.torrent files are created incorrectly when the content is a single file inside a subdirectory

[nonzenze]

When instructed to create a torrent from a directory containing a single file, Transmission creates a single file torrent from the contents. To confirm, I created a torrent from a directory containing a single file then ran it through bdecode and found that the 'info' directory did not contain the key 'files'.

I understand that this behavior is by design. I am requesting a UI element or preference setting (of the developer's chosing, hardly matters to me) to force the creation of a directory torrent containing only a single file. One the one hand, this is trivial. On the other, it should be wicked easy to implement. :-)

[charles]

This seems to bend the intent of the BT spec and could possibly cause confusion in other BitTorrent? clients' code.

What is the use case for using multi-file mode when generating a single file torrent?

[nonzenze]

(1) The BT spec absolutely permits creating a multi-file mode containing a single path. The section "Info in Multiple File Mode" simply states that you create a entry for each file, not that there needs to be more than one.

(1A) Virtually every other client, when presented with a directory containing a single file, will create a multi-file-mode torrent containing a single path. Tranmission is aberrant (although not contrary to the spec) in this respect. Tested: uTorrent, Vuze, mktorrent, make_meta_file.py from the original BT python library released by Bram Cohen.

(1B) None of the above clients have a problem with a multi-file-mode torrent containing only a single path. Neither does Transmission, for that matter.

(2) The use case is that some private trackers forbid single-file torrents. Transmission users are then forced to either add a dummy second file or use another torrent client to create the metadata.

(3) Since this use case is relatively rare, I am not advocating for a change in default behavior. Only some manner of user control to allow Transmission users which of the two possible legal meta-files they want created.

[livings124]

This appears to be a bug. If I create a torrent from folder "Folder" with file "File" in it, it creates a single-file torrent with the data named "Folder". It should create a multi-file torrent with the directory name "Folder" but with a single data entry named "File".

[charles]

livings124 is right. We're using single-file-mode whenever there's a single file, even if it's inside a folder.

[charles]

fixed in trunk by r11244

[Longinus00]

Except now if you tell transmission to create a torrent that is only a single file by specifying the full path, like the gtk and qt guis do, it won't create a valid torrent.

$ cd /tmp
$ echo "test" > test
$ transmission-create test
WARNING: no trackers specified
Creating torrent "/tmp/test.torrent" .... done!
$ transmission-show test.torrent | grep -A5 FILES
FILES

  test (0.00 KiB)

$ transmission-create /tmp/test
WARNING: no trackers specified
Creating torrent "/tmp/test.torrent" .... done!
$ transmission-show test.torrent | grep -A5 FILES
FILES

  test/ (0.00 KiB)

Instead of checking if the filename starts with '/', makeInfoDict should be checking isSingleFile.

--- libtransmission/makemeta.c
+++ libtransmission/makemeta.c
@@ -336,11 +336,10 @@ makeInfoDict( tr_benc *             dict,
 {
     uint8_t * pch;
     char    * base;
-    const tr_bool single_file_mode = ( builder->fileCount == 1 ) && ( strchr( builder->files[0].filename, '/' ) == NULL );
 
     tr_bencDictReserve( dict, 5 );
 
-    if( single_file_mode )
+    if( builder->isSingleFile )
     {
         tr_bencDictAddInt( dict, "length", builder->files[0].size );
     }

[charles]

Great catch. Please commit.

[Longinus00]

Fixed by r11272.