+# Copyright (C) 2018 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Base class for per-inbox locking
+package PublicInbox::Lock;
+use strict;
+use warnings;
+use Fcntl qw(:flock :DEFAULT);
+use Carp qw(croak);
+
+# we only acquire the flock if creating or reindexing;
+# PublicInbox::Import already has the lock on its own.
+sub lock_acquire {
+ my ($self) = @_;
+ croak 'already locked' if $self->{lockfh};
+ my $lock_path = $self->{lock_path} or return;
+ sysopen(my $lockfh, $lock_path, O_WRONLY|O_CREAT) or
+ die "failed to open lock $lock_path: $!\n";
+ flock($lockfh, LOCK_EX) or die "lock failed: $!\n";
+ $self->{lockfh} = $lockfh;
+}
+
+sub lock_release {
+ my ($self) = @_;
+ return unless $self->{lock_path};
+ my $lockfh = delete $self->{lockfh} or croak 'not locked';
+ flock($lockfh, LOCK_UN) or die "unlock failed: $!\n";
+ close $lockfh or die "close failed: $!\n";
+}
+
+1;