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an "archives first" approach to mailing lists
blob 9baf0e76a3e33c3d32502061c93ceb15b4028e33 2619 bytes (raw)
$ git show ci-WIP:lib/PublicInbox/ContentId.pm	# shows this blob on the CLI

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# Copyright (C) 2018 all contributors <meta@public-inbox.org>
# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>

# Unstable internal API.
# Used for on-the-fly duplicate detection in V2 inboxes.
# This is not stored in any database anywhere and may change
# as changes in duplicate detection are needed.
# See L<public-inbox-v2-format(5)> manpage for more details.
package PublicInbox::ContentId;
use strict;
use warnings;
use base qw/Exporter/;
our @EXPORT_OK = qw/content_id content_digest/;
use PublicInbox::MID qw(mids references);
use PublicInbox::MsgIter;

# not sure if less-widely supported hash families are worth bothering with
use Digest::SHA;

sub digest_addr ($$$) {
	my ($dig, $h, $v) = @_;
	$v =~ tr/"//d;
	$v =~ s/@([a-z0-9\_\.\-\(\)]*([A-Z])\S*)/'@'.lc($1)/ge;
	utf8::encode($v);
	$dig->add("$h\0$v\0");
}

sub content_digest ($) {
	my ($mime) = @_;
	my $dig = Digest::SHA->new(256);
	my $hdr = $mime->header_obj;

	# References: and In-Reply-To: get used interchangeably
	# in some "duplicates" in LKML.  We treat them the same
	# in SearchIdx, so treat them the same for this:
	my %seen;
	foreach my $mid (@{mids($hdr)}) {
		# do NOT consider the Message-ID as part of the content_id
		# if we got here, we've already got Message-ID reuse
		$seen{$mid} = 1;
	}
	foreach my $mid (@{references($hdr)}) {
		next if $seen{$mid};
		$dig->add("ref\0$mid\0");
	}

	# Only use Sender: if From is not present
	foreach my $h (qw(From Sender)) {
		my @v = $hdr->header($h);
		if (@v) {
			digest_addr($dig, $h, $_) foreach @v;
		}
	}
	foreach my $h (qw(Subject Date)) {
		my @v = $hdr->header($h);
		foreach my $v (@v) {
			utf8::encode($v);
			$dig->add("$h\0$v\0");
		}
	}
	# Some mail processors will add " to unquoted names that were
	# not in the original message.  For the purposes of deduplication,
	# do not take it into account:
	foreach my $h (qw(To Cc)) {
		my @v = $hdr->header($h);
		digest_addr($dig, $h, $_) foreach @v;
	}
	msg_iter($mime, sub {
		my ($part, $depth, @idx) = @{$_[0]};
		$dig->add("\0$depth:".join('.', @idx)."\0");
		my $fn = $part->filename;
		if (defined $fn) {
			utf8::encode($fn);
			$dig->add("fn\0$fn\0");
		}
		my @d = $part->header('Content-Description');
		foreach my $d (@d) {
			utf8::encode($d);
			$dig->add("d\0$d\0");
		}
		$dig->add("b\0");
		my $ct = $part->content_type || 'text/plain';
		my ($s, undef) = msg_part_text($part, $ct);
		if (defined $s) {
			$s =~ s/\r\n/\n/gs;
			$s =~ s/\s*\z//s;
			utf8::encode($s);
		} else {
			$s = $part->body;
		}
		$dig->add($s);
	});
	$dig;
}

sub content_id ($) {
	content_digest($_[0])->digest;
}

1;

git clone https://public-inbox.org/public-inbox.git
git clone http://7fh6tueqddpjyxjmgtdiueylzoqt6pt7hec3pukyptlmohoowvhde4yd.onion/public-inbox.git