Cache file priorities

Speedup access to file priorities by avoiding extra blocking call to libtorrent thread.
Improve the Torrent interface by hiding the asynchrony of file priority changes behind the scenes.

PR #16425.

src/base/bittorrent/torrentimpl.cpp

@@ -234,6 +234,14 @@ namespace
         status.pieces = params.have_pieces;
         status.verified_pieces = params.verified_pieces;
     }
+
+    template <typename Vector>
+    Vector resized(const Vector &inVector, const typename Vector::size_type size, const typename Vector::value_type &defaultValue)
+    {
+        Vector outVector = inVector;
+        outVector.resize(size, defaultValue);
+        return outVector;
+    }
 }
 
 // TorrentImpl
@@ -275,16 +283,23 @@ TorrentImpl::TorrentImpl(Session *session, lt::session *nativeSession
         const int filesCount = m_torrentInfo.filesCount();
         m_filePaths.reserve(filesCount);
         m_indexMap.reserve(filesCount);
+        m_filePriorities.reserve(filesCount);
         const std::shared_ptr<const lt::torrent_info> currentInfo = m_nativeHandle.torrent_file();
         const lt::file_storage &fileStorage = currentInfo->files();
+        const std::vector<lt::download_priority_t> filePriorities =
+                resized(m_ltAddTorrentParams.file_priorities, fileStorage.num_files(), LT::toNative(DownloadPriority::Normal));
         for (int i = 0; i < filesCount; ++i)
         {
             const lt::file_index_t nativeIndex = m_torrentInfo.nativeIndexes().at(i);
             m_indexMap[nativeIndex] = i;
+
             Path filePath {fileStorage.file_path(nativeIndex)};
             if (filePath.hasExtension(QB_EXT))
                 filePath.removeExtension();
             m_filePaths.append(filePath);
+
+            const auto priority = LT::fromNative(filePriorities[LT::toUnderlyingType(nativeIndex)]);
+            m_filePriorities.append(priority);
         }
     }
 
@@ -821,20 +836,7 @@ PathList TorrentImpl::filePaths() const
 
 QVector<DownloadPriority> TorrentImpl::filePriorities() const
 {
-    if (!hasMetadata())
-        return {};
-
-    const std::vector<lt::download_priority_t> fp = m_nativeHandle.get_file_priorities();
-
-    QVector<DownloadPriority> ret;
-    ret.reserve(filesCount());
-    for (const lt::file_index_t nativeIndex : asConst(m_torrentInfo.nativeIndexes()))
-    {
-        const auto priority = LT::fromNative(fp[LT::toUnderlyingType(nativeIndex)]);
-        ret.append(priority);
-    }
-
-    return ret;
+    return m_filePriorities;
 }
 
 TorrentInfo TorrentImpl::info() const
@@ -1444,21 +1446,19 @@ void TorrentImpl::setFirstLastPiecePriority(const bool enabled)
     m_session->handleTorrentNeedSaveResumeData(this);
 }
 
-void TorrentImpl::applyFirstLastPiecePriority(const bool enabled, const QVector<DownloadPriority> &updatedFilePrio)
+void TorrentImpl::applyFirstLastPiecePriority(const bool enabled)
 {
     Q_ASSERT(hasMetadata());
 
     // Download first and last pieces first for every file in the torrent
 
-    const QVector<DownloadPriority> filePriorities =
-            !updatedFilePrio.isEmpty() ? updatedFilePrio : this->filePriorities();
     std::vector<lt::download_priority_t> piecePriorities = nativeHandle().get_piece_priorities();
 
     // Updating file priorities is an async operation in libtorrent, when we just updated it and immediately query it
     // we might get the old/wrong values, so we rely on `updatedFilePrio` in this case.
-    for (int index = 0; index < filePriorities.size(); ++index)
+    for (int index = 0; index < m_filePriorities.size(); ++index)
     {
-        const DownloadPriority filePrio = filePriorities[index];
+        const DownloadPriority filePrio = m_filePriorities[index];
         if (filePrio <= DownloadPriority::Ignored)
             continue;
 
@@ -1499,7 +1499,10 @@ void TorrentImpl::endReceivedMetadataHandling(const Path &savePath, const PathLi
     const std::shared_ptr<lt::torrent_info> metadata = std::const_pointer_cast<lt::torrent_info>(m_nativeHandle.torrent_file());
     m_torrentInfo = TorrentInfo(*metadata);
     m_indexMap.reserve(filesCount());
+    m_filePriorities.reserve(filesCount());
     const auto nativeIndexes = m_torrentInfo.nativeIndexes();
+    const std::vector<lt::download_priority_t> filePriorities =
+            resized(p.file_priorities, metadata->files().num_files(), LT::toNative(DownloadPriority::Normal));
     for (int i = 0; i < fileNames.size(); ++i)
     {
         const auto nativeIndex = nativeIndexes.at(i);
@@ -1511,6 +1514,9 @@ void TorrentImpl::endReceivedMetadataHandling(const Path &savePath, const PathLi
         if (filePath.hasExtension(QB_EXT))
             filePath.removeExtension();
         m_filePaths.append(filePath);
+
+        const auto priority = LT::fromNative(filePriorities[LT::toUnderlyingType(nativeIndex)]);
+        m_filePriorities.append(priority);
     }
     p.save_path = savePath.toString().toStdString();
     p.ti = metadata;
@@ -2218,9 +2224,10 @@ void TorrentImpl::prioritizeFiles(const QVector<DownloadPriority> &priorities)
     qDebug() << Q_FUNC_INFO << "Changing files priorities...";
     m_nativeHandle.prioritize_files(nativePriorities);
 
+    m_filePriorities = priorities;
     // Restore first/last piece first option if necessary
     if (m_hasFirstLastPiecePriority)
-        applyFirstLastPiecePriority(true, priorities);
+        applyFirstLastPiecePriority(true);
 }
 
 QVector<qreal> TorrentImpl::availableFileFractions() const

src/base/bittorrent/torrentimpl.h

@@ -272,7 +272,7 @@ namespace BitTorrent
         void adjustStorageLocation();
         void moveStorage(const Path &newPath, MoveStorageMode mode);
         void manageIncompleteFiles();
-        void applyFirstLastPiecePriority(bool enabled, const QVector<DownloadPriority> &updatedFilePrio = {});
+        void applyFirstLastPiecePriority(bool enabled);
 
         void prepareResumeData(const lt::add_torrent_params &params);
         void endReceivedMetadataHandling(const Path &savePath, const PathList &fileNames);
@@ -286,6 +286,7 @@ namespace BitTorrent
         TorrentInfo m_torrentInfo;
         PathList m_filePaths;
         QHash<lt::file_index_t, int> m_indexMap;
+        QVector<DownloadPriority> m_filePriorities;
         SpeedMonitor m_speedMonitor;
 
         InfoHash m_infoHash;