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180 lines
5.2 KiB
Plaintext
180 lines
5.2 KiB
Plaintext
Format of Version 5 Babyl Files:
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(Babyl was the storage format used by Rmail before Emacs 23.1.
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Since then it uses mbox format.)
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Warning:
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This was written Tuesday, 12 April 1983 (by Eugene Ciccarelli),
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based on looking at a particular Babyl file and recalling various
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issues. Therefore it is not guaranteed to be complete, but it is a
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start, and I will try to point the reader to various Babyl functions
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that will serve to clarify certain format questions.
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Also note that this file will not contain control-characters,
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but instead have two-character sequences starting with Uparrow.
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Unless otherwise stated, an Uparrow <character> is to be read as
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Control-<character>, e.g. ^L is a Control-L.
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Versions:
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First, note that each Babyl file contains in its BABYL OPTIONS
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section the version for the Babyl file format. In principle, the
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format can be changed in any way as long as we increment the format
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version number; then programs can support both old and new formats.
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In practice, version 5 is the only format version used, and the
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previous versions have been obsolete for so long that Emacs does not
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support them.
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Overall Babyl File Structure:
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A Babyl file consists of a BABYL OPTIONS section followed by
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0 or more message sections. The BABYL OPTIONS section starts
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with the line "BABYL OPTIONS:". Message sections start with
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Control-Underscore Control-L Newline. Each section ends
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with a Control-Underscore. (That is also the first character
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of the starter for the next section, if any.) Thus, a three
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message Babyl file looks like:
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BABYL OPTIONS:
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...the stuff within the Babyl Options section...
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^_^L
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...the stuff within the 1st message section...
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^_^L
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...the stuff within the 2nd message section...
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^_^L
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...the stuff within the last message section...
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^_
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Babyl is tolerant about some whitespace at the end of the
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file -- the file may end with the final ^_ or it may have some
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whitespace, e.g. a newline, after it.
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The BABYL OPTIONS Section:
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Each Babyl option is specified on one line (thus restricting
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string values these options can currently have). Values are
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either numbers or strings. The format is name, colon, and the
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value, with whitespace after the colon ignored, e.g.:
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Mail: ~/special-inbox
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Unrecognized options are ignored.
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Here are those options and the kind of values currently expected:
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MAIL Filename, the input mail file for this
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Babyl file. You may also use several file names
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separated by commas.
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Version Number. This should always be 5.
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Labels String, list of labels, separated by commas.
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Message Sections:
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A message section contains one message and information
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associated with it. The first line is the "status line", which
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contains a bit (0 or 1 character) saying whether the message has
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been reformed yet, and a list of the labels attached to this
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message. Certain labels, called basic labels, are built into
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Babyl in a fundamental way, and are separated in the status line
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for convenience of operation. For example, consider the status
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line:
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1, answered,, zval, bug,
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The 1 means this message has been reformed. This message is
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labeled "answered", "zval", and "bug". The first, "answered", is
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a basic label, and the other two are user labels. The basic
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labels come before the double-comma in the line. Each label is
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preceded by ", " and followed by ",". (The last basic label is
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in fact followed by ",,".) If this message had no labels at all,
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it would look like:
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1,,
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Or, if it had two basic labels, "answered" and "deleted", it
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would look like:
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1, answered, deleted,, zval, bug,
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The & Label Babyl Message knows which are the basic labels.
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Currently they are: deleted, unseen, recent, and answered.
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After the status line comes the original header if any.
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Following that is the EOOH line, which contains exactly the
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characters "*** EOOH ***" (which stands for "end of original
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header"). Note that the original header, if a network format
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header, includes the trailing newline. And finally, following the
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EOOH line is the visible message, header and text. For example,
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here is a complete message section, starting with the message
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starter, and ending with the terminator:
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^_^L
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1,, wordab, eccmacs,
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Date: 11 May 1982 21:40-EDT
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From: Eugene C. Ciccarelli <ECC at MIT-AI>
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Subject: notes
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To: ECC at MIT-AI
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*** EOOH ***
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Date: Tuesday, 11 May 1982 21:40-EDT
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From: Eugene C. Ciccarelli <ECC>
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To: ECC
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Re: notes
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Remember to pickup check at cashier's office, and deposit it
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soon. Pay rent.
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^_
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;;; Babyl File BNF:
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;;; Overall Babyl file structure:
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Babyl-File ::= Babyl-Options-Section (Message-Section)*
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;;; Babyl Options section:
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Babyl-Options-Section
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::= "BABYL OPTIONS:" newline (Babyl-Option)* Terminator
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Babyl-Option ::= Option-Name ":" Horiz-Whitespace BOptValue newline
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BOptValue ::= Number | 1-Line-String
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;;; Message section:
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Message-Section ::= Message-Starter Status-Line Orig-Header
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EOOH-Line Message Terminator
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Message-Starter ::= "^L" newline
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Status-Line ::= Bit-Char "," (Basic-Label)* "," (User-Label)* newline
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Basic-Label ::= Space BLabel-Name ","
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User-Label ::= Space ULabel-Name ","
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EOOH-Line ::= "*** EOOH ***" newline
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Message ::= Visible-Header Message-Text
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;;; Utilities:
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Terminator ::= "^_"
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Horiz-Whitespace
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::= (Space | Tab)*
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Bit-Char ::= "0" | "1"
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