+#! /usr/bin/env perl
+# Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the Apache License 2.0 (the "License"). You may not use
+# this file except in compliance with the License. You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+use strict;
+use warnings;
+
+package OpenSSL::copyright;
+
+sub year_of {
+ my $file = shift;
+
+ return $ENV{'OSSL_COPYRIGHT_YEAR'} if defined $ENV{'OSSL_COPYRIGHT_YEAR'};
+
+ # Use the file date for backward compatibility.
+ my $YEAR = [localtime([stat($file)]->[9])]->[5] + 1900;
+
+ # See if git's available
+ open my $FH,
+ "git log -1 --date=short --format=format:%cd $file 2>/dev/null|"
+ or return $YEAR;
+ my $LINE = <$FH>;
+ close $FH;
+ $LINE =~ s/^([0-9]*)-.*/$1/ if $LINE;
+ $YEAR = $LINE if $LINE;
+ return $YEAR;
+}
+
+sub latest {
+ my $l = 0;
+ foreach my $f (@_ ) {
+ my $y = year_of($f);
+ $l = $y if $y > $l;
+ }
+ return $l
+}
+1;