SFTP SSH_FXP_REALPATH packet question

["Nickolay L." <ni4%ukr.net@localhost>]

Hello,

  In draft-ietf-secsh-filexfer-10.txt said, that packet has the
  following format :

  byte   SSH_FXP_REALPATH
  uint32 request-id
  string original-path [UTF-8]
  byte   control-byte [optional]
  string compose-path[0..n] [optional]

  So the question is : how do I logicaly-correct recognize, is the
  control-byte present, or absent? The way is to see the first byte
  after other fields, if it zero (It seems that compose-path will not
  be bigger than 2^24), the control-byte is absent. But this way not
  looks like the best..

  And another question, are there any available implementations of
  clients/server which supports versions 5 or/and 6 of SFTP protocol?

-- 
  Best regards,Nickolay mailto:<ni4%ukr.net@localhost>