Refactor DownloadHandlerFactory

20 files changed, 235 insertions, 345 deletions

diff --git a/src/BtPostDownloadHandler.cc b/src/BtPostDownloadHandler.cc
index 0b2e73ea..9639a6da 100644
--- a/src/BtPostDownloadHandler.cc
+++ b/src/BtPostDownloadHandler.cc
@@ -57,17 +57,13 @@ namespace aria2 {
 
 BtPostDownloadHandler::BtPostDownloadHandler()
 {
-  std::shared_ptr<RequestGroupCriteria> cri
-    (new ContentTypeRequestGroupCriteria
-     (getBtContentTypes(), getBtExtensions()));
-  setCriteria(cri);
+  setCriteria(make_unique<ContentTypeRequestGroupCriteria>
+              (getBtContentTypes(), getBtExtensions()));
 }
 
-BtPostDownloadHandler::~BtPostDownloadHandler() {}
-
 void BtPostDownloadHandler::getNextRequestGroups
 (std::vector<std::shared_ptr<RequestGroup> >& groups,
- RequestGroup* requestGroup)
+ RequestGroup* requestGroup) const
 {
   A2_LOG_INFO(fmt("Generating RequestGroups for Torrent file %s",
                   requestGroup->getFirstFilePath().c_str()));
@@ -100,13 +96,13 @@ void BtPostDownloadHandler::getNextRequestGroups
     throw DL_ABORT_EX2("Could not parse BitTorrent metainfo",
                        error_code::BENCODE_PARSE_ERROR);
   }
-  std::vector<std::shared_ptr<RequestGroup> > newRgs;
+  std::vector<std::shared_ptr<RequestGroup>> newRgs;
   createRequestGroupForBitTorrent(newRgs, requestGroup->getOption(),
                                   std::vector<std::string>(),
                                   "",
                                   torrent.get());
   requestGroup->followedBy(newRgs.begin(), newRgs.end());
-  std::shared_ptr<MetadataInfo> mi =
+  auto mi =
     createMetadataInfoFromFirstFileEntry(requestGroup->getGroupId(),
                                          requestGroup->getDownloadContext());
   if(mi) {
diff --git a/src/BtPostDownloadHandler.h b/src/BtPostDownloadHandler.h
index 006ab2a8..6e99b956 100644
--- a/src/BtPostDownloadHandler.h
+++ b/src/BtPostDownloadHandler.h
@@ -44,11 +44,9 @@ class BtPostDownloadHandler:public PostDownloadHandler
 public:
   BtPostDownloadHandler();
 
-  virtual ~BtPostDownloadHandler();
-
   virtual void
   getNextRequestGroups(std::vector<std::shared_ptr<RequestGroup> >& groups,
-                       RequestGroup* requestGroup) CXX11_OVERRIDE;
+                       RequestGroup* requestGroup) const CXX11_OVERRIDE;
 };
 
 } // namespace aria2
diff --git a/src/DownloadHandler.cc b/src/DownloadHandler.cc
index 48b53636..91b17aa3 100644
--- a/src/DownloadHandler.cc
+++ b/src/DownloadHandler.cc
@@ -39,19 +39,15 @@
 
 namespace aria2 {
 
-DownloadHandler::DownloadHandler() {}
-
-DownloadHandler::~DownloadHandler() {}
-
 bool DownloadHandler::canHandle(const RequestGroup* requestGroup) const
 {
-  return criteria_ && criteria_->match(requestGroup);
+  return !criteria_ || criteria_->match(requestGroup);
 }
 
 void DownloadHandler::setCriteria
-(const std::shared_ptr<RequestGroupCriteria>& criteria)
+(std::unique_ptr<RequestGroupCriteria> criteria)
 {
-  criteria_ = criteria;
+  criteria_ = std::move(criteria);
 }
 
 } // namespace aria2
diff --git a/src/DownloadHandler.h b/src/DownloadHandler.h
index 220a126f..8757e6a5 100644
--- a/src/DownloadHandler.h
+++ b/src/DownloadHandler.h
@@ -47,16 +47,14 @@ class RequestGroupCriteria;
 
 class DownloadHandler
 {
-private:
-  std::shared_ptr<RequestGroupCriteria> criteria_;
 public:
-  DownloadHandler();
-
-  virtual ~DownloadHandler();
+  virtual ~DownloadHandler() {}
 
   bool canHandle(const RequestGroup* requestGroup) const;
 
-  void setCriteria(const std::shared_ptr<RequestGroupCriteria>& criteria);
+  void setCriteria(std::unique_ptr<RequestGroupCriteria> criteria);
+private:
+  std::unique_ptr<RequestGroupCriteria> criteria_;
 };
 
 } // namespace aria2
diff --git a/src/DownloadHandlerFactory.cc b/src/DownloadHandlerFactory.cc
deleted file mode 100644
index 3263fc71..00000000
--- a/src/DownloadHandlerFactory.cc
+++ /dev/null
@@ -1,131 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#include "DownloadHandlerFactory.h"
-#include "MemoryBufferPreDownloadHandler.h"
-#include "MetalinkPostDownloadHandler.h"
-#include "BtPostDownloadHandler.h"
-#include "DownloadHandlerConstants.h"
-#include "ContentTypeRequestGroupCriteria.h"
-#include "UTMetadataPostDownloadHandler.h"
-
-namespace aria2 {
-
-#ifdef ENABLE_METALINK
-
-std::shared_ptr<PreDownloadHandler>
-DownloadHandlerFactory::metalinkPreDownloadHandler_;
-
-std::shared_ptr<PostDownloadHandler>
-DownloadHandlerFactory::metalinkPostDownloadHandler_;
-
-#endif // ENABLE_METALINK
-
-#ifdef ENABLE_BITTORRENT
-
-std::shared_ptr<PreDownloadHandler>
-DownloadHandlerFactory::btPreDownloadHandler_;
-
-std::shared_ptr<PostDownloadHandler>
-DownloadHandlerFactory::btPostDownloadHandler_;
-
-std::shared_ptr<PostDownloadHandler>
-DownloadHandlerFactory::btMetadataPostDownloadHandler_;
-#endif // ENABLE_BITTORRENT
-
-#ifdef ENABLE_METALINK
-
-std::shared_ptr<PreDownloadHandler>
-DownloadHandlerFactory::getMetalinkPreDownloadHandler()
-{
-  if(!metalinkPreDownloadHandler_) {
-    metalinkPreDownloadHandler_.reset(new MemoryBufferPreDownloadHandler());
-
-    std::shared_ptr<RequestGroupCriteria> criteria
-      (new ContentTypeRequestGroupCriteria
-       (getMetalinkContentTypes(), getMetalinkExtensions()));
-    metalinkPreDownloadHandler_->setCriteria(criteria);
-  }
-  return metalinkPreDownloadHandler_;
-}
-
-std::shared_ptr<PostDownloadHandler>
-DownloadHandlerFactory::getMetalinkPostDownloadHandler()
-{
-  if(!metalinkPostDownloadHandler_) {
-    metalinkPostDownloadHandler_.reset(new MetalinkPostDownloadHandler());
-  }
-  return metalinkPostDownloadHandler_;
-}
-
-#endif // ENABLE_METALINK
-
-#ifdef ENABLE_BITTORRENT
-
-std::shared_ptr<PreDownloadHandler>
-DownloadHandlerFactory::getBtPreDownloadHandler()
-{
-  if(!btPreDownloadHandler_) {
-    btPreDownloadHandler_.reset
-      (new bittorrent::MemoryBencodePreDownloadHandler());
-
-    std::shared_ptr<RequestGroupCriteria> criteria
-      (new ContentTypeRequestGroupCriteria
-       (getBtContentTypes(), getBtExtensions()));
-    btPreDownloadHandler_->setCriteria(criteria);
-  }
-  return btPreDownloadHandler_;
-}
-
-std::shared_ptr<PostDownloadHandler>
-DownloadHandlerFactory::getBtPostDownloadHandler()
-{
-  if(!btPostDownloadHandler_) {
-    btPostDownloadHandler_.reset(new BtPostDownloadHandler());
-  }
-  return btPostDownloadHandler_;
-}
-
-std::shared_ptr<PostDownloadHandler>
-DownloadHandlerFactory::getUTMetadataPostDownloadHandler()
-{
-  if(!btMetadataPostDownloadHandler_) {
-    btMetadataPostDownloadHandler_.reset(new UTMetadataPostDownloadHandler());
-  }
-  return btMetadataPostDownloadHandler_;
-}
-
-#endif // ENABLE_BITTORRENT
-
-} // namespace aria2
diff --git a/src/DownloadHandlerFactory.h b/src/DownloadHandlerFactory.h
deleted file mode 100644
index 5aff1f89..00000000
--- a/src/DownloadHandlerFactory.h
+++ /dev/null
@@ -1,101 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#ifndef D_DOWNLOAD_HANDLER_FACTORY_H
-#define D_DOWNLOAD_HANDLER_FACTORY_H
-
-#include "common.h"
-
-#include <memory>
-
-#include "MemoryBufferPreDownloadHandler.h"
-#ifdef ENABLE_BITTORRENT
-#  include "MemoryBencodePreDownloadHandler.h"
-#endif // ENABLE_BITTORRENT
-
-namespace aria2 {
-
-#ifdef ENABLE_METALINK
-class MetalinkPostDownloadHandler;
-#endif // ENABLE_METALINK
-#ifdef ENABLE_BITTORRENT
-class BtPostDownloadHandler;
-class UTMetadataPostDownloadHandler;
-#endif // ENABLE_BITTORRENT
-
-class DownloadHandlerFactory
-{
-private:
-#ifdef ENABLE_METALINK
-  static std::shared_ptr<PreDownloadHandler>
-  metalinkPreDownloadHandler_;
-
-  static std::shared_ptr<PostDownloadHandler>
-  metalinkPostDownloadHandler_;
-#endif // ENABLE_METALINK
-
-#ifdef ENABLE_BITTORRENT
-  static std::shared_ptr<PreDownloadHandler>
-  btPreDownloadHandler_;
-
-  static std::shared_ptr<PostDownloadHandler>
-  btPostDownloadHandler_;
-
-  static std::shared_ptr<PostDownloadHandler>
-  btMetadataPostDownloadHandler_;
-#endif // ENABLE_BITTORRENT
-public:
-#ifdef ENABLE_METALINK
-  static std::shared_ptr<PreDownloadHandler>
-  getMetalinkPreDownloadHandler();
-
-  static std::shared_ptr<PostDownloadHandler>
-  getMetalinkPostDownloadHandler();
-#endif // ENABLE_METALINK
-
-#ifdef ENABLE_BITTORRENT
-  static std::shared_ptr<PreDownloadHandler>
-  getBtPreDownloadHandler();
-
-  static std::shared_ptr<PostDownloadHandler>
-  getBtPostDownloadHandler();
-
-  static std::shared_ptr<PostDownloadHandler>
-  getUTMetadataPostDownloadHandler();
-#endif // ENABLE_BITTORRENT
-};
-
-} // namespace aria2
-
-#endif // D_DOWNLOAD_HANDLER_FACTORY_H
diff --git a/src/Makefile.am b/src/Makefile.am
index 6499eeda..91146686 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -115,7 +115,7 @@ SRCS =  option_processing.cc\
 	ContentTypeRequestGroupCriteria.cc ContentTypeRequestGroupCriteria.h\
 	DownloadHandler.cc DownloadHandler.h\
 	DownloadHandlerConstants.cc DownloadHandlerConstants.h\
-	DownloadHandlerFactory.cc DownloadHandlerFactory.h\
+	download_handlers.cc download_handlers.h\
 	MemoryPreDownloadHandler.h\
 	MemoryBufferPreDownloadHandler.h\
 	HaveEraseCommand.cc HaveEraseCommand.h\
diff --git a/src/MemoryPreDownloadHandler.h b/src/MemoryPreDownloadHandler.h
index d8598d42..4b9f6451 100644
--- a/src/MemoryPreDownloadHandler.h
+++ b/src/MemoryPreDownloadHandler.h
@@ -44,13 +44,9 @@ template<class DiskWriterFactoryType>
 class MemoryPreDownloadHandler:public PreDownloadHandler
 {
 public:
-  MemoryPreDownloadHandler() {}
-
-  virtual ~MemoryPreDownloadHandler() {}
-
-  virtual void execute(RequestGroup* requestGroup) CXX11_OVERRIDE
+  virtual void execute(RequestGroup* requestGroup) const CXX11_OVERRIDE
   {
-    std::shared_ptr<DiskWriterFactory> dwf(new DiskWriterFactoryType());
+    auto dwf = std::make_shared<DiskWriterFactoryType>();
     requestGroup->setDiskWriterFactory(dwf);
     requestGroup->setFileAllocationEnabled(false);
     requestGroup->setPreLocalFileCheckEnabled(false);
diff --git a/src/Metalink2RequestGroup.cc b/src/Metalink2RequestGroup.cc
index 2a856bb9..87a36779 100644
--- a/src/Metalink2RequestGroup.cc
+++ b/src/Metalink2RequestGroup.cc
@@ -47,7 +47,6 @@
 #include "metalink_helper.h"
 #include "BinaryStream.h"
 #include "MemoryBufferPreDownloadHandler.h"
-#include "TrueRequestGroupCriteria.h"
 #include "MetalinkEntry.h"
 #include "MetalinkResource.h"
 #include "MetalinkMetaurl.h"
@@ -59,6 +58,8 @@
 #include "SegList.h"
 #include "DownloadFailureException.h"
 #include "Signature.h"
+#include "download_handlers.h"
+#include "RequestGroupCriteria.h"
 #ifdef ENABLE_BITTORRENT
 # include "BtDependency.h"
 # include "download_helper.h"
@@ -233,9 +234,8 @@ Metalink2RequestGroup::createRequestGroup
         // tranparent metalink
         torrentRg->getDownloadContext()->setAcceptMetalink(false);
         // make it in-memory download
-        auto preh = std::make_shared<MemoryBufferPreDownloadHandler>();
-        preh->setCriteria(std::make_shared<TrueRequestGroupCriteria>());
-        torrentRg->addPreDownloadHandler(preh);
+        torrentRg->addPreDownloadHandler
+          (download_handlers::getMemoryPreDownloadHandler());
         groups.push_back(torrentRg);
       }
     }
diff --git a/src/MetalinkPostDownloadHandler.cc b/src/MetalinkPostDownloadHandler.cc
index fbd47030..44696084 100644
--- a/src/MetalinkPostDownloadHandler.cc
+++ b/src/MetalinkPostDownloadHandler.cc
@@ -56,27 +56,22 @@ namespace aria2 {
 
 MetalinkPostDownloadHandler::MetalinkPostDownloadHandler()
 {
-  std::shared_ptr<RequestGroupCriteria> cri
-    (new ContentTypeRequestGroupCriteria
-     (getMetalinkContentTypes(), getMetalinkExtensions()));
-  setCriteria(cri);
+  setCriteria(make_unique<ContentTypeRequestGroupCriteria>
+              (getMetalinkContentTypes(), getMetalinkExtensions()));
 }
 
-MetalinkPostDownloadHandler::~MetalinkPostDownloadHandler() {}
-
 namespace {
 const std::string& getBaseUri(RequestGroup* requestGroup)
 {
-  const std::shared_ptr<DownloadContext>& dctx =
-    requestGroup->getDownloadContext();
+  auto& dctx = requestGroup->getDownloadContext();
   if(dctx->getFileEntries().empty()) {
     return A2STR::NIL;
   } else {
     // TODO Check download result for each URI
-    const std::shared_ptr<FileEntry>& entry = dctx->getFirstFileEntry();
-    const std::deque<std::string>& spentUris = entry->getSpentUris();
+    auto& entry = dctx->getFirstFileEntry();
+    auto& spentUris = entry->getSpentUris();
     if(spentUris.empty()) {
-      const std::deque<std::string>& remainingUris = entry->getRemainingUris();
+      auto& remainingUris = entry->getRemainingUris();
       if(remainingUris.empty()) {
         return A2STR::NIL;
       } else {
@@ -90,22 +85,21 @@ const std::string& getBaseUri(RequestGroup* requestGroup)
 } // namespace
 
 void MetalinkPostDownloadHandler::getNextRequestGroups
-(std::vector<std::shared_ptr<RequestGroup> >& groups,
- RequestGroup* requestGroup)
+(std::vector<std::shared_ptr<RequestGroup>>& groups,
+ RequestGroup* requestGroup) const
 {
   A2_LOG_DEBUG(fmt("Generating RequestGroups for Metalink file %s",
                    requestGroup->getFirstFilePath().c_str()));
-  std::shared_ptr<DiskAdaptor> diskAdaptor =
-    requestGroup->getPieceStorage()->getDiskAdaptor();
+  auto diskAdaptor = requestGroup->getPieceStorage()->getDiskAdaptor();
   try {
     diskAdaptor->openExistingFile();
     //requestOption.put(PREF_DIR, requestGroup->getDownloadContext()->getDir());
     const std::string& baseUri = getBaseUri(requestGroup);
-    std::vector<std::shared_ptr<RequestGroup> > newRgs;
+    std::vector<std::shared_ptr<RequestGroup>> newRgs;
     Metalink2RequestGroup().generate(newRgs, diskAdaptor,
                                      requestGroup->getOption(), baseUri);
     requestGroup->followedBy(newRgs.begin(), newRgs.end());
-    std::shared_ptr<MetadataInfo> mi =
+    auto mi =
       createMetadataInfoFromFirstFileEntry(requestGroup->getGroupId(),
                                            requestGroup->getDownloadContext());
     if(mi) {
diff --git a/src/MetalinkPostDownloadHandler.h b/src/MetalinkPostDownloadHandler.h
index 8b3fe195..b219d42f 100644
--- a/src/MetalinkPostDownloadHandler.h
+++ b/src/MetalinkPostDownloadHandler.h
@@ -44,11 +44,9 @@ class MetalinkPostDownloadHandler:public PostDownloadHandler
 public:
   MetalinkPostDownloadHandler();
 
-  virtual ~MetalinkPostDownloadHandler();
-
   virtual void
-  getNextRequestGroups(std::vector<std::shared_ptr<RequestGroup> >& groups,
-                       RequestGroup* requestGroup) CXX11_OVERRIDE;
+  getNextRequestGroups(std::vector<std::shared_ptr<RequestGroup>>& groups,
+                       RequestGroup* requestGroup) const CXX11_OVERRIDE;
 };
 
 } // namespace aria2
diff --git a/src/PostDownloadHandler.h b/src/PostDownloadHandler.h
index fe21dbfc..eebd2432 100644
--- a/src/PostDownloadHandler.h
+++ b/src/PostDownloadHandler.h
@@ -44,13 +44,11 @@ namespace aria2 {
 class PostDownloadHandler:public DownloadHandler
 {
 public:
-  PostDownloadHandler() {}
-
   virtual ~PostDownloadHandler() {}
 
   virtual void
-  getNextRequestGroups(std::vector<std::shared_ptr<RequestGroup> >& groups,
-                       RequestGroup* requestGroup) = 0;
+  getNextRequestGroups(std::vector<std::shared_ptr<RequestGroup>>& groups,
+                       RequestGroup* requestGroup) const = 0;
 };
 
 } // namespace aria2
diff --git a/src/PreDownloadHandler.h b/src/PreDownloadHandler.h
index fbb5cd5a..7c31eecd 100644
--- a/src/PreDownloadHandler.h
+++ b/src/PreDownloadHandler.h
@@ -46,7 +46,7 @@ public:
 
   virtual ~PreDownloadHandler() {}
 
-  virtual void execute(RequestGroup* requestGroup) = 0;
+  virtual void execute(RequestGroup* requestGroup) const = 0;
 };
 
 } // namespace aria2
diff --git a/src/RequestGroup.cc b/src/RequestGroup.cc
index b7332e03..f8db9c91 100644
--- a/src/RequestGroup.cc
+++ b/src/RequestGroup.cc
@@ -61,7 +61,7 @@
 #include "RequestGroupMan.h"
 #include "DefaultBtProgressInfoFile.h"
 #include "DefaultPieceStorage.h"
-#include "DownloadHandlerFactory.h"
+#include "download_handlers.h"
 #include "MemoryBufferPreDownloadHandler.h"
 #include "DownloadHandlerConstants.h"
 #include "Option.h"
@@ -78,6 +78,7 @@
 #include "SimpleRandomizer.h"
 #include "Segment.h"
 #include "SocketRecvBuffer.h"
+#include "RequestGroupCriteria.h"
 #ifdef ENABLE_MESSAGE_DIGEST
 # include "CheckIntegrityCommand.h"
 # include "ChecksumCheckIntegrityEntry.h"
@@ -1052,12 +1053,14 @@ void RequestGroup::initializePreDownloadHandler()
 {
 #ifdef ENABLE_BITTORRENT
   if(option_->get(PREF_FOLLOW_TORRENT) == V_MEM) {
-    preDownloadHandlers_.push_back(DownloadHandlerFactory::getBtPreDownloadHandler());
+    preDownloadHandlers_.push_back
+      (download_handlers::getBtPreDownloadHandler());
   }
 #endif // ENABLE_BITTORRENT
 #ifdef ENABLE_METALINK
   if(option_->get(PREF_FOLLOW_METALINK) == V_MEM) {
-    preDownloadHandlers_.push_back(DownloadHandlerFactory::getMetalinkPreDownloadHandler());
+    preDownloadHandlers_.push_back
+      (download_handlers::getMetalinkPreDownloadHandler());
   }
 #endif // ENABLE_METALINK
 }
@@ -1067,13 +1070,15 @@ void RequestGroup::initializePostDownloadHandler()
 #ifdef ENABLE_BITTORRENT
   if(option_->getAsBool(PREF_FOLLOW_TORRENT) ||
      option_->get(PREF_FOLLOW_TORRENT) == V_MEM) {
-    postDownloadHandlers_.push_back(DownloadHandlerFactory::getBtPostDownloadHandler());
+    postDownloadHandlers_.push_back
+      (download_handlers::getBtPostDownloadHandler());
   }
 #endif // ENABLE_BITTORRENT
 #ifdef ENABLE_METALINK
   if(option_->getAsBool(PREF_FOLLOW_METALINK) ||
      option_->get(PREF_FOLLOW_METALINK) == V_MEM) {
-    postDownloadHandlers_.push_back(DownloadHandlerFactory::getMetalinkPostDownloadHandler());
+    postDownloadHandlers_.push_back
+      (download_handlers::getMetalinkPostDownloadHandler());
   }
 #endif // ENABLE_METALINK
 }
@@ -1097,14 +1102,12 @@ void RequestGroup::setDiskWriterFactory(
   diskWriterFactory_ = diskWriterFactory;
 }
 
-void RequestGroup::addPostDownloadHandler
-(const std::shared_ptr<PostDownloadHandler>& handler)
+void RequestGroup::addPostDownloadHandler(const PostDownloadHandler* handler)
 {
   postDownloadHandlers_.push_back(handler);
 }
 
-void RequestGroup::addPreDownloadHandler(
-    const std::shared_ptr<PreDownloadHandler>& handler)
+void RequestGroup::addPreDownloadHandler(const PreDownloadHandler* handler)
 {
   preDownloadHandlers_.push_back(handler);
 }
diff --git a/src/RequestGroup.h b/src/RequestGroup.h
index 22662e5b..dfc81cc4 100644
--- a/src/RequestGroup.h
+++ b/src/RequestGroup.h
@@ -131,9 +131,9 @@ private:
 
   bool pauseRequested_;
 
-  std::vector<std::shared_ptr<PreDownloadHandler> > preDownloadHandlers_;
+  std::vector<const PreDownloadHandler*> preDownloadHandlers_;
 
-  std::vector<std::shared_ptr<PostDownloadHandler> > postDownloadHandlers_;
+  std::vector<const PostDownloadHandler*> postDownloadHandlers_;
 
   std::unique_ptr<URISelector> uriSelector_;
 
@@ -375,13 +375,13 @@ public:
 
   void postDownloadProcessing(std::vector<std::shared_ptr<RequestGroup> >& groups);
 
-  void addPostDownloadHandler(const std::shared_ptr<PostDownloadHandler>& handler);
+  void addPostDownloadHandler(const PostDownloadHandler* handler);
 
   void clearPostDownloadHandler();
 
   void preDownloadProcessing();
 
-  void addPreDownloadHandler(const std::shared_ptr<PreDownloadHandler>& handler);
+  void addPreDownloadHandler(const PreDownloadHandler* handler);
 
   void clearPreDownloadHandler();
 
diff --git a/src/UTMetadataPostDownloadHandler.cc b/src/UTMetadataPostDownloadHandler.cc
index 58e3002a..ff006d8a 100644
--- a/src/UTMetadataPostDownloadHandler.cc
+++ b/src/UTMetadataPostDownloadHandler.cc
@@ -53,29 +53,33 @@
 
 namespace aria2 {
 
-bool UTMetadataPostDownloadHandler::Criteria::match
-(const RequestGroup* requestGroup) const
+namespace {
+class Criteria:public RequestGroupCriteria
 {
-  const std::shared_ptr<DownloadContext>& dctx =
-    requestGroup->getDownloadContext();
-  if(dctx->hasAttribute(CTX_ATTR_BT)) {
-    if(bittorrent::getTorrentAttrs(dctx)->metadata.empty()) {
-      return true;
+public:
+  virtual bool match(const RequestGroup* requestGroup) const CXX11_OVERRIDE
+  {
+    auto& dctx = requestGroup->getDownloadContext();
+    if(dctx->hasAttribute(CTX_ATTR_BT)) {
+      if(bittorrent::getTorrentAttrs(dctx)->metadata.empty()) {
+        return true;
+      }
     }
+    return false;
   }
-  return false;
-}
+};
+} // namespace
 
 UTMetadataPostDownloadHandler::UTMetadataPostDownloadHandler()
 {
-  std::shared_ptr<Criteria> cri(new Criteria());
-  setCriteria(cri);
+  setCriteria(make_unique<Criteria>());
 }
 
 void UTMetadataPostDownloadHandler::getNextRequestGroups
-(std::vector<std::shared_ptr<RequestGroup> >& groups, RequestGroup* requestGroup)
+(std::vector<std::shared_ptr<RequestGroup> >& groups,
+ RequestGroup* requestGroup) const
 {
-  const std::shared_ptr<DownloadContext>& dctx =requestGroup->getDownloadContext();
+  auto& dctx =requestGroup->getDownloadContext();
   auto attrs = bittorrent::getTorrentAttrs(dctx);
   std::string metadata =
     util::toString(requestGroup->getPieceStorage()->getDiskAdaptor());
@@ -92,7 +96,7 @@ void UTMetadataPostDownloadHandler::getNextRequestGroups
     }
   }
   if(!requestGroup->getOption()->getAsBool(PREF_BT_METADATA_ONLY)) {
-    std::vector<std::shared_ptr<RequestGroup> > newRgs;
+    std::vector<std::shared_ptr<RequestGroup>> newRgs;
     // Don't adjust announce URI because it has been done when
     // RequestGroup is created with magnet URI.
     createRequestGroupForBitTorrent(newRgs, requestGroup->getOption(),
diff --git a/src/UTMetadataPostDownloadHandler.h b/src/UTMetadataPostDownloadHandler.h
index a0c3484d..dc3b88fb 100644
--- a/src/UTMetadataPostDownloadHandler.h
+++ b/src/UTMetadataPostDownloadHandler.h
@@ -43,17 +43,12 @@ namespace aria2 {
 class UTMetadataPostDownloadHandler:public PostDownloadHandler
 {
 private:
-  class Criteria:public RequestGroupCriteria
-  {
-  public:
-    virtual bool match(const RequestGroup* requestGroup) const CXX11_OVERRIDE;
-  };
 public:
   UTMetadataPostDownloadHandler();
 
   virtual void
   getNextRequestGroups(std::vector<std::shared_ptr<RequestGroup> >& groups,
-                       RequestGroup* requestGroup) CXX11_OVERRIDE;
+                       RequestGroup* requestGroup) const CXX11_OVERRIDE;
 };
 
 } // namespace aria2
diff --git a/src/download_handlers.cc b/src/download_handlers.cc
new file mode 100644
index 00000000..2d3ab757
--- /dev/null
+++ b/src/download_handlers.cc
@@ -0,0 +1,134 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#include "download_handlers.h"
+#include "DownloadHandlerConstants.h"
+#include "ContentTypeRequestGroupCriteria.h"
+#include "MemoryBufferPreDownloadHandler.h"
+#include "a2functional.h"
+#ifdef ENABLE_METALINK
+#  include "MetalinkPostDownloadHandler.h"
+#endif // ENABLE_METALINK
+#ifdef ENABLE_BITTORRENT
+#  include "BtPostDownloadHandler.h"
+#  include "MemoryBencodePreDownloadHandler.h"
+#  include "UTMetadataPostDownloadHandler.h"
+#endif // ENABLE_BITTORRENT
+
+namespace aria2 {
+
+namespace download_handlers {
+
+namespace {
+std::unique_ptr<PreDownloadHandler> memoryPreDownloadHandler;
+} // namespace
+
+const PreDownloadHandler* getMemoryPreDownloadHandler()
+{
+  if(!memoryPreDownloadHandler) {
+    memoryPreDownloadHandler = make_unique<MemoryBufferPreDownloadHandler>();
+  }
+  return memoryPreDownloadHandler.get();
+}
+
+#ifdef ENABLE_METALINK
+
+namespace {
+std::unique_ptr<PreDownloadHandler> metalinkPreDownloadHandler;
+std::unique_ptr<PostDownloadHandler> metalinkPostDownloadHandler;
+} // namespace
+
+const PreDownloadHandler* getMetalinkPreDownloadHandler()
+{
+  if(!metalinkPreDownloadHandler) {
+    metalinkPreDownloadHandler = make_unique<MemoryBufferPreDownloadHandler>();
+    metalinkPreDownloadHandler->setCriteria
+      (make_unique<ContentTypeRequestGroupCriteria>(getMetalinkContentTypes(),
+                                                    getMetalinkExtensions()));
+  }
+  return metalinkPreDownloadHandler.get();
+}
+
+const PostDownloadHandler* getMetalinkPostDownloadHandler()
+{
+  if(!metalinkPostDownloadHandler) {
+    metalinkPostDownloadHandler = make_unique<MetalinkPostDownloadHandler>();
+  }
+  return metalinkPostDownloadHandler.get();
+}
+
+#endif // ENABLE_METALINK
+
+#ifdef ENABLE_BITTORRENT
+
+namespace {
+std::unique_ptr<PreDownloadHandler> btPreDownloadHandler;
+std::unique_ptr<PostDownloadHandler> btPostDownloadHandler;
+std::unique_ptr<PostDownloadHandler> btMetadataPostDownloadHandler;
+} // namespace
+
+const PreDownloadHandler* getBtPreDownloadHandler()
+{
+  if(!btPreDownloadHandler) {
+    btPreDownloadHandler =
+      make_unique<bittorrent::MemoryBencodePreDownloadHandler>();
+    btPreDownloadHandler->setCriteria
+      (make_unique<ContentTypeRequestGroupCriteria>(getBtContentTypes(),
+                                                    getBtExtensions()));
+  }
+  return btPreDownloadHandler.get();
+}
+
+const PostDownloadHandler* getBtPostDownloadHandler()
+{
+  if(!btPostDownloadHandler) {
+    btPostDownloadHandler = make_unique<BtPostDownloadHandler>();
+  }
+  return btPostDownloadHandler.get();
+}
+
+const PostDownloadHandler* getUTMetadataPostDownloadHandler()
+{
+  if(!btMetadataPostDownloadHandler) {
+    btMetadataPostDownloadHandler =
+      make_unique<UTMetadataPostDownloadHandler>();
+  }
+  return btMetadataPostDownloadHandler.get();
+}
+
+#endif // ENABLE_BITTORRENT
+
+} // namespace download_handlers
+
+} // namespace aria2
diff --git a/src/TrueRequestGroupCriteria.h b/src/download_handlers.h
index d1a4d7a0..26d2367d 100644
--- a/src/TrueRequestGroupCriteria.h
+++ b/src/download_handlers.h
@@ -32,26 +32,39 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef D_TRUE_REQUEST_GROUP_CRITERIA_H
-#define D_TRUE_REQUEST_GROUP_CRITERIA_H
+#ifndef D_DOWNLOAD_HANDLER_FACTORY_H
+#define D_DOWNLOAD_HANDLER_FACTORY_H
 
-#include "RequestGroupCriteria.h"
+#include "common.h"
+
+#include <memory>
 
 namespace aria2 {
 
-class TrueRequestGroupCriteria:public RequestGroupCriteria
-{
-public:
-  TrueRequestGroupCriteria() {}
+class PreDownloadHandler;
+class PostDownloadHandler;
+
+namespace download_handlers {
+
+const PreDownloadHandler* getMemoryPreDownloadHandler();
+
+#ifdef ENABLE_METALINK
+
+const PreDownloadHandler* getMetalinkPreDownloadHandler();
+const PostDownloadHandler* getMetalinkPostDownloadHandler();
+
+#endif // ENABLE_METALINK
+
+#ifdef ENABLE_BITTORRENT
+
+const PreDownloadHandler* getBtPreDownloadHandler();
+const PostDownloadHandler* getBtPostDownloadHandler();
+const PostDownloadHandler* getUTMetadataPostDownloadHandler();
 
-  virtual ~TrueRequestGroupCriteria() {}
+#endif // ENABLE_BITTORRENT
 
-  virtual bool match(const RequestGroup* requestGroup) const CXX11_OVERRIDE
-  {
-    return true;
-  }
-};
+} // namespace download_handlers
 
 } // namespace aria2
 
-#endif // D_TRUE_REQUEST_GROUP_CRITERIA_H
+#endif // D_DOWNLOAD_HANDLER_FACTORY_H
diff --git a/src/download_helper.cc b/src/download_helper.cc
index e4c2c6f0..fc23682f 100644
--- a/src/download_helper.cc
+++ b/src/download_helper.cc
@@ -61,10 +61,10 @@
 #include "MetadataInfo.h"
 #include "OptionParser.h"
 #include "SegList.h"
+#include "download_handlers.h"
 #ifdef ENABLE_BITTORRENT
 #  include "bittorrent_helper.h"
 #  include "BtConstants.h"
-#  include "UTMetadataPostDownloadHandler.h"
 #  include "ValueBaseBencodeParser.h"
 #endif // ENABLE_BITTORRENT
 
@@ -244,9 +244,8 @@ createBtMagnetRequestGroup
   dctx->getFirstFileEntry()->setPath(torrentAttrs->name);
   rg->setDownloadContext(dctx);
   rg->clearPostDownloadHandler();
-  auto utMetadataPostHandler =
-    std::make_shared<UTMetadataPostDownloadHandler>();
-  rg->addPostDownloadHandler(utMetadataPostHandler);
+  rg->addPostDownloadHandler
+    (download_handlers::getUTMetadataPostDownloadHandler());
   rg->setDiskWriterFactory(std::make_shared<ByteArrayDiskWriterFactory>());
   rg->setMetadataInfo(createMetadataInfo(gid, magnetLink));
   rg->markInMemoryDownload();