dirEntries removes entire branches of empty directories

[Ali Çehreli]

On 11/11/22 05:13, kdevel wrote:

 > dmd -O compiled patched (see below!) version applied to /usr/bin on my
 > desktop
 > yields:
 >
 > ftw       : 363 ms, 750 ÎŒs, and 5 [*]
 > dirEntries: 18 secs, 831 ms, 738 ÎŒs, and 3 [*]

Great. I did not use -O with my test. It may have to do something with 
the performance of the hard disk.

ftw wins big time. Being just a D binding of a C library function, its 
compilation should be quick too.

 >>             entries ~= DirectoryEntry(entry, entry.getSize);
 >>         }
 >
 > strace reports that entry.getSize invokes stat on the file a second
 > time. Isn't
 > the stat buf saved in the entry?

That's my bad. entry.size is the cached version of the file size.

 > This also gives rise for a complication with symlinks pointing to the
 > directory
 > which contain them:
 >
 >     $ pwd
 >     /tmp/k/sub
 >     $ ln -s . foo
 >     $ ../direntrybenchmark .
 > 
std.file.FileException at 8[...]/linux/bin64/../../src/phobos/std/file.d(1150): 
./foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo/foo: 
Too many levels of symbolic links

So, ftw does not have that problem? Perhaps because of its default 
symlink behavior? There is also the more capable nftw, where the caller 
can specify some flags. And yes, there it is:

  FTW_PHYS
         If set, do not follow symbolic links.  (This is what you  want.)
         If not set, symbolic links are followed, but no file is reported
         twice.

         If FTW_PHYS is not set, but FTW_DEPTH is set, then the  function
         fn()  is never called for a directory that would be a descendant
         of itself.

 > -    const dir = buildNormalizedPath("/home/ali/dlang");
 > +    const dir = buildNormalizedPath(args[1]);

That one, and I had switched the arguments on the following call. One 
more example where string interpolation would be useful:

         writefln!"Ignoring type %s file: %s\n(See 'man nftw')b"(
             path, typeflag);

I meant the arguments in the reverse order there.

OT: And there is a 'b' character at the end of that format string which 
almost certainly appeared when I botched a Ctrl-b command in my editor. :)

Ali