Store minimal metadata for "restore torrent" purposes (#15191)

We can no longer save valid torrent files in the general case, because
for torrents of version 2, we need a full merkle tree to do it, but if
a torrent is added from magnet link, full merkle tree may not be available
even before the end of downloading all the data. Actually, we don't need
the full torrent file for the purposes of resuming the torrent, so we can
allow libtorrent to produce only a minimal part of the metadata as part
complete resume data, but we still want to store it in a separate file,
so we extract the resulting metadata from the complete resume data before
saving and merge it together before loading.

src/base/bittorrent/bencoderesumedatastorage.cpp

@@ -30,9 +30,9 @@
 
 #include <libtorrent/bdecode.hpp>
 #include <libtorrent/bencode.hpp>
-#include <libtorrent/create_torrent.hpp>
 #include <libtorrent/entry.hpp>
 #include <libtorrent/read_resume_data.hpp>
+#include <libtorrent/torrent_info.hpp>
 #include <libtorrent/write_resume_data.hpp>
 
 #include <QByteArray>
@@ -51,7 +51,6 @@
 #include "base/utils/string.h"
 #include "infohash.h"
 #include "loadtorrentparams.h"
-#include "torrentinfo.h"
 
 namespace BitTorrent
 {
@@ -151,25 +150,36 @@ std::optional<BitTorrent::LoadTorrentParams> BitTorrent::BencodeResumeDataStorag
     const QString fastresumePath = m_resumeDataDir.absoluteFilePath(QString::fromLatin1("%1.fastresume").arg(idString));
     const QString torrentFilePath = m_resumeDataDir.absoluteFilePath(QString::fromLatin1("%1.torrent").arg(idString));
 
-    QFile file {fastresumePath};
-    if (!file.open(QIODevice::ReadOnly))
+    QFile resumeDataFile {fastresumePath};
+    if (!resumeDataFile.open(QIODevice::ReadOnly))
     {
-        LogMsg(tr("Cannot read file %1: %2").arg(fastresumePath, file.errorString()), Log::WARNING);
+        LogMsg(tr("Cannot read file %1: %2").arg(fastresumePath, resumeDataFile.errorString()), Log::WARNING);
         return std::nullopt;
     }
 
-    const QByteArray data = file.readAll();
-    const TorrentInfo metadata = TorrentInfo::loadFromFile(torrentFilePath);
+    QFile metadataFile {torrentFilePath};
+    if (metadataFile.exists() && !metadataFile.open(QIODevice::ReadOnly))
+    {
+        LogMsg(tr("Cannot read file %1: %2").arg(torrentFilePath, metadataFile.errorString()), Log::WARNING);
+        return std::nullopt;
+    }
+
+    const QByteArray data = resumeDataFile.readAll();
+    const QByteArray metadata = (metadataFile.isOpen() ? metadataFile.readAll() : "");
 
     return loadTorrentResumeData(data, metadata);
 }
 
 std::optional<BitTorrent::LoadTorrentParams> BitTorrent::BencodeResumeDataStorage::loadTorrentResumeData(
-        const QByteArray &data, const TorrentInfo &metadata) const
+        const QByteArray &data, const QByteArray &metadata) const
 {
+    const QByteArray allData = ((metadata.isEmpty() || data.isEmpty())
+                                ? data : (data.chopped(1) + metadata.mid(1)));
+
     lt::error_code ec;
-    const lt::bdecode_node root = lt::bdecode(data, ec);
-    if (ec || (root.type() != lt::bdecode_node::dict_t)) return std::nullopt;
+    const lt::bdecode_node root = lt::bdecode(allData, ec);
+    if (ec || (root.type() != lt::bdecode_node::dict_t))
+        return std::nullopt;
 
     LoadTorrentParams torrentParams;
     torrentParams.restored = true;
@@ -220,8 +230,6 @@ std::optional<BitTorrent::LoadTorrentParams> BitTorrent::BencodeResumeDataStorag
 
     p = lt::read_resume_data(root, ec);
     p.save_path = Profile::instance()->fromPortablePath(fromLTString(p.save_path)).toStdString();
-    if (metadata.isValid())
-        p.ti = metadata.nativeInfo();
 
     if (p.flags & lt::torrent_flags::stop_when_ready)
     {
@@ -333,15 +341,22 @@ void BitTorrent::BencodeResumeDataStorage::Worker::store(const TorrentID &id, co
         }
     }
 
+    lt::entry data = lt::write_resume_data(p);
+
     // metadata is stored in separate .torrent file
-    const std::shared_ptr<lt::torrent_info> torrentInfo = std::move(p.ti);
-    if (torrentInfo)
+    if (p.ti)
     {
+        lt::entry::dictionary_type &dataDict = data.dict();
+        lt::entry metadata {lt::entry::dictionary_t};
+        lt::entry::dictionary_type &metadataDict = metadata.dict();
+        metadataDict.insert(dataDict.extract("info"));
+        metadataDict.insert(dataDict.extract("creation date"));
+        metadataDict.insert(dataDict.extract("created by"));
+        metadataDict.insert(dataDict.extract("comment"));
+
         const QString torrentFilepath = m_resumeDataDir.absoluteFilePath(QString::fromLatin1("%1.torrent").arg(id.toString()));
         try
         {
-            const auto torrentCreator = lt::create_torrent(*torrentInfo);
-            const lt::entry metadata = torrentCreator.generate();
             writeEntryToFile(torrentFilepath, metadata);
         }
         catch (const RuntimeError &err)
@@ -350,16 +365,8 @@ void BitTorrent::BencodeResumeDataStorage::Worker::store(const TorrentID &id, co
                    .arg(torrentFilepath, err.message()), Log::CRITICAL);
             return;
         }
-        catch (const std::exception &err)
-        {
-            LogMsg(tr("Couldn't save torrent metadata to '%1'. Error: %2.")
-                   .arg(torrentFilepath, QString::fromLocal8Bit(err.what())), Log::CRITICAL);
-            return;
-        }
     }
 
-    lt::entry data = lt::write_resume_data(p);
-
     data["qBt-savePath"] = Profile::instance()->toPortablePath(resumeData.savePath).toStdString();
     data["qBt-ratioLimit"] = static_cast<int>(resumeData.ratioLimit * 1000);
     data["qBt-seedingTimeLimit"] = resumeData.seedingTimeLimit;

src/base/bittorrent/bencoderesumedatastorage.h

@@ -38,8 +38,6 @@ class QThread;
 
 namespace BitTorrent
 {
-    class TorrentInfo;
-
     class BencodeResumeDataStorage final : public ResumeDataStorage
     {
         Q_OBJECT
@@ -57,7 +55,7 @@ namespace BitTorrent
 
     private:
         void loadQueue(const QString &queueFilename);
-        std::optional<LoadTorrentParams> loadTorrentResumeData(const QByteArray &data, const TorrentInfo &metadata) const;
+        std::optional<LoadTorrentParams> loadTorrentResumeData(const QByteArray &data, const QByteArray &metadata) const;
 
         const QDir m_resumeDataDir;
         QVector<TorrentID> m_registeredTorrents;

src/base/bittorrent/dbresumedatastorage.cpp

@@ -30,9 +30,9 @@
 
 #include <libtorrent/bdecode.hpp>
 #include <libtorrent/bencode.hpp>
-#include <libtorrent/create_torrent.hpp>
 #include <libtorrent/entry.hpp>
 #include <libtorrent/read_resume_data.hpp>
+#include <libtorrent/torrent_info.hpp>
 #include <libtorrent/write_resume_data.hpp>
 
 #include <QByteArray>
@@ -52,7 +52,6 @@
 #include "base/utils/string.h"
 #include "infohash.h"
 #include "loadtorrentparams.h"
-#include "torrentinfo.h"
 
 namespace
 {
@@ -290,20 +289,19 @@ std::optional<BitTorrent::LoadTorrentParams> BitTorrent::DBResumeDataStorage::lo
     resumeData.stopped = query.value(DB_COLUMN_STOPPED.name).toBool();
 
     const QByteArray bencodedResumeData = query.value(DB_COLUMN_RESUMEDATA.name).toByteArray();
+    const QByteArray bencodedMetadata = query.value(DB_COLUMN_METADATA.name).toByteArray();
+    const QByteArray allData = ((bencodedMetadata.isEmpty() || bencodedResumeData.isEmpty())
+                                ? bencodedResumeData
+                                : (bencodedResumeData.chopped(1) + bencodedMetadata.mid(1)));
 
     lt::error_code ec;
-    const lt::bdecode_node root = lt::bdecode(bencodedResumeData, ec);
+    const lt::bdecode_node root = lt::bdecode(allData, ec);
 
     lt::add_torrent_params &p = resumeData.ltAddTorrentParams;
 
     p = lt::read_resume_data(root, ec);
     p.save_path = Profile::instance()->fromPortablePath(fromLTString(p.save_path)).toStdString();
 
-    const QByteArray bencodedMetadata = query.value(DB_COLUMN_METADATA.name).toByteArray();
-    auto metadata = TorrentInfo::load(bencodedMetadata);
-    if (metadata.isValid())
-        p.ti = metadata.nativeInfo();
-
     return resumeData;
 }
 
@@ -453,16 +451,23 @@ void BitTorrent::DBResumeDataStorage::Worker::store(const TorrentID &id, const L
         DB_COLUMN_RESUMEDATA
     };
 
+    lt::entry data = lt::write_resume_data(p);
+
     // metadata is stored in separate column
     QByteArray bencodedMetadata;
-    bencodedMetadata.reserve(512 * 1024);
-    const std::shared_ptr<lt::torrent_info> torrentInfo = std::move(p.ti);
-    if (torrentInfo)
+    if (p.ti)
     {
+        lt::entry::dictionary_type &dataDict = data.dict();
+        lt::entry metadata {lt::entry::dictionary_t};
+        lt::entry::dictionary_type &metadataDict = metadata.dict();
+        metadataDict.insert(dataDict.extract("info"));
+        metadataDict.insert(dataDict.extract("creation date"));
+        metadataDict.insert(dataDict.extract("created by"));
+        metadataDict.insert(dataDict.extract("comment"));
+
         try
         {
-            const auto torrentCreator = lt::create_torrent(*torrentInfo);
-            const lt::entry metadata = torrentCreator.generate();
+            bencodedMetadata.reserve(512 * 1024);
             lt::bencode(std::back_inserter(bencodedMetadata), metadata);
         }
         catch (const std::exception &err)
@@ -477,7 +482,7 @@ void BitTorrent::DBResumeDataStorage::Worker::store(const TorrentID &id, const L
 
     QByteArray bencodedResumeData;
     bencodedResumeData.reserve(256 * 1024);
-    lt::bencode(std::back_inserter(bencodedResumeData), lt::write_resume_data(p));
+    lt::bencode(std::back_inserter(bencodedResumeData), data);
 
     const QString insertTorrentStatement = makeInsertStatement(DB_TABLE_TORRENTS, columns)
             + makeOnConflictUpdateStatement(DB_COLUMN_TORRENT_ID, columns);
@@ -503,7 +508,7 @@ void BitTorrent::DBResumeDataStorage::Worker::store(const TorrentID &id, const L
         query.bindValue(DB_COLUMN_OPERATING_MODE.placeholder, Utils::String::fromEnum(resumeData.operatingMode));
         query.bindValue(DB_COLUMN_STOPPED.placeholder, resumeData.stopped);
         query.bindValue(DB_COLUMN_RESUMEDATA.placeholder, bencodedResumeData);
-        if (torrentInfo)
+        if (!bencodedMetadata.isEmpty())
             query.bindValue(DB_COLUMN_METADATA.placeholder, bencodedMetadata);
 
         if (!query.exec())