summaryrefslogtreecommitdiff
path: root/db/perl/DB_File/t/db-recno.t
blob: f2cd97bbf14b348e56a3322396c4d494b3349b91 (plain)
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
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
#!./perl -w

BEGIN {
    unless(grep /blib/, @INC) {
        chdir 't' if -d 't';
        @INC = '../lib' if -d '../lib';
    }
}
 
use warnings;
use strict;
use Config;
 
BEGIN {
    if(-d "lib" && -f "TEST") {
        if ($Config{'extensions'} !~ /\bDB_File\b/ ) {
            print "1..0 # Skip: DB_File was not built\n";
            exit 0;
        }
    }
}

use DB_File; 
use Fcntl;
our ($dbh, $Dfile, $bad_ones, $FA);

# full tied array support started in Perl 5.004_57
# Double check to see if it is available.

{
    sub try::TIEARRAY { bless [], "try" }
    sub try::FETCHSIZE { $FA = 1 }
    $FA = 0 ;
    my @a ; 
    tie @a, 'try' ;
    my $a = @a ;
}


sub ok
{
    my $no = shift ;
    my $result = shift ;

    print "not " unless $result ;
    print "ok $no\n" ;

    return $result ;
}

{
    package Redirect ;
    use Symbol ;

    sub new
    {
        my $class = shift ;
        my $filename = shift ;
	my $fh = gensym ;
	open ($fh, ">$filename") || die "Cannot open $filename: $!" ;
	my $real_stdout = select($fh) ;
	return bless [$fh, $real_stdout ] ;

    }
    sub DESTROY
    {
        my $self = shift ;
	close $self->[0] ;
	select($self->[1]) ;
    }
}

sub docat
{
    my $file = shift;
    local $/ = undef;
    open(CAT,$file) || die "Cannot open $file:$!";
    my $result = <CAT>;
    close(CAT);
    normalise($result) ;
    return $result;
}

sub docat_del
{ 
    my $file = shift;
    my $result = docat($file);
    unlink $file ;
    return $result;
}   

sub safeUntie
{
    my $hashref = shift ;
    my $no_inner = 1;
    local $SIG{__WARN__} = sub {-- $no_inner } ;
    untie @$hashref;
    return $no_inner;
}

sub bad_one
{
    unless ($bad_ones++) {
	print STDERR <<EOM ;
#
# Some older versions of Berkeley DB version 1 will fail db-recno
# tests 61, 63, 64 and 65.
EOM
        if ($^O eq 'darwin'
	    && $Config{db_version_major} == 1
	    && $Config{db_version_minor} == 0
	    && $Config{db_version_patch} == 0) {
	    print STDERR <<EOM ;
#
# For example Mac OS X 10.2 (or earlier) has such an old
# version of Berkeley DB.
EOM
	}

	print STDERR <<EOM ;
#
# You can safely ignore the errors if you're never going to use the
# broken functionality (recno databases with a modified bval). 
# Otherwise you'll have to upgrade your DB library.
#
# If you want to use Berkeley DB version 1, then 1.85 and 1.86 are the
# last versions that were released. Berkeley DB version 2 is continually
# being updated -- Check out http://www.sleepycat.com/ for more details.
#
EOM
    }
}

sub normalise
{
    return unless $^O eq 'cygwin' ;
    foreach (@_)
      { s#\r\n#\n#g }     
}

BEGIN 
{ 
    { 
        local $SIG{__DIE__} ; 
        eval { require Data::Dumper ; import Data::Dumper } ; 
    }
 
    if ($@) {
        *Dumper = sub { my $a = shift; return "[ @{ $a } ]" } ;
    }          
}

my $splice_tests = 10 + 12 + 1; # ten regressions, plus the randoms
my $total_tests = 158 ;
$total_tests += $splice_tests if $FA ;
print "1..$total_tests\n";   

$Dfile = "recno.tmp";
unlink $Dfile ;

umask(0);

# Check the interface to RECNOINFO

$dbh = new DB_File::RECNOINFO ;
ok(1, ! defined $dbh->{bval}) ;
ok(2, ! defined $dbh->{cachesize}) ;
ok(3, ! defined $dbh->{psize}) ;
ok(4, ! defined $dbh->{flags}) ;
ok(5, ! defined $dbh->{lorder}) ;
ok(6, ! defined $dbh->{reclen}) ;
ok(7, ! defined $dbh->{bfname}) ;

$dbh->{bval} = 3000 ;
ok(8, $dbh->{bval} == 3000 );

$dbh->{cachesize} = 9000 ;
ok(9, $dbh->{cachesize} == 9000 );

$dbh->{psize} = 400 ;
ok(10, $dbh->{psize} == 400 );

$dbh->{flags} = 65 ;
ok(11, $dbh->{flags} == 65 );

$dbh->{lorder} = 123 ;
ok(12, $dbh->{lorder} == 123 );

$dbh->{reclen} = 1234 ;
ok(13, $dbh->{reclen} == 1234 );

$dbh->{bfname} = 1234 ;
ok(14, $dbh->{bfname} == 1234 );


# Check that an invalid entry is caught both for store & fetch
eval '$dbh->{fred} = 1234' ;
ok(15, $@ =~ /^DB_File::RECNOINFO::STORE - Unknown element 'fred' at/ );
eval 'my $q = $dbh->{fred}' ;
ok(16, $@ =~ /^DB_File::RECNOINFO::FETCH - Unknown element 'fred' at/ );

# Now check the interface to RECNOINFO

my $X  ;
my @h ;
ok(17, $X = tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $DB_RECNO ) ;

my %noMode = map { $_, 1} qw( amigaos MSWin32 NetWare cygwin ) ;

ok(18, ((stat($Dfile))[2] & 0777) == (($^O eq 'os2' || $^O eq 'MacOS') ? 0666 : 0640)
	||  $noMode{$^O} );

#my $l = @h ;
my $l = $X->length ;
ok(19, ($FA ? @h == 0 : !$l) );

my @data = qw( a b c d ever f g h  i j k longername m n o p) ;

$h[0] = shift @data ;
ok(20, $h[0] eq 'a' );

my $ i;
foreach (@data)
  { $h[++$i] = $_ }

unshift (@data, 'a') ;

ok(21, defined $h[1] );
ok(22, ! defined $h[16] );
ok(23, $FA ? @h == @data : $X->length == @data );


# Overwrite an entry & check fetch it
$h[3] = 'replaced' ;
$data[3] = 'replaced' ;
ok(24, $h[3] eq 'replaced' );

#PUSH
my @push_data = qw(added to the end) ;
($FA ? push(@h, @push_data) : $X->push(@push_data)) ;
push (@data, @push_data) ;
ok(25, $h[++$i] eq 'added' );
ok(26, $h[++$i] eq 'to' );
ok(27, $h[++$i] eq 'the' );
ok(28, $h[++$i] eq 'end' );

# POP
my $popped = pop (@data) ;
my $value = ($FA ? pop @h : $X->pop) ;
ok(29, $value eq $popped) ;

# SHIFT
$value = ($FA ? shift @h : $X->shift) ;
my $shifted = shift @data ;
ok(30, $value eq $shifted );

# UNSHIFT

# empty list
($FA ? unshift @h,() : $X->unshift) ;
ok(31, ($FA ? @h == @data : $X->length == @data ));

my @new_data = qw(add this to the start of the array) ;
$FA ? unshift (@h, @new_data) : $X->unshift (@new_data) ;
unshift (@data, @new_data) ;
ok(32, $FA ? @h == @data : $X->length == @data );
ok(33, $h[0] eq "add") ;
ok(34, $h[1] eq "this") ;
ok(35, $h[2] eq "to") ;
ok(36, $h[3] eq "the") ;
ok(37, $h[4] eq "start") ;
ok(38, $h[5] eq "of") ;
ok(39, $h[6] eq "the") ;
ok(40, $h[7] eq "array") ;
ok(41, $h[8] eq $data[8]) ;

# Brief test for SPLICE - more thorough 'soak test' is later.
my @old;
if ($FA) {
    @old = splice(@h, 1, 2, qw(bananas just before));
}
else {
    @old = $X->splice(1, 2, qw(bananas just before));
}
ok(42, $h[0] eq "add") ;
ok(43, $h[1] eq "bananas") ;
ok(44, $h[2] eq "just") ;
ok(45, $h[3] eq "before") ;
ok(46, $h[4] eq "the") ;
ok(47, $h[5] eq "start") ;
ok(48, $h[6] eq "of") ;
ok(49, $h[7] eq "the") ;
ok(50, $h[8] eq "array") ;
ok(51, $h[9] eq $data[8]) ;
$FA ? splice(@h, 1, 3, @old) : $X->splice(1, 3, @old);

# Now both arrays should be identical

my $ok = 1 ;
my $j = 0 ;
foreach (@data)
{
   $ok = 0, last if $_ ne $h[$j ++] ; 
}
ok(52, $ok );

# Neagtive subscripts

# get the last element of the array
ok(53, $h[-1] eq $data[-1] );
ok(54, $h[-1] eq $h[ ($FA ? @h : $X->length) -1] );

# get the first element using a negative subscript
eval '$h[ - ( $FA ? @h : $X->length)] = "abcd"' ;
ok(55, $@ eq "" );
ok(56, $h[0] eq "abcd" );

# now try to read before the start of the array
eval '$h[ - (1 + ($FA ? @h : $X->length))] = 1234' ;
ok(57, $@ =~ '^Modification of non-creatable array value attempted' );

# IMPORTANT - $X must be undefined before the untie otherwise the
#             underlying DB close routine will not get called.
undef $X ;
ok(58, safeUntie \@h);

unlink $Dfile;


{
    # Check bval defaults to \n

    my @h = () ;
    my $dbh = new DB_File::RECNOINFO ;
    ok(59, tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $dbh ) ;
    $h[0] = "abc" ;
    $h[1] = "def" ;
    $h[3] = "ghi" ;
    ok(60, safeUntie \@h);
    my $x = docat($Dfile) ;
    unlink $Dfile;
    ok(61, $x eq "abc\ndef\n\nghi\n") ;
}

{
    # Change bval

    my @h = () ;
    my $dbh = new DB_File::RECNOINFO ;
    $dbh->{bval} = "-" ;
    ok(62, tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $dbh ) ;
    $h[0] = "abc" ;
    $h[1] = "def" ;
    $h[3] = "ghi" ;
    ok(63, safeUntie \@h);
    my $x = docat($Dfile) ;
    unlink $Dfile;
    my $ok = ($x eq "abc-def--ghi-") ;
    bad_one() unless $ok ;
    ok(64, $ok) ;
}

{
    # Check R_FIXEDLEN with default bval (space)

    my @h = () ;
    my $dbh = new DB_File::RECNOINFO ;
    $dbh->{flags} = R_FIXEDLEN ;
    $dbh->{reclen} = 5 ;
    ok(65, tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $dbh ) ;
    $h[0] = "abc" ;
    $h[1] = "def" ;
    $h[3] = "ghi" ;
    ok(66, safeUntie \@h);
    my $x = docat($Dfile) ;
    unlink $Dfile;
    my $ok = ($x eq "abc  def       ghi  ") ;
    bad_one() unless $ok ;
    ok(67, $ok) ;
}

{
    # Check R_FIXEDLEN with user-defined bval

    my @h = () ;
    my $dbh = new DB_File::RECNOINFO ;
    $dbh->{flags} = R_FIXEDLEN ;
    $dbh->{bval} = "-" ;
    $dbh->{reclen} = 5 ;
    ok(68, tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $dbh ) ;
    $h[0] = "abc" ;
    $h[1] = "def" ;
    $h[3] = "ghi" ;
    ok(69, safeUntie \@h);
    my $x = docat($Dfile) ;
    unlink $Dfile;
    my $ok = ($x eq "abc--def-------ghi--") ;
    bad_one() unless $ok ;
    ok(70, $ok) ;
}

{
    # check that attempting to tie an associative array to a DB_RECNO will fail

    my $filename = "xyz" ;
    my %x ;
    eval { tie %x, 'DB_File', $filename, O_RDWR|O_CREAT, 0640, $DB_RECNO ; } ;
    ok(71, $@ =~ /^DB_File can only tie an array to a DB_RECNO database/) ;
    unlink $filename ;
}

{
   # sub-class test

   package Another ;

   use warnings ;
   use strict ;

   open(FILE, ">SubDB.pm") or die "Cannot open SubDB.pm: $!\n" ;
   print FILE <<'EOM' ;

   package SubDB ;

   use warnings ;
   use strict ;
   our (@ISA, @EXPORT);

   require Exporter ;
   use DB_File;
   @ISA=qw(DB_File);
   @EXPORT = @DB_File::EXPORT ;

   sub STORE { 
	my $self = shift ;
        my $key = shift ;
        my $value = shift ;
        $self->SUPER::STORE($key, $value * 2) ;
   }

   sub FETCH { 
	my $self = shift ;
        my $key = shift ;
        $self->SUPER::FETCH($key) - 1 ;
   }

   sub put { 
	my $self = shift ;
        my $key = shift ;
        my $value = shift ;
        $self->SUPER::put($key, $value * 3) ;
   }

   sub get { 
	my $self = shift ;
        $self->SUPER::get($_[0], $_[1]) ;
	$_[1] -= 2 ;
   }

   sub A_new_method
   {
	my $self = shift ;
        my $key = shift ;
        my $value = $self->FETCH($key) ;
	return "[[$value]]" ;
   }

   1 ;
EOM

    close FILE  or die "Could not close: $!";

    BEGIN { push @INC, '.'; } 
    eval 'use SubDB ; ';
    main::ok(72, $@ eq "") ;
    my @h ;
    my $X ;
    eval '
	$X = tie(@h, "SubDB","recno.tmp", O_RDWR|O_CREAT, 0640, $DB_RECNO );
	' ;
    die "Could not tie: $!" unless $X;

    main::ok(73, $@ eq "") ;

    my $ret = eval '$h[3] = 3 ; return $h[3] ' ;
    main::ok(74, $@ eq "") ;
    main::ok(75, $ret == 5) ;

    my $value = 0;
    $ret = eval '$X->put(1, 4) ; $X->get(1, $value) ; return $value' ;
    main::ok(76, $@ eq "") ;
    main::ok(77, $ret == 10) ;

    $ret = eval ' R_NEXT eq main::R_NEXT ' ;
    main::ok(78, $@ eq "" ) ;
    main::ok(79, $ret == 1) ;

    $ret = eval '$X->A_new_method(1) ' ;
    main::ok(80, $@ eq "") ;
    main::ok(81, $ret eq "[[11]]") ;

    undef $X;
    main::ok(82, main::safeUntie \@h);
    unlink "SubDB.pm", "recno.tmp" ;

}

{

    # test $#
    my $self ;
    unlink $Dfile;
    ok(83, $self = tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $DB_RECNO ) ;
    $h[0] = "abc" ;
    $h[1] = "def" ;
    $h[2] = "ghi" ;
    $h[3] = "jkl" ;
    ok(84, $FA ? $#h == 3 : $self->length() == 4) ;
    undef $self ;
    ok(85, safeUntie \@h);
    my $x = docat($Dfile) ;
    ok(86, $x eq "abc\ndef\nghi\njkl\n") ;

    # $# sets array to same length
    ok(87, $self = tie @h, 'DB_File', $Dfile, O_RDWR, 0640, $DB_RECNO ) ;
    if ($FA)
      { $#h = 3 }
    else 
      { $self->STORESIZE(4) }
    ok(88, $FA ? $#h == 3 : $self->length() == 4) ;
    undef $self ;
    ok(89, safeUntie \@h);
    $x = docat($Dfile) ;
    ok(90, $x eq "abc\ndef\nghi\njkl\n") ;

    # $# sets array to bigger
    ok(91, $self = tie @h, 'DB_File', $Dfile, O_RDWR, 0640, $DB_RECNO ) ;
    if ($FA)
      { $#h = 6 }
    else 
      { $self->STORESIZE(7) }
    ok(92, $FA ? $#h == 6 : $self->length() == 7) ;
    undef $self ;
    ok(93, safeUntie \@h);
    $x = docat($Dfile) ;
    ok(94, $x eq "abc\ndef\nghi\njkl\n\n\n\n") ;

    # $# sets array smaller
    ok(95, $self = tie @h, 'DB_File', $Dfile, O_RDWR, 0640, $DB_RECNO ) ;
    if ($FA)
      { $#h = 2 }
    else 
      { $self->STORESIZE(3) }
    ok(96, $FA ? $#h == 2 : $self->length() == 3) ;
    undef $self ;
    ok(97, safeUntie \@h);
    $x = docat($Dfile) ;
    ok(98, $x eq "abc\ndef\nghi\n") ;

    unlink $Dfile;


}

{
   # DBM Filter tests
   use warnings ;
   use strict ;
   my (@h, $db) ;
   my ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   unlink $Dfile;

   sub checkOutput
   {
       my($fk, $sk, $fv, $sv) = @_ ;

       print "# Fetch Key   : expected '$fk' got '$fetch_key'\n" 
           if $fetch_key ne $fk ;
       print "# Fetch Value : expected '$fv' got '$fetch_value'\n" 
           if $fetch_value ne $fv ;
       print "# Store Key   : expected '$sk' got '$store_key'\n" 
           if $store_key ne $sk ;
       print "# Store Value : expected '$sv' got '$store_value'\n" 
           if $store_value ne $sv ;
       print "# \$_          : expected 'original' got '$_'\n" 
           if $_ ne 'original' ;

       return
           $fetch_key   eq $fk && $store_key   eq $sk && 
	   $fetch_value eq $fv && $store_value eq $sv &&
	   $_ eq 'original' ;
   }
   
   ok(99, $db = tie(@h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $DB_RECNO ) );

   $db->filter_fetch_key   (sub { $fetch_key = $_ }) ;
   $db->filter_store_key   (sub { $store_key = $_ }) ;
   $db->filter_fetch_value (sub { $fetch_value = $_}) ;
   $db->filter_store_value (sub { $store_value = $_ }) ;

   $_ = "original" ;

   $h[0] = "joe" ;
   #                   fk   sk     fv   sv
   ok(100, checkOutput( "", 0, "", "joe")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(101, $h[0] eq "joe");
   #                   fk  sk  fv    sv
   ok(102, checkOutput( "", 0, "joe", "")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(103, $db->FIRSTKEY() == 0) ;
   #                    fk     sk  fv  sv
   ok(104, checkOutput( 0, "", "", "")) ;

   # replace the filters, but remember the previous set
   my ($old_fk) = $db->filter_fetch_key   
   			(sub { ++ $_ ; $fetch_key = $_ }) ;
   my ($old_sk) = $db->filter_store_key   
   			(sub { $_ *= 2 ; $store_key = $_ }) ;
   my ($old_fv) = $db->filter_fetch_value 
   			(sub { $_ = "[$_]"; $fetch_value = $_ }) ;
   my ($old_sv) = $db->filter_store_value 
   			(sub { s/o/x/g; $store_value = $_ }) ;
   
   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   $h[1] = "Joe" ;
   #                   fk   sk     fv    sv
   ok(105, checkOutput( "", 2, "", "Jxe")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(106, $h[1] eq "[Jxe]");
   #                   fk   sk     fv    sv
   ok(107, checkOutput( "", 2, "[Jxe]", "")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(108, $db->FIRSTKEY() == 1) ;
   #                   fk   sk     fv    sv
   ok(109, checkOutput( 1, "", "", "")) ;
   
   # put the original filters back
   $db->filter_fetch_key   ($old_fk);
   $db->filter_store_key   ($old_sk);
   $db->filter_fetch_value ($old_fv);
   $db->filter_store_value ($old_sv);

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   $h[0] = "joe" ;
   ok(110, checkOutput( "", 0, "", "joe")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(111, $h[0] eq "joe");
   ok(112, checkOutput( "", 0, "joe", "")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(113, $db->FIRSTKEY() == 0) ;
   ok(114, checkOutput( 0, "", "", "")) ;

   # delete the filters
   $db->filter_fetch_key   (undef);
   $db->filter_store_key   (undef);
   $db->filter_fetch_value (undef);
   $db->filter_store_value (undef);

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   $h[0] = "joe" ;
   ok(115, checkOutput( "", "", "", "")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(116, $h[0] eq "joe");
   ok(117, checkOutput( "", "", "", "")) ;

   ($fetch_key, $store_key, $fetch_value, $store_value) = ("") x 4 ;
   ok(118, $db->FIRSTKEY() == 0) ;
   ok(119, checkOutput( "", "", "", "")) ;

   undef $db ;
   ok(120, safeUntie \@h);
   unlink $Dfile;
}

{    
    # DBM Filter with a closure

    use warnings ;
    use strict ;
    my (@h, $db) ;

    unlink $Dfile;
    ok(121, $db = tie(@h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $DB_RECNO ) );

    my %result = () ;

    sub Closure
    {
        my ($name) = @_ ;
	my $count = 0 ;
	my @kept = () ;

	return sub { ++$count ; 
		     push @kept, $_ ; 
		     $result{$name} = "$name - $count: [@kept]" ;
		   }
    }

    $db->filter_store_key(Closure("store key")) ;
    $db->filter_store_value(Closure("store value")) ;
    $db->filter_fetch_key(Closure("fetch key")) ;
    $db->filter_fetch_value(Closure("fetch value")) ;

    $_ = "original" ;

    $h[0] = "joe" ;
    ok(122, $result{"store key"} eq "store key - 1: [0]");
    ok(123, $result{"store value"} eq "store value - 1: [joe]");
    ok(124, ! defined $result{"fetch key"} );
    ok(125, ! defined $result{"fetch value"} );
    ok(126, $_ eq "original") ;

    ok(127, $db->FIRSTKEY() == 0 ) ;
    ok(128, $result{"store key"} eq "store key - 1: [0]");
    ok(129, $result{"store value"} eq "store value - 1: [joe]");
    ok(130, $result{"fetch key"} eq "fetch key - 1: [0]");
    ok(131, ! defined $result{"fetch value"} );
    ok(132, $_ eq "original") ;

    $h[7]  = "john" ;
    ok(133, $result{"store key"} eq "store key - 2: [0 7]");
    ok(134, $result{"store value"} eq "store value - 2: [joe john]");
    ok(135, $result{"fetch key"} eq "fetch key - 1: [0]");
    ok(136, ! defined $result{"fetch value"} );
    ok(137, $_ eq "original") ;

    ok(138, $h[0] eq "joe");
    ok(139, $result{"store key"} eq "store key - 3: [0 7 0]");
    ok(140, $result{"store value"} eq "store value - 2: [joe john]");
    ok(141, $result{"fetch key"} eq "fetch key - 1: [0]");
    ok(142, $result{"fetch value"} eq "fetch value - 1: [joe]");
    ok(143, $_ eq "original") ;

    undef $db ;
    ok(144, safeUntie \@h);
    unlink $Dfile;
}		

{
   # DBM Filter recursion detection
   use warnings ;
   use strict ;
   my (@h, $db) ;
   unlink $Dfile;

   ok(145, $db = tie(@h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $DB_RECNO ) );

   $db->filter_store_key (sub { $_ = $h[0] }) ;

   eval '$h[1] = 1234' ;
   ok(146, $@ =~ /^recursion detected in filter_store_key at/ );
   
   undef $db ;
   ok(147, safeUntie \@h);
   unlink $Dfile;
}


{
   # Examples from the POD

  my $file = "xyzt" ;
  {
    my $redirect = new Redirect $file ;

    use warnings FATAL => qw(all);
    use strict ;
    use DB_File ;

    my $filename = "text" ;
    unlink $filename ;

    my @h ;
    my $x = tie @h, "DB_File", $filename, O_RDWR|O_CREAT, 0640, $DB_RECNO 
        or die "Cannot open file 'text': $!\n" ;

    # Add a few key/value pairs to the file
    $h[0] = "orange" ;
    $h[1] = "blue" ;
    $h[2] = "yellow" ;

    $FA ? push @h, "green", "black" 
        : $x->push("green", "black") ;

    my $elements = $FA ? scalar @h : $x->length ;
    print "The array contains $elements entries\n" ;

    my $last = $FA ? pop @h : $x->pop ;
    print "popped $last\n" ;

    $FA ? unshift @h, "white" 
        : $x->unshift("white") ;
    my $first = $FA ? shift @h : $x->shift ;
    print "shifted $first\n" ;

    # Check for existence of a key
    print "Element 1 Exists with value $h[1]\n" if $h[1] ;

    # use a negative index
    print "The last element is $h[-1]\n" ;
    print "The 2nd last element is $h[-2]\n" ;

    undef $x ;
    untie @h ;

    unlink $filename ;
  }  

  ok(148, docat_del($file) eq <<'EOM') ;
The array contains 5 entries
popped black
shifted white
Element 1 Exists with value blue
The last element is green
The 2nd last element is yellow
EOM

  my $save_output = "xyzt" ;
  {
    my $redirect = new Redirect $save_output ;

    use warnings FATAL => qw(all);
    use strict ;
    our (@h, $H, $file, $i);
    use DB_File ;
    use Fcntl ;
    
    $file = "text" ;

    unlink $file ;

    $H = tie @h, "DB_File", $file, O_RDWR|O_CREAT, 0640, $DB_RECNO 
        or die "Cannot open file $file: $!\n" ;
    
    # first create a text file to play with
    $h[0] = "zero" ;
    $h[1] = "one" ;
    $h[2] = "two" ;
    $h[3] = "three" ;
    $h[4] = "four" ;

    
    # Print the records in order.
    #
    # The length method is needed here because evaluating a tied
    # array in a scalar context does not return the number of
    # elements in the array.  

    print "\nORIGINAL\n" ;
    foreach $i (0 .. $H->length - 1) {
        print "$i: $h[$i]\n" ;
    }

    # use the push & pop methods
    $a = $H->pop ;
    $H->push("last") ;
    print "\nThe last record was [$a]\n" ;

    # and the shift & unshift methods
    $a = $H->shift ;
    $H->unshift("first") ;
    print "The first record was [$a]\n" ;

    # Use the API to add a new record after record 2.
    $i = 2 ;
    $H->put($i, "Newbie", R_IAFTER) ;

    # and a new record before record 1.
    $i = 1 ;
    $H->put($i, "New One", R_IBEFORE) ;

    # delete record 3
    $H->del(3) ;

    # now print the records in reverse order
    print "\nREVERSE\n" ;
    for ($i = $H->length - 1 ; $i >= 0 ; -- $i)
      { print "$i: $h[$i]\n" }

    # same again, but use the API functions instead
    print "\nREVERSE again\n" ;
    my ($s, $k, $v)  = (0, 0, 0) ;
    for ($s = $H->seq($k, $v, R_LAST) ; 
             $s == 0 ; 
             $s = $H->seq($k, $v, R_PREV))
      { print "$k: $v\n" }

    undef $H ;
    untie @h ;    

    unlink $file ;
  }  

  ok(149, docat_del($save_output) eq <<'EOM') ;

ORIGINAL
0: zero
1: one
2: two
3: three
4: four

The last record was [four]
The first record was [zero]

REVERSE
5: last
4: three
3: Newbie
2: one
1: New One
0: first

REVERSE again
5: last
4: three
3: Newbie
2: one
1: New One
0: first
EOM
   
}

{
    # Bug ID 20001013.009
    #
    # test that $hash{KEY} = undef doesn't produce the warning
    #     Use of uninitialized value in null operation 
    use warnings ;
    use strict ;
    use DB_File ;

    unlink $Dfile;
    my @h ;
    my $a = "";
    local $SIG{__WARN__} = sub {$a = $_[0]} ;
    
    tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0664, $DB_RECNO 
	or die "Can't open file: $!\n" ;
    $h[0] = undef;
    ok(150, $a eq "") ;
    ok(151, safeUntie \@h);
    unlink $Dfile;
}

{
    # test that %hash = () doesn't produce the warning
    #     Argument "" isn't numeric in entersub
    use warnings ;
    use strict ;
    use DB_File ;
    my $a = "";
    local $SIG{__WARN__} = sub {$a = $_[0]} ;

    unlink $Dfile;
    my @h ;
    
    tie @h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0664, $DB_RECNO 
	or die "Can't open file: $!\n" ;
    @h = (); ;
    ok(152, $a eq "") ;
    ok(153, safeUntie \@h);
    unlink $Dfile;
}

{
   # Check that DBM Filter can cope with read-only $_

   use warnings ;
   use strict ;
   my (@h, $db) ;
   unlink $Dfile;

   ok(154, $db = tie(@h, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0640, $DB_RECNO ) );

   $db->filter_fetch_key   (sub { }) ;
   $db->filter_store_key   (sub { }) ;
   $db->filter_fetch_value (sub { }) ;
   $db->filter_store_value (sub { }) ;

   $_ = "original" ;

   $h[0] = "joe" ;
   ok(155, $h[0] eq "joe");

   eval { grep { $h[$_] } (1, 2, 3) };
   ok (156, ! $@);


   # delete the filters
   $db->filter_fetch_key   (undef);
   $db->filter_store_key   (undef);
   $db->filter_fetch_value (undef);
   $db->filter_store_value (undef);

   $h[1] = "joe" ;

   ok(157, $h[1] eq "joe");

   eval { grep { $h[$_] } (1, 2, 3) };
   ok (158, ! $@);

   undef $db ;
   untie @h;
   unlink $Dfile;
}

# Only test splice if this is a newish version of Perl
exit unless $FA ;

# Test SPLICE

{
    # check that the splice warnings are under the same lexical control
    # as their non-tied counterparts.

    use warnings;
    use strict;

    my $a = '';
    my @a = (1);
    local $SIG{__WARN__} = sub {$a = $_[0]} ;

    unlink $Dfile;
    my @tied ;
    
    tie @tied, 'DB_File', $Dfile, O_RDWR|O_CREAT, 0664, $DB_RECNO 
	or die "Can't open file: $!\n" ;

    # uninitialized offset
    use warnings;
    my $offset ;
    $a = '';
    splice(@a, $offset);
    ok(159, $a =~ /^Use of uninitialized value /);
    $a = '';
    splice(@tied, $offset);
    ok(160, $a =~ /^Use of uninitialized value in splice/);

    no warnings 'uninitialized';
    $a = '';
    splice(@a, $offset);
    ok(161, $a eq '');
    $a = '';
    splice(@tied, $offset);
    ok(162, $a eq '');

    # uninitialized length
    use warnings;
    my $length ;
    $a = '';
    splice(@a, 0, $length);
    ok(163, $a =~ /^Use of uninitialized value /);
    $a = '';
    splice(@tied, 0, $length);
    ok(164, $a =~ /^Use of uninitialized value in splice/);

    no warnings 'uninitialized';
    $a = '';
    splice(@a, 0, $length);
    ok(165, $a eq '');
    $a = '';
    splice(@tied, 0, $length);
    ok(166, $a eq '');

    # offset past end of array
    use warnings;
    $a = '';
    splice(@a, 3);
    my $splice_end_array = ($a =~ /^splice\(\) offset past end of array/);
    $a = '';
    splice(@tied, 3);
    ok(167, !$splice_end_array || $a =~ /^splice\(\) offset past end of array/);

    no warnings 'misc';
    $a = '';
    splice(@a, 3);
    ok(168, $a eq '');
    $a = '';
    splice(@tied, 3);
    ok(169, $a eq '');

    ok(170, safeUntie \@tied);
    unlink $Dfile;
}

# 
# These are a few regression tests: bundles of five arguments to pass
# to test_splice().  The first four arguments correspond to those
# given to splice(), and the last says which context to call it in
# (scalar, list or void).
# 
# The expected result is not needed because we get that by running
# Perl's built-in splice().
# 
my @tests = ([ [ 'falsely', 'dinosaur', 'remedy', 'commotion',
		 'rarely', 'paleness' ],
	       -4, -2,
	       [ 'redoubled', 'Taylorize', 'Zoe', 'halogen' ],
	       'void' ],

	     [ [ 'a' ], -2, 1, [ 'B' ], 'void' ],

	     [ [ 'Hartley', 'Islandia', 'assents', 'wishful' ],
	       0, -4,
	       [ 'maids' ],
	       'void' ],

	     [ [ 'visibility', 'pocketful', 'rectangles' ],
	       -10, 0,
	       [ 'garbages' ],
	       'void' ],

	     [ [ 'sleeplessly' ],
	       8, -4,
	       [ 'Margery', 'clearing', 'repercussion', 'clubs',
		 'arise' ],
	       'void' ],

	     [ [ 'chastises', 'recalculates' ],
	       0, 0,
	       [ 'momentariness', 'mediates', 'accents', 'toils',
		 'regaled' ],
	       'void' ],

	     [ [ 'b', '' ],
	       9, 8,
	       [ 'otrb', 'stje', 'ixrpw', 'vxfx', 'lhhf' ],
	       'scalar' ],

	     [ [ 'b', '' ],
	       undef, undef,
	       [ 'otrb', 'stje', 'ixrpw', 'vxfx', 'lhhf' ],
	       'scalar' ],
	     
	     [ [ 'riheb' ], -8, undef, [], 'void' ],

	     [ [ 'uft', 'qnxs', '' ],
	       6, -2,
	       [ 'znp', 'mhnkh', 'bn' ],
	       'void' ],
	    );

my $testnum = 171;
my $failed = 0;
require POSIX; my $tmp = POSIX::tmpnam();
foreach my $test (@tests) {
    my $err = test_splice(@$test);
    if (defined $err) {
	print STDERR "# failed: ", Dumper($test);
	print STDERR "# error: $err\n";
	$failed = 1;
	ok($testnum++, 0);
    }
    else { ok($testnum++, 1) }
}

if ($failed) {
    # Not worth running the random ones
    print STDERR '# skipping ', $testnum++, "\n";
}
else {
    # A thousand randomly-generated tests
    $failed = 0;
    srand(0);
    foreach (0 .. 1000 - 1) {
	my $test = rand_test();
	my $err = test_splice(@$test);
	if (defined $err) {
	    print STDERR "# failed: ", Dumper($test);
	    print STDERR "# error: $err\n";
	    $failed = 1;
	    print STDERR "# skipping any remaining random tests\n";
	    last;
	}
    }

    ok($testnum++, not $failed);
}

die "testnum ($testnum) != total_tests ($total_tests) + 1" 
    if $testnum != $total_tests + 1;

exit ;

# Subroutines for SPLICE testing

# test_splice()
# 
# Test the new splice() against Perl's built-in one.  The first four
# parameters are those passed to splice(), except that the lists must
# be (explicitly) passed by reference, and are not actually modified.
# (It's just a test!)  The last argument specifies the context in
# which to call the functions: 'list', 'scalar', or 'void'.
# 
# Returns:
#   undef, if the two splices give the same results for the given
#     arguments and context;
# 
#   an error message showing the difference, otherwise.
# 
# Reads global variable $tmp.
# 
sub test_splice {
    die 'usage: test_splice(array, offset, length, list, context)' if @_ != 5;
    my ($array, $offset, $length, $list, $context) = @_;
    my @array = @$array;
    my @list = @$list;

    unlink $tmp;
    
    my @h;
    my $H = tie @h, 'DB_File', $tmp, O_CREAT|O_RDWR, 0644, $DB_RECNO
      or die "cannot open $tmp: $!";

    my $i = 0;
    foreach ( @array ) { $h[$i++] = $_ }
    
    return "basic DB_File sanity check failed"
      if list_diff(\@array, \@h);

    # Output from splice():
    # Returned value (munged a bit), error msg, warnings
    # 
    my ($s_r, $s_error, @s_warnings);

    my $gather_warning = sub { push @s_warnings, $_[0] };
    if ($context eq 'list') {
	my @r;
	eval {
	    local $SIG{__WARN__} = $gather_warning;
	    @r = splice @array, $offset, $length, @list;
	};
	$s_error = $@;
	$s_r = \@r;
    }
    elsif ($context eq 'scalar') {
	my $r;
	eval {
	    local $SIG{__WARN__} = $gather_warning;
	    $r = splice @array, $offset, $length, @list;
	};
	$s_error = $@;
	$s_r = [ $r ];
    }
    elsif ($context eq 'void') {
	eval {
	    local $SIG{__WARN__} = $gather_warning;
	    splice @array, $offset, $length, @list;
	};
	$s_error = $@;
	$s_r = [];
    }
    else {
	die "bad context $context";
    }

    foreach ($s_error, @s_warnings) {
	chomp;
	s/ at \S+ line \d+\.$//;
    }

    # Now do the same for DB_File's version of splice
    my ($ms_r, $ms_error, @ms_warnings);
    $gather_warning = sub { push @ms_warnings, $_[0] };
    if ($context eq 'list') {
	my @r;
	eval {
	    local $SIG{__WARN__} = $gather_warning;
	    @r = splice @h, $offset, $length, @list;
	};
	$ms_error = $@;
	$ms_r = \@r;
    }
    elsif ($context eq 'scalar') {
	my $r;
	eval {
	    local $SIG{__WARN__} = $gather_warning;
	    $r = splice @h, $offset, $length, @list;
	};
	$ms_error = $@;
	$ms_r = [ $r ];
    }
    elsif ($context eq 'void') {
	eval {
	    local $SIG{__WARN__} = $gather_warning;
	    splice @h, $offset, $length, @list;
	};
	$ms_error = $@;
	$ms_r = [];
    }
    else {
	die "bad context $context";
    }

    foreach ($ms_error, @ms_warnings) {
	chomp;
	s/ at \S+ line \d+\.?.*//s;
    }

    return "different errors: '$s_error' vs '$ms_error'"
      if $s_error ne $ms_error;
    return('different return values: ' . Dumper($s_r) . ' vs ' . Dumper($ms_r))
      if list_diff($s_r, $ms_r);
    return('different changed list: ' . Dumper(\@array) . ' vs ' . Dumper(\@h))
      if list_diff(\@array, \@h);

    if ((scalar @s_warnings) != (scalar @ms_warnings)) {
	return 'different number of warnings';
    }

    while (@s_warnings) {
	my $sw  = shift @s_warnings;
	my $msw = shift @ms_warnings;
	
	if (defined $sw and defined $msw) {
	    $msw =~ s/ \(.+\)$//;
	    $msw =~ s/ in splice$// if $] < 5.006;
	    if ($sw ne $msw) {
		return "different warning: '$sw' vs '$msw'";
	    }
	}
	elsif (not defined $sw and not defined $msw) {
	    # Okay.
	}
	else {
	    return "one warning defined, another undef";
	}
    }
    
    undef $H;
    untie @h;
    
    open(TEXT, $tmp) or die "cannot open $tmp: $!";
    @h = <TEXT>; normalise @h; chomp @h;
    close TEXT or die "cannot close $tmp: $!";
    return('list is different when re-read from disk: '
	   . Dumper(\@array) . ' vs ' . Dumper(\@h))
      if list_diff(\@array, \@h);

    unlink $tmp;

    return undef; # success
}


# list_diff()
#
# Do two lists differ?
#
# Parameters:
#   reference to first list
#   reference to second list
#
# Returns true iff they differ.  Only works for lists of (string or
# undef). 
# 
# Surely there is a better way to do this?
# 
sub list_diff {
    die 'usage: list_diff(ref to first list, ref to second list)'
      if @_ != 2;
    my ($a, $b) = @_;
    my @a = @$a; my @b = @$b;
    return 1 if (scalar @a) != (scalar @b);
    for (my $i = 0; $i < @a; $i++) {
	my ($ae, $be) = ($a[$i], $b[$i]);
	if (defined $ae and defined $be) {
	    return 1 if $ae ne $be;
	}
	elsif (not defined $ae and not defined $be) {
	    # Two undefined values are 'equal'
	}
	else {
	    return 1;
	}
    }
    return 0;
} 


# rand_test()
# 
# Think up a random ARRAY, OFFSET, LENGTH, LIST, and context.
# ARRAY or LIST might be empty, and OFFSET or LENGTH might be
# undefined.  Return a 'test' - a listref of these five things.
# 
sub rand_test {
    die 'usage: rand_test()' if @_;
    my @contexts = qw<list scalar void>;
    my $context = $contexts[int(rand @contexts)];
    return [ rand_list(),
	     (rand() < 0.5) ? (int(rand(20)) - 10) : undef,
	     (rand() < 0.5) ? (int(rand(20)) - 10) : undef,
	     rand_list(),
	     $context ];
}


sub rand_list {
    die 'usage: rand_list()' if @_;
    my @r;

    while (rand() > 0.1 * (scalar @r + 1)) {
	push @r, rand_word();
    }
    return \@r;
}


sub rand_word {
    die 'usage: rand_word()' if @_;
    my $r = '';
    my @chars = qw<a b c d e f g h i j k l m n o p q r s t u v w x y z>;
    while (rand() > 0.1 * (length($r) + 1)) {
	$r .= $chars[int(rand(scalar @chars))];
    }
    return $r;
}