RSS: parse lastBuildDate tag and abort parsing if the feed has not changed since last time.

Optimization to address issue #34.

src/rss/rss_imp.cpp

@@ -46,6 +46,7 @@
 #include "rssmanager.h"
 #include "rssfolder.h"
 #include "rssarticle.h"
+#include "rssparser.h"
 #include "rssfeed.h"
 #include "rsssettings.h"
 #include "automatedrssdownloader.h"
@@ -261,6 +262,11 @@ void RSSImp::deleteSelectedItems() {
         updateItemInfos (parent);
         parent = parent->parent();
       }
+      // Clear feed data from RSS parser (possible caching).
+      RssFeed* rssFeed = dynamic_cast<RssFeed*>(rss_item.data());
+      if (rssFeed) {
+        m_rssManager->rssParser()->clearFeedData(rssFeed->url());
+      }
     }
     m_rssManager->saveStreamList();
     // Update Unread items

src/rss/rssparser.cpp

@@ -221,6 +221,13 @@ void RssParser::parseRssFile(const QString& feedUrl, const QString& filePath)
   m_mutex.unlock();
 }
 
+void RssParser::clearFeedData(const QString &feedUrl)
+{
+  m_mutex.lock();
+  m_lastBuildDates.remove(feedUrl);
+  m_mutex.unlock();
+}
+
 void RssParser::run()
 {
   while (m_running) {
@@ -300,6 +307,17 @@ void RssParser::parseRSSChannel(QXmlStreamReader& xml, const QString& feedUrl)
         QString title = xml.readElementText();
         emit feedTitle(feedUrl, title);
       }
+      else if (xml.name() == "lastBuildDate") {
+        QString lastBuildDate = xml.readElementText();
+        if (!lastBuildDate.isEmpty()) {
+          QMutexLocker locker(&m_mutex);
+          if (m_lastBuildDates.value(feedUrl, "") == lastBuildDate) {
+            qDebug() << "The RSS feed has not changed since last time, aborting parsing.";
+            return;
+          }
+          m_lastBuildDates[feedUrl] = lastBuildDate;
+        }
+      }
       else if (xml.name() == "item") {
         parseRssArticle(xml, feedUrl);
       }

src/rss/rssparser.h

@@ -54,6 +54,7 @@ signals:
 
 public slots:
   void parseRssFile(const QString& feedUrl, const QString& filePath);
+  void clearFeedData(const QString& feedUrl);
 
 protected:
   virtual void run();
@@ -68,6 +69,7 @@ private:
   QMutex m_mutex;
   QQueue<ParsingJob> m_queue;
   QWaitCondition m_waitCondition;
+  QHash<QString/*feedUrl*/, QString/*lastBuildDate*/> m_lastBuildDates; // Optimization
 };
 
 #endif // RSSPARSER_H