lei: support reading MH for convert+import+index

The MH format is widely-supported and used by various MUAs such
as mutt and sylpheed, and a MH-like format is used by mlmmj for
archives, as well.  Locking implementations for writes are
inconsistent, so this commit doesn't support writes, yet.

inotify|EVFILT_VNODE watches aren't supported, yet, but that'll
have to come since MH allows packing unused integers and
renaming files.

1 files changed, 46 insertions, 0 deletions

diff --git a/lib/PublicInbox/MdirSort.pm b/lib/PublicInbox/MdirSort.pm
new file mode 100644
index 00000000..6bd9fb6c
--- /dev/null
+++ b/lib/PublicInbox/MdirSort.pm
@@ -0,0 +1,46 @@
+# Copyright (C) all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# used for sorting MH (and (TODO) Maildir) names
+# TODO: consider sort(1) to parallelize sorting of gigantic directories
+package PublicInbox::MdirSort;
+use v5.12;
+use Time::HiRes ();
+use parent qw(Exporter);
+use Fcntl qw(S_ISREG);
+our @EXPORT = qw(mdir_sort);
+my %ST = (sequence => 0, size => 1, atime => 2, mtime => 3, ctime => 4);
+
+sub mdir_sort ($$;$) {
+        my ($ent, $sort, $max) = @_;
+        my @st;
+        my @ent = map {
+                @st = Time::HiRes::stat $_;
+                # name, size, {a,m,c}time
+                S_ISREG($st[2]) ? [ $_, @st[7..10] ] : ();
+        } @$ent;
+        @ent = grep { $_->[1] <= $max } @ent if $max;
+        use sort 'stable';
+        for my $s (@$sort) {
+                if ($s =~ /\A(\-|\+|)name\z/) {
+                        if ($1 eq '-') {
+                                @ent = sort { $b->[0] cmp $a->[0] } @ent;
+                        } else {
+                                @ent = sort { $a->[0] cmp $b->[0] } @ent;
+                        }
+                } elsif ($s =~ /\A(\-|\+|)
+                                (sequence|size|ctime|mtime|atime)\z/x) {
+                        my $key = $ST{$2};
+                        if ($1 eq '-') {
+                                @ent = sort { $b->[$key] <=> $a->[$key] } @ent;
+                        } else {
+                                @ent = sort { $a->[$key] <=> $b->[$key] } @ent;
+                        }
+                } else {
+                        die "E: unrecognized sort parameter: `$s'";
+                }
+        }
+        @$ent = map { $_->[0] } @ent;
+}
+
+1;