support for resuming magnet links (#2702)

* support for resuming magnet links

magnet links are now saved as a text file the `Torrents` folder as `.magnet` files.

libtransmission/magnet-metainfo.cc

@@ -181,7 +181,6 @@ std::string tr_magnet_metainfo::magnet() const
 bool tr_magnet_metainfo::parseMagnet(std::string_view magnet_link, tr_error** error)
 {
     magnet_link = tr_strvStrip(magnet_link);
-
     if (auto const hash = parseHash(magnet_link); hash)
     {
         return parseMagnet(tr_strvJoin("magnet:?xt=urn:btih:", tr_sha1_to_string(*hash)));

libtransmission/magnet-metainfo.h

@@ -27,6 +27,7 @@ public:
     {
         return info_hash_;
     }
+
     auto const& name() const
     {
         return name_;

libtransmission/session.cc

@@ -2041,13 +2041,25 @@ static void sessionLoadTorrents(void* vdata)
         char const* name = nullptr;
         while ((name = tr_sys_dir_read_name(odir, nullptr)) != nullptr)
         {
-            if (!tr_strvEndsWith(name, ".torrent"sv))
+            if (!tr_strvEndsWith(name, ".torrent"sv) && !tr_strvEndsWith(name, ".magnet"sv))
             {
                 continue;
             }
 
             tr_buildBuf(path, dirname_sv, "/", name);
-            tr_ctorSetMetainfoFromFile(data->ctor, path, nullptr);
+
+            // is a magnet link?
+            if (!tr_ctorSetMetainfoFromFile(data->ctor, path, nullptr))
+            {
+                if (auto buf = std::vector<char>{}; tr_loadFile(buf, path))
+                {
+                    tr_ctorSetMetainfoFromMagnetLink(
+                        data->ctor,
+                        std::string{ std::data(buf), std::size(buf) }.c_str(),
+                        nullptr);
+                }
+            }
+
             if (tr_torrent* const tor = tr_torrentNew(data->ctor, nullptr); tor != nullptr)
             {
                 torrents.push_back(tor);

libtransmission/torrent-ctor.cc

@@ -127,6 +127,20 @@ bool tr_ctorSaveContents(tr_ctor const* ctor, std::string const& filename, tr_er
     return tr_saveFile(filename, { std::data(ctor->contents), std::size(ctor->contents) }, error);
 }
 
+bool tr_ctorSaveMagnetContents(tr_torrent* tor, std::string const& filename, tr_error** error)
+{
+    TR_ASSERT(tor != nullptr);
+    TR_ASSERT(!std::empty(filename));
+
+    auto const magnet = tor->magnet();
+    if (std::empty(magnet))
+    {
+        tr_error_set(error, EINVAL, "torrent has no magnetlink to save"sv);
+        return false;
+    }
+    return tr_saveFile(filename, magnet, error);
+}
+
 /***
 ****
 ***/

libtransmission/torrent-magnet.cc

@@ -278,6 +278,9 @@ static bool useNewMetainfo(tr_torrent* tor, tr_incomplete_metadata const* m, tr_
         return false;
     }
 
+    // remove .magnet file
+    tr_sys_path_remove(tor->magnetFile().c_str(), nullptr);
+
     // tor should keep this metainfo
     tor->setMetainfo(metainfo);
 

libtransmission/torrent-metainfo.h

@@ -139,6 +139,11 @@ public:
         return makeFilename(torrent_dir, name(), infoHashString(), BasenameFormat::Hash, ".torrent");
     }
 
+    [[nodiscard]] std::string magnetFile(std::string_view torrent_dir) const
+    {
+        return makeFilename(torrent_dir, name(), infoHashString(), BasenameFormat::Hash, ".magnet");
+    }
+
     [[nodiscard]] std::string resumeFile(std::string_view resume_dir) const
     {
         return makeFilename(resume_dir, name(), infoHashString(), BasenameFormat::Hash, ".resume");

libtransmission/torrent.cc

@@ -767,17 +767,31 @@ static void torrentInit(tr_torrent* tor, tr_ctor const* ctor)
 
     tr_sessionAddTorrent(session, tor);
 
-    // if we don't have a local .torrent file already, assume the torrent is new
-    auto const filename = tor->torrentFile();
+    // if we don't have a local .torrent or .magnet file already, assume the torrent is new
+    auto const filename = tor->hasMetadata() ? tor->torrentFile() : tor->magnetFile();
+
     bool const is_new_torrent = !tr_sys_path_exists(filename.c_str(), nullptr);
     if (is_new_torrent)
     {
         tr_error* error = nullptr;
-        if (!tr_ctorSaveContents(ctor, filename, &error))
+        if (tor->hasMetadata())
         {
-            tor->setLocalError(
-                tr_strvJoin("Unable to save torrent file: ", error->message, " ("sv, std::to_string(error->code), ")"sv));
+            if (!tr_ctorSaveContents(ctor, filename, &error))
+            {
+                tor->setLocalError(
+                    tr_strvJoin("Unable to save torrent file: ", error->message, " ("sv, std::to_string(error->code), ")"sv));
+            }
         }
+        else
+        {
+            // magnet link
+            if (!tr_ctorSaveMagnetContents(tor, filename, &error))
+            {
+                tor->setLocalError(
+                    tr_strvJoin("Unable to save magnet file: ", error->message, " ("sv, std::to_string(error->code), ")"sv));
+            }
+        }
+
         tr_error_clear(&error);
     }
 
@@ -1566,6 +1580,7 @@ static void closeTorrent(void* vtor)
     if (tor->isDeleting)
     {
         tr_torrent_metainfo::removeFile(tor->session->torrent_dir, tor->name(), tor->infoHashString(), ".torrent"sv);
+        tr_torrent_metainfo::removeFile(tor->session->torrent_dir, tor->name(), tor->infoHashString(), ".magnet"sv);
         tr_torrent_metainfo::removeFile(tor->session->resume_dir, tor->name(), tor->infoHashString(), ".resume"sv);
     }
 

libtransmission/torrent.h

@@ -53,6 +53,8 @@ void tr_ctorInitTorrentWanted(tr_ctor const* ctor, tr_torrent* tor);
 
 bool tr_ctorSaveContents(tr_ctor const* ctor, std::string const& filename, tr_error** error);
 
+bool tr_ctorSaveMagnetContents(tr_torrent* tor, std::string const& filename, tr_error** error);
+
 std::string_view tr_ctorGetContents(tr_ctor const* ctor);
 
 tr_session* tr_ctorGetSession(tr_ctor const* ctor);
@@ -463,11 +465,21 @@ public:
         return metainfo_.torrentFile(this->session->torrent_dir);
     }
 
+    [[nodiscard]] auto magnetFile() const
+    {
+        return metainfo_.magnetFile(this->session->torrent_dir);
+    }
+
     [[nodiscard]] auto resumeFile() const
     {
         return metainfo_.resumeFile(this->session->resume_dir);
     }
 
+    [[nodiscard]] auto magnet() const
+    {
+        return metainfo_.magnet();
+    }
+
     [[nodiscard]] auto const& comment() const
     {
         return metainfo_.comment();
@@ -763,4 +775,5 @@ tr_peer_id_t const& tr_torrentGetPeerId(tr_torrent* tor);
 tr_torrent_metainfo&& tr_ctorStealMetainfo(tr_ctor* ctor);
 
 bool tr_ctorSetMetainfoFromFile(tr_ctor* ctor, std::string const& filename, tr_error** error);
+bool tr_ctorSetMetainfoFromMagnetLink(tr_ctor* ctor, std::string const& filename, tr_error** error);
 void tr_ctorSetLabels(tr_ctor* ctor, tr_labels_t&& labels);