This file is indexed.

/usr/bin/xscreensaver-getimage-file is in xscreensaver-data 5.15-2ubuntu1.

This file is owned by root:root, with mode 0o755.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
#!/usr/bin/perl -w
# Copyright © 2001-2011 Jamie Zawinski <jwz@jwz.org>.
#
# Permission to use, copy, modify, distribute, and sell this software and its
# documentation for any purpose is hereby granted without fee, provided that
# the above copyright notice appear in all copies and that both that
# copyright notice and this permission notice appear in supporting
# documentation.  No representations are made about the suitability of this
# software for any purpose.  It is provided "as is" without express or 
# implied warranty.
#
# This program chooses a random file from under the given directory, and
# prints its name.  The file will be an image file whose dimensions are
# larger than a certain minimum size.
#
# If the directory is a URL, it is assumed to be an RSS or Atom feed.
# The images from that feed will be downloaded, cached, and selected from
# at random.  The feed will be re-polled periodically, as needed.
#
# The various xscreensaver hacks that manipulate images ("jigsaw", etc.) get
# the image to manipulate by running the "xscreensaver-getimage" program.
#
# Under X11, the "xscreensaver-getimage" program invokes this script,
# depending on the value of the "chooseRandomImages" and "imageDirectory"
# settings in the ~/.xscreensaver file (or .../app-defaults/XScreenSaver).
# The screen savers invoke "xscreensaver-getimage" via utils/grabclient.c,
# which then invokes this script.
#
# Under Cocoa, this script lives inside the .saver bundle, and is invoked
# directly from utils/grabclient.c.
#
# Created: 12-Apr-01.

require 5;
#use diagnostics;	# Fails on some MacOS 10.5 systems
use strict;

use POSIX;
use Fcntl;

use Fcntl ':flock'; # import LOCK_* constants

use POSIX ':fcntl_h';				# S_ISDIR was here in Perl 5.6
import Fcntl ':mode' unless defined &S_ISUID;	# but it is here in Perl 5.8
	# but in Perl 5.10, both of these load, and cause errors!
	# So we have to check for S_ISUID instead of S_ISDIR?  WTF?

use bytes;  # Larry can take Unicode and shove it up his ass sideways.
            # Perl 5.8.0 causes us to start getting incomprehensible
            # errors about UTF-8 all over the place without this.

use Digest::MD5 qw(md5_base64);
use LWP::Simple qw($ua);


my $progname = $0; $progname =~ s@.*/@@g;
my $version = q{ $Revision: 1.30 $ }; $version =~ s/^[^0-9]+([0-9.]+).*$/$1/;

my $verbose = 0;

# Whether to use MacOS X's Spotlight to generate the list of files.
# When set to -1, uses Spotlight if "mdfind" exists.
#
# (In my experience, this isn't actually any faster, and might not find
# everything if your Spotlight index is out of date, which happens often.)
#
my $use_spotlight_p = 0;

# Whether to cache the results of the last run.
#
my $cache_p = 1;

# Regenerate the cache if it is older than this many seconds.
#
my $cache_max_age = 60 * 60 * 3;   # 3 hours

# Re-poll RSS/Atom feeds when local copy is older than this many seconds.
#
my $feed_max_age = $cache_max_age;


# This matches files that we are allowed to use as images (case-insensitive.)
# Anything not matching this is ignored.  This is so you can point your
# imageDirectory at directory trees that have things other than images in
# them, but it assumes that you gave your images sensible file extensions.
#
my @good_extensions = ('jpg', 'jpeg', 'pjpeg', 'pjpg', 'png', 'gif',
                       'tif', 'tiff', 'xbm', 'xpm');
my $good_file_re = '\.(' . join("|", @good_extensions) . ')$';

# This matches file extensions that might occur in an image directory,
# and that are never used in the name of a subdirectory.  This is an
# optimization that prevents us from having to stat() those files to
# tell whether they are directories or not.  (It speeds things up a
# lot.  Don't give your directories stupid names.)
#
my @nondir_extensions = ('ai', 'bmp', 'bz2', 'cr2', 'crw', 'db',
   'dmg', 'eps', 'gz', 'hqx', 'htm', 'html', 'icns', 'ilbm', 'mov',
   'nef', 'pbm', 'pdf', 'pl', 'ppm', 'ps', 'psd', 'sea', 'sh', 'shtml',
   'tar', 'tgz', 'thb', 'txt', 'xcf', 'xmp', 'Z', 'zip' );
my $nondir_re = '\.(' . join("|", @nondir_extensions) . ')$';


# JPEG, GIF, and PNG files that are are smaller than this are rejected:
# this is so that you can use an image directory that contains both big
# images and thumbnails, and have it only select the big versions.
#
my $min_image_width  = 255;
my $min_image_height = 255;

my @all_files = ();         # list of "good" files we've collected
my %seen_inodes;            # for breaking recursive symlink loops

# For diagnostic messages:
#
my $dir_count = 1;          # number of directories seen
my $stat_count = 0;	    # number of files/dirs stat'ed
my $skip_count_unstat = 0;  # number of files skipped without stat'ing
my $skip_count_stat = 0;    # number of files skipped after stat

sub find_all_files($);
sub find_all_files($) {
  my ($dir) = @_;

  print STDERR "$progname:  + reading dir $dir/...\n" if ($verbose > 1);

  my $dd;
  if (! opendir ($dd, $dir)) {
    print STDERR "$progname: couldn't open $dir: $!\n" if ($verbose);
    return;
  }
  my @files = readdir ($dd);
  closedir ($dd);

  my @dirs = ();

  foreach my $file (@files) {
    next if ($file =~ m/^\./);      # silently ignore dot files/dirs

    if ($file =~ m/[~%\#]$/) {      # ignore backup files (and dirs...)
      $skip_count_unstat++;
      print STDERR "$progname:  - skip file  $file\n" if ($verbose > 1);
    }

    $file = "$dir/$file";

    if ($file =~ m/$good_file_re/io) {
      #
      # Assume that files ending in .jpg exist and are not directories.
      #
      push @all_files, $file;
      print STDERR "$progname:  - found file $file\n" if ($verbose > 1);

    } elsif ($file =~ m/$nondir_re/io) {
      #
      # Assume that files ending in .html are not directories.
      #
      $skip_count_unstat++;
      print STDERR "$progname: -- skip file  $file\n" if ($verbose > 1);

    } else {
      #
      # Now we need to stat the file to see if it's a subdirectory.
      #
      # Note: we could use the trick of checking "nlinks" on the parent
      # directory to see if this directory contains any subdirectories,
      # but that would exclude any symlinks to directories.
      #
      my @st = stat($file);
      my ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
          $atime,$mtime,$ctime,$blksize,$blocks) = @st;

      $stat_count++;

      if ($#st == -1) {
        if ($verbose) {
          my $ll = readlink $file;
          if (defined ($ll)) {
            print STDERR "$progname: + dangling symlink: $file -> $ll\n";
          } else {
            print STDERR "$progname: + unreadable: $file\n";
          }
        }
        next;
      }

      next if ($seen_inodes{"$dev:$ino"}); # break symlink loops
      $seen_inodes{"$dev:$ino"} = 1;

      if (S_ISDIR($mode)) {
        push @dirs, $file;
        $dir_count++;
        print STDERR "$progname:  + found dir  $file\n" if ($verbose > 1);

      } else {
        $skip_count_stat++;
        print STDERR "$progname:  + skip file  $file\n" if ($verbose > 1);
      }
    }
  }

  foreach (@dirs) {
    find_all_files ($_);
  }
}


sub spotlight_all_files($) {
  my ($dir) = @_;

  my @terms = ();
  # "public.image" matches all (indexed) images, including Photoshop, etc.
#  push @terms, "kMDItemContentTypeTree == 'public.image'";
  foreach (@good_extensions) {

    # kMDItemFSName hits the file system every time: much worse than "find".
#    push @terms, "kMDItemFSName == '*.$_'";

    # kMDItemDisplayName matches against the name in the Spotlight index,
    # but won't find files that (for whatever reason) didn't get indexed.
    push @terms, "kMDItemDisplayName == '*.$_'";
  }

  $dir =~ s@([^-_/a-z\d.,])@\\$1@gsi;  # quote for sh
  my $cmd = "mdfind -onlyin $dir \"" . join (' || ', @terms) . "\"";

  print STDERR "$progname: executing: $cmd\n" if ($verbose > 1);
  @all_files = split (/[\r\n]+/, `$cmd`);
}


# If we're using cacheing, read the cache file and return its contents,
# if any.  This also holds an exclusive lock on the cache file, which 
# has the additional benefit that if two copies of this program are
# running at once, one will wait for the other, instead of both of
# them spanking the same file system at the same time.
#
my $cache_fd = undef;
my $cache_file_name = undef;
my $read_cache_p = 0;

sub read_cache($) {
  my ($dir) = @_;

  return () unless ($cache_p);

  my $dd = "$ENV{HOME}/Library/Caches";    # MacOS location
  if (-d $dd) {
    $cache_file_name = "$dd/org.jwz.xscreensaver.getimage.cache";
  } elsif (-d "$ENV{HOME}/tmp") {
    $cache_file_name = "$ENV{HOME}/tmp/.xscreensaver-getimage.cache";
  } else {
    $cache_file_name = "$ENV{HOME}/.xscreensaver-getimage.cache";
  }

  print STDERR "$progname: awaiting lock: $cache_file_name\n"
    if ($verbose > 1);

  my $file = $cache_file_name;
  open ($cache_fd, '+>>', $file) || error ("unable to write $file: $!");
  flock ($cache_fd, LOCK_EX)     || error ("unable to lock $file: $!");
  seek ($cache_fd, 0, 0)         || error ("unable to rewind $file: $!");

  my $mtime = (stat($cache_fd))[9];

  if ($mtime + $cache_max_age < time) {
    print STDERR "$progname: cache is too old\n" if ($verbose);
    return ();
  }

  my $odir = <$cache_fd>;
  $odir =~ s/[\r\n]+$//s if defined ($odir);
  if (!defined ($odir) || ($dir ne $odir)) {
    print STDERR "$progname: cache is for $odir, not $dir\n"
      if ($verbose && $odir);
    return ();
  }

  my @files = ();
  while (<$cache_fd>) { 
    s/[\r\n]+$//s;
    push @files, "$odir/$_";
  }

  print STDERR "$progname: " . ($#files+1) . " files in cache\n"
    if ($verbose);

  $read_cache_p = 1;
  return @files;
}


sub write_cache($) {
  my ($dir) = @_;

  return unless ($cache_p);

  # If we read the cache, just close it without rewriting it.
  # If we didn't read it, then write it now.

  if (! $read_cache_p) {

    truncate ($cache_fd, 0) ||
      error ("unable to truncate $cache_file_name: $!");
    seek ($cache_fd, 0, 0) ||
      error ("unable to rewind $cache_file_name: $!");

    if ($#all_files >= 0) {
      print $cache_fd "$dir\n";
      foreach (@all_files) {
        my $f = $_; # stupid Perl. do this to avoid modifying @all_files!
        $f =~ s@^\Q$dir\L/@@so || die;  # remove $dir from front
        print $cache_fd "$f\n";
      }
    }

    print STDERR "$progname: cached " . ($#all_files+1) . " files\n"
      if ($verbose);
  }

  flock ($cache_fd, LOCK_UN) ||
    error ("unable to unlock $cache_file_name: $!");
  close ($cache_fd);
  $cache_fd = undef;
}


# Returns a list of the image enclosures in the RSS or Atom feed.
# Elements of the list are references, [ "url", "guid" ].
#
sub parse_feed($) {
  my ($url) = @_;

  $ua->agent ("$progname/$version");
  $ua->timeout (10);  # bail sooner than the default of 3 minutes

  my $body = (LWP::Simple::get($url) || '');

  error ("not an RSS or Atom feed: $url")
    unless ($body =~ m@^<\?xml\s@si);

  $body =~ s@(<ENTRY|<ITEM)@\001$1@gsi;
  my @items = split(/\001/, $body);
  shift @items;

  my @imgs = ();
  my %ids;

  foreach my $item (@items) {
    my $iurl = undef;
    my $id = undef;

    # First look for <link rel="enclosure" href="...">
    #
    if (! $iurl) {
      $item =~ s!(<LINK[^<>]*>)!{
        my $link = $1;
        my ($rel)  = ($link =~ m/\bREL\s*=\s*[\"\']?([^<>\'\"]+)/si);
        my ($type) = ($link =~ m/\bTYPE\s*=\s*[\"\']?([^<>\'\"]+)/si);
        my ($href) = ($link =~ m/\bHREF\s*=\s*[\"\']([^<>\'\"]+)/si);

        if ($rel && lc($rel) eq 'enclosure') {
          if ($type) {
            $href = undef unless ($type =~ m@^image/@si);  # omit videos
          }
          $iurl = $href if ($href);
        }
        $link;
      }!gsexi;
    }

    # Then look for <media:content url="...">
    #
    if (! $iurl) {
      $item =~ s!(<MEDIA:CONTENT[^<>]*>)!{
        my $link = $1;
        my ($href) = ($link =~ m/\bURL\s*=\s*[\"\']([^<>\'\"]+)/si);
        $iurl = $href if $href;
        $link;
      }!gsexi;
    }

    # Then look for <description>... with an <img href="..."> inside.
    #
    if (! $iurl) {
      $item =~ s!(<description[^<>]*>.*?</description>)!{
        my $desc = $1;
        $desc =~ s/&lt;/</gs;
        $desc =~ s/&gt;/>/gs;
        $desc =~ s/&quot;/\"/gs;
        $desc =~ s/&apos;/\'/gs;
        $desc =~ s/&amp;/&/gs;
        my ($href) = ($desc =~ m@<IMG[^<>]*\bSRC=[\"\']?([^\"\'<>]+)@si);
        $iurl = $href if ($href);
        $desc;
      }!gsexi;
    }

    # Could also do <content:encoded>, but the above probably covers all
    # of the real-world possibilities.


    # Find a unique ID for this image, to defeat image farms.
    # First look for <id>...</id>
    ($id) = ($item =~ m!<ID\b[^<>]*>\s*([^<>]+?)\s*</ID>!si) unless $id;

    # Then look for <guid isPermaLink=...> ... </guid>
    ($id) = ($item =~ m!<GUID\b[^<>]*>\s*([^<>]+?)\s*</GUID>!si) unless $id;

    # Then look for <link> ... </link>
    ($id) = ($item =~ m!<LINK\b[^<>]*>\s*([^<>]+?)\s*</LINK>!si) unless $id;


    if ($iurl) {
      $id = $iurl unless $id;
      my $o = $ids{$id};
      if (! $o) {
        $ids{$id} = $iurl;
        my @P = ($iurl, $id);
        push @imgs, \@P;
      } elsif ($iurl ne $o) {
        print STDERR "$progname: WARNING: dup ID \"$id\"" .
                     " for \"$o\" and \"$iurl\"\n";
      }
    }
  }

  return @imgs;
}


# Like md5_base64 but uses filename-safe characters.
#
sub md5_file($) {
  my ($s) = @_;
  $s = md5_base64($s);
  $s =~ s@[/]@_@gs;
  $s =~ s@[+]@-@gs;
  return $s;
}


# Given the URL of an image, download it into the given directory
# and return the file name.
#
sub download_image($$$) {
  my ($url, $uid, $dir) = @_;

  my ($ext) = ($url =~ m@\.([a-z\d]+)$@si);
  my $file = md5_file ($uid);
  $file .= '.' . lc($ext) if $ext;

  # Don't bother doing If-Modified-Since to see if the URL has changed.
  # If we have already downloaded it, assume it's good.
  if (-f "$dir/$file") {
    print STDERR "$progname: exists: $dir/$file for $uid / $url\n" 
      if ($verbose > 1);
    return $file;
  }

  # Special-case kludge for Flickr:
  # Their RSS feeds sometimes include only the small versions of the images.
  # So if the URL ends in "s" (75x75), "t" (100x100) or "m" (240x240),then
  # munge it to be "b" (1024x1024).
  #
  $url =~ s@_[stm](\.[a-z]+)$@_b$1@si
    if ($url =~ m@^https?://[^/?#&]*?flickr\.com/@si);

  print STDERR "$progname: downloading: $dir/$file for $uid / $url\n" 
    if ($verbose > 1);
  $ua->agent ("$progname/$version");
  my $status = LWP::Simple::mirror ($url, "$dir/$file");
  if (!LWP::Simple::is_success ($status)) {
    print STDERR "$progname: error $status: $url\n";   # keep going
  }

  return $file;
}


sub mirror_feed($) {
  my ($url) = @_;

  if ($url !~ m/^https?:/si) {   # not a URL: local directory.
    return (undef, $url);
  }

  my $dir = "$ENV{HOME}/Library/Caches";    # MacOS location
  if (-d $dir) {
    $dir = "$dir/org.jwz.xscreensaver.feeds";
  } elsif (-d "$ENV{HOME}/tmp") {
    $dir = "$ENV{HOME}/tmp/.xscreensaver-feeds";
  } else {
    $dir = "$ENV{HOME}/.xscreensaver-feeds";
  }

  if (! -d $dir) {
    mkdir ($dir) || error ("mkdir $dir: $!");
    print STDERR "$progname: mkdir $dir/\n" if ($verbose);
  }

  # MD5 for directory name to use for cache of a feed URL.
  $dir .= '/' . md5_file ($url);

  if (! -d $dir) {
    mkdir ($dir) || error ("mkdir $dir: $!");
    print STDERR "$progname: mkdir $dir/ for $url\n" if ($verbose);
  }

  # At this point, we have the directory corresponding to this URL.
  # Now check to see if the files in it are up to date, and download
  # them if not.

  my $stamp = '.timestamp';
  my $lock = "$dir/$stamp";

  print STDERR "$progname: awaiting lock: $lock\n"
    if ($verbose > 1);

  my $mtime = ((stat($lock))[9]) || 0;

  my $lock_fd;
  open ($lock_fd, '+>>', $lock) || error ("unable to write $lock: $!");
  flock ($lock_fd, LOCK_EX)     || error ("unable to lock $lock: $!");
  seek ($lock_fd, 0, 0)         || error ("unable to rewind $lock: $!");

  my $poll_p = ($mtime + $feed_max_age < time);

  $poll_p = 1 unless ($cache_p);  # poll again now with --no-cache cmd line arg.

  # Even if the cache is young, let's make sure there are at least
  # a few files in it, and re-check if not.
  #
  if (! $poll_p) {
    my $count = 0;
    opendir (my $dirh, $dir) || error ("$dir: $!");
    foreach my $f (readdir ($dirh)) {
      next if ($f =~ m/^\./s);
      $count++;
      last;
    }
    closedir $dirh;

    if ($count <= 0) {
      print STDERR "$progname: no files in cache of $url\n" if ($verbose);
      $poll_p = 1;
    }
  }

  if ($poll_p) {

    print STDERR "$progname: loading $url\n" if ($verbose);

    my %files;
    opendir (my $dirh, $dir) || error ("$dir: $!");
    foreach my $f (readdir ($dirh)) {
      next if ($f eq '.' || $f eq '..');
      $files{$f} = 0;  # 0 means "file exists, should be deleted"
    }
    closedir $dirh;

    $files{$stamp} = 1;

    # Download each image currently in the feed.
    #
    my $count = 0;
    my @urls = parse_feed ($url);
    foreach my $p (@urls) {
      my ($furl, $id) = @$p;
      my $f = download_image ($furl, $id, $dir);
      next unless $f;
      $files{$f} = 1;    # Got it, don't delete
      $count++;
    }

    print STDERR "$progname: empty feed: $url\n" if ($count <= 0);

    # Now delete any files that are no longer in the feed.
    # But if there was nothing in the feed (network failure?)
    # then don't blow away the old files.
    #
    my $kept = 0;
    foreach my $f (keys(%files)) {
      if ($count <= 0) {
        $kept++;
      } elsif ($files{$f}) {
        $kept++;
      } else {
        if (unlink ("$dir/$f")) {
          print STDERR "$progname: rm $dir/$f\n" if ($verbose > 1);
        } else {
          print STDERR "$progname: rm $dir/$f: $!\n";   # don't bail
        }
      }
    }

    # Both feed and cache are empty. No files at all.
    error ("empty feed: $url") if ($kept <= 1);

    $mtime = time();	# update the timestamp

  } else {

    # Not yet time to re-check the URL.
    print STDERR "$progname: using cache: $url\n" if ($verbose);

  }

  # Unlock and update the write date on the .timestamp file.
  #
  truncate ($lock_fd, 0) || error ("unable to truncate $lock: $!");
  seek ($lock_fd, 0, 0)  || error ("unable to rewind $lock: $!");
  utime ($mtime, $mtime, $lock_fd) || error ("unable to touch $lock: $!");
  flock ($lock_fd, LOCK_UN) || error ("unable to unlock $lock: $!");
  close ($lock_fd);
  $lock_fd = undef;
  print STDERR "$progname: unlocked $lock\n" if ($verbose > 1);

  # Don't bother using the imageDirectory cache.  We know that this directory
  # is flat, and we can assume that an RSS feed doesn't contain 100,000 images
  # like ~/Pictures/ might.
  #
  $cache_p = 0;

  # Return the URL and directory name of the files of that URL's local cache.
  #
  return ($url, $dir);
}


sub find_random_file($) {
  my ($dir) = @_;

  if ($use_spotlight_p == -1) {
    $use_spotlight_p = 0;
    if (-x '/usr/bin/mdfind') {
      $use_spotlight_p = 1;
    }
  }

  my $url;
  ($url, $dir) = mirror_feed ($dir);

  if ($url) {
    $use_spotlight_p = 0;
    print STDERR "$progname: $dir is cache for $url\n" if ($verbose > 1);
  }

  @all_files = read_cache ($dir);

  if ($#all_files >= 0) {
    # got it from the cache...

  } elsif ($use_spotlight_p) {
    print STDERR "$progname: spotlighting $dir...\n" if ($verbose);
    spotlight_all_files ($dir);
    print STDERR "$progname: found " . ($#all_files+1) .
                 " file" . ($#all_files == 0 ? "" : "s") .
                 " via Spotlight\n"
      if ($verbose);
  } else {
    print STDERR "$progname: recursively reading $dir...\n" if ($verbose);
    find_all_files ($dir);
    print STDERR "$progname: " .
                 "f=" . ($#all_files+1) . "; " .
                 "d=$dir_count; " .
                 "s=$stat_count; " .
                 "skip=${skip_count_unstat}+$skip_count_stat=" .
                  ($skip_count_unstat + $skip_count_stat) .
                 ".\n"
      if ($verbose);
  }

  write_cache ($dir);

#  @all_files = sort(@all_files);

  if ($#all_files < 0) {
    print STDERR "$progname: no files in $dir\n";
    exit 1;
  }

  my $max_tries = 50;
  for (my $i = 0; $i < $max_tries; $i++) {

    # Default to random image
    my $n = int (rand ($#all_files + 1));

    # But check if the user wants a sequential image
    if (open(IN, "<$ENV{HOME}/.xscreensaver-image-index")) {
         read(IN, $n, 8);
         close(IN);
         $n++;
         if (open (IN, ">$ENV{HOME}/.xscreensaver-image-index")) {
             print(IN $n--);
             close(IN);
         }
    }

    my $file = $all_files[$n];
    if (large_enough_p ($file)) {
      if (! $url) {
        $file =~ s@^\Q$dir\L/@@so || die;  # remove $dir from front
      }
      return $file;
    }
  }

  print STDERR "$progname: no suitable images in $dir " .
               "(after $max_tries tries)\n";
  exit 1;
}


sub large_enough_p($) {
  my ($file) = @_;

  my ($w, $h) = image_file_size ($file);

  if (!defined ($h)) {
    print STDERR "$progname: $file: unable to determine image size\n"
      if ($verbose);
    # Assume that unknown files are of good sizes: this will happen if
    # they matched $good_file_re, but we don't have code to parse them.
    # (This will also happen if the file is junk...)
    return 1;
  }

  if ($w < $min_image_width || $h < $min_image_height) {
    print STDERR "$progname: $file: too small ($w x $h)\n" if ($verbose);
    return 0;
  }

  print STDERR "$progname: $file: $w x $h\n" if ($verbose);
  return 1;
}



# Given the raw body of a GIF document, returns the dimensions of the image.
#
sub gif_size($) {
  my ($body) = @_;
  my $type = substr($body, 0, 6);
  my $s;
  return () unless ($type =~ /GIF8[7,9]a/);
  $s = substr ($body, 6, 10);
  my ($a,$b,$c,$d) = unpack ("C"x4, $s);
  return (($b<<8|$a), ($d<<8|$c));
}

# Given the raw body of a JPEG document, returns the dimensions of the image.
#
sub jpeg_size($) {
  my ($body) = @_;
  my $i = 0;
  my $L = length($body);

  my $c1 = substr($body, $i, 1); $i++;
  my $c2 = substr($body, $i, 1); $i++;
  return () unless (ord($c1) == 0xFF && ord($c2) == 0xD8);

  my $ch = "0";
  while (ord($ch) != 0xDA && $i < $L) {
    # Find next marker, beginning with 0xFF.
    while (ord($ch) != 0xFF) {
      return () if (length($body) <= $i);
      $ch = substr($body, $i, 1); $i++;
    }
    # markers can be padded with any number of 0xFF.
    while (ord($ch) == 0xFF) {
      return () if (length($body) <= $i);
      $ch = substr($body, $i, 1); $i++;
    }

    # $ch contains the value of the marker.
    my $marker = ord($ch);

    if (($marker >= 0xC0) &&
        ($marker <= 0xCF) &&
        ($marker != 0xC4) &&
        ($marker != 0xCC)) {  # it's a SOFn marker
      $i += 3;
      return () if (length($body) <= $i);
      my $s = substr($body, $i, 4); $i += 4;
      my ($a,$b,$c,$d) = unpack("C"x4, $s);
      return (($c<<8|$d), ($a<<8|$b));

    } else {
      # We must skip variables, since FFs in variable names aren't
      # valid JPEG markers.
      return () if (length($body) <= $i);
      my $s = substr($body, $i, 2); $i += 2;
      my ($c1, $c2) = unpack ("C"x2, $s);
      my $length = ($c1 << 8) | $c2;
      return () if ($length < 2);
      $i += $length-2;
    }
  }
  return ();
}

# Given the raw body of a PNG document, returns the dimensions of the image.
#
sub png_size($) {
  my ($body) = @_;
  return () unless ($body =~ m/^\211PNG\r/s);
  my ($bits) = ($body =~ m/^.{12}(.{12})/s);
  return () unless defined ($bits);
  return () unless ($bits =~ /^IHDR/);
  my ($ign, $w, $h) = unpack("a4N2", $bits);
  return ($w, $h);
}


# Given the raw body of a GIF, JPEG, or PNG document, returns the dimensions
# of the image.
#
sub image_size($) {
  my ($body) = @_;
  return () if (length($body) < 10);
  my ($w, $h) = gif_size ($body);
  if ($w && $h) { return ($w, $h); }
  ($w, $h) = jpeg_size ($body);
  if ($w && $h) { return ($w, $h); }
  # #### TODO: need image parsers for TIFF, XPM, XBM.
  return png_size ($body);
}

# Returns the dimensions of the image file.
#
sub image_file_size($) {
  my ($file) = @_;
  my $in;
  if (! open ($in, '<', $file)) {
    print STDERR "$progname: $file: $!\n" if ($verbose);
    return undef;
  }
  binmode ($in);  # Larry can take Unicode and shove it up his ass sideways.
  my $body = '';
  sysread ($in, $body, 1024 * 50);  # The first 50k should be enough.
  close $in;			    # (It's not for certain huge jpegs...
  return image_size ($body);	    # but we know they're huge!)
}


sub error($) {
  my ($err) = @_;
  print STDERR "$progname: $err\n";
  exit 1;
}

sub usage() {
  print STDERR "usage: $progname [--verbose] directory\n" .
  "       Prints the name of a randomly-selected image file.  The directory\n" .
  "       is searched recursively.  Images smaller than " .
         "${min_image_width}x${min_image_height} are excluded.\n" .
  "\n" .
  "       The directory may also be the URL of an RSS/Atom feed.  Enclosed\n" .
  "       images will be downloaded cached locally.\n" .
  "\n";
  exit 1;
}

sub main() {
  my $dir = undef;

  while ($_ = $ARGV[0]) {
    shift @ARGV;
    if ($_ eq "--verbose") { $verbose++; }
    elsif (m/^-v+$/) { $verbose += length($_)-1; }
    elsif ($_ eq "--name") { }     # ignored, for compatibility
    elsif ($_ eq "--spotlight")    { $use_spotlight_p = 1; }
    elsif ($_ eq "--no-spotlight") { $use_spotlight_p = 0; }
    elsif ($_ eq "--cache")        { $cache_p = 1; }
    elsif ($_ eq "--no-cache")     { $cache_p = 0; }
    elsif (m/^-./) { usage; }
    elsif (!defined($dir)) { $dir = $_; }
    else { usage; }
  }

  usage unless (defined($dir));

  $dir =~ s@^feed:@http:@si;

  if ($dir =~ m/^https?:/si) {
    # ok
  } else {
    $dir =~ s@^~/@$ENV{HOME}/@s;     # allow literal "~/"
    $dir =~ s@/+$@@s;		   # omit trailing /

    if (! -d $dir) {
      print STDERR "$progname: $dir: not a directory or URL\n";
      usage;
    }
  }

  my $file = find_random_file ($dir);
  print STDOUT "$file\n";
}

main;
exit 0;