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25f64a11 |
1 | # |
2 | # Copyright (c) 1995-2000, Raphael Manfredi |
3 | # |
4 | # You may redistribute only under the same terms as Perl 5, as specified |
5 | # in the README file that comes with the distribution. |
6 | # |
7a6a85bf |
7 | |
8 | require DynaLoader; |
9 | require Exporter; |
10 | package Storable; @ISA = qw(Exporter DynaLoader); |
11 | |
12 | @EXPORT = qw(store retrieve); |
13 | @EXPORT_OK = qw( |
9e21b3d0 |
14 | nstore store_fd nstore_fd fd_retrieve |
7a6a85bf |
15 | freeze nfreeze thaw |
16 | dclone |
9e21b3d0 |
17 | retrieve_fd |
dd19458b |
18 | lock_store lock_nstore lock_retrieve |
7a6a85bf |
19 | ); |
20 | |
21 | use AutoLoader; |
01d7b99e |
22 | use vars qw($canonical $forgive_me $VERSION); |
7a6a85bf |
23 | |
17374ab3 |
24 | $VERSION = '2.04'; |
7a6a85bf |
25 | *AUTOLOAD = \&AutoLoader::AUTOLOAD; # Grrr... |
26 | |
27 | # |
28 | # Use of Log::Agent is optional |
29 | # |
30 | |
31 | eval "use Log::Agent"; |
32 | |
530b72ba |
33 | require Carp; |
7a6a85bf |
34 | |
dd19458b |
35 | # |
36 | # They might miss :flock in Fcntl |
37 | # |
38 | |
39 | BEGIN { |
596596d5 |
40 | if (eval { require Fcntl; 1 } && exists $Fcntl::EXPORT_TAGS{'flock'}) { |
dd19458b |
41 | Fcntl->import(':flock'); |
42 | } else { |
43 | eval q{ |
44 | sub LOCK_SH () {1} |
45 | sub LOCK_EX () {2} |
46 | }; |
47 | } |
48 | } |
49 | |
b8778c7c |
50 | # Can't Autoload cleanly as this clashes 8.3 with &retrieve |
9e21b3d0 |
51 | sub retrieve_fd { &fd_retrieve } # Backward compatibility |
cb3d9de5 |
52 | |
530b72ba |
53 | # By default restricted hashes are downgraded on earlier perls. |
54 | |
55 | $Storable::downgrade_restricted = 1; |
e8189732 |
56 | $Storable::accept_future_minor = 1; |
b8778c7c |
57 | bootstrap Storable; |
58 | 1; |
59 | __END__ |
530b72ba |
60 | # |
61 | # Use of Log::Agent is optional. If it hasn't imported these subs then |
62 | # Autoloader will kindly supply our fallback implementation. |
63 | # |
64 | |
65 | sub logcroak { |
66 | Carp::croak(@_); |
67 | } |
68 | |
69 | sub logcarp { |
70 | Carp::carp(@_); |
71 | } |
b8778c7c |
72 | |
862382c7 |
73 | # |
74 | # Determine whether locking is possible, but only when needed. |
75 | # |
76 | |
530b72ba |
77 | sub CAN_FLOCK; my $CAN_FLOCK; sub CAN_FLOCK { |
862382c7 |
78 | return $CAN_FLOCK if defined $CAN_FLOCK; |
79 | require Config; import Config; |
80 | return $CAN_FLOCK = |
81 | $Config{'d_flock'} || |
82 | $Config{'d_fcntl_can_lock'} || |
83 | $Config{'d_lockf'}; |
84 | } |
85 | |
0a0da639 |
86 | sub show_file_magic { |
87 | print <<EOM; |
88 | # |
89 | # To recognize the data files of the Perl module Storable, |
90 | # the following lines need to be added to the local magic(5) file, |
91 | # usually either /usr/share/misc/magic or /etc/magic. |
0a0da639 |
92 | # |
93 | 0 string perl-store perl Storable(v0.6) data |
8b793558 |
94 | >4 byte >0 (net-order %d) |
95 | >>4 byte &01 (network-ordered) |
96 | >>4 byte =3 (major 1) |
97 | >>4 byte =2 (major 1) |
98 | |
0a0da639 |
99 | 0 string pst0 perl Storable(v0.7) data |
8b793558 |
100 | >4 byte >0 |
101 | >>4 byte &01 (network-ordered) |
102 | >>4 byte =5 (major 2) |
103 | >>4 byte =4 (major 2) |
104 | >>5 byte >0 (minor %d) |
0a0da639 |
105 | EOM |
106 | } |
107 | |
b8778c7c |
108 | sub read_magic { |
109 | my $header = shift; |
110 | return unless defined $header and length $header > 11; |
111 | my $result; |
112 | if ($header =~ s/^perl-store//) { |
113 | die "Can't deal with version 0 headers"; |
114 | } elsif ($header =~ s/^pst0//) { |
115 | $result->{file} = 1; |
116 | } |
117 | # Assume it's a string. |
118 | my ($major, $minor, $bytelen) = unpack "C3", $header; |
119 | |
120 | my $net_order = $major & 1; |
121 | $major >>= 1; |
122 | @$result{qw(major minor netorder)} = ($major, $minor, $net_order); |
123 | |
124 | return $result if $net_order; |
125 | |
126 | # I assume that it is rare to find v1 files, so this is an intentionally |
127 | # inefficient way of doing it, to make the rest of the code constant. |
128 | if ($major < 2) { |
129 | delete $result->{minor}; |
130 | $header = '.' . $header; |
131 | $bytelen = $minor; |
132 | } |
133 | |
134 | @$result{qw(byteorder intsize longsize ptrsize)} = |
135 | unpack "x3 A$bytelen C3", $header; |
136 | |
137 | if ($major >= 2 and $minor >= 2) { |
138 | $result->{nvsize} = unpack "x6 x$bytelen C", $header; |
139 | } |
140 | $result; |
141 | } |
7a6a85bf |
142 | |
143 | # |
144 | # store |
145 | # |
146 | # Store target object hierarchy, identified by a reference to its root. |
147 | # The stored object tree may later be retrieved to memory via retrieve. |
148 | # Returns undef if an I/O error occurred, in which case the file is |
149 | # removed. |
150 | # |
151 | sub store { |
dd19458b |
152 | return _store(\&pstore, @_, 0); |
7a6a85bf |
153 | } |
154 | |
155 | # |
156 | # nstore |
157 | # |
158 | # Same as store, but in network order. |
159 | # |
160 | sub nstore { |
dd19458b |
161 | return _store(\&net_pstore, @_, 0); |
162 | } |
163 | |
164 | # |
165 | # lock_store |
166 | # |
167 | # Same as store, but flock the file first (advisory locking). |
168 | # |
169 | sub lock_store { |
170 | return _store(\&pstore, @_, 1); |
171 | } |
172 | |
173 | # |
174 | # lock_nstore |
175 | # |
176 | # Same as nstore, but flock the file first (advisory locking). |
177 | # |
178 | sub lock_nstore { |
179 | return _store(\&net_pstore, @_, 1); |
7a6a85bf |
180 | } |
181 | |
182 | # Internal store to file routine |
183 | sub _store { |
184 | my $xsptr = shift; |
185 | my $self = shift; |
dd19458b |
186 | my ($file, $use_locking) = @_; |
7a6a85bf |
187 | logcroak "not a reference" unless ref($self); |
b12202d0 |
188 | logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist |
7a6a85bf |
189 | local *FILE; |
dd19458b |
190 | if ($use_locking) { |
6e0ac6f5 |
191 | open(FILE, ">>$file") || logcroak "can't write into $file: $!"; |
862382c7 |
192 | unless (&CAN_FLOCK) { |
b29b780f |
193 | logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; |
194 | return undef; |
f567092b |
195 | } |
dd19458b |
196 | flock(FILE, LOCK_EX) || |
197 | logcroak "can't get exclusive lock on $file: $!"; |
198 | truncate FILE, 0; |
199 | # Unlocking will happen when FILE is closed |
6e0ac6f5 |
200 | } else { |
201 | open(FILE, ">$file") || logcroak "can't create $file: $!"; |
dd19458b |
202 | } |
6e0ac6f5 |
203 | binmode FILE; # Archaic systems... |
7a6a85bf |
204 | my $da = $@; # Don't mess if called from exception handler |
205 | my $ret; |
206 | # Call C routine nstore or pstore, depending on network order |
207 | eval { $ret = &$xsptr(*FILE, $self) }; |
208 | close(FILE) or $ret = undef; |
209 | unlink($file) or warn "Can't unlink $file: $!\n" if $@ || !defined $ret; |
210 | logcroak $@ if $@ =~ s/\.?\n$/,/; |
211 | $@ = $da; |
212 | return $ret ? $ret : undef; |
213 | } |
214 | |
215 | # |
216 | # store_fd |
217 | # |
218 | # Same as store, but perform on an already opened file descriptor instead. |
219 | # Returns undef if an I/O error occurred. |
220 | # |
221 | sub store_fd { |
222 | return _store_fd(\&pstore, @_); |
223 | } |
224 | |
225 | # |
226 | # nstore_fd |
227 | # |
228 | # Same as store_fd, but in network order. |
229 | # |
230 | sub nstore_fd { |
231 | my ($self, $file) = @_; |
232 | return _store_fd(\&net_pstore, @_); |
233 | } |
234 | |
235 | # Internal store routine on opened file descriptor |
236 | sub _store_fd { |
237 | my $xsptr = shift; |
238 | my $self = shift; |
239 | my ($file) = @_; |
240 | logcroak "not a reference" unless ref($self); |
241 | logcroak "too many arguments" unless @_ == 1; # No @foo in arglist |
242 | my $fd = fileno($file); |
243 | logcroak "not a valid file descriptor" unless defined $fd; |
244 | my $da = $@; # Don't mess if called from exception handler |
245 | my $ret; |
246 | # Call C routine nstore or pstore, depending on network order |
247 | eval { $ret = &$xsptr($file, $self) }; |
248 | logcroak $@ if $@ =~ s/\.?\n$/,/; |
596596d5 |
249 | local $\; print $file ''; # Autoflush the file if wanted |
7a6a85bf |
250 | $@ = $da; |
251 | return $ret ? $ret : undef; |
252 | } |
253 | |
254 | # |
255 | # freeze |
256 | # |
257 | # Store oject and its hierarchy in memory and return a scalar |
258 | # containing the result. |
259 | # |
260 | sub freeze { |
261 | _freeze(\&mstore, @_); |
262 | } |
263 | |
264 | # |
265 | # nfreeze |
266 | # |
267 | # Same as freeze but in network order. |
268 | # |
269 | sub nfreeze { |
270 | _freeze(\&net_mstore, @_); |
271 | } |
272 | |
273 | # Internal freeze routine |
274 | sub _freeze { |
275 | my $xsptr = shift; |
276 | my $self = shift; |
277 | logcroak "not a reference" unless ref($self); |
278 | logcroak "too many arguments" unless @_ == 0; # No @foo in arglist |
279 | my $da = $@; # Don't mess if called from exception handler |
280 | my $ret; |
281 | # Call C routine mstore or net_mstore, depending on network order |
282 | eval { $ret = &$xsptr($self) }; |
283 | logcroak $@ if $@ =~ s/\.?\n$/,/; |
284 | $@ = $da; |
285 | return $ret ? $ret : undef; |
286 | } |
287 | |
288 | # |
289 | # retrieve |
290 | # |
291 | # Retrieve object hierarchy from disk, returning a reference to the root |
292 | # object of that tree. |
293 | # |
294 | sub retrieve { |
dd19458b |
295 | _retrieve($_[0], 0); |
296 | } |
297 | |
298 | # |
299 | # lock_retrieve |
300 | # |
301 | # Same as retrieve, but with advisory locking. |
302 | # |
303 | sub lock_retrieve { |
304 | _retrieve($_[0], 1); |
305 | } |
306 | |
307 | # Internal retrieve routine |
308 | sub _retrieve { |
309 | my ($file, $use_locking) = @_; |
7a6a85bf |
310 | local *FILE; |
dd19458b |
311 | open(FILE, $file) || logcroak "can't open $file: $!"; |
7a6a85bf |
312 | binmode FILE; # Archaic systems... |
313 | my $self; |
314 | my $da = $@; # Could be from exception handler |
dd19458b |
315 | if ($use_locking) { |
862382c7 |
316 | unless (&CAN_FLOCK) { |
8be2b38b |
317 | logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; |
b29b780f |
318 | return undef; |
319 | } |
8be2b38b |
320 | flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!"; |
dd19458b |
321 | # Unlocking will happen when FILE is closed |
322 | } |
7a6a85bf |
323 | eval { $self = pretrieve(*FILE) }; # Call C routine |
324 | close(FILE); |
325 | logcroak $@ if $@ =~ s/\.?\n$/,/; |
326 | $@ = $da; |
327 | return $self; |
328 | } |
329 | |
330 | # |
9e21b3d0 |
331 | # fd_retrieve |
7a6a85bf |
332 | # |
333 | # Same as retrieve, but perform from an already opened file descriptor instead. |
334 | # |
9e21b3d0 |
335 | sub fd_retrieve { |
7a6a85bf |
336 | my ($file) = @_; |
337 | my $fd = fileno($file); |
338 | logcroak "not a valid file descriptor" unless defined $fd; |
339 | my $self; |
340 | my $da = $@; # Could be from exception handler |
341 | eval { $self = pretrieve($file) }; # Call C routine |
342 | logcroak $@ if $@ =~ s/\.?\n$/,/; |
343 | $@ = $da; |
344 | return $self; |
345 | } |
346 | |
347 | # |
348 | # thaw |
349 | # |
350 | # Recreate objects in memory from an existing frozen image created |
351 | # by freeze. If the frozen image passed is undef, return undef. |
352 | # |
353 | sub thaw { |
354 | my ($frozen) = @_; |
355 | return undef unless defined $frozen; |
356 | my $self; |
357 | my $da = $@; # Could be from exception handler |
358 | eval { $self = mretrieve($frozen) }; # Call C routine |
359 | logcroak $@ if $@ =~ s/\.?\n$/,/; |
360 | $@ = $da; |
361 | return $self; |
362 | } |
363 | |
364 | =head1 NAME |
365 | |
f062ea6c |
366 | Storable - persistence for Perl data structures |
7a6a85bf |
367 | |
368 | =head1 SYNOPSIS |
369 | |
370 | use Storable; |
371 | store \%table, 'file'; |
372 | $hashref = retrieve('file'); |
373 | |
374 | use Storable qw(nstore store_fd nstore_fd freeze thaw dclone); |
375 | |
376 | # Network order |
377 | nstore \%table, 'file'; |
378 | $hashref = retrieve('file'); # There is NO nretrieve() |
379 | |
380 | # Storing to and retrieving from an already opened file |
381 | store_fd \@array, \*STDOUT; |
382 | nstore_fd \%table, \*STDOUT; |
9e21b3d0 |
383 | $aryref = fd_retrieve(\*SOCKET); |
384 | $hashref = fd_retrieve(\*SOCKET); |
7a6a85bf |
385 | |
386 | # Serializing to memory |
387 | $serialized = freeze \%table; |
388 | %table_clone = %{ thaw($serialized) }; |
389 | |
390 | # Deep (recursive) cloning |
391 | $cloneref = dclone($ref); |
392 | |
dd19458b |
393 | # Advisory locking |
394 | use Storable qw(lock_store lock_nstore lock_retrieve) |
395 | lock_store \%table, 'file'; |
396 | lock_nstore \%table, 'file'; |
397 | $hashref = lock_retrieve('file'); |
398 | |
7a6a85bf |
399 | =head1 DESCRIPTION |
400 | |
f062ea6c |
401 | The Storable package brings persistence to your Perl data structures |
7a6a85bf |
402 | containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be |
c261f00e |
403 | conveniently stored to disk and retrieved at a later time. |
7a6a85bf |
404 | |
405 | It can be used in the regular procedural way by calling C<store> with |
406 | a reference to the object to be stored, along with the file name where |
407 | the image should be written. |
775ecd75 |
408 | |
7a6a85bf |
409 | The routine returns C<undef> for I/O problems or other internal error, |
410 | a true value otherwise. Serious errors are propagated as a C<die> exception. |
411 | |
f062ea6c |
412 | To retrieve data stored to disk, use C<retrieve> with a file name. |
413 | The objects stored into that file are recreated into memory for you, |
414 | and a I<reference> to the root object is returned. In case an I/O error |
7a6a85bf |
415 | occurs while reading, C<undef> is returned instead. Other serious |
416 | errors are propagated via C<die>. |
417 | |
418 | Since storage is performed recursively, you might want to stuff references |
419 | to objects that share a lot of common data into a single array or hash |
420 | table, and then store that object. That way, when you retrieve back the |
421 | whole thing, the objects will continue to share what they originally shared. |
422 | |
423 | At the cost of a slight header overhead, you may store to an already |
424 | opened file descriptor using the C<store_fd> routine, and retrieve |
9e21b3d0 |
425 | from a file via C<fd_retrieve>. Those names aren't imported by default, |
c261f00e |
426 | so you will have to do that explicitly if you need those routines. |
7a6a85bf |
427 | The file descriptor you supply must be already opened, for read |
428 | if you're going to retrieve and for write if you wish to store. |
429 | |
430 | store_fd(\%table, *STDOUT) || die "can't store to stdout\n"; |
9e21b3d0 |
431 | $hashref = fd_retrieve(*STDIN); |
7a6a85bf |
432 | |
433 | You can also store data in network order to allow easy sharing across |
434 | multiple platforms, or when storing on a socket known to be remotely |
435 | connected. The routines to call have an initial C<n> prefix for I<network>, |
436 | as in C<nstore> and C<nstore_fd>. At retrieval time, your data will be |
437 | correctly restored so you don't have to know whether you're restoring |
dd19458b |
438 | from native or network ordered data. Double values are stored stringified |
439 | to ensure portability as well, at the slight risk of loosing some precision |
440 | in the last decimals. |
7a6a85bf |
441 | |
9e21b3d0 |
442 | When using C<fd_retrieve>, objects are retrieved in sequence, one |
7a6a85bf |
443 | object (i.e. one recursive tree) per associated C<store_fd>. |
444 | |
445 | If you're more from the object-oriented camp, you can inherit from |
446 | Storable and directly store your objects by invoking C<store> as |
447 | a method. The fact that the root of the to-be-stored tree is a |
448 | blessed reference (i.e. an object) is special-cased so that the |
449 | retrieve does not provide a reference to that object but rather the |
450 | blessed object reference itself. (Otherwise, you'd get a reference |
451 | to that blessed object). |
452 | |
453 | =head1 MEMORY STORE |
454 | |
455 | The Storable engine can also store data into a Perl scalar instead, to |
456 | later retrieve them. This is mainly used to freeze a complex structure in |
457 | some safe compact memory place (where it can possibly be sent to another |
458 | process via some IPC, since freezing the structure also serializes it in |
459 | effect). Later on, and maybe somewhere else, you can thaw the Perl scalar |
460 | out and recreate the original complex structure in memory. |
461 | |
462 | Surprisingly, the routines to be called are named C<freeze> and C<thaw>. |
463 | If you wish to send out the frozen scalar to another machine, use |
464 | C<nfreeze> instead to get a portable image. |
465 | |
466 | Note that freezing an object structure and immediately thawing it |
467 | actually achieves a deep cloning of that structure: |
468 | |
469 | dclone(.) = thaw(freeze(.)) |
470 | |
471 | Storable provides you with a C<dclone> interface which does not create |
472 | that intermediary scalar but instead freezes the structure in some |
c261f00e |
473 | internal memory space and then immediately thaws it out. |
7a6a85bf |
474 | |
dd19458b |
475 | =head1 ADVISORY LOCKING |
476 | |
f062ea6c |
477 | The C<lock_store> and C<lock_nstore> routine are equivalent to |
478 | C<store> and C<nstore>, except that they get an exclusive lock on |
479 | the file before writing. Likewise, C<lock_retrieve> does the same |
480 | as C<retrieve>, but also gets a shared lock on the file before reading. |
dd19458b |
481 | |
f062ea6c |
482 | As with any advisory locking scheme, the protection only works if you |
483 | systematically use C<lock_store> and C<lock_retrieve>. If one side of |
484 | your application uses C<store> whilst the other uses C<lock_retrieve>, |
dd19458b |
485 | you will get no protection at all. |
486 | |
f062ea6c |
487 | The internal advisory locking is implemented using Perl's flock() |
488 | routine. If your system does not support any form of flock(), or if |
489 | you share your files across NFS, you might wish to use other forms |
490 | of locking by using modules such as LockFile::Simple which lock a |
491 | file using a filesystem entry, instead of locking the file descriptor. |
dd19458b |
492 | |
7a6a85bf |
493 | =head1 SPEED |
494 | |
495 | The heart of Storable is written in C for decent speed. Extra low-level |
4d3295e3 |
496 | optimizations have been made when manipulating perl internals, to |
497 | sacrifice encapsulation for the benefit of greater speed. |
7a6a85bf |
498 | |
499 | =head1 CANONICAL REPRESENTATION |
500 | |
f062ea6c |
501 | Normally, Storable stores elements of hashes in the order they are |
7a6a85bf |
502 | stored internally by Perl, i.e. pseudo-randomly. If you set |
503 | C<$Storable::canonical> to some C<TRUE> value, Storable will store |
504 | hashes with the elements sorted by their key. This allows you to |
505 | compare data structures by comparing their frozen representations (or |
506 | even the compressed frozen representations), which can be useful for |
507 | creating lookup tables for complicated queries. |
508 | |
f062ea6c |
509 | Canonical order does not imply network order; those are two orthogonal |
7a6a85bf |
510 | settings. |
511 | |
c261f00e |
512 | =head1 FORWARD COMPATIBILITY |
513 | |
514 | This release of Storable can be used on a newer version of Perl to |
f062ea6c |
515 | serialize data which is not supported by earlier Perls. By default, |
c261f00e |
516 | Storable will attempt to do the right thing, by C<croak()>ing if it |
775ecd75 |
517 | encounters data that it cannot deserialize. However, the defaults |
f062ea6c |
518 | can be changed as follows: |
c261f00e |
519 | |
520 | =over 4 |
521 | |
522 | =item utf8 data |
523 | |
524 | Perl 5.6 added support for Unicode characters with code points > 255, |
525 | and Perl 5.8 has full support for Unicode characters in hash keys. |
526 | Perl internally encodes strings with these characters using utf8, and |
527 | Storable serializes them as utf8. By default, if an older version of |
528 | Perl encounters a utf8 value it cannot represent, it will C<croak()>. |
529 | To change this behaviour so that Storable deserializes utf8 encoded |
530 | values as the string of bytes (effectively dropping the I<is_utf8> flag) |
531 | set C<$Storable::drop_utf8> to some C<TRUE> value. This is a form of |
532 | data loss, because with C<$drop_utf8> true, it becomes impossible to tell |
533 | whether the original data was the Unicode string, or a series of bytes |
534 | that happen to be valid utf8. |
535 | |
536 | =item restricted hashes |
537 | |
f062ea6c |
538 | Perl 5.8 adds support for restricted hashes, which have keys |
539 | restricted to a given set, and can have values locked to be read only. |
540 | By default, when Storable encounters a restricted hash on a perl |
541 | that doesn't support them, it will deserialize it as a normal hash, |
542 | silently discarding any placeholder keys and leaving the keys and |
543 | all values unlocked. To make Storable C<croak()> instead, set |
544 | C<$Storable::downgrade_restricted> to a C<FALSE> value. To restore |
545 | the default set it back to some C<TRUE> value. |
c261f00e |
546 | |
e8189732 |
547 | =item files from future versions of Storable |
548 | |
549 | Earlier versions of Storable would immediately croak if they encountered |
550 | a file with a higher internal version number than the reading Storable |
551 | knew about. Internal version numbers are increased each time new data |
552 | types (such as restricted hashes) are added to the vocabulary of the file |
553 | format. This meant that a newer Storable module had no way of writing a |
f062ea6c |
554 | file readable by an older Storable, even if the writer didn't store newer |
e8189732 |
555 | data types. |
556 | |
557 | This version of Storable will defer croaking until it encounters a data |
558 | type in the file that it does not recognize. This means that it will |
559 | continue to read files generated by newer Storable modules which are careful |
560 | in what they write out, making it easier to upgrade Storable modules in a |
561 | mixed environment. |
562 | |
563 | The old behaviour of immediate croaking can be re-instated by setting |
f062ea6c |
564 | C<$Storable::accept_future_minor> to some C<FALSE> value. |
e8189732 |
565 | |
c261f00e |
566 | =back |
567 | |
f062ea6c |
568 | All these variables have no effect on a newer Perl which supports the |
c261f00e |
569 | relevant feature. |
570 | |
7a6a85bf |
571 | =head1 ERROR REPORTING |
572 | |
573 | Storable uses the "exception" paradigm, in that it does not try to workaround |
574 | failures: if something bad happens, an exception is generated from the |
575 | caller's perspective (see L<Carp> and C<croak()>). Use eval {} to trap |
576 | those exceptions. |
577 | |
578 | When Storable croaks, it tries to report the error via the C<logcroak()> |
579 | routine from the C<Log::Agent> package, if it is available. |
580 | |
212e9bde |
581 | Normal errors are reported by having store() or retrieve() return C<undef>. |
582 | Such errors are usually I/O errors (or truncated stream errors at retrieval). |
583 | |
7a6a85bf |
584 | =head1 WIZARDS ONLY |
585 | |
586 | =head2 Hooks |
587 | |
588 | Any class may define hooks that will be called during the serialization |
589 | and deserialization process on objects that are instances of that class. |
590 | Those hooks can redefine the way serialization is performed (and therefore, |
c261f00e |
591 | how the symmetrical deserialization should be conducted). |
7a6a85bf |
592 | |
593 | Since we said earlier: |
594 | |
595 | dclone(.) = thaw(freeze(.)) |
596 | |
597 | everything we say about hooks should also hold for deep cloning. However, |
598 | hooks get to know whether the operation is a mere serialization, or a cloning. |
599 | |
600 | Therefore, when serializing hooks are involved, |
601 | |
602 | dclone(.) <> thaw(freeze(.)) |
603 | |
604 | Well, you could keep them in sync, but there's no guarantee it will always |
605 | hold on classes somebody else wrote. Besides, there is little to gain in |
f062ea6c |
606 | doing so: a serializing hook could keep only one attribute of an object, |
7a6a85bf |
607 | which is probably not what should happen during a deep cloning of that |
608 | same object. |
609 | |
610 | Here is the hooking interface: |
611 | |
bbc7dcd2 |
612 | =over 4 |
7a6a85bf |
613 | |
614 | =item C<STORABLE_freeze> I<obj>, I<cloning> |
615 | |
616 | The serializing hook, called on the object during serialization. It can be |
617 | inherited, or defined in the class itself, like any other method. |
618 | |
619 | Arguments: I<obj> is the object to serialize, I<cloning> is a flag indicating |
620 | whether we're in a dclone() or a regular serialization via store() or freeze(). |
621 | |
622 | Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized |
623 | is the serialized form to be used, and the optional $ref1, $ref2, etc... are |
624 | extra references that you wish to let the Storable engine serialize. |
625 | |
626 | At deserialization time, you will be given back the same LIST, but all the |
627 | extra references will be pointing into the deserialized structure. |
628 | |
629 | The B<first time> the hook is hit in a serialization flow, you may have it |
630 | return an empty list. That will signal the Storable engine to further |
631 | discard that hook for this class and to therefore revert to the default |
632 | serialization of the underlying Perl data. The hook will again be normally |
633 | processed in the next serialization. |
634 | |
635 | Unless you know better, serializing hook should always say: |
636 | |
637 | sub STORABLE_freeze { |
638 | my ($self, $cloning) = @_; |
639 | return if $cloning; # Regular default serialization |
640 | .... |
641 | } |
642 | |
643 | in order to keep reasonable dclone() semantics. |
644 | |
645 | =item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ... |
646 | |
647 | The deserializing hook called on the object during deserialization. |
f062ea6c |
648 | But wait: if we're deserializing, there's no object yet... right? |
7a6a85bf |
649 | |
650 | Wrong: the Storable engine creates an empty one for you. If you know Eiffel, |
651 | you can view C<STORABLE_thaw> as an alternate creation routine. |
652 | |
653 | This means the hook can be inherited like any other method, and that |
654 | I<obj> is your blessed reference for this particular instance. |
655 | |
656 | The other arguments should look familiar if you know C<STORABLE_freeze>: |
657 | I<cloning> is true when we're part of a deep clone operation, I<serialized> |
658 | is the serialized string you returned to the engine in C<STORABLE_freeze>, |
659 | and there may be an optional list of references, in the same order you gave |
660 | them at serialization time, pointing to the deserialized objects (which |
661 | have been processed courtesy of the Storable engine). |
662 | |
212e9bde |
663 | When the Storable engine does not find any C<STORABLE_thaw> hook routine, |
664 | it tries to load the class by requiring the package dynamically (using |
665 | the blessed package name), and then re-attempts the lookup. If at that |
666 | time the hook cannot be located, the engine croaks. Note that this mechanism |
c261f00e |
667 | will fail if you define several classes in the same file, but L<perlmod> |
212e9bde |
668 | warned you. |
669 | |
f062ea6c |
670 | It is up to you to use this information to populate I<obj> the way you want. |
7a6a85bf |
671 | |
672 | Returned value: none. |
673 | |
674 | =back |
675 | |
676 | =head2 Predicates |
677 | |
c261f00e |
678 | Predicates are not exportable. They must be called by explicitly prefixing |
7a6a85bf |
679 | them with the Storable package name. |
680 | |
bbc7dcd2 |
681 | =over 4 |
7a6a85bf |
682 | |
683 | =item C<Storable::last_op_in_netorder> |
684 | |
685 | The C<Storable::last_op_in_netorder()> predicate will tell you whether |
686 | network order was used in the last store or retrieve operation. If you |
687 | don't know how to use this, just forget about it. |
688 | |
689 | =item C<Storable::is_storing> |
690 | |
691 | Returns true if within a store operation (via STORABLE_freeze hook). |
692 | |
693 | =item C<Storable::is_retrieving> |
694 | |
f062ea6c |
695 | Returns true if within a retrieve operation (via STORABLE_thaw hook). |
7a6a85bf |
696 | |
697 | =back |
698 | |
699 | =head2 Recursion |
700 | |
f062ea6c |
701 | With hooks comes the ability to recurse back to the Storable engine. |
702 | Indeed, hooks are regular Perl code, and Storable is convenient when |
703 | it comes to serializing and deserializing things, so why not use it |
704 | to handle the serialization string? |
7a6a85bf |
705 | |
f062ea6c |
706 | There are a few things you need to know, however: |
7a6a85bf |
707 | |
bbc7dcd2 |
708 | =over 4 |
7a6a85bf |
709 | |
710 | =item * |
711 | |
712 | You can create endless loops if the things you serialize via freeze() |
f062ea6c |
713 | (for instance) point back to the object we're trying to serialize in |
714 | the hook. |
7a6a85bf |
715 | |
716 | =item * |
717 | |
718 | Shared references among objects will not stay shared: if we're serializing |
719 | the list of object [A, C] where both object A and C refer to the SAME object |
720 | B, and if there is a serializing hook in A that says freeze(B), then when |
721 | deserializing, we'll get [A', C'] where A' refers to B', but C' refers to D, |
722 | a deep clone of B'. The topology was not preserved. |
723 | |
724 | =back |
725 | |
726 | That's why C<STORABLE_freeze> lets you provide a list of references |
727 | to serialize. The engine guarantees that those will be serialized in the |
728 | same context as the other objects, and therefore that shared objects will |
729 | stay shared. |
730 | |
731 | In the above [A, C] example, the C<STORABLE_freeze> hook could return: |
732 | |
733 | ("something", $self->{B}) |
734 | |
735 | and the B part would be serialized by the engine. In C<STORABLE_thaw>, you |
736 | would get back the reference to the B' object, deserialized for you. |
737 | |
738 | Therefore, recursion should normally be avoided, but is nonetheless supported. |
739 | |
740 | =head2 Deep Cloning |
741 | |
f062ea6c |
742 | There is a Clone module available on CPAN which implements deep cloning |
7a6a85bf |
743 | natively, i.e. without freezing to memory and thawing the result. It is |
744 | aimed to replace Storable's dclone() some day. However, it does not currently |
745 | support Storable hooks to redefine the way deep cloning is performed. |
746 | |
0a0da639 |
747 | =head1 Storable magic |
748 | |
749 | Yes, there's a lot of that :-) But more precisely, in UNIX systems |
750 | there's a utility called C<file>, which recognizes data files based on |
751 | their contents (usually their first few bytes). For this to work, |
8b793558 |
752 | a certain file called F<magic> needs to taught about the I<signature> |
0a0da639 |
753 | of the data. Where that configuration file lives depends on the UNIX |
f062ea6c |
754 | flavour; often it's something like F</usr/share/misc/magic> or |
8b793558 |
755 | F</etc/magic>. Your system administrator needs to do the updating of |
756 | the F<magic> file. The necessary signature information is output to |
f062ea6c |
757 | STDOUT by invoking Storable::show_file_magic(). Note that the GNU |
758 | implementation of the C<file> utility, version 3.38 or later, |
759 | is expected to contain support for recognising Storable files |
760 | out-of-the-box, in addition to other kinds of Perl files. |
0a0da639 |
761 | |
7a6a85bf |
762 | =head1 EXAMPLES |
763 | |
764 | Here are some code samples showing a possible usage of Storable: |
765 | |
766 | use Storable qw(store retrieve freeze thaw dclone); |
767 | |
768 | %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1); |
769 | |
770 | store(\%color, '/tmp/colors') or die "Can't store %a in /tmp/colors!\n"; |
771 | |
772 | $colref = retrieve('/tmp/colors'); |
773 | die "Unable to retrieve from /tmp/colors!\n" unless defined $colref; |
774 | printf "Blue is still %lf\n", $colref->{'Blue'}; |
775 | |
776 | $colref2 = dclone(\%color); |
777 | |
778 | $str = freeze(\%color); |
779 | printf "Serialization of %%color is %d bytes long.\n", length($str); |
780 | $colref3 = thaw($str); |
781 | |
782 | which prints (on my machine): |
783 | |
784 | Blue is still 0.100000 |
785 | Serialization of %color is 102 bytes long. |
786 | |
787 | =head1 WARNING |
788 | |
789 | If you're using references as keys within your hash tables, you're bound |
f062ea6c |
790 | to be disappointed when retrieving your data. Indeed, Perl stringifies |
7a6a85bf |
791 | references used as hash table keys. If you later wish to access the |
792 | items via another reference stringification (i.e. using the same |
793 | reference that was used for the key originally to record the value into |
794 | the hash table), it will work because both references stringify to the |
795 | same string. |
796 | |
6fe6778b |
797 | It won't work across a sequence of C<store> and C<retrieve> operations, |
798 | however, because the addresses in the retrieved objects, which are |
799 | part of the stringified references, will probably differ from the |
800 | original addresses. The topology of your structure is preserved, |
801 | but not hidden semantics like those. |
7a6a85bf |
802 | |
803 | On platforms where it matters, be sure to call C<binmode()> on the |
804 | descriptors that you pass to Storable functions. |
805 | |
806 | Storing data canonically that contains large hashes can be |
807 | significantly slower than storing the same data normally, as |
c261f00e |
808 | temporary arrays to hold the keys for each hash have to be allocated, |
7a6a85bf |
809 | populated, sorted and freed. Some tests have shown a halving of the |
810 | speed of storing -- the exact penalty will depend on the complexity of |
811 | your data. There is no slowdown on retrieval. |
812 | |
813 | =head1 BUGS |
814 | |
f062ea6c |
815 | You can't store GLOB, CODE, FORMLINE, etc.... If you can define |
7a6a85bf |
816 | semantics for those operations, feel free to enhance Storable so that |
817 | it can deal with them. |
818 | |
819 | The store functions will C<croak> if they run into such references |
820 | unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that |
821 | case, the fatal message is turned in a warning and some |
822 | meaningless string is stored instead. |
823 | |
824 | Setting C<$Storable::canonical> may not yield frozen strings that |
825 | compare equal due to possible stringification of numbers. When the |
f062ea6c |
826 | string version of a scalar exists, it is the form stored; therefore, |
7a6a85bf |
827 | if you happen to use your numbers as strings between two freezing |
828 | operations on the same data structures, you will get different |
829 | results. |
830 | |
dd19458b |
831 | When storing doubles in network order, their value is stored as text. |
832 | However, you should also not expect non-numeric floating-point values |
833 | such as infinity and "not a number" to pass successfully through a |
834 | nstore()/retrieve() pair. |
835 | |
836 | As Storable neither knows nor cares about character sets (although it |
837 | does know that characters may be more than eight bits wide), any difference |
838 | in the interpretation of character codes between a host and a target |
839 | system is your problem. In particular, if host and target use different |
840 | code points to represent the characters used in the text representation |
841 | of floating-point numbers, you will not be able be able to exchange |
842 | floating-point data, even with nstore(). |
843 | |
c261f00e |
844 | C<Storable::drop_utf8> is a blunt tool. There is no facility either to |
845 | return B<all> strings as utf8 sequences, or to attempt to convert utf8 |
846 | data back to 8 bit and C<croak()> if the conversion fails. |
847 | |
ee0f7aac |
848 | Prior to Storable 2.01, no distinction was made between signed and |
849 | unsigned integers on storing. By default Storable prefers to store a |
850 | scalars string representation (if it has one) so this would only cause |
851 | problems when storing large unsigned integers that had never been coverted |
852 | to string or floating point. In other words values that had been generated |
853 | by integer operations such as logic ops and then not used in any string or |
854 | arithmetic context before storing. |
855 | |
856 | =head2 64 bit data in perl 5.6.0 and 5.6.1 |
857 | |
858 | This section only applies to you if you have existing data written out |
859 | by Storable 2.02 or earlier on perl 5.6.0 or 5.6.1 on Unix or Linux which |
860 | has been configured with 64 bit integer support (not the default) |
861 | If you got a precompiled perl, rather than running Configure to build |
862 | your own perl from source, then it almost certainly does not affect you, |
863 | and you can stop reading now (unless you're curious). If you're using perl |
864 | on Windows it does not affect you. |
865 | |
866 | Storable writes a file header which contains the sizes of various C |
867 | language types for the C compiler that built Storable (when not writing in |
868 | network order), and will refuse to load files written by a Storable not |
869 | on the same (or compatible) architecture. This check and a check on |
870 | machine byteorder is needed because the size of various fields in the file |
871 | are given by the sizes of the C language types, and so files written on |
872 | different architectures are incompatible. This is done for increased speed. |
873 | (When writing in network order, all fields are written out as standard |
874 | lengths, which allows full interworking, but takes longer to read and write) |
875 | |
876 | Perl 5.6.x introduced the ability to optional configure the perl interpreter |
877 | to use C's C<long long> type to allow scalars to store 64 bit integers on 32 |
878 | bit systems. However, due to the way the Perl configuration system |
879 | generated the C configuration files on non-Windows platforms, and the way |
880 | Storable generates its header, nothing in the Storable file header reflected |
881 | whether the perl writing was using 32 or 64 bit integers, despite the fact |
882 | that Storable was storing some data differently in the file. Hence Storable |
883 | running on perl with 64 bit integers will read the header from a file |
884 | written by a 32 bit perl, not realise that the data is actually in a subtly |
885 | incompatible format, and then go horribly wrong (possibly crashing) if it |
886 | encountered a stored integer. This is a design failure. |
887 | |
888 | Storable has now been changed to write out and read in a file header with |
889 | information about the size of integers. It's impossible to detect whether |
890 | an old file being read in was written with 32 or 64 bit integers (they have |
891 | the same header) so it's impossible to automatically switch to a correct |
892 | backwards compatibility mode. Hence this Storable defaults to the new, |
893 | correct behaviour. |
894 | |
895 | What this means is that if you have data written by Storable 1.x running |
896 | on perl 5.6.0 or 5.6.1 configured with 64 bit integers on Unix or Linux |
897 | then by default this Storable will refuse to read it, giving the error |
898 | I<Byte order is not compatible>. If you have such data then you you |
899 | should set C<$Storable::interwork_56_64bit> to a true value to make this |
900 | Storable read and write files with the old header. You should also |
901 | migrate your data, or any older perl you are communicating with, to this |
902 | current version of Storable. |
903 | |
904 | If you don't have data written with specific configuration of perl described |
905 | above, then you do not and should not do anything. Don't set the flag - |
906 | not only will Storable on an identically configured perl refuse to load them, |
907 | but Storable a differently configured perl will load them believing them |
908 | to be correct for it, and then may well fail or crash part way through |
909 | reading them. |
910 | |
7a6a85bf |
911 | =head1 CREDITS |
912 | |
913 | Thank you to (in chronological order): |
914 | |
915 | Jarkko Hietaniemi <jhi@iki.fi> |
916 | Ulrich Pfeifer <pfeifer@charly.informatik.uni-dortmund.de> |
917 | Benjamin A. Holzman <bah@ecnvantage.com> |
918 | Andrew Ford <A.Ford@ford-mason.co.uk> |
919 | Gisle Aas <gisle@aas.no> |
920 | Jeff Gresham <gresham_jeffrey@jpmorgan.com> |
921 | Murray Nesbitt <murray@activestate.com> |
922 | Marc Lehmann <pcg@opengroup.org> |
9e21b3d0 |
923 | Justin Banks <justinb@wamnet.com> |
924 | Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!) |
dd19458b |
925 | Salvador Ortiz Garcia <sog@msg.com.mx> |
926 | Dominic Dunlop <domo@computer.org> |
927 | Erik Haugan <erik@solbors.no> |
7a6a85bf |
928 | |
929 | for their bug reports, suggestions and contributions. |
930 | |
931 | Benjamin Holzman contributed the tied variable support, Andrew Ford |
932 | contributed the canonical order for hashes, and Gisle Aas fixed |
f062ea6c |
933 | a few misunderstandings of mine regarding the perl internals, |
7a6a85bf |
934 | and optimized the emission of "tags" in the output streams by |
935 | simply counting the objects instead of tagging them (leading to |
936 | a binary incompatibility for the Storable image starting at version |
f062ea6c |
937 | 0.6--older images are, of course, still properly understood). |
7a6a85bf |
938 | Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading |
f062ea6c |
939 | and references to tied items support. |
7a6a85bf |
940 | |
7a6a85bf |
941 | =head1 AUTHOR |
942 | |
0ba8809e |
943 | Storable was written by Raphael Manfredi F<E<lt>Raphael_Manfredi@pobox.comE<gt>> |
775ecd75 |
944 | Maintenance is now done by the perl5-porters F<E<lt>perl5-porters@perl.orgE<gt>> |
0ba8809e |
945 | |
946 | Please e-mail us with problems, bug fixes, comments and complaints, |
947 | although if you have complements you should send them to Raphael. |
948 | Please don't e-mail Raphael with problems, as he no longer works on |
949 | Storable, and your message will be delayed while he forwards it to us. |
7a6a85bf |
950 | |
951 | =head1 SEE ALSO |
952 | |
c261f00e |
953 | L<Clone>. |
7a6a85bf |
954 | |
955 | =cut |