clean ':' from filenames on macOS

[bwrightkc]

libtorrent currently sanitizes ':' on Windows but not on macOS.
Since ':' is illegal on HFS+/APFS, this results in unusable filenames being passed to clients on macOS.
This patch adds ':' to invalid_chars for APPLE builds, consistent with Windows handling.

[arvidn]

do you have a source for this?
https://en.wikipedia.org/wiki/HFS_Plus seems to contradict your assertion

[bwrightkc]

do you have a source for this? https://en.wikipedia.org/wiki/HFS_Plus seems to contradict your assertion

You're right - I have to correct myself - after a quick search, I can't find anything authoritative to back me up on that. macOS does prohibit using a colon in the filename, but apparently that isn't so much a file system restriction as it is a restrictions based on how macOS used to use the colon to separate directories eg bwright:Downloads:My Torrent.torrent.

You can, however, find quite a few people online discussing how macOS doesn't allow you to use a colon in a filename, however. Can also do touch test:file.torrent in Terminal and it will instead create a file with the name test/file.torrent.

[xavier2k6]

https://www.computerhardwareinc.com/2022/06/04/the-best-characters-to-use-when-naming-files-and-folders/

[xavier2k6]

Perhaps / (forward slash) should be added for Windows??

What is \b for?

libtorrent/src/torrent_info.cpp

Line 96 in 163d364

static const char invalid_chars[] = "?<>\"|\b*:";

[bwrightkc]

What is \b for?

libtorrent/src/torrent_info.cpp

Line 96 in 163d364

static const char invalid_chars[] = "?<>\"|\b*:";

\b is the backspace character.

[xavier2k6]

backspace character

👍

Ya, googled it afterwards......

[xavier2k6]

xref:

• Enhance filename validation qbittorrent/qBittorrent#23386

[arvidn]

Ok. it seems like a reasonable change. The main thing I worry about with changing this filter is if someone has downloaded (and is seeding) a torrent with this filename in it. If that person upgrades it will no longer be seeding the file (but possible re-download it under the new name).

But if it hasn't been possible to create these files on mac anyway, it shouldn't be a problem.

[arvidn]

the unit tests need to be updated

[vafada]

touch test:file.torrent

i tried this and it created test:file.torrent on my Mac

[bwrightkc]

touch test:file.torrent

i tried this and it created test:file.torrent on my Mac

Correct. Note, however, that when you go look for the file in Finder, it will be named test/file.torrent. My understanding of this is that classic macOS used : as the folder separator, unix uses /, and OS X at release wanted to keep the capability of referencing paths using : in applications so finder translates : to /.

[vafada]

touch test:file.torrent

i tried this and it created test:file.torrent on my Mac

Correct. Note, however, that when you go look for the file in Finder, it will be named test/file.torrent. My understanding of this is that classic macOS used : as the folder separator, unix uses /, and OS X at release wanted to keep the capability of referencing paths using : in applications so finder translates : to /.

Oh yes, I see now. Though it doesn't seems like : is an invalid character... Its just Finder being dumb 🤷

[arvidn]

I think this makes my concern much stronger. Anyone, on a Mac, seeding a torrent where a filename has a : in it would break on an upgrade.

[101Dude]

I think the issue can be summarized as follows:

Stored  ":"  → Finder displays "/"
Typed "/"   → Finder stores ":"
Typed ":"   → Finder rejects it and reverts to Stored  ":"  → Finder displays "/"

The only issue with colons in filenames is that Finder.app won't show them as colons.

Therefore this PR would not make an otherwise unusable torrent usable. It would change a valid on-disk filename solely to work around how Finder displays it.