Individually (un)selecting files makes no difference?

[Theo Racle]

When I open a .torrent with Transmission, I get the popup where I can individually (un)select any files in the torrent for downloading.

However, I noticed it doesn't have any actual effect, even if I uncheck certain files, they still get downloaded anyway.

Is this a bug, or am I mistaken in how this is supposed to work?

[cfpp2p]

https://trac.transmissionbt.com/ticket/532

I helped with the patch and it works flawlessly.

[timta2]

Bittorent uses chunks, pieces, or blocks, not files. Sometimes multiple files are included in one chunk (piece/block) and you can't deselect one without deselecting the other, and vice-versa. Other clients can handle this differently and hide the files you deselected from you. So it's working the way it's supposed to be working, although some people don't like it.

[Theo Racle]

A late reply to this request, but for argument's sake, suppose I'm downloading a 52 GB torrent, containing 37000 files, and I only need 3 specific files. And I don't have 52 GB free disk space. I would possibly be getting hundreds of partial crap files which I don't need.

Couldn't it just download all necessary blocks/chunks/pieces/whatever that span the 3 selected files, and only write to disk the parts of those blocks/chunks/pieces that are part of the 3 files? And simply discard the rest of any downloaded block/chunk/piece, i.e. any data for any other file, which I didn't want to save.

Perhaps a visual example makes this more clear:



I think this would be the ideal way (definitely from the user's perspective) to handle this.

[Theo Racle]

Ok, well regardless of how many (partial) unwanted files I'd get, I would say the approach I visualized in the example image above would exactly be what the user want?

I understand each piece must be fully downloaded (and verified), I'm just suggesting it doesn't necessarily need to be saved and written to disk. At least not the parts that belong to files that I don't want to keep.

[Theo Racle]

I'm just suggesting it doesn't necessarily need to be saved and written to disk. At least not the parts that belong to files that I don't want to keep.

But it does, because you will be seeding that piece while downloading continues and quite likely long afterwards.

I see. But technically, would it be a problem if those 'downloaded and partially saved' pieces can't be seeded? (similar to other pieces which I don't download at all)

That said, for the Mac Client, many of us have used a form of the patch from #532 for years now.

Thanks, sounds good — I'd love to check that out, but I have no experience with Mac software development or building own versions with custom patches.
I realize this might be out of scope here, but is there a quick guide how to put this patch to practice? (which I guess boils down to: how to compile or build my own Transmission version with that particular patch?)