-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 According to Eric Blake on 9/1/2009 7:10 PM: > 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.
Actually, it looks like Linux has only d_reclen (and that d_namlen is a documentation bug): http://www.kernel.org/doc/man-pages/online/pages/man3/readdir.3.html and that Linus prefers d_reclen over d_namlen from the kernel side of things (where, in the Linux kernel, d_reclen is always aligned, such that adjusting d_reclen by offsetof(struct dirent,d_name) can be larger than strlen(d_name)): http://lkml.indiana.edu/hypermail/linux/kernel/9506/0033.html So Linux doesn't provide d_namlen, and coreutils can't optimize for known lengths on Linux. But BSD does: http://www.gsp.com/cgi-bin/man.cgi?section=5&topic=dir At any rate, coreutils uses a macro _D_EXACT_NAMELEN(dirent), which evaluates to either d_namlen, a calculation on d_reclen (if d_reclen is accurate enough*), or a call to strlen() if all else fails; so that it is portable to whichever the underlying semantics happen to be. * If d_reclen minimally rounds up to an aligned size, for example if it is only at most 8 bytes larger than strlen(d_name), then it is still faster to do a strchr(,0)-d_name from a starting point 8 bytes before where d_reclen says the record ends, rather than strlen(d_name[0]). - -- Don't work too hard, make some time for fun as well! Eric Blake e...@byu.net -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Cygwin) Comment: Public key at home.comcast.net/~ericblake/eblake.gpg Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkqdzKQACgkQ84KuGfSFAYBtsQCgvYcI8Y7CLJOYxPKIySgwCpJn dvAAoIVO47y0+F24lGktxBAF6gbj0rlh =Zctr -----END PGP SIGNATURE----- -- 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
