl-Z
      str->append(STRING_WITH_LEN("\\Z"));
      break;
    default:
      str->append(c);
    }
  }
}