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1 | =head1 NAME |
2 | |
3 | perltie - how to hide an object class in a simple variable |
4 | |
5 | =head1 SYNOPSIS |
6 | |
7 | tie VARIABLE, CLASSNAME, LIST |
8 | |
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9 | $object = tied VARIABLE |
10 | |
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11 | untie VARIABLE |
12 | |
13 | =head1 DESCRIPTION |
14 | |
15 | Prior to release 5.0 of Perl, a programmer could use dbmopen() |
16 | to magically connect an on-disk database in the standard Unix dbm(3x) |
17 | format to a %HASH in their program. However, their Perl was either |
18 | built with one particular dbm library or another, but not both, and |
19 | you couldn't extend this mechanism to other packages or types of variables. |
20 | |
21 | Now you can. |
22 | |
23 | The tie() function binds a variable to a class (package) that will provide |
24 | the implementation for access methods for that variable. Once this magic |
25 | has been performed, accessing a tied variable automatically triggers |
26 | method calls in the proper class. All of the complexity of the class is |
27 | hidden behind magic methods calls. The method names are in ALL CAPS, |
28 | which is a convention that Perl uses to indicate that they're called |
29 | implicitly rather than explicitly--just like the BEGIN() and END() |
30 | functions. |
31 | |
32 | In the tie() call, C<VARIABLE> is the name of the variable to be |
33 | enchanted. C<CLASSNAME> is the name of a class implementing objects of |
34 | the correct type. Any additional arguments in the C<LIST> are passed to |
35 | the appropriate constructor method for that class--meaning TIESCALAR(), |
36 | TIEARRAY(), or TIEHASH(). (Typically these are arguments such as might be |
37 | passed to the dbminit() function of C.) The object returned by the "new" |
38 | method is also returned by the tie() function, which would be useful if |
39 | you wanted to access other methods in C<CLASSNAME>. (You don't actually |
40 | have to return a reference to a right "type" (e.g. HASH or C<CLASSNAME>) |
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41 | so long as it's a properly blessed object.) You can also retrieve |
42 | a reference to the underlying object using the tied() function. |
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43 | |
44 | Unlike dbmopen(), the tie() function will not C<use> or C<require> a module |
45 | for you--you need to do that explicitly yourself. |
46 | |
47 | =head2 Tying Scalars |
48 | |
49 | A class implementing a tied scalar should define the following methods: |
50 | TIESCALAR, FETCH, STORE, and possibly DESTROY. |
51 | |
52 | Let's look at each in turn, using as an example a tie class for |
53 | scalars that allows the user to do something like: |
54 | |
55 | tie $his_speed, 'Nice', getppid(); |
56 | tie $my_speed, 'Nice', $$; |
57 | |
58 | And now whenever either of those variables is accessed, its current |
59 | system priority is retrieved and returned. If those variables are set, |
60 | then the process's priority is changed! |
61 | |
62 | We'll use Jarkko Hietaniemi F<E<lt>Jarkko.Hietaniemi@hut.fiE<gt>>'s |
63 | BSD::Resource class (not included) to access the PRIO_PROCESS, PRIO_MIN, |
64 | and PRIO_MAX constants from your system, as well as the getpriority() and |
65 | setpriority() system calls. Here's the preamble of the class. |
66 | |
67 | package Nice; |
68 | use Carp; |
69 | use BSD::Resource; |
70 | use strict; |
71 | $Nice::DEBUG = 0 unless defined $Nice::DEBUG; |
72 | |
73 | =over |
74 | |
75 | =item TIESCALAR classname, LIST |
76 | |
77 | This is the constructor for the class. That means it is |
78 | expected to return a blessed reference to a new scalar |
79 | (probably anonymous) that it's creating. For example: |
80 | |
81 | sub TIESCALAR { |
82 | my $class = shift; |
83 | my $pid = shift || $$; # 0 means me |
84 | |
85 | if ($pid !~ /^\d+$/) { |
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86 | carp "Nice::Tie::Scalar got non-numeric pid $pid" if $^W; |
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87 | return undef; |
88 | } |
89 | |
90 | unless (kill 0, $pid) { # EPERM or ERSCH, no doubt |
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91 | carp "Nice::Tie::Scalar got bad pid $pid: $!" if $^W; |
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92 | return undef; |
93 | } |
94 | |
95 | return bless \$pid, $class; |
96 | } |
97 | |
98 | This tie class has chosen to return an error rather than raising an |
99 | exception if its constructor should fail. While this is how dbmopen() works, |
100 | other classes may well not wish to be so forgiving. It checks the global |
101 | variable C<$^W> to see whether to emit a bit of noise anyway. |
102 | |
103 | =item FETCH this |
104 | |
105 | This method will be triggered every time the tied variable is accessed |
106 | (read). It takes no arguments beyond its self reference, which is the |
107 | object representing the scalar we're dealing with. Since in this case |
108 | we're just using a SCALAR ref for the tied scalar object, a simple $$self |
109 | allows the method to get at the real value stored there. In our example |
110 | below, that real value is the process ID to which we've tied our variable. |
111 | |
112 | sub FETCH { |
113 | my $self = shift; |
114 | confess "wrong type" unless ref $self; |
115 | croak "usage error" if @_; |
116 | my $nicety; |
117 | local($!) = 0; |
118 | $nicety = getpriority(PRIO_PROCESS, $$self); |
119 | if ($!) { croak "getpriority failed: $!" } |
120 | return $nicety; |
121 | } |
122 | |
123 | This time we've decided to blow up (raise an exception) if the renice |
124 | fails--there's no place for us to return an error otherwise, and it's |
125 | probably the right thing to do. |
126 | |
127 | =item STORE this, value |
128 | |
129 | This method will be triggered every time the tied variable is set |
130 | (assigned). Beyond its self reference, it also expects one (and only one) |
131 | argument--the new value the user is trying to assign. |
132 | |
133 | sub STORE { |
134 | my $self = shift; |
135 | confess "wrong type" unless ref $self; |
136 | my $new_nicety = shift; |
137 | croak "usage error" if @_; |
138 | |
139 | if ($new_nicety < PRIO_MIN) { |
140 | carp sprintf |
141 | "WARNING: priority %d less than minimum system priority %d", |
142 | $new_nicety, PRIO_MIN if $^W; |
143 | $new_nicety = PRIO_MIN; |
144 | } |
145 | |
146 | if ($new_nicety > PRIO_MAX) { |
147 | carp sprintf |
148 | "WARNING: priority %d greater than maximum system priority %d", |
149 | $new_nicety, PRIO_MAX if $^W; |
150 | $new_nicety = PRIO_MAX; |
151 | } |
152 | |
153 | unless (defined setpriority(PRIO_PROCESS, $$self, $new_nicety)) { |
154 | confess "setpriority failed: $!"; |
155 | } |
156 | return $new_nicety; |
157 | } |
158 | |
159 | =item DESTROY this |
160 | |
161 | This method will be triggered when the tied variable needs to be destructed. |
162 | As with other object classes, such a method is seldom ncessary, since Perl |
163 | deallocates its moribund object's memory for you automatically--this isn't |
164 | C++, you know. We'll use a DESTROY method here for debugging purposes only. |
165 | |
166 | sub DESTROY { |
167 | my $self = shift; |
168 | confess "wrong type" unless ref $self; |
169 | carp "[ Nice::DESTROY pid $$self ]" if $Nice::DEBUG; |
170 | } |
171 | |
172 | =back |
173 | |
174 | That's about all there is to it. Actually, it's more than all there |
175 | is to it, since we've done a few nice things here for the sake |
176 | of completeness, robustness, and general aesthetics. Simpler |
177 | TIESCALAR classes are certainly possible. |
178 | |
179 | =head2 Tying Arrays |
180 | |
181 | A class implementing a tied ordinary array should define the following |
182 | methods: TIEARRAY, FETCH, STORE, and perhaps DESTROY. |
183 | |
184 | B<WARNING>: Tied arrays are I<incomplete>. They are also distinctly lacking |
185 | something for the C<$#ARRAY> access (which is hard, as it's an lvalue), as |
186 | well as the other obvious array functions, like push(), pop(), shift(), |
187 | unshift(), and splice(). |
188 | |
189 | For this discussion, we'll implement an array whose indices are fixed at |
190 | its creation. If you try to access anything beyond those bounds, you'll |
191 | take an exception. (Well, if you access an individual element; an |
192 | aggregate assignment would be missed.) For example: |
193 | |
194 | require Bounded_Array; |
195 | tie @ary, Bounded_Array, 2; |
196 | $| = 1; |
197 | for $i (0 .. 10) { |
198 | print "setting index $i: "; |
199 | $ary[$i] = 10 * $i; |
200 | $ary[$i] = 10 * $i; |
201 | print "value of elt $i now $ary[$i]\n"; |
202 | } |
203 | |
204 | The preamble code for the class is as follows: |
205 | |
206 | package Bounded_Array; |
207 | use Carp; |
208 | use strict; |
209 | |
210 | =over |
211 | |
212 | =item TIEARRAY classname, LIST |
213 | |
214 | This is the constructor for the class. That means it is expected to |
215 | return a blessed reference through which the new array (probably an |
216 | anonymous ARRAY ref) will be accessed. |
217 | |
218 | In our example, just to show you that you don't I<really> have to return an |
219 | ARRAY reference, we'll choose a HASH reference to represent our object. |
220 | A HASH works out well as a generic record type: the C<{BOUND}> field will |
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221 | store the maximum bound allowed, and the C<{ARRAY}> field will hold the |
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222 | true ARRAY ref. If someone outside the class tries to dereference the |
223 | object returned (doubtless thinking it an ARRAY ref), they'll blow up. |
224 | This just goes to show you that you should respect an object's privacy. |
225 | |
226 | sub TIEARRAY { |
227 | my $class = shift; |
228 | my $bound = shift; |
229 | confess "usage: tie(\@ary, 'Bounded_Array', max_subscript)" |
230 | if @_ || $bound =~ /\D/; |
231 | return bless { |
232 | BOUND => $bound, |
233 | ARRAY => [], |
234 | }, $class; |
235 | } |
236 | |
237 | =item FETCH this, index |
238 | |
239 | This method will be triggered every time an individual element the tied array |
240 | is accessed (read). It takes one argument beyond its self reference: the |
241 | index whose value we're trying to fetch. |
242 | |
243 | sub FETCH { |
244 | my($self,$idx) = @_; |
245 | if ($idx > $self->{BOUND}) { |
246 | confess "Array OOB: $idx > $self->{BOUND}"; |
247 | } |
248 | return $self->{ARRAY}[$idx]; |
249 | } |
250 | |
251 | As you may have noticed, the name of the FETCH method (et al.) is the same |
252 | for all accesses, even though the constructors differ in names (TIESCALAR |
253 | vs TIEARRAY). While in theory you could have the same class servicing |
254 | several tied types, in practice this becomes cumbersome, and it's easiest |
255 | to simply keep them at one tie type per class. |
256 | |
257 | =item STORE this, index, value |
258 | |
259 | This method will be triggered every time an element in the tied array is set |
260 | (written). It takes two arguments beyond its self reference: the index at |
261 | which we're trying to store something and the value we're trying to put |
262 | there. For example: |
263 | |
264 | sub STORE { |
265 | my($self, $idx, $value) = @_; |
266 | print "[STORE $value at $idx]\n" if _debug; |
267 | if ($idx > $self->{BOUND} ) { |
268 | confess "Array OOB: $idx > $self->{BOUND}"; |
269 | } |
270 | return $self->{ARRAY}[$idx] = $value; |
271 | } |
272 | |
273 | =item DESTROY this |
274 | |
275 | This method will be triggered when the tied variable needs to be destructed. |
276 | As with the sclar tie class, this is almost never needed in a |
277 | language that does its own garbage collection, so this time we'll |
278 | just leave it out. |
279 | |
280 | =back |
281 | |
282 | The code we presented at the top of the tied array class accesses many |
283 | elements of the array, far more than we've set the bounds to. Therefore, |
284 | it will blow up once they try to access beyond the 2nd element of @ary, as |
285 | the following output demonstrates: |
286 | |
287 | setting index 0: value of elt 0 now 0 |
288 | setting index 1: value of elt 1 now 10 |
289 | setting index 2: value of elt 2 now 20 |
290 | setting index 3: Array OOB: 3 > 2 at Bounded_Array.pm line 39 |
291 | Bounded_Array::FETCH called at testba line 12 |
292 | |
293 | =head2 Tying Hashes |
294 | |
295 | As the first Perl data type to be tied (see dbmopen()), associative arrays |
296 | have the most complete and useful tie() implementation. A class |
297 | implementing a tied associative array should define the following |
298 | methods: TIEHASH is the constructor. FETCH and STORE access the key and |
299 | value pairs. EXISTS reports whether a key is present in the hash, and |
300 | DELETE deletes one. CLEAR empties the hash by deleting all the key and |
301 | value pairs. FIRSTKEY and NEXTKEY implement the keys() and each() |
302 | functions to iterate over all the keys. And DESTROY is called when the |
303 | tied variable is garbage collected. |
304 | |
305 | If this seems like a lot, then feel free to merely inherit |
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306 | from the standard Tie::Hash module for most of your methods, redefining only |
307 | the interesting ones. See L<Tie::Hash> for details. |
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308 | |
309 | Remember that Perl distinguishes between a key not existing in the hash, |
310 | and the key existing in the hash but having a corresponding value of |
311 | C<undef>. The two possibilities can be tested with the C<exists()> and |
312 | C<defined()> functions. |
313 | |
314 | Here's an example of a somewhat interesting tied hash class: it gives you |
315 | a hash representing a particular user's dotfiles. You index into the hash |
316 | with the name of the file (minus the dot) and you get back that dotfile's |
317 | contents. For example: |
318 | |
319 | use DotFiles; |
320 | tie %dot, DotFiles; |
321 | if ( $dot{profile} =~ /MANPATH/ || |
322 | $dot{login} =~ /MANPATH/ || |
323 | $dot{cshrc} =~ /MANPATH/ ) |
324 | { |
325 | print "you seem to set your manpath\n"; |
326 | } |
327 | |
328 | Or here's another sample of using our tied class: |
329 | |
330 | tie %him, DotFiles, 'daemon'; |
331 | foreach $f ( keys %him ) { |
332 | printf "daemon dot file %s is size %d\n", |
333 | $f, length $him{$f}; |
334 | } |
335 | |
336 | In our tied hash DotFiles example, we use a regular |
337 | hash for the object containing several important |
338 | fields, of which only the C<{LIST}> field will be what the |
339 | user thinks of as the real hash. |
340 | |
341 | =over 5 |
342 | |
343 | =item USER |
344 | |
345 | whose dot files this object represents |
346 | |
347 | =item HOME |
348 | |
349 | where those dotfiles live |
350 | |
351 | =item CLOBBER |
352 | |
353 | whether we should try to change or remove those dot files |
354 | |
355 | =item LIST |
356 | |
357 | the hash of dotfile names and content mappings |
358 | |
359 | =back |
360 | |
361 | Here's the start of F<Dotfiles.pm>: |
362 | |
363 | package DotFiles; |
364 | use Carp; |
365 | sub whowasi { (caller(1))[3] . '()' } |
366 | my $DEBUG = 0; |
367 | sub debug { $DEBUG = @_ ? shift : 1 } |
368 | |
369 | For our example, we want to able to emit debugging info to help in tracing |
370 | during development. We keep also one convenience function around |
371 | internally to help print out warnings; whowasi() returns the function name |
372 | that calls it. |
373 | |
374 | Here are the methods for the DotFiles tied hash. |
375 | |
376 | =over |
377 | |
378 | =item TIEHASH classname, LIST |
379 | |
380 | This is the constructor for the class. That means it is expected to |
381 | return a blessed reference through which the new object (probably but not |
382 | necessarily an anonymous hash) will be accessed. |
383 | |
384 | Here's the constructor: |
385 | |
386 | sub TIEHASH { |
387 | my $self = shift; |
388 | my $user = shift || $>; |
389 | my $dotdir = shift || ''; |
390 | croak "usage: @{[&whowasi]} [USER [DOTDIR]]" if @_; |
391 | $user = getpwuid($user) if $user =~ /^\d+$/; |
392 | my $dir = (getpwnam($user))[7] |
393 | || croak "@{[&whowasi]}: no user $user"; |
394 | $dir .= "/$dotdir" if $dotdir; |
395 | |
396 | my $node = { |
397 | USER => $user, |
398 | HOME => $dir, |
399 | LIST => {}, |
400 | CLOBBER => 0, |
401 | }; |
402 | |
403 | opendir(DIR, $dir) |
404 | || croak "@{[&whowasi]}: can't opendir $dir: $!"; |
405 | foreach $dot ( grep /^\./ && -f "$dir/$_", readdir(DIR)) { |
406 | $dot =~ s/^\.//; |
407 | $node->{LIST}{$dot} = undef; |
408 | } |
409 | closedir DIR; |
410 | return bless $node, $self; |
411 | } |
412 | |
413 | It's probably worth mentioning that if you're going to filetest the |
414 | return values out of a readdir, you'd better prepend the directory |
415 | in question. Otherwise, since we didn't chdir() there, it would |
416 | have been testing the wrong file. |
417 | |
418 | =item FETCH this, key |
419 | |
420 | This method will be triggered every time an element in the tied hash is |
421 | accessed (read). It takes one argument beyond its self reference: the key |
422 | whose value we're trying to fetch. |
423 | |
424 | Here's the fetch for our DotFiles example. |
425 | |
426 | sub FETCH { |
427 | carp &whowasi if $DEBUG; |
428 | my $self = shift; |
429 | my $dot = shift; |
430 | my $dir = $self->{HOME}; |
431 | my $file = "$dir/.$dot"; |
432 | |
433 | unless (exists $self->{LIST}->{$dot} || -f $file) { |
434 | carp "@{[&whowasi]}: no $dot file" if $DEBUG; |
435 | return undef; |
436 | } |
437 | |
438 | if (defined $self->{LIST}->{$dot}) { |
439 | return $self->{LIST}->{$dot}; |
440 | } else { |
441 | return $self->{LIST}->{$dot} = `cat $dir/.$dot`; |
442 | } |
443 | } |
444 | |
445 | It was easy to write by having it call the Unix cat(1) command, but it |
446 | would probably be more portable to open the file manually (and somewhat |
447 | more efficient). Of course, since dot files are a Unixy concept, we're |
448 | not that concerned. |
449 | |
450 | =item STORE this, key, value |
451 | |
452 | This method will be triggered every time an element in the tied hash is set |
453 | (written). It takes two arguments beyond its self reference: the index at |
454 | which we're trying to store something, and the value we're trying to put |
455 | there. |
456 | |
457 | Here in our DotFiles example, we'll be careful not to let |
458 | them try to overwrite the file unless they've called the clobber() |
459 | method on the original object reference returned by tie(). |
460 | |
461 | sub STORE { |
462 | carp &whowasi if $DEBUG; |
463 | my $self = shift; |
464 | my $dot = shift; |
465 | my $value = shift; |
466 | my $file = $self->{HOME} . "/.$dot"; |
467 | my $user = $self->{USER}; |
468 | |
469 | croak "@{[&whowasi]}: $file not clobberable" |
470 | unless $self->{CLOBBER}; |
471 | |
472 | open(F, "> $file") || croak "can't open $file: $!"; |
473 | print F $value; |
474 | close(F); |
475 | } |
476 | |
477 | If they wanted to clobber something, they might say: |
478 | |
479 | $ob = tie %daemon_dots, 'daemon'; |
480 | $ob->clobber(1); |
481 | $daemon_dots{signature} = "A true daemon\n"; |
482 | |
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483 | Another way to lay hands on a reference to the underlying object is to |
484 | use the tied() function, so they might alternately have set clobber |
485 | using: |
486 | |
487 | tie %daemon_dots, 'daemon'; |
488 | tied(%daemon_dots)->clobber(1); |
489 | |
490 | The clobber method is simply: |
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491 | |
492 | sub clobber { |
493 | my $self = shift; |
494 | $self->{CLOBBER} = @_ ? shift : 1; |
495 | } |
496 | |
497 | =item DELETE this, key |
498 | |
499 | This method is triggered when we remove an element from the hash, |
500 | typically by using the delete() function. Again, we'll |
501 | be careful to check whether they really want to clobber files. |
502 | |
503 | sub DELETE { |
504 | carp &whowasi if $DEBUG; |
505 | |
506 | my $self = shift; |
507 | my $dot = shift; |
508 | my $file = $self->{HOME} . "/.$dot"; |
509 | croak "@{[&whowasi]}: won't remove file $file" |
510 | unless $self->{CLOBBER}; |
511 | delete $self->{LIST}->{$dot}; |
512 | unlink($file) || carp "@{[&whowasi]}: can't unlink $file: $!"; |
513 | } |
514 | |
515 | =item CLEAR this |
516 | |
517 | This method is triggered when the whole hash is to be cleared, usually by |
518 | assigning the empty list to it. |
519 | |
520 | In our example, that would remove all the user's dotfiles! It's such a |
521 | dangerous thing that they'll have to set CLOBBER to something higher than |
522 | 1 to make it happen. |
523 | |
524 | sub CLEAR { |
525 | carp &whowasi if $DEBUG; |
526 | my $self = shift; |
527 | croak "@{[&whowasi]}: won't remove all dotfiles for $self->{USER}" |
528 | unless $self->{CLOBBER} > 1; |
529 | my $dot; |
530 | foreach $dot ( keys %{$self->{LIST}}) { |
531 | $self->DELETE($dot); |
532 | } |
533 | } |
534 | |
535 | =item EXISTS this, key |
536 | |
537 | This method is triggered when the user uses the exists() function |
538 | on a particular hash. In our example, we'll look at the C<{LIST}> |
539 | hash element for this: |
540 | |
541 | sub EXISTS { |
542 | carp &whowasi if $DEBUG; |
543 | my $self = shift; |
544 | my $dot = shift; |
545 | return exists $self->{LIST}->{$dot}; |
546 | } |
547 | |
548 | =item FIRSTKEY this |
549 | |
550 | This method will be triggered when the user is going |
551 | to iterate through the hash, such as via a keys() or each() |
552 | call. |
553 | |
554 | sub FIRSTKEY { |
555 | carp &whowasi if $DEBUG; |
556 | my $self = shift; |
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557 | my $a = keys %{$self->{LIST}}; # reset each() iterator |
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558 | each %{$self->{LIST}} |
559 | } |
560 | |
561 | =item NEXTKEY this, lastkey |
562 | |
563 | This method gets triggered during a keys() or each() iteration. It has a |
564 | second argument which is the last key that had been accessed. This is |
565 | useful if you're carrying about ordering or calling the iterator from more |
566 | than one sequence, or not really storing things in a hash anywhere. |
567 | |
568 | For our example, we our using a real hash so we'll just do the simple |
569 | thing, but we'll have to indirect through the LIST field. |
570 | |
571 | sub NEXTKEY { |
572 | carp &whowasi if $DEBUG; |
573 | my $self = shift; |
574 | return each %{ $self->{LIST} } |
575 | } |
576 | |
577 | =item DESTROY this |
578 | |
579 | This method is triggered when a tied hash is about to go out of |
580 | scope. You don't really need it unless you're trying to add debugging |
581 | or have auxiliary state to clean up. Here's a very simple function: |
582 | |
583 | sub DESTROY { |
584 | carp &whowasi if $DEBUG; |
585 | } |
586 | |
587 | =back |
588 | |
589 | Note that functions such as keys() and values() may return huge array |
590 | values when used on large objects, like DBM files. You may prefer to |
591 | use the each() function to iterate over such. Example: |
592 | |
593 | # print out history file offsets |
594 | use NDBM_File; |
595 | tie(%HIST, NDBM_File, '/usr/lib/news/history', 1, 0); |
596 | while (($key,$val) = each %HIST) { |
597 | print $key, ' = ', unpack('L',$val), "\n"; |
598 | } |
599 | untie(%HIST); |
600 | |
601 | =head2 Tying FileHandles |
602 | |
603 | This isn't implemented yet. Sorry; maybe someday. |
604 | |
605 | =head1 SEE ALSO |
606 | |
607 | See L<DB_File> or L<Config> for some interesting tie() implementations. |
608 | |
609 | =head1 BUGS |
610 | |
611 | Tied arrays are I<incomplete>. They are also distinctly lacking something |
612 | for the C<$#ARRAY> access (which is hard, as it's an lvalue), as well as |
613 | the other obvious array functions, like push(), pop(), shift(), unshift(), |
614 | and splice(). |
615 | |
c07a80fd |
616 | You cannot easily tie a multilevel data structure (such as a hash of |
617 | hashes) to a dbm file. The first problem is that all but GDBM and |
618 | Berkeley DB have size limitations, but beyond that, you also have problems |
619 | with how references are to be represented on disk. One experimental |
620 | module that does attempt to partially address this need is the MLDBM |
621 | module. Check your nearest CPAN site as described in L<perlmod> for |
622 | source code to MLDBM. |
623 | |
cb1a09d0 |
624 | =head1 AUTHOR |
625 | |
626 | Tom Christiansen |