SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
...in addition to the existing function CreateVolume
(renamed from CreateVolumeFromFilename).
Lets code easily add constraints such as not letting the user
select a WAD file when using the disc changing functionality.
This makes it possible to catch errors earlier so that file systems
simply fail to load instead of behaving oddly. It also makes it possible
to check for errors that weren't checkable before, like the end of a
directory being after the end of the parent directory.
Instead of expecting callers to know how the size of directory file infos
relates to which files are in which directories, filesystems now offer a
GetRoot() method, and file infos offer a way to get their children. As
a bonus, m_FileInfoVector no longer has to be created and kept around
in RAM. Only the file info objects that actually are used are created.
Not initializing until the filesystem is used is good when
a filesystem is constructed and then never used, but nobody does that.
This simplifies the code a little and lets all methods be const.
Instead of using lots of small scattered reads to read the FST,
only one big read is used, which is more efficient.
This also means that the FST only allocates memory once and stores all
strings close to each other - good for the CPU cache. The file info
objects use pointers to this FST memory of containing data themselves.
Keeping around the big m_FileInfoVector containing objects with only
pointers is a bit unnecessary, but that will be fixed soon.
Instead of calling GetPathFromFSTOffset for every file info, FindFileInfo
now only looks at names in directories that are included in the path.
For the common case of searching for "opening.bnr", this means that
only root-level files and directories have to be searched through.
Some callers already have the file info, making the relatively slow
FindFileInfo calls unnecessary. Callers that didn't have the file info
will now need to call FindFileInfo on their own.
Some callers (i.e. ISOProperties) don't want the full path, so giving them
it is unnecessary. Those that do want it can use GetPathFromFSTOffset.
Not storing full paths everywhere also saves a small bit of RAM and is
necessary for a later commit. The code isn't especially pretty right now
(callers need to use FST offsets...) but it'll become better later.
GC/Wii filesystem internals shouldn't be exposed to other classes.
This change isn't especially useful by itself, but it opens up the
way for some neat stuff in the following commits.
I replaced m_OffsetShift with m_Wii in bb93336 to support
the decrypt parameter for read functions. Doing that is no
longer necessary, so m_offset_shift is now used like before.
By removing mutable state in VolumeWiiCrypted, this change makes
partition-related code simpler. It also gets rid of other ugly things,
like ISOProperties's "over 9000" loop that creates a list of
partitions by trying possible combinations, and DiscScrubber's
volume swapping that recreates the entire volume when it needs to
change partition.
Callers can now check whether reads fail, either by checking the return
value or by setting the buffer to a known bad value and seeing if it stays
untouched. I've added error checks to FileSystemGCWii and Boot_BS2Emu,
but not to Boot since it doesn't check any of its other reads either.
