Tribler does not corrently handle BitComet, "Align File to Piece Boundary", padding files

[teddyrogers]

Tribler 8.0.7, is unable to process and handle correctly a torrent file created with BitComet that has enabled, "Align File to Piece Boundary", https://wiki.bitcomet.com/Align_File_to_Piece_Boundary

When viewing the torrent there can be many hundreds or even thousands of, "____padding_file", files in the torrent file list. Other torrent clients seem to correctly process and ignore these files and are not visible in the torrent directory/ file list.

Tribler recognises these files as separate individual files that it wants to download. If these are alignment files it should be safe to not download and fill with zeros or random data?

https://en.wikipedia.org/wiki/BitComet#Padding_files

[qstokkink]

It seems like our torrent library supports storage.pad_file_at(file_index) -> bool to check if a given file index is a pad file. When presenting data to the GUI, we can filter these.

Ref: https://libtorrent.org/reference-Storage.html#root-symlink-file-path-mtime-root-ptr-hash-file-size-pad-file-at-file-name-file-offset

[teddyrogers]

@qstokkink if this can be handled at GUI it should save a bit of work. What about at the back end for calculating percentages, peer requests for pad file pieces, etc. will it have any impact on Tribler?

Does Tribler make use of piece suggestions (suggest_mode) or (piece_extent_affinity)? I query this as I have noticed when pad files have not been selected for download on torrent completion some of the padding can have 2-3% completed.

[qstokkink]

It could impact the backend, but making sure the backend works as expected is part of the software development process, I guess.

The padding files having non-100% progress is a bit odd. This padding is used for file <-> piece alignment and should always fill up a piece to accommodate for smaller files. So if you have a piece, the padding file should always be 100% (and 0% if you don't have the piece). That said, the padding file could be misaligned due to a bug, or misconfiguration, when creating the torrent.