From 4b28462f6dccd2437a3313b02a2ec678a4bf674b Mon Sep 17 00:00:00 2001
From: Mischa POSLAWSKY <perl@shiar.org>
Date: Mon, 12 Apr 2010 17:45:00 +0000
Subject: [PATCH 1/1] export and check last-modified header

Avoid resending unaltered pages.
---
 common.inc.plp | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/common.inc.plp b/common.inc.plp
index b3a9a70..d51e3e6 100644
--- a/common.inc.plp
+++ b/common.inc.plp
@@ -6,6 +6,8 @@ no  warnings 'qw';  # you know what you doing
 no  warnings 'uninitialized';  # save some useless checks for more legible code
 use open IO => ':utf8';
 
+use File::stat 'stat';
+use HTTP::Date;
 use Shiar_Sheet::KeySigns qw(%sign);  # dependant on $get{ascii}
 
 our $style;
@@ -36,9 +38,33 @@ sub stylesheet {
 	) } @_;
 }
 
+sub checkmodified {
+	my $lastmod;
+	for (@_) {
+		my $mod = stat $_ or next;
+		$mod = $mod->mtime or next;
+		$lastmod = $mod if $mod gt $lastmod;
+	}
+
+	for ($ENV{HTTP_IF_MODIFIED_SINCE} || ()) {
+		next if str2time($_) < $lastmod;
+		$header{status} = '304 Same old';
+		exit;
+	}
+
+	$header{'Last-Modified'} = time2str($lastmod);
+}
+
 sub Html {
 	my ($meta) = @_;
 
+	# announce and check data modification
+	checkmodified(
+		$ENV{SCRIPT_FILENAME},
+		(grep { /^Shiar_/ } values %INC),
+		$meta->{data} ? @{ $meta->{data} } : (),
+	);
+
 	# default fallbacks
 	$meta->{stylesheet} ||= [qw'light dark circus mono red terse'];
 	$meta->{charset} ||= 'utf-8';
-- 
2.30.0