Add M-Status header

2 files changed, 65 insertions, 36 deletions

diff --git a/doc/mum.ms b/doc/mum.ms
index df0eeed..d35b27b 100644
--- a/doc/mum.ms
+++ b/doc/mum.ms
@@ -10,26 +10,28 @@
 .DE
 ..
 .TL
-mum \(en modern UNIX mail interface
+.BI mum
+\(en a modern UNIX mail interface
 .AU
 John Ankarström
-.SH \" -----------------------------------------------------------------
-Introduction
+.AB \" -----------------------------------------------------------------
 .LP
 Mum is a text-based e-mail client for UNIX and UNIX-like operating
 systems that supports both plain-text and HTML e-mail.
 It introduces a couple of innovations to the landscape of UNIX
 e-mail clients:
-.IP \h'2n'1.
-Reasonable support for HTML e-mail out of the box.
-.IP \h'2n'2.
-A new method for local storage of e-mail, called
-.I "indexed mbox" .
-.IP \h'2n'3.
-.I Views
+1)
+reasonable support for HTML e-mail out of the box,
+2)
+a new method for local storage of e-mail, called
+.I "indexed mbox" ,
+and
+3)
+.I views
 \(en simple scripts that filter messages \(en instead of folders.
-.LP
-In this document, the fundamental concepts of mum are explained.
+In this document, the fundamental concepts underlying mum are
+explained.
+.AE
 .SH \" -----------------------------------------------------------------
 The indexed mbox format
 .LP
@@ -45,29 +47,57 @@ enhances it with an additional file called an
 .I index ,
 which carries the same name as the mbox plus the extension
 .I .i .
-The index contains all headers from the mbox file, including the
+Mum and its associated view scripts use the index for most operations.
+Whenever it is time to read the actual contents of a message, the
+message is retrieved from the mbox using the offset specified in
+the index.
+.PP
+The index contains all headers from the mbox file, as well as the
 .I From_
-line, without the actual contents of the corresponding messages.
-Further, each block of headers contains three additional headers:
+line, but without the actual contents of the corresponding messages.
+Further, each block of headers contains four additional headers:
 .IP \h'2n'1.
-.I UID ,
-containing the unique identifier of the message provided by the
-mail server (optional).
-.IP \h'2n'2.
-.I Offset ,
+.I M-Offset ,
 containing the starting position of the corresponding message in
 the original mbox file, described as a byte offset.
-(It is important to note that the mbox and mbox.i files are
-append-only.)
-.IP \h'2n'3.
-.I Message-Length ,
+(It is important to note that the mbox file is append-only.)
+.IP \h'2n'2.
+.I M-Length ,
 containing the length of the entire message in the mbox file,
 including both headers and body, in number of bytes.
+.IP \h'2n'3.
+.I M-Status ,
+containing a one-byte value in hexadecimal notation, e.g.
+.CW 0F .
+.IP \h'2n'4.
+.I M-UID ,
+containing the unique identifier of the message provided by the
+mail server (optional).
 .LP
-Mum and its associated view scripts use the index for most operations.
-Whenever it is time to read the actual contents of a message, the
-message is retrieved from the mbox using the offset specified in
-the index.
+The hexadecimal value specified in the
+.I M-Status
+describes the status of the message.
+One byte enough to fit eight different flags:
+.IP "\h'2n'\fC00 (0000 0000)"
+no status (default)
+.IP "\h'2n'\fC01 (0000 0001)"
+read
+.IP "\h'2n'\fC02 (0000 0010)"
+ignored
+.IP "\h'2n'\fC04 (0000 0100)"
+important
+.IP "\h'2n'\fC08 (0000 1000)"
+(reserved but yet undecided)
+.PP
+.in 2n
+The other byte can be freely used by the user themselves to store
+any statuses they wish.
+.LP
+.I M-Status
+is the only header that is allowed to be modified after a message
+has been recorded in the index file.
+Note, however, that any updates made to the value must not change
+the size of the index file.
 .SH \" -----------------------------------------------------------------
 Retrieval methods
 .LP
diff --git a/src/pop b/src/pop
index 8151010..dbdd8c6 100755
--- a/src/pop
+++ b/src/pop
@@ -23,11 +23,9 @@ if (@ARGV != 2) {
 my ($mbox, $index, @existing_uids);
 if (-e $ARGV[1]) {
 	open $index, '<', $ARGV[1] or die "Could not open $ARGV[1]: $!";
-	{
-		local $/ = ''; # paragraph mode
-		while (<$index>) {
-			push @existing_uids, $1 if /^UID: (.*)$/m;
-		}
+	local $/ = ''; # paragraph mode
+	while (<$index>) {
+		push @existing_uids, $1 if /^M-UID: (.*)$/m;
 	}
 	close $index;
 }
@@ -112,9 +110,10 @@ $from_
 MBOX
 	print $index <<INDEX;
 $from_
-UID: $uids{$id}
-Offset: $offset
-Message-Length: $message_length
+M-Offset: $offset
+M-Length: $message_length
+M-Status: 00
+M-UID: $uids{$id}
 @msg[0..$j-1]
 
 INDEX