Function CEscapeInternal

be/src/gutil/strings/escaping.cc:508–551

---------------------------------------------------------------------- CEscapeString() CHexEscapeString() Utf8SafeCEscapeString() Utf8SafeCHexEscapeString() Copies 'src' to 'dest', escaping dangerous characters using C-style escape sequences. This is very useful for preparing query flags. 'src' and 'dest' should not overlap. The 'Hex' version uses hexadecimal rather than octal sequences. The 'Utf8

//    Currently only \n, \r, \t, ", ', \ and !ascii_isprint() chars are escaped.
// ----------------------------------------------------------------------
int CEscapeInternal(const char* src, int src_len, char* dest,
                    int dest_len, bool use_hex, bool utf8_safe) {
  const char* src_end = src + src_len;
  int used = 0;
  bool last_hex_escape = false;  // true if last output char was \xNN

  for (; src < src_end; src++) {
    if (dest_len - used < 2)   // Need space for two letter escape
      return -1;

    bool is_hex_escape = false;
    switch (*src) {
      case '\n': dest[used++] = '\\'; dest[used++] = 'n';  break;
      case '\r': dest[used++] = '\\'; dest[used++] = 'r';  break;
      case '\t': dest[used++] = '\\'; dest[used++] = 't';  break;
      case '\"': dest[used++] = '\\'; dest[used++] = '\"'; break;
      case '\'': dest[used++] = '\\'; dest[used++] = '\''; break;
      case '\\': dest[used++] = '\\'; dest[used++] = '\\'; break;
      default:
        // Note that if we emit \xNN and the src character after that is a hex
        // digit then that digit must be escaped too to prevent it being
        // interpreted as part of the character code by C.
        if ((!utf8_safe || *src < 0x80) &&
            (!ascii_isprint(*src) ||
             (last_hex_escape && ascii_isxdigit(*src)))) {
          if (dest_len - used < 4)  // need space for 4 letter escape
            return -1;
          sprintf(dest + used, (use_hex ? "\\x%02x" : "\\%03o"), *src);
          is_hex_escape = use_hex;
          used += 4;
        } else {
          dest[used++] = *src;
          break;
        }
    }
    last_hex_escape = is_hex_escape;
  }

  if (dest_len - used < 1)   // make sure that there is room for \0
    return -1;

  dest[used] = '\0';   // doesn't count towards return value though
  return used;
}

int CEscapeString(const char* src, int src_len, char* dest, int dest_len) {
  return CEscapeInternal(src, src_len, dest, dest_len, false, false);