From eab216e5a8a9f305b24263797df23d343ac4c0bc Mon Sep 17 00:00:00 2001
From: Christophe Dumez <chris@qbittorrent.org>
Date: Mon, 16 Nov 2009 20:28:58 +0000
Subject: [PATCH] - Improved ETA calculation for big torrents

---
 src/bittorrent.cpp | 69 ++++++++++++++++++++++++++++++++++++++--------
 src/bittorrent.h   |  7 ++++-
 2 files changed, 63 insertions(+), 13 deletions(-)

diff --git a/src/bittorrent.cpp b/src/bittorrent.cpp
index 0cc770e15..fe0da1aee 100644
--- a/src/bittorrent.cpp
+++ b/src/bittorrent.cpp
@@ -116,6 +116,8 @@ bittorrent::~bittorrent() {
   if(FSWatcher) {
     delete FSWatcher;
   }
+  if(timerETA)
+    delete timerETA;
   // Delete BT session
   qDebug("Deleting session");
   delete s;
@@ -459,21 +461,64 @@ void bittorrent::configureSession() {
   qDebug("Session configured");
 }
 
-// Calculate the ETA using GASA
-// GASA: global Average Speed Algorithm
-qlonglong bittorrent::getETA(QString hash) const {
+void bittorrent::takeETASamples() {
+  bool change = false;;
+  foreach(const QString &hash, ETA_samples.keys()) {
+    QTorrentHandle h = getTorrentHandle(hash);
+    if(h.is_valid() && !h.is_paused() && !h.is_seed()) {
+      QList<int> samples = ETA_samples.value(h.hash(), QList<int>());
+      if(samples.size() >= MAX_SAMPLES)
+        samples.removeFirst();
+      samples.append(h.download_payload_rate());
+      ETA_samples[h.hash()] = samples;
+      change = true;
+    } else {
+      ETA_samples.remove(hash);
+    }
+  }
+  if(!change && timerETA) {
+    delete timerETA;
+  }
+}
+
+// This algorithm was inspired from KTorrent - http://www.ktorrent.org
+// Calculate the ETA using a combination of several algorithms:
+// GASA: Global Average Speed Algorithm
+// CSA: Current Speed Algorithm
+// WINX: Window of X Algorithm
+qlonglong bittorrent::getETA(QString hash) {
   QTorrentHandle h = getTorrentHandle(hash);
-  if(!h.is_valid()) return -1;
-  switch(h.state()) {
-  case torrent_status::downloading: {
-      if(h.active_time() == 0)
-        return -1;
-      double avg_speed = (double)h.all_time_download() / h.active_time();
-      return (qlonglong) floor((double) (h.actual_size() - h.total_wanted_done()) / avg_speed);
-    }
-  default:
+  if(!h.is_valid() || h.state() != torrent_status::downloading || !h.active_time())
     return -1;
+  // See if the torrent is going to be completed soon
+  qulonglong bytes_left = h.actual_size() - h.total_wanted_done();
+  if(h.actual_size() > 10485760L) { // Size > 10MiB
+    if(h.progress() >= (float)0.99 && bytes_left < 10485760L) { // Progress>99% but less than 10MB left.
+      // Compute by taking samples
+      if(!ETA_samples.contains(h.hash())) {
+        ETA_samples[h.hash()] = QList<int>();
+      }
+      if(!timerETA) {
+        timerETA = new QTimer(this);
+        connect(timerETA, SIGNAL(timeout()), this, SLOT(takeETASamples()));
+        timerETA->start();
+      } else {
+        QList<int> samples = ETA_samples.value(h.hash(), QList<int>());
+        int nb_samples = samples.size();
+        if(nb_samples > 3) {
+          long sum_samples = 0;
+          foreach(int val, samples) {
+            sum_samples += val;
+          }
+          // Use WINX
+          return (qlonglong)(((double)bytes_left) / (((double)sum_samples) / ((double)nb_samples)));
+        }
+      }
+    }
   }
+  // Normal case: Use GASA
+  double avg_speed = (double)h.all_time_download() / h.active_time();
+  return (qlonglong) floor((double) (bytes_left) / avg_speed);
 }
 
 std::vector<torrent_handle> bittorrent::getTorrents() const {
diff --git a/src/bittorrent.h b/src/bittorrent.h
index f6fdbc29d..509d0c1d6 100644
--- a/src/bittorrent.h
+++ b/src/bittorrent.h
@@ -42,6 +42,8 @@
 
 using namespace libtorrent;
 
+#define MAX_SAMPLES 20
+
 class downloadThread;
 class QTimer;
 class FileSystemWatcher;
@@ -77,6 +79,8 @@ class bittorrent : public QObject {
     QHash<QString, QString> savepath_fromurl;
     bool resolve_countries;
     bool geoipDBLoaded;
+    QPointer<QTimer> timerETA;
+    QHash<QString, QList<int> > ETA_samples;
 
   protected:
     QString getSavePath(QString hash);
@@ -106,7 +110,7 @@ class bittorrent : public QObject {
     int loadTorrentPriority(QString hash);
     QStringList getConsoleMessages() const;
     QStringList getPeerBanMessages() const;
-    qlonglong getETA(QString hash) const;
+    qlonglong getETA(QString hash);
     bool useTemporaryFolder() const;
     QString getDefaultSavePath() const;
 
@@ -177,6 +181,7 @@ class bittorrent : public QObject {
     void readAlerts();
     void loadTrackerFile(QString hash);
     void deleteBigRatios();
+    void takeETASamples();
 
   signals:
     void addedTorrent(QTorrentHandle& h);