Investigate more performant alternatives to File.isHidden()

[mlinkert]

File.isHidden() is known to be very slow on Windows and network drives.

One possibility is to replace the call to File.isHidden() with the
following (in pseudo code):

if (macOS

*nix) {

hidden = filename.startsWith(".");

}
else if (windows) {

hidden = false;
try {

FileInputStream? fis = new FileInputStream?(filename);
fis.read();

}
catch (Exception e) {

hidden = true;

}

}
else error;

I don't know what if any performance gain that would provide, though.

[mlinkert]

Partial fix for this is in ​https://github.com/openmicroscopy/bioformats/pull/1003, though that doesn't address performance on Windows.

[mlinkert]

Per this ome-users thread, it likely also makes sense to review the OMERO importer code base for usage of File.isHidden() once this is resolved in Bio-Formats.

[mlinkert]

Some progress has been made on this in 5.1.0, and we now have the CI infrastructure to fully test on Windows. Pushing to 5.1.2 as part of ​https://trello.com/c/l9k0Zon4/199-bio-formats-windows

[mlinkert]

performance test case for File.isHidden alternatives

[mlinkert]

Test case with several alternatives attached. When run on Windows with a file on a local disk:

java.io.File total time (10000)  calls: 148 ms
java.io.File avg time per call: 0.0148 ms
java.nio.file.Files total time (10000)  calls: 218 ms
java.nio.file.Files avg time per call: 0.0218 ms
dos:hidden total time (10000)  calls: 223 ms
dos:hidden avg time per call: 0.0223 ms
FileInputStream total time (10000)  calls: 1036 ms
FileInputStream avg time per call: 0.1036 ms
Apache Commons VFS total time (10000)  calls: 1598 ms
Apache Commons VFS avg time per call: 0.1598 ms

and when run on the same system, with the same file copied to a network disk:

java.io.File total time (10000)  calls: 14440 ms
java.io.File avg time per call: 1.444 ms
java.nio.file.Files total time (10000)  calls: 14755 ms
java.nio.file.Files avg time per call: 1.4755 ms
dos:hidden total time (10000)  calls: 14372 ms
dos:hidden avg time per call: 1.4372 ms
FileInputStream total time (10000)  calls: 136307 ms
FileInputStream avg time per call: 13.6307 ms
Apache Commons VFS total time (10000)  calls: 44687 ms
Apache Commons VFS avg time per call: 4.4687 ms

Closing as I don't have any further ideas, but feel free to reopen if there are concrete suggestions for other things to try.