The rules for forwarding/bursting are described in terms of regular
   expressions.  The first author originally derived simple finite-state
   automata for the rules, but was unable to legibly represent them in
   this memo.  It is suggested that the implementors sketch the automata
   to understand the grammar.

   The conventions used for the grammar are simple.  Each state is
   followed by one or more alternatives, which are separated by the "|"
   character.  Each alternative starts with a character that is received
   as input. (CRLF, although two characters is treated as one character
   herein.)  The last alternative for a state is the character "c",
   which represents any character not specified in the preceeding
   alternatives.  Optionally following the input character is an output
   string enclosed by curly-braces.  Following this is the state that
   the automata enters.  The reader should note that these grammars are
   extremely simple to implement (and, in most cases, can be implemented
   quite efficiently).

   When the forwarding agent encapsulates a message, it should apply the
   following finite-state automaton.  The initial state is S1.

      S1 ::   CRLF {CRLF} S1
            | "-" {"- -"} S2
            | c {c} S2

      S2 ::   CRLF {CRLF} S1
            | c {c} S2

   This simply says that anytime a "-" is found at the beginning of a
   line, a "- " is output prior to outputting the line.











 


RFC 934                                                     January 1985
Message Encapsulation


   When the bursting agent decapsulates the text portion of a draft, it
   should apply the following finite-state automaton.  The initial state
   is S1.

      S1 ::   "-" S3
            | CRLF {CRLF} S1
            | c {c} S2

      S2 ::   CRLF {CRLF} S1
            | c {c} S2

      S3 ::   " " S2
            | c S4

      S4 ::   CRLF S5
            | c S4

      S5 ::   CRLF S5
            | c {c} S2

   Although more complicated than the grammar used by the forwarding
   agent to encapsulate a single message, this grammer is still quite
   simple.  Let us make the simplifying assumption that both the initial
   and final text sections of the draft are messages in addition to the
   encapsulated messages.

   To begin, the current message being burst is scanned at state S1. All
   characters are output until the EB is found (state S3).  If "- " is
   found, the automaton enters state S2 and characters from the current
   message are continued to be output.  Finally, a true EB is found
   (state S4).  As the automaton traverses from state S3 to S4, the
   bursting agent should consider the current message ended.  The
   remainder of the EB is discarded (states S4 and S5).  As the
   automaton traverses from state S5 to S2, the bursting agent should
   consider a new message started and output the first character.  In
   state S2, all characters are output until the EB is found.

Blind Carbon Copies

   Many user agents support a blind-carbon-copy facility.  With this
   facility a draft has two types of addressees: visible and blind
   recipients.  The visible recipients are listed as addresses in the
   "To:" and "cc:" fields of the draft, and the blind recipients are
   listed as addresses in the "Bcc:" fields of the draft.  The basis of
   this facility is that copies of the draft which are delivered to the
   recipients list the visible recipients only.