On Tue, Sep 01, 2009 at 07:10:20PM -0600, Eric Blake wrote: >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > >According to Christopher Faylor on 9/1/2009 5:37 PM: >> Maybe you mean d_namlen? > >Yes; serves me right for confusing readdir(2) and readdir(3) man pages. > >>It is not a given that adding d_reclen would speed anything up since it >>cause every single program that uses dirent to effectively perform a >>strlen on every record returned by readdir whether it needed that field >>or not. Making sure that field was filled out would also complicate >>Cygwin's internal logic. > >Not so. For example, fhandler_disk_file::readdir_helper is already doing >a sys_wcstombs to populate the d_name buffer, and that returns the length >as a side effect. In other words, the cost of providing the length to the >client is an O(1) single assignment of an already-existing value per entry >(and when you consider that we are already assigning __d_unused1 to 0, >that means no net increase in cost to clients that don't care about the >length); whereas the current situation requires clients that care about >the length to use O(n) strlen() and duplicate something that was >previously calculated by cygwin1.dll.
Ok, I shouldn't have said "every record". For disk files, The length is even available in fname->Length. However, there are other places where the length is not available and would have to be calculated. I know it's a negligible cost but I'm not convinced that it is one worth taking. (And, FWIW, setting a variable to zero is a very cheap operation) Anyway, if we were going to do something like this, we'd make Cygwin more like linux. It sets d_reclen to the size of the structure. There's some more calculation for every readdir. cgf -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
