...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.
