7bit

/* Encode 7-bit ASCII data into the buffer out[], which must be at least
** "len" bytes in length.  The encoded data will have the same size as
** the decoded data.  You must append a 0 byte to terminate the string.
** The buffers in[] and out[] may be the same. Call this function again
** to decode. Return the length encoded, or -1 on error.
*/
int ascii7enc(char *out, const char *in, int len)
{
  int ct = len;
  if (!in || !out || len < 0) return -1;

  while (ct-- > 0)
  {
    char ch = (*in == 0 || *in == '\'' || *in == 0x80 || *in == '\''^0x80)?
     (*in++ ^ 0x80): *in++;
    *out++ = ch;
  }

  return len;
}