From 7a01dc776ed6e124eac9db1a288d4aa5ab63b53d Mon Sep 17 00:00:00 2001
From: Andrew Dolgov <fox@madoka.volgo-balt.ru>
Date: Sat, 30 Mar 2013 15:10:53 +0400
Subject: [PATCH] support If-Modified-Since

---
 include/functions.php | 11 ++++++++++-
 include/rssfuncs.php  | 19 +++++++++++++++----
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/include/functions.php b/include/functions.php
index 36d349b54..307f66200 100644
--- a/include/functions.php
+++ b/include/functions.php
@@ -6,6 +6,7 @@
 	define('PLUGIN_FEED_BASE_INDEX', -128);
 
 	$fetch_last_error = false;
+	$fetch_last_error_code = false;
 	$pluginhost = false;
 
 	function __autoload($class) {
@@ -287,9 +288,10 @@
 		}
 	}
 
-	function fetch_file_contents($url, $type = false, $login = false, $pass = false, $post_query = false, $timeout = false) {
+	function fetch_file_contents($url, $type = false, $login = false, $pass = false, $post_query = false, $timeout = false, $timestamp = 0) {
 
 		global $fetch_last_error;
+		global $fetch_last_error_code;
 
 		if (function_exists('curl_init') && !ini_get("open_basedir")) {
 
@@ -299,6 +301,11 @@
 				$ch = curl_init($url);
 			}
 
+			if ($timestamp) {
+				curl_setopt($ch, CURLOPT_HTTPHEADER,
+					array("If-Modified-Since: ".gmdate('D, d M Y H:i:s \G\M\T', $timestamp)));
+			}
+
 			curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout ? $timeout : 15);
 			curl_setopt($ch, CURLOPT_TIMEOUT, $timeout ? $timeout : 45);
 			curl_setopt($ch, CURLOPT_FOLLOWLOCATION, !ini_get("safe_mode"));
@@ -335,6 +342,8 @@
 			$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
 			$content_type = curl_getinfo($ch, CURLINFO_CONTENT_TYPE);
 
+			$fetch_last_error_code = $http_code;
+
 			if ($http_code != 200 || $type && strpos($content_type, "$type") === false) {
 				if (curl_errno($ch) != 0) {
 					$fetch_last_error = curl_errno($ch) . " " . curl_error($ch);
diff --git a/include/rssfuncs.php b/include/rssfuncs.php
index e82e94b09..7c668f69f 100644
--- a/include/rssfuncs.php
+++ b/include/rssfuncs.php
@@ -239,6 +239,7 @@
 
 		$rss = false;
 		$rss_hash = false;
+		$cache_timestamp = file_exists($cache_filename) ? filemtime($cache_filename) : 0;
 
 		if (file_exists($cache_filename) &&
 			is_readable($cache_filename) &&
@@ -261,11 +262,11 @@
 
 			if (!$feed_data) {
 				if ($debug_enabled) {
-					_debug("update_rss_feed: fetching [$fetch_url]...");
+					_debug("update_rss_feed: fetching [$fetch_url] (ts: $cache_timestamp)");
 				}
 
 				$feed_data = fetch_file_contents($fetch_url, false,
-					$auth_login, $auth_pass, false, $no_cache ? 15 : 45);
+					$auth_login, $auth_pass, false, $no_cache ? 15 : 45, $cache_timestamp);
 
 				if ($debug_enabled) {
 					_debug("update_rss_feed: fetch done.");
@@ -275,12 +276,22 @@
 
 			if (!$feed_data) {
 				global $fetch_last_error;
+				global $fetch_last_error_code;
 
 				if ($debug_enabled) {
-					_debug("update_rss_feed: unable to fetch: $fetch_last_error");
+					_debug("update_rss_feed: unable to fetch: $fetch_last_error [$fetch_last_error_code]");
 				}
 
-				$error_escaped = db_escape_string($link, $fetch_last_error);
+				$error_escaped = '';
+
+				// If-Modified-Since
+				if ($fetch_last_error_code != 304) {
+					$error_escaped = db_escape_string($link, $fetch_last_error);
+				} else {
+					if ($debug_enabled) {
+						_debug("update_rss_feed: source claims data not modified, nothing to do.");
+					}
+				}
 
 				db_query($link,
 					"UPDATE ttrss_feeds SET last_error = '$error_escaped',