Add sessionConfigSetKeepRunning and shutdown API function

Setting sessionConfigSetKeepRunning to true makes aria2 core keep
running even if there is no download to perform, just like --enable-rpc
option.

src/RequestGroupMan.cc

@@ -107,7 +107,7 @@ RequestGroupMan::RequestGroupMan
     (option->getAsInt(PREF_MAX_OVERALL_DOWNLOAD_LIMIT)),
     maxOverallUploadSpeedLimit_(option->getAsInt
                                 (PREF_MAX_OVERALL_UPLOAD_LIMIT)),
-    rpc_(option->getAsBool(PREF_ENABLE_RPC)),
+    keepRunning_(option->getAsBool(PREF_ENABLE_RPC)),
     queueCheck_(true),
     removedErrorResult_(0),
     removedLastErrorResult_(error_code::FINISHED),
@@ -125,7 +125,7 @@ RequestGroupMan::~RequestGroupMan()
 
 bool RequestGroupMan::downloadFinished()
 {
-  if(rpc_) {
+  if(keepRunning_) {
     return false;
   }
   return requestGroups_.empty() && reservedGroups_.empty();
@@ -474,7 +474,7 @@ void RequestGroupMan::fillRequestGroupFromReserver(DownloadEngine* e)
     }
     SharedHandle<RequestGroup> groupToAdd = *reservedGroups_.begin();
     reservedGroups_.pop_front();
-    if((rpc_ && groupToAdd->isPauseRequested()) ||
+    if((keepRunning_ && groupToAdd->isPauseRequested()) ||
        !groupToAdd->isDependencyResolved()) {
       pending.push_back(groupToAdd);
       continue;

src/RequestGroupMan.h

@@ -84,8 +84,9 @@ private:
 
   NetStat netStat_;
 
-  // true if JSON-RPC/XML-RPC is enabled.
-  bool rpc_;
+  // true if download engine should keep running even if there is no
+  // download to perform.
+  bool keepRunning_;
 
   bool queueCheck_;
 
@@ -335,6 +336,11 @@ public:
   // Initializes WrDiskCache according to PREF_DISK_CACHE option.  If
   // its value is 0, cache storage will not be initialized.
   void initWrDiskCache();
+
+  void setKeepRunning(bool flag)
+  {
+    keepRunning_ = flag;
+  }
 };
 
 } // namespace aria2

src/aria2api.cc

@@ -106,6 +106,13 @@ int sessionFinal(Session* session)
   return rv;
 }
 
+int sessionConfigSetKeepRunning(Session* session, bool flag)
+{
+  session->context->reqinfo->getDownloadEngine()->getRequestGroupMan()
+    ->setKeepRunning(flag);
+  return 0;
+}
+
 int run(Session* session, RUN_MODE mode)
 {
   const SharedHandle<DownloadEngine>& e =
@@ -113,6 +120,18 @@ int run(Session* session, RUN_MODE mode)
   return e->run(mode == RUN_ONCE);
 }
 
+int shutdown(Session* session, bool force)
+{
+  const SharedHandle<DownloadEngine>& e =
+    session->context->reqinfo->getDownloadEngine();
+  if(force) {
+    e->requestForceHalt();
+  } else {
+    e->requestHalt();
+  }
+  return 0;
+}
+
 std::string gidToHex(const A2Gid& gid)
 {
   return GroupId::toHex(gid);

src/includes/aria2/aria2.h

@@ -94,6 +94,13 @@ enum RUN_MODE {
   RUN_ONCE
 };
 
+// If the |flag| is true, run(session, RUN_ONCE) will return 1 even if
+// there are no download to perform. The behavior is very similar to
+// RPC server, except that this option does not enable RPC
+// functionality. To stop aria2, use shutdown() function.  This
+// function returns 0 if it succeeds, or -1.
+int sessionConfigSetKeepRunning(Session* session, bool flag);
+
 // Performs event polling and actions for them. If the |mode| is
 // RUN_DEFAULT, this function returns when no downloads are left to be
 // processed. In this case, this function returns 0.
@@ -147,9 +154,13 @@ int removeDownload(Session* session, const A2Gid& gid, bool force = false);
 // download is placed on the first position of waiting queue. As long
 // as the status is DOWNLOAD_PAUSED, the download will not start. To
 // change status to DOWNLOAD_WAITING, use unpauseDownload() function.
-// If the |force| is true, removal will take place without any action
+// If the |force| is true, pause will take place without any action
 // which takes time such as contacting BitTorrent tracker. This
-// function returns 0 if it succeeds, or -1.
+// function returns 0 if it succeeds, or -1.  Please note that, to
+// make pause work, the application must call
+// sessionConfigSetKeepRunning() function with the |flag| argument to
+// true. Without this call, download may be paused at first, but it
+// will be restarted automatically.
 int pauseDownload(Session* session, const A2Gid& gid, bool force = false);
 
 // Changes the status of the download denoted by the |gid| from
@@ -157,6 +168,13 @@ int pauseDownload(Session* session, const A2Gid& gid, bool force = false);
 // eligible to restart. This function returns 0 if it succeeds, or -1.
 int unpauseDownload(Session* session, const A2Gid& gid);
 
+// Schedules shutdown. If the |force| is true, shutdown will take
+// place without any action which takes time such as contacting
+// BitTorrent tracker. After this call, the application must keep
+// calling run() method until it returns 0.  This function returns 0
+// if it succeeds, or -1.
+int shutdown(Session* session, bool force = false);
+
 enum UriStatus {
   URI_USED,
   URI_WAITING