Add --bt-detach-seed-only option

This option excludes seed only downloads when counting concurrent
active downloads (-j option).  This means that if -j3 is given and
this option is turned on and 3 downloads are active and one of those
enters seed mode, then it is excluded from active download count (thus
it becomes 2), and the next download waiting in queue gets started.
But be aware that seeding item is still recognized as active download
in RPC method.

doc/manual-src/en/aria2c.rst

@@ -595,6 +595,16 @@ BitTorrent/Metalink Options
 BitTorrent Specific Options
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+.. option:: --bt-detach-seed-only[=true|false]
+
+  Exclude seed only downloads when counting concurrent active
+  downloads (See :option:`-j` option).  This means that if ``-j3`` is
+  given and this option is turned on and 3 downloads are active and
+  one of those enters seed mode, then it is excluded from active
+  download count (thus it becomes 2), and the next download waiting in
+  queue gets started. But be aware that seeding item is still
+  recognized as active download in RPC method.  Default: ``false``
+
 .. option:: --bt-enable-lpd[=true|false]
 
   Enable Local Peer Discovery.  If a private flag is set in a torrent,

src/BtFileAllocationEntry.cc

@@ -89,6 +89,7 @@ void BtFileAllocationEntry::prepareForNextAction
       diskAdaptor->openFile();
     }
 #endif // __MINGW32__
+    getRequestGroup()->enableSeedOnly();
   }
 }
 

src/DefaultPieceStorage.cc

@@ -490,11 +490,14 @@ void DefaultPieceStorage::completePiece(const std::shared_ptr<Piece>& piece)
         diskAdaptor_->enableReadOnly();
         diskAdaptor_->openFile();
 #endif // __MINGW32__
-        util::executeHookByOptName(downloadContext_->getOwnerRequestGroup(),
-                                   option_, PREF_ON_BT_DOWNLOAD_COMPLETE);
+        auto group = downloadContext_->getOwnerRequestGroup();
+
+        util::executeHookByOptName(group, option_,
+                                   PREF_ON_BT_DOWNLOAD_COMPLETE);
         SingletonHolder<Notifier>::instance()->
-          notifyDownloadEvent(EVENT_ON_BT_DOWNLOAD_COMPLETE,
-                              downloadContext_->getOwnerRequestGroup());
+          notifyDownloadEvent(EVENT_ON_BT_DOWNLOAD_COMPLETE, group);
+
+        group->enableSeedOnly();
       }
     }
 #endif // ENABLE_BITTORRENT

src/OptionHandlerFactory.cc

@@ -1700,6 +1700,15 @@ std::vector<OptionHandler*> OptionHandlerFactory::createOptionHandlers()
 #endif // ENABLE_BITTORRENT || ENABLE_METALINK
   // BitTorrent Specific Options
 #ifdef ENABLE_BITTORRENT
+  {
+    OptionHandler* op(new BooleanOptionHandler
+                      (PREF_BT_DETACH_SEED_ONLY,
+                       TEXT_BT_DETACH_SEED_ONLY,
+                       A2_V_FALSE,
+                       OptionHandler::OPT_ARG));
+    op->addTag(TAG_BITTORRENT);
+    handlers.push_back(op);
+  }
   {
     OptionHandler* op(new BooleanOptionHandler
                       (PREF_BT_ENABLE_LPD,

src/RequestGroup.cc

@@ -149,7 +149,8 @@ RequestGroup::RequestGroup(const std::shared_ptr<GroupId>& gid,
     haltRequested_(false),
     forceHaltRequested_(false),
     pauseRequested_(false),
-    inMemoryDownload_(false)
+    inMemoryDownload_(false),
+    seedOnly_(false)
 {
   fileAllocationEnabled_ = option_->get(PREF_FILE_ALLOCATION) != V_NONE;
   if(!option_->getAsBool(PREF_DRY_RUN)) {
@@ -1265,4 +1266,18 @@ bool RequestGroup::p2pInvolved() const
 #endif // !ENABLE_BITTORRENT
 }
 
+void RequestGroup::enableSeedOnly()
+{
+  if(seedOnly_ || !option_->getAsBool(PREF_BT_DETACH_SEED_ONLY)) {
+    return;
+  }
+
+  if(requestGroupMan_) {
+    seedOnly_ = true;
+
+    requestGroupMan_->decreaseNumActive();
+    requestGroupMan_->requestQueueCheck();
+  }
+}
+
 } // namespace aria2

src/RequestGroup.h

@@ -179,6 +179,7 @@ class RequestGroup {
   // just sits in memory.
   bool inMemoryDownload_;
 
+  bool seedOnly_;
 
   void validateFilename(const std::string& expectedFilename,
                         const std::string& actualFilename) const;
@@ -563,6 +564,13 @@ class RequestGroup {
   {
     state_ = state;
   }
+
+  bool isSeedOnlyEnabled()
+  {
+    return seedOnly_;
+  }
+
+  void enableSeedOnly();
 };
 
 } // namespace aria2

src/RequestGroupMan.cc

@@ -105,6 +105,7 @@ RequestGroupMan::RequestGroupMan
  int maxSimultaneousDownloads,
  const Option* option)
   : maxSimultaneousDownloads_(maxSimultaneousDownloads),
+    numActive_(0),
     option_(option),
     serverStatMan_(std::make_shared<ServerStatMan>()),
     maxOverallDownloadSpeedLimit_
@@ -140,6 +141,7 @@ bool RequestGroupMan::downloadFinished()
 void RequestGroupMan::addRequestGroup
 (const std::shared_ptr<RequestGroup>& group)
 {
+  ++numActive_;
   requestGroups_.push_back(group->getGID(), group);
 }
 
@@ -320,6 +322,11 @@ class ProcessStoppedRequestGroup {
     if(group->getNumCommand() == 0) {
       collectStat(group);
       const std::shared_ptr<DownloadContext>& dctx = group->getDownloadContext();
+
+      if(!group->isSeedOnlyEnabled()) {
+        e_->getRequestGroupMan()->decreaseNumActive();
+      }
+
       // DownloadContext::resetDownloadStopTime() is only called when
       // download completed. If
       // DownloadContext::getDownloadStopTime().isZero() is true, then
@@ -453,11 +460,11 @@ std::vector<std::unique_ptr<Command>> createInitialCommand
 void RequestGroupMan::fillRequestGroupFromReserver(DownloadEngine* e)
 {
   removeStoppedGroup(e);
-  if(static_cast<size_t>(maxSimultaneousDownloads_) <= requestGroups_.size()) {
+  if(static_cast<size_t>(maxSimultaneousDownloads_) <= numActive_) {
     return;
   }
   int count = 0;
-  int num = maxSimultaneousDownloads_-requestGroups_.size();
+  int num = maxSimultaneousDownloads_ - numActive_;
   std::vector<std::shared_ptr<RequestGroup> > pending;
 
   while(count < num && (uriListParser_ || !reservedGroups_.empty())) {
@@ -488,6 +495,7 @@ void RequestGroupMan::fillRequestGroupFromReserver(DownloadEngine* e)
     configureRequestGroup(groupToAdd);
     groupToAdd->setRequestGroupMan(this);
     groupToAdd->setState(RequestGroup::STATE_ACTIVE);
+    ++numActive_;
     requestGroups_.push_back(groupToAdd->getGID(), groupToAdd);
     try {
       auto res = createInitialCommand(groupToAdd, e);
@@ -965,4 +973,10 @@ void RequestGroupMan::initWrDiskCache()
   }
 }
 
+void RequestGroupMan::decreaseNumActive()
+{
+  assert(numActive_ > 0);
+  --numActive_;
+}
+
 } // namespace aria2

src/RequestGroupMan.h

@@ -75,6 +75,13 @@ class RequestGroupMan {
 
   int maxSimultaneousDownloads_;
 
+  // The number of simultaneous active downloads, excluding seed only
+  // item if PREF_BT_DETACH_SEED_ONLY is true.  We rely on this
+  // variable to maintain the number of concurrent downloads.  If
+  // PREF_BT_DETACH_SEED_ONLY is false, this variable is equal to
+  // requestGroups_.size().
+  size_t numActive_;
+
   const Option* option_;
 
   std::shared_ptr<ServerStatMan> serverStatMan_;
@@ -376,6 +383,8 @@ class RequestGroupMan {
   {
     return openedFileCounter_;
   }
+
+  void decreaseNumActive();
 };
 
 } // namespace aria2

src/prefs.cc

@@ -542,6 +542,7 @@ PrefPtr PREF_BT_EXCLUDE_TRACKER = makePref("bt-exclude-tracker");
 // values: true | false
 PrefPtr PREF_BT_REMOVE_UNSELECTED_FILE =
   makePref("bt-remove-unselected-file");
+PrefPtr PREF_BT_DETACH_SEED_ONLY = makePref("bt-detach-seed-only");
 
 /**
  * Metalink related preferences

src/prefs.h

@@ -478,6 +478,8 @@ extern PrefPtr PREF_BT_TRACKER;
 extern PrefPtr PREF_BT_EXCLUDE_TRACKER;
 // values: true | false
 extern PrefPtr PREF_BT_REMOVE_UNSELECTED_FILE;
+// values: true |false
+extern PrefPtr PREF_BT_DETACH_SEED_ONLY;
 
 /**
  * Metalink related preferences

src/usage_text.h

@@ -1000,3 +1000,14 @@
     "                              using their metadata. This option pauses these\n" \
     "                              subsequent downloads. This option is effective\n" \
     "                              only when --enable-rpc=true is given.")
+#define TEXT_BT_DETACH_SEED_ONLY                \
+  _(" --bt-detach-seed-only[=true|false]\n"     \
+  "                              Exclude seed only downloads when counting\n" \
+  "                              concurrent active downloads (See -j option).\n" \
+  "                              This means that if -j3 is given and this option\n" \
+  "                              is turned on and 3 downloads are active and one\n" \
+  "                              of those enters seed mode, then it is excluded\n" \
+  "                              from active download count (thus it becomes 2),\n" \
+  "                              and the next download waiting in queue gets\n" \
+  "                              started. But be aware that seeding item is still\n" \
+  "                              recognized as active download in RPC method.")