This apparently fixes https://bugs.dolphin-emu.org/issues/10499 somehow.
The first changed line of this commit is just for performance - the
second changed line is where the difference in behavior is.
ifstream::read() sets the failbit if trying to read over the end, which
means that (!input) would be hit for the 'last' block if it wasn't
exactly BSIZE (1024) bytes.
Some code was calling more than one of these functions in a row
(in particular, FileUtil.cpp itself did it a lot...), which is
a waste since it's possible to call stat a single time and then
read all three values from the stat struct. This commit adds a
File::FileInfo class that calls stat once on construction and
then lets Exists/IsDirectory/GetSize be executed very quickly.
The performance improvement mostly matters for functions that
can be handling a lot of files, such as File::ScanDirectoryTree.
I've also done some cleanup in code that uses these functions.
For instance, some code had checks like !Exists() || !IsDirectory(),
which is functionally equivalent to !IsDirectory(), and some
code was using File::GetSize even though there was an IOFile
object that the code could call GetSize on.
stat() returns an error code in errno on both POSIX compliant
platforms and Windows.
This means we should always use errno instead of GetLastErrorMsg
which uses GetLastError() (Win32) on Windows.
POSIX allows one or more trailing slashes for directories.
From POSIX.1-2008, section 3.271 (Base Definitions / Pathname):
> A pathname can optionally contain one or more trailing <slash>
> characters. Multiple successive <slash> characters are considered to
> be the same as one <slash>, except for the case of exactly two
> leading <slash> characters.
On Windows, the extra trailing slashes are ignored for directories too.
