bug#13539: Use fdopendir, fstatat and readlinkat, for efficiency.

[Paul Eggert]

On 01/28/2013 06:37 AM, Eli Zaretskii wrote:
> perhaps a
> further optimization would be to avoid the call to
> file_name_completion_stat if completion-ignored-extensions is devoid
> of elements that end in a slash.

Yes, something like that might make sense.

>> +  fd = (int) name;
>           ^^^^^
> I think we should use ptrdiff_t rather than int here, since that could
> make a difference in 64-bit builds on Windows.

Unfortunately that won't work because the existing API uses int elsewhere
and we can't easily change int to ptrdiff_t there.
But there's another approach: simply set fd = 0, and use 
dir_pathname inside w32.c.  This should be good enough for what Emacs needs.
Revised patch attached.

fdopendis.txt
Description: Text document