Commit | Line | Data |
---|---|---|
25f64a11 AMS |
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 RG |
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 RG |
15 | freeze nfreeze thaw |
16 | dclone | |
9e21b3d0 | 17 | retrieve_fd |
dd19458b | 18 | lock_store lock_nstore lock_retrieve |
7a6a85bf RG |
19 | ); |
20 | ||
21 | use AutoLoader; | |
01d7b99e | 22 | use vars qw($canonical $forgive_me $VERSION); |
7a6a85bf | 23 | |
fa523c3a | 24 | $VERSION = '2.13'; |
7a6a85bf RG |
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 JH |
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 JH |
41 | Fcntl->import(':flock'); |
42 | } else { | |
43 | eval q{ | |
44 | sub LOCK_SH () {1} | |
45 | sub LOCK_EX () {2} | |
46 | }; | |
47 | } | |
48 | } | |
49 | ||
a8b7ef86 AMS |
50 | sub CLONE { |
51 | # clone context under threads | |
52 | Storable::init_perinterp(); | |
53 | } | |
54 | ||
b8778c7c | 55 | # Can't Autoload cleanly as this clashes 8.3 with &retrieve |
9e21b3d0 | 56 | sub retrieve_fd { &fd_retrieve } # Backward compatibility |
cb3d9de5 | 57 | |
530b72ba NC |
58 | # By default restricted hashes are downgraded on earlier perls. |
59 | ||
60 | $Storable::downgrade_restricted = 1; | |
e8189732 | 61 | $Storable::accept_future_minor = 1; |
b8778c7c NC |
62 | bootstrap Storable; |
63 | 1; | |
64 | __END__ | |
530b72ba NC |
65 | # |
66 | # Use of Log::Agent is optional. If it hasn't imported these subs then | |
67 | # Autoloader will kindly supply our fallback implementation. | |
68 | # | |
69 | ||
70 | sub logcroak { | |
71 | Carp::croak(@_); | |
72 | } | |
73 | ||
74 | sub logcarp { | |
75 | Carp::carp(@_); | |
76 | } | |
b8778c7c | 77 | |
862382c7 JH |
78 | # |
79 | # Determine whether locking is possible, but only when needed. | |
80 | # | |
81 | ||
530b72ba | 82 | sub CAN_FLOCK; my $CAN_FLOCK; sub CAN_FLOCK { |
862382c7 JH |
83 | return $CAN_FLOCK if defined $CAN_FLOCK; |
84 | require Config; import Config; | |
85 | return $CAN_FLOCK = | |
86 | $Config{'d_flock'} || | |
87 | $Config{'d_fcntl_can_lock'} || | |
88 | $Config{'d_lockf'}; | |
89 | } | |
90 | ||
0a0da639 JH |
91 | sub show_file_magic { |
92 | print <<EOM; | |
93 | # | |
94 | # To recognize the data files of the Perl module Storable, | |
95 | # the following lines need to be added to the local magic(5) file, | |
96 | # usually either /usr/share/misc/magic or /etc/magic. | |
0a0da639 JH |
97 | # |
98 | 0 string perl-store perl Storable(v0.6) data | |
8b793558 JH |
99 | >4 byte >0 (net-order %d) |
100 | >>4 byte &01 (network-ordered) | |
101 | >>4 byte =3 (major 1) | |
102 | >>4 byte =2 (major 1) | |
103 | ||
0a0da639 | 104 | 0 string pst0 perl Storable(v0.7) data |
8b793558 JH |
105 | >4 byte >0 |
106 | >>4 byte &01 (network-ordered) | |
107 | >>4 byte =5 (major 2) | |
108 | >>4 byte =4 (major 2) | |
109 | >>5 byte >0 (minor %d) | |
0a0da639 JH |
110 | EOM |
111 | } | |
112 | ||
b8778c7c NC |
113 | sub read_magic { |
114 | my $header = shift; | |
115 | return unless defined $header and length $header > 11; | |
116 | my $result; | |
117 | if ($header =~ s/^perl-store//) { | |
118 | die "Can't deal with version 0 headers"; | |
119 | } elsif ($header =~ s/^pst0//) { | |
120 | $result->{file} = 1; | |
121 | } | |
122 | # Assume it's a string. | |
123 | my ($major, $minor, $bytelen) = unpack "C3", $header; | |
124 | ||
125 | my $net_order = $major & 1; | |
126 | $major >>= 1; | |
127 | @$result{qw(major minor netorder)} = ($major, $minor, $net_order); | |
128 | ||
129 | return $result if $net_order; | |
130 | ||
131 | # I assume that it is rare to find v1 files, so this is an intentionally | |
132 | # inefficient way of doing it, to make the rest of the code constant. | |
133 | if ($major < 2) { | |
134 | delete $result->{minor}; | |
135 | $header = '.' . $header; | |
136 | $bytelen = $minor; | |
137 | } | |
138 | ||
139 | @$result{qw(byteorder intsize longsize ptrsize)} = | |
140 | unpack "x3 A$bytelen C3", $header; | |
141 | ||
142 | if ($major >= 2 and $minor >= 2) { | |
143 | $result->{nvsize} = unpack "x6 x$bytelen C", $header; | |
144 | } | |
145 | $result; | |
146 | } | |
7a6a85bf RG |
147 | |
148 | # | |
149 | # store | |
150 | # | |
151 | # Store target object hierarchy, identified by a reference to its root. | |
152 | # The stored object tree may later be retrieved to memory via retrieve. | |
153 | # Returns undef if an I/O error occurred, in which case the file is | |
154 | # removed. | |
155 | # | |
156 | sub store { | |
dd19458b | 157 | return _store(\&pstore, @_, 0); |
7a6a85bf RG |
158 | } |
159 | ||
160 | # | |
161 | # nstore | |
162 | # | |
163 | # Same as store, but in network order. | |
164 | # | |
165 | sub nstore { | |
dd19458b JH |
166 | return _store(\&net_pstore, @_, 0); |
167 | } | |
168 | ||
169 | # | |
170 | # lock_store | |
171 | # | |
172 | # Same as store, but flock the file first (advisory locking). | |
173 | # | |
174 | sub lock_store { | |
175 | return _store(\&pstore, @_, 1); | |
176 | } | |
177 | ||
178 | # | |
179 | # lock_nstore | |
180 | # | |
181 | # Same as nstore, but flock the file first (advisory locking). | |
182 | # | |
183 | sub lock_nstore { | |
184 | return _store(\&net_pstore, @_, 1); | |
7a6a85bf RG |
185 | } |
186 | ||
187 | # Internal store to file routine | |
188 | sub _store { | |
189 | my $xsptr = shift; | |
190 | my $self = shift; | |
dd19458b | 191 | my ($file, $use_locking) = @_; |
7a6a85bf | 192 | logcroak "not a reference" unless ref($self); |
b12202d0 | 193 | logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist |
7a6a85bf | 194 | local *FILE; |
dd19458b | 195 | if ($use_locking) { |
6e0ac6f5 | 196 | open(FILE, ">>$file") || logcroak "can't write into $file: $!"; |
862382c7 | 197 | unless (&CAN_FLOCK) { |
b29b780f RM |
198 | logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; |
199 | return undef; | |
f567092b | 200 | } |
dd19458b JH |
201 | flock(FILE, LOCK_EX) || |
202 | logcroak "can't get exclusive lock on $file: $!"; | |
203 | truncate FILE, 0; | |
204 | # Unlocking will happen when FILE is closed | |
6e0ac6f5 JH |
205 | } else { |
206 | open(FILE, ">$file") || logcroak "can't create $file: $!"; | |
dd19458b | 207 | } |
6e0ac6f5 | 208 | binmode FILE; # Archaic systems... |
7a6a85bf RG |
209 | my $da = $@; # Don't mess if called from exception handler |
210 | my $ret; | |
211 | # Call C routine nstore or pstore, depending on network order | |
212 | eval { $ret = &$xsptr(*FILE, $self) }; | |
213 | close(FILE) or $ret = undef; | |
214 | unlink($file) or warn "Can't unlink $file: $!\n" if $@ || !defined $ret; | |
215 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
216 | $@ = $da; | |
217 | return $ret ? $ret : undef; | |
218 | } | |
219 | ||
220 | # | |
221 | # store_fd | |
222 | # | |
223 | # Same as store, but perform on an already opened file descriptor instead. | |
224 | # Returns undef if an I/O error occurred. | |
225 | # | |
226 | sub store_fd { | |
227 | return _store_fd(\&pstore, @_); | |
228 | } | |
229 | ||
230 | # | |
231 | # nstore_fd | |
232 | # | |
233 | # Same as store_fd, but in network order. | |
234 | # | |
235 | sub nstore_fd { | |
236 | my ($self, $file) = @_; | |
237 | return _store_fd(\&net_pstore, @_); | |
238 | } | |
239 | ||
240 | # Internal store routine on opened file descriptor | |
241 | sub _store_fd { | |
242 | my $xsptr = shift; | |
243 | my $self = shift; | |
244 | my ($file) = @_; | |
245 | logcroak "not a reference" unless ref($self); | |
246 | logcroak "too many arguments" unless @_ == 1; # No @foo in arglist | |
247 | my $fd = fileno($file); | |
248 | logcroak "not a valid file descriptor" unless defined $fd; | |
249 | my $da = $@; # Don't mess if called from exception handler | |
250 | my $ret; | |
251 | # Call C routine nstore or pstore, depending on network order | |
252 | eval { $ret = &$xsptr($file, $self) }; | |
253 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
596596d5 | 254 | local $\; print $file ''; # Autoflush the file if wanted |
7a6a85bf RG |
255 | $@ = $da; |
256 | return $ret ? $ret : undef; | |
257 | } | |
258 | ||
259 | # | |
260 | # freeze | |
261 | # | |
262 | # Store oject and its hierarchy in memory and return a scalar | |
263 | # containing the result. | |
264 | # | |
265 | sub freeze { | |
266 | _freeze(\&mstore, @_); | |
267 | } | |
268 | ||
269 | # | |
270 | # nfreeze | |
271 | # | |
272 | # Same as freeze but in network order. | |
273 | # | |
274 | sub nfreeze { | |
275 | _freeze(\&net_mstore, @_); | |
276 | } | |
277 | ||
278 | # Internal freeze routine | |
279 | sub _freeze { | |
280 | my $xsptr = shift; | |
281 | my $self = shift; | |
282 | logcroak "not a reference" unless ref($self); | |
283 | logcroak "too many arguments" unless @_ == 0; # No @foo in arglist | |
284 | my $da = $@; # Don't mess if called from exception handler | |
285 | my $ret; | |
286 | # Call C routine mstore or net_mstore, depending on network order | |
287 | eval { $ret = &$xsptr($self) }; | |
288 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
289 | $@ = $da; | |
290 | return $ret ? $ret : undef; | |
291 | } | |
292 | ||
293 | # | |
294 | # retrieve | |
295 | # | |
296 | # Retrieve object hierarchy from disk, returning a reference to the root | |
297 | # object of that tree. | |
298 | # | |
299 | sub retrieve { | |
dd19458b JH |
300 | _retrieve($_[0], 0); |
301 | } | |
302 | ||
303 | # | |
304 | # lock_retrieve | |
305 | # | |
306 | # Same as retrieve, but with advisory locking. | |
307 | # | |
308 | sub lock_retrieve { | |
309 | _retrieve($_[0], 1); | |
310 | } | |
311 | ||
312 | # Internal retrieve routine | |
313 | sub _retrieve { | |
314 | my ($file, $use_locking) = @_; | |
7a6a85bf | 315 | local *FILE; |
dd19458b | 316 | open(FILE, $file) || logcroak "can't open $file: $!"; |
7a6a85bf RG |
317 | binmode FILE; # Archaic systems... |
318 | my $self; | |
319 | my $da = $@; # Could be from exception handler | |
dd19458b | 320 | if ($use_locking) { |
862382c7 | 321 | unless (&CAN_FLOCK) { |
8be2b38b | 322 | logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; |
b29b780f RM |
323 | return undef; |
324 | } | |
8be2b38b | 325 | flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!"; |
dd19458b JH |
326 | # Unlocking will happen when FILE is closed |
327 | } | |
7a6a85bf RG |
328 | eval { $self = pretrieve(*FILE) }; # Call C routine |
329 | close(FILE); | |
330 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
331 | $@ = $da; | |
332 | return $self; | |
333 | } | |
334 | ||
335 | # | |
9e21b3d0 | 336 | # fd_retrieve |
7a6a85bf RG |
337 | # |
338 | # Same as retrieve, but perform from an already opened file descriptor instead. | |
339 | # | |
9e21b3d0 | 340 | sub fd_retrieve { |
7a6a85bf RG |
341 | my ($file) = @_; |
342 | my $fd = fileno($file); | |
343 | logcroak "not a valid file descriptor" unless defined $fd; | |
344 | my $self; | |
345 | my $da = $@; # Could be from exception handler | |
346 | eval { $self = pretrieve($file) }; # Call C routine | |
347 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
348 | $@ = $da; | |
349 | return $self; | |
350 | } | |
351 | ||
352 | # | |
353 | # thaw | |
354 | # | |
355 | # Recreate objects in memory from an existing frozen image created | |
356 | # by freeze. If the frozen image passed is undef, return undef. | |
357 | # | |
358 | sub thaw { | |
359 | my ($frozen) = @_; | |
360 | return undef unless defined $frozen; | |
361 | my $self; | |
362 | my $da = $@; # Could be from exception handler | |
363 | eval { $self = mretrieve($frozen) }; # Call C routine | |
364 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
365 | $@ = $da; | |
366 | return $self; | |
367 | } | |
368 | ||
a2307be4 NC |
369 | 1; |
370 | __END__ | |
371 | ||
7a6a85bf RG |
372 | =head1 NAME |
373 | ||
f062ea6c | 374 | Storable - persistence for Perl data structures |
7a6a85bf RG |
375 | |
376 | =head1 SYNOPSIS | |
377 | ||
378 | use Storable; | |
379 | store \%table, 'file'; | |
380 | $hashref = retrieve('file'); | |
381 | ||
382 | use Storable qw(nstore store_fd nstore_fd freeze thaw dclone); | |
383 | ||
384 | # Network order | |
385 | nstore \%table, 'file'; | |
386 | $hashref = retrieve('file'); # There is NO nretrieve() | |
387 | ||
388 | # Storing to and retrieving from an already opened file | |
389 | store_fd \@array, \*STDOUT; | |
390 | nstore_fd \%table, \*STDOUT; | |
9e21b3d0 JH |
391 | $aryref = fd_retrieve(\*SOCKET); |
392 | $hashref = fd_retrieve(\*SOCKET); | |
7a6a85bf RG |
393 | |
394 | # Serializing to memory | |
395 | $serialized = freeze \%table; | |
396 | %table_clone = %{ thaw($serialized) }; | |
397 | ||
398 | # Deep (recursive) cloning | |
399 | $cloneref = dclone($ref); | |
400 | ||
dd19458b JH |
401 | # Advisory locking |
402 | use Storable qw(lock_store lock_nstore lock_retrieve) | |
403 | lock_store \%table, 'file'; | |
404 | lock_nstore \%table, 'file'; | |
405 | $hashref = lock_retrieve('file'); | |
406 | ||
7a6a85bf RG |
407 | =head1 DESCRIPTION |
408 | ||
f062ea6c | 409 | The Storable package brings persistence to your Perl data structures |
7a6a85bf | 410 | containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be |
c261f00e | 411 | conveniently stored to disk and retrieved at a later time. |
7a6a85bf RG |
412 | |
413 | It can be used in the regular procedural way by calling C<store> with | |
414 | a reference to the object to be stored, along with the file name where | |
415 | the image should be written. | |
775ecd75 | 416 | |
7a6a85bf RG |
417 | The routine returns C<undef> for I/O problems or other internal error, |
418 | a true value otherwise. Serious errors are propagated as a C<die> exception. | |
419 | ||
f062ea6c PN |
420 | To retrieve data stored to disk, use C<retrieve> with a file name. |
421 | The objects stored into that file are recreated into memory for you, | |
422 | and a I<reference> to the root object is returned. In case an I/O error | |
7a6a85bf RG |
423 | occurs while reading, C<undef> is returned instead. Other serious |
424 | errors are propagated via C<die>. | |
425 | ||
426 | Since storage is performed recursively, you might want to stuff references | |
427 | to objects that share a lot of common data into a single array or hash | |
428 | table, and then store that object. That way, when you retrieve back the | |
429 | whole thing, the objects will continue to share what they originally shared. | |
430 | ||
431 | At the cost of a slight header overhead, you may store to an already | |
432 | opened file descriptor using the C<store_fd> routine, and retrieve | |
9e21b3d0 | 433 | from a file via C<fd_retrieve>. Those names aren't imported by default, |
c261f00e | 434 | so you will have to do that explicitly if you need those routines. |
7a6a85bf RG |
435 | The file descriptor you supply must be already opened, for read |
436 | if you're going to retrieve and for write if you wish to store. | |
437 | ||
438 | store_fd(\%table, *STDOUT) || die "can't store to stdout\n"; | |
9e21b3d0 | 439 | $hashref = fd_retrieve(*STDIN); |
7a6a85bf RG |
440 | |
441 | You can also store data in network order to allow easy sharing across | |
442 | multiple platforms, or when storing on a socket known to be remotely | |
443 | connected. The routines to call have an initial C<n> prefix for I<network>, | |
444 | as in C<nstore> and C<nstore_fd>. At retrieval time, your data will be | |
445 | correctly restored so you don't have to know whether you're restoring | |
dd19458b JH |
446 | from native or network ordered data. Double values are stored stringified |
447 | to ensure portability as well, at the slight risk of loosing some precision | |
448 | in the last decimals. | |
7a6a85bf | 449 | |
9e21b3d0 | 450 | When using C<fd_retrieve>, objects are retrieved in sequence, one |
7a6a85bf RG |
451 | object (i.e. one recursive tree) per associated C<store_fd>. |
452 | ||
453 | If you're more from the object-oriented camp, you can inherit from | |
454 | Storable and directly store your objects by invoking C<store> as | |
455 | a method. The fact that the root of the to-be-stored tree is a | |
456 | blessed reference (i.e. an object) is special-cased so that the | |
457 | retrieve does not provide a reference to that object but rather the | |
458 | blessed object reference itself. (Otherwise, you'd get a reference | |
459 | to that blessed object). | |
460 | ||
461 | =head1 MEMORY STORE | |
462 | ||
463 | The Storable engine can also store data into a Perl scalar instead, to | |
464 | later retrieve them. This is mainly used to freeze a complex structure in | |
465 | some safe compact memory place (where it can possibly be sent to another | |
466 | process via some IPC, since freezing the structure also serializes it in | |
467 | effect). Later on, and maybe somewhere else, you can thaw the Perl scalar | |
468 | out and recreate the original complex structure in memory. | |
469 | ||
470 | Surprisingly, the routines to be called are named C<freeze> and C<thaw>. | |
471 | If you wish to send out the frozen scalar to another machine, use | |
472 | C<nfreeze> instead to get a portable image. | |
473 | ||
474 | Note that freezing an object structure and immediately thawing it | |
475 | actually achieves a deep cloning of that structure: | |
476 | ||
477 | dclone(.) = thaw(freeze(.)) | |
478 | ||
479 | Storable provides you with a C<dclone> interface which does not create | |
480 | that intermediary scalar but instead freezes the structure in some | |
c261f00e | 481 | internal memory space and then immediately thaws it out. |
7a6a85bf | 482 | |
dd19458b JH |
483 | =head1 ADVISORY LOCKING |
484 | ||
f062ea6c PN |
485 | The C<lock_store> and C<lock_nstore> routine are equivalent to |
486 | C<store> and C<nstore>, except that they get an exclusive lock on | |
487 | the file before writing. Likewise, C<lock_retrieve> does the same | |
488 | as C<retrieve>, but also gets a shared lock on the file before reading. | |
dd19458b | 489 | |
f062ea6c PN |
490 | As with any advisory locking scheme, the protection only works if you |
491 | systematically use C<lock_store> and C<lock_retrieve>. If one side of | |
492 | your application uses C<store> whilst the other uses C<lock_retrieve>, | |
dd19458b JH |
493 | you will get no protection at all. |
494 | ||
f062ea6c PN |
495 | The internal advisory locking is implemented using Perl's flock() |
496 | routine. If your system does not support any form of flock(), or if | |
497 | you share your files across NFS, you might wish to use other forms | |
498 | of locking by using modules such as LockFile::Simple which lock a | |
499 | file using a filesystem entry, instead of locking the file descriptor. | |
dd19458b | 500 | |
7a6a85bf RG |
501 | =head1 SPEED |
502 | ||
503 | The heart of Storable is written in C for decent speed. Extra low-level | |
4d3295e3 PN |
504 | optimizations have been made when manipulating perl internals, to |
505 | sacrifice encapsulation for the benefit of greater speed. | |
7a6a85bf RG |
506 | |
507 | =head1 CANONICAL REPRESENTATION | |
508 | ||
f062ea6c | 509 | Normally, Storable stores elements of hashes in the order they are |
7a6a85bf RG |
510 | stored internally by Perl, i.e. pseudo-randomly. If you set |
511 | C<$Storable::canonical> to some C<TRUE> value, Storable will store | |
512 | hashes with the elements sorted by their key. This allows you to | |
513 | compare data structures by comparing their frozen representations (or | |
514 | even the compressed frozen representations), which can be useful for | |
515 | creating lookup tables for complicated queries. | |
516 | ||
f062ea6c | 517 | Canonical order does not imply network order; those are two orthogonal |
7a6a85bf RG |
518 | settings. |
519 | ||
d2b96869 SR |
520 | =head1 CODE REFERENCES |
521 | ||
522 | Since Storable version 2.05, CODE references may be serialized with | |
523 | the help of L<B::Deparse>. To enable this feature, set | |
524 | C<$Storable::Deparse> to a true value. To enable deserializazion, | |
525 | C<$Storable::Eval> should be set to a true value. Be aware that | |
526 | deserialization is done through C<eval>, which is dangerous if the | |
527 | Storable file contains malicious data. You can set C<$Storable::Eval> | |
528 | to a subroutine reference which would be used instead of C<eval>. See | |
529 | below for an example using a L<Safe> compartment for deserialization | |
530 | of CODE references. | |
531 | ||
197b90bc SR |
532 | If C<$Storable::Deparse> and/or C<$Storable::Eval> are set to false |
533 | values, then the value of C<$Storable::forgive_me> (see below) is | |
534 | respected while serializing and deserializing. | |
535 | ||
c261f00e NC |
536 | =head1 FORWARD COMPATIBILITY |
537 | ||
538 | This release of Storable can be used on a newer version of Perl to | |
f062ea6c | 539 | serialize data which is not supported by earlier Perls. By default, |
c261f00e | 540 | Storable will attempt to do the right thing, by C<croak()>ing if it |
775ecd75 | 541 | encounters data that it cannot deserialize. However, the defaults |
f062ea6c | 542 | can be changed as follows: |
c261f00e NC |
543 | |
544 | =over 4 | |
545 | ||
546 | =item utf8 data | |
547 | ||
548 | Perl 5.6 added support for Unicode characters with code points > 255, | |
549 | and Perl 5.8 has full support for Unicode characters in hash keys. | |
550 | Perl internally encodes strings with these characters using utf8, and | |
551 | Storable serializes them as utf8. By default, if an older version of | |
552 | Perl encounters a utf8 value it cannot represent, it will C<croak()>. | |
553 | To change this behaviour so that Storable deserializes utf8 encoded | |
554 | values as the string of bytes (effectively dropping the I<is_utf8> flag) | |
555 | set C<$Storable::drop_utf8> to some C<TRUE> value. This is a form of | |
556 | data loss, because with C<$drop_utf8> true, it becomes impossible to tell | |
557 | whether the original data was the Unicode string, or a series of bytes | |
558 | that happen to be valid utf8. | |
559 | ||
560 | =item restricted hashes | |
561 | ||
f062ea6c PN |
562 | Perl 5.8 adds support for restricted hashes, which have keys |
563 | restricted to a given set, and can have values locked to be read only. | |
564 | By default, when Storable encounters a restricted hash on a perl | |
565 | that doesn't support them, it will deserialize it as a normal hash, | |
566 | silently discarding any placeholder keys and leaving the keys and | |
567 | all values unlocked. To make Storable C<croak()> instead, set | |
568 | C<$Storable::downgrade_restricted> to a C<FALSE> value. To restore | |
569 | the default set it back to some C<TRUE> value. | |
c261f00e | 570 | |
e8189732 NC |
571 | =item files from future versions of Storable |
572 | ||
573 | Earlier versions of Storable would immediately croak if they encountered | |
574 | a file with a higher internal version number than the reading Storable | |
575 | knew about. Internal version numbers are increased each time new data | |
576 | types (such as restricted hashes) are added to the vocabulary of the file | |
577 | format. This meant that a newer Storable module had no way of writing a | |
f062ea6c | 578 | file readable by an older Storable, even if the writer didn't store newer |
e8189732 NC |
579 | data types. |
580 | ||
581 | This version of Storable will defer croaking until it encounters a data | |
582 | type in the file that it does not recognize. This means that it will | |
583 | continue to read files generated by newer Storable modules which are careful | |
584 | in what they write out, making it easier to upgrade Storable modules in a | |
585 | mixed environment. | |
586 | ||
587 | The old behaviour of immediate croaking can be re-instated by setting | |
f062ea6c | 588 | C<$Storable::accept_future_minor> to some C<FALSE> value. |
e8189732 | 589 | |
c261f00e NC |
590 | =back |
591 | ||
f062ea6c | 592 | All these variables have no effect on a newer Perl which supports the |
c261f00e NC |
593 | relevant feature. |
594 | ||
7a6a85bf RG |
595 | =head1 ERROR REPORTING |
596 | ||
597 | Storable uses the "exception" paradigm, in that it does not try to workaround | |
598 | failures: if something bad happens, an exception is generated from the | |
599 | caller's perspective (see L<Carp> and C<croak()>). Use eval {} to trap | |
600 | those exceptions. | |
601 | ||
602 | When Storable croaks, it tries to report the error via the C<logcroak()> | |
603 | routine from the C<Log::Agent> package, if it is available. | |
604 | ||
212e9bde JH |
605 | Normal errors are reported by having store() or retrieve() return C<undef>. |
606 | Such errors are usually I/O errors (or truncated stream errors at retrieval). | |
607 | ||
7a6a85bf RG |
608 | =head1 WIZARDS ONLY |
609 | ||
610 | =head2 Hooks | |
611 | ||
612 | Any class may define hooks that will be called during the serialization | |
613 | and deserialization process on objects that are instances of that class. | |
614 | Those hooks can redefine the way serialization is performed (and therefore, | |
c261f00e | 615 | how the symmetrical deserialization should be conducted). |
7a6a85bf RG |
616 | |
617 | Since we said earlier: | |
618 | ||
619 | dclone(.) = thaw(freeze(.)) | |
620 | ||
621 | everything we say about hooks should also hold for deep cloning. However, | |
622 | hooks get to know whether the operation is a mere serialization, or a cloning. | |
623 | ||
624 | Therefore, when serializing hooks are involved, | |
625 | ||
626 | dclone(.) <> thaw(freeze(.)) | |
627 | ||
628 | Well, you could keep them in sync, but there's no guarantee it will always | |
629 | hold on classes somebody else wrote. Besides, there is little to gain in | |
f062ea6c | 630 | doing so: a serializing hook could keep only one attribute of an object, |
7a6a85bf RG |
631 | which is probably not what should happen during a deep cloning of that |
632 | same object. | |
633 | ||
634 | Here is the hooking interface: | |
635 | ||
bbc7dcd2 | 636 | =over 4 |
7a6a85bf RG |
637 | |
638 | =item C<STORABLE_freeze> I<obj>, I<cloning> | |
639 | ||
640 | The serializing hook, called on the object during serialization. It can be | |
641 | inherited, or defined in the class itself, like any other method. | |
642 | ||
643 | Arguments: I<obj> is the object to serialize, I<cloning> is a flag indicating | |
644 | whether we're in a dclone() or a regular serialization via store() or freeze(). | |
645 | ||
646 | Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized | |
647 | is the serialized form to be used, and the optional $ref1, $ref2, etc... are | |
648 | extra references that you wish to let the Storable engine serialize. | |
649 | ||
650 | At deserialization time, you will be given back the same LIST, but all the | |
651 | extra references will be pointing into the deserialized structure. | |
652 | ||
653 | The B<first time> the hook is hit in a serialization flow, you may have it | |
654 | return an empty list. That will signal the Storable engine to further | |
655 | discard that hook for this class and to therefore revert to the default | |
656 | serialization of the underlying Perl data. The hook will again be normally | |
657 | processed in the next serialization. | |
658 | ||
659 | Unless you know better, serializing hook should always say: | |
660 | ||
661 | sub STORABLE_freeze { | |
662 | my ($self, $cloning) = @_; | |
663 | return if $cloning; # Regular default serialization | |
664 | .... | |
665 | } | |
666 | ||
667 | in order to keep reasonable dclone() semantics. | |
668 | ||
669 | =item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ... | |
670 | ||
671 | The deserializing hook called on the object during deserialization. | |
f062ea6c | 672 | But wait: if we're deserializing, there's no object yet... right? |
7a6a85bf RG |
673 | |
674 | Wrong: the Storable engine creates an empty one for you. If you know Eiffel, | |
675 | you can view C<STORABLE_thaw> as an alternate creation routine. | |
676 | ||
677 | This means the hook can be inherited like any other method, and that | |
678 | I<obj> is your blessed reference for this particular instance. | |
679 | ||
680 | The other arguments should look familiar if you know C<STORABLE_freeze>: | |
681 | I<cloning> is true when we're part of a deep clone operation, I<serialized> | |
682 | is the serialized string you returned to the engine in C<STORABLE_freeze>, | |
683 | and there may be an optional list of references, in the same order you gave | |
684 | them at serialization time, pointing to the deserialized objects (which | |
685 | have been processed courtesy of the Storable engine). | |
686 | ||
212e9bde JH |
687 | When the Storable engine does not find any C<STORABLE_thaw> hook routine, |
688 | it tries to load the class by requiring the package dynamically (using | |
689 | the blessed package name), and then re-attempts the lookup. If at that | |
690 | time the hook cannot be located, the engine croaks. Note that this mechanism | |
c261f00e | 691 | will fail if you define several classes in the same file, but L<perlmod> |
212e9bde JH |
692 | warned you. |
693 | ||
f062ea6c | 694 | It is up to you to use this information to populate I<obj> the way you want. |
7a6a85bf RG |
695 | |
696 | Returned value: none. | |
697 | ||
698 | =back | |
699 | ||
700 | =head2 Predicates | |
701 | ||
c261f00e | 702 | Predicates are not exportable. They must be called by explicitly prefixing |
7a6a85bf RG |
703 | them with the Storable package name. |
704 | ||
bbc7dcd2 | 705 | =over 4 |
7a6a85bf RG |
706 | |
707 | =item C<Storable::last_op_in_netorder> | |
708 | ||
709 | The C<Storable::last_op_in_netorder()> predicate will tell you whether | |
710 | network order was used in the last store or retrieve operation. If you | |
711 | don't know how to use this, just forget about it. | |
712 | ||
713 | =item C<Storable::is_storing> | |
714 | ||
715 | Returns true if within a store operation (via STORABLE_freeze hook). | |
716 | ||
717 | =item C<Storable::is_retrieving> | |
718 | ||
f062ea6c | 719 | Returns true if within a retrieve operation (via STORABLE_thaw hook). |
7a6a85bf RG |
720 | |
721 | =back | |
722 | ||
723 | =head2 Recursion | |
724 | ||
f062ea6c PN |
725 | With hooks comes the ability to recurse back to the Storable engine. |
726 | Indeed, hooks are regular Perl code, and Storable is convenient when | |
727 | it comes to serializing and deserializing things, so why not use it | |
728 | to handle the serialization string? | |
7a6a85bf | 729 | |
f062ea6c | 730 | There are a few things you need to know, however: |
7a6a85bf | 731 | |
bbc7dcd2 | 732 | =over 4 |
7a6a85bf RG |
733 | |
734 | =item * | |
735 | ||
736 | You can create endless loops if the things you serialize via freeze() | |
f062ea6c PN |
737 | (for instance) point back to the object we're trying to serialize in |
738 | the hook. | |
7a6a85bf RG |
739 | |
740 | =item * | |
741 | ||
742 | Shared references among objects will not stay shared: if we're serializing | |
743 | the list of object [A, C] where both object A and C refer to the SAME object | |
744 | B, and if there is a serializing hook in A that says freeze(B), then when | |
745 | deserializing, we'll get [A', C'] where A' refers to B', but C' refers to D, | |
746 | a deep clone of B'. The topology was not preserved. | |
747 | ||
748 | =back | |
749 | ||
750 | That's why C<STORABLE_freeze> lets you provide a list of references | |
751 | to serialize. The engine guarantees that those will be serialized in the | |
752 | same context as the other objects, and therefore that shared objects will | |
753 | stay shared. | |
754 | ||
755 | In the above [A, C] example, the C<STORABLE_freeze> hook could return: | |
756 | ||
757 | ("something", $self->{B}) | |
758 | ||
759 | and the B part would be serialized by the engine. In C<STORABLE_thaw>, you | |
760 | would get back the reference to the B' object, deserialized for you. | |
761 | ||
762 | Therefore, recursion should normally be avoided, but is nonetheless supported. | |
763 | ||
764 | =head2 Deep Cloning | |
765 | ||
f062ea6c | 766 | There is a Clone module available on CPAN which implements deep cloning |
7a6a85bf RG |
767 | natively, i.e. without freezing to memory and thawing the result. It is |
768 | aimed to replace Storable's dclone() some day. However, it does not currently | |
769 | support Storable hooks to redefine the way deep cloning is performed. | |
770 | ||
0a0da639 JH |
771 | =head1 Storable magic |
772 | ||
773 | Yes, there's a lot of that :-) But more precisely, in UNIX systems | |
774 | there's a utility called C<file>, which recognizes data files based on | |
775 | their contents (usually their first few bytes). For this to work, | |
8b793558 | 776 | a certain file called F<magic> needs to taught about the I<signature> |
0a0da639 | 777 | of the data. Where that configuration file lives depends on the UNIX |
f062ea6c | 778 | flavour; often it's something like F</usr/share/misc/magic> or |
8b793558 JH |
779 | F</etc/magic>. Your system administrator needs to do the updating of |
780 | the F<magic> file. The necessary signature information is output to | |
f062ea6c PN |
781 | STDOUT by invoking Storable::show_file_magic(). Note that the GNU |
782 | implementation of the C<file> utility, version 3.38 or later, | |
783 | is expected to contain support for recognising Storable files | |
784 | out-of-the-box, in addition to other kinds of Perl files. | |
0a0da639 | 785 | |
7a6a85bf RG |
786 | =head1 EXAMPLES |
787 | ||
788 | Here are some code samples showing a possible usage of Storable: | |
789 | ||
790 | use Storable qw(store retrieve freeze thaw dclone); | |
791 | ||
792 | %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1); | |
793 | ||
2359510d | 794 | store(\%color, 'mycolors') or die "Can't store %a in mycolors!\n"; |
7a6a85bf | 795 | |
2359510d SD |
796 | $colref = retrieve('mycolors'); |
797 | die "Unable to retrieve from mycolors!\n" unless defined $colref; | |
7a6a85bf RG |
798 | printf "Blue is still %lf\n", $colref->{'Blue'}; |
799 | ||
800 | $colref2 = dclone(\%color); | |
801 | ||
802 | $str = freeze(\%color); | |
803 | printf "Serialization of %%color is %d bytes long.\n", length($str); | |
804 | $colref3 = thaw($str); | |
805 | ||
806 | which prints (on my machine): | |
807 | ||
808 | Blue is still 0.100000 | |
809 | Serialization of %color is 102 bytes long. | |
810 | ||
d2b96869 SR |
811 | Serialization of CODE references and deserialization in a safe |
812 | compartment: | |
813 | ||
197b90bc SR |
814 | =for example begin |
815 | ||
d2b96869 SR |
816 | use Storable qw(freeze thaw); |
817 | use Safe; | |
818 | use strict; | |
819 | my $safe = new Safe; | |
197b90bc | 820 | # because of opcodes used in "use strict": |
d1e2299c | 821 | $safe->permit(qw(:default require)); |
d2b96869 SR |
822 | local $Storable::Deparse = 1; |
823 | local $Storable::Eval = sub { $safe->reval($_[0]) }; | |
197b90bc | 824 | my $serialized = freeze(sub { 42 }); |
d2b96869 | 825 | my $code = thaw($serialized); |
197b90bc SR |
826 | $code->() == 42; |
827 | ||
828 | =for example end | |
829 | ||
830 | =for example_testing | |
831 | is( $code->(), 42 ); | |
d2b96869 | 832 | |
7a6a85bf RG |
833 | =head1 WARNING |
834 | ||
835 | If you're using references as keys within your hash tables, you're bound | |
f062ea6c | 836 | to be disappointed when retrieving your data. Indeed, Perl stringifies |
7a6a85bf RG |
837 | references used as hash table keys. If you later wish to access the |
838 | items via another reference stringification (i.e. using the same | |
839 | reference that was used for the key originally to record the value into | |
840 | the hash table), it will work because both references stringify to the | |
841 | same string. | |
842 | ||
6fe6778b PN |
843 | It won't work across a sequence of C<store> and C<retrieve> operations, |
844 | however, because the addresses in the retrieved objects, which are | |
845 | part of the stringified references, will probably differ from the | |
846 | original addresses. The topology of your structure is preserved, | |
847 | but not hidden semantics like those. | |
7a6a85bf RG |
848 | |
849 | On platforms where it matters, be sure to call C<binmode()> on the | |
850 | descriptors that you pass to Storable functions. | |
851 | ||
852 | Storing data canonically that contains large hashes can be | |
853 | significantly slower than storing the same data normally, as | |
c261f00e | 854 | temporary arrays to hold the keys for each hash have to be allocated, |
7a6a85bf RG |
855 | populated, sorted and freed. Some tests have shown a halving of the |
856 | speed of storing -- the exact penalty will depend on the complexity of | |
857 | your data. There is no slowdown on retrieval. | |
858 | ||
859 | =head1 BUGS | |
860 | ||
197b90bc SR |
861 | You can't store GLOB, FORMLINE, etc.... If you can define semantics |
862 | for those operations, feel free to enhance Storable so that it can | |
863 | deal with them. | |
7a6a85bf RG |
864 | |
865 | The store functions will C<croak> if they run into such references | |
866 | unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that | |
867 | case, the fatal message is turned in a warning and some | |
868 | meaningless string is stored instead. | |
869 | ||
870 | Setting C<$Storable::canonical> may not yield frozen strings that | |
871 | compare equal due to possible stringification of numbers. When the | |
f062ea6c | 872 | string version of a scalar exists, it is the form stored; therefore, |
7a6a85bf RG |
873 | if you happen to use your numbers as strings between two freezing |
874 | operations on the same data structures, you will get different | |
875 | results. | |
876 | ||
dd19458b JH |
877 | When storing doubles in network order, their value is stored as text. |
878 | However, you should also not expect non-numeric floating-point values | |
879 | such as infinity and "not a number" to pass successfully through a | |
880 | nstore()/retrieve() pair. | |
881 | ||
882 | As Storable neither knows nor cares about character sets (although it | |
883 | does know that characters may be more than eight bits wide), any difference | |
884 | in the interpretation of character codes between a host and a target | |
885 | system is your problem. In particular, if host and target use different | |
886 | code points to represent the characters used in the text representation | |
887 | of floating-point numbers, you will not be able be able to exchange | |
888 | floating-point data, even with nstore(). | |
889 | ||
c261f00e NC |
890 | C<Storable::drop_utf8> is a blunt tool. There is no facility either to |
891 | return B<all> strings as utf8 sequences, or to attempt to convert utf8 | |
892 | data back to 8 bit and C<croak()> if the conversion fails. | |
893 | ||
ee0f7aac NC |
894 | Prior to Storable 2.01, no distinction was made between signed and |
895 | unsigned integers on storing. By default Storable prefers to store a | |
896 | scalars string representation (if it has one) so this would only cause | |
897 | problems when storing large unsigned integers that had never been coverted | |
898 | to string or floating point. In other words values that had been generated | |
899 | by integer operations such as logic ops and then not used in any string or | |
900 | arithmetic context before storing. | |
901 | ||
902 | =head2 64 bit data in perl 5.6.0 and 5.6.1 | |
903 | ||
904 | This section only applies to you if you have existing data written out | |
905 | by Storable 2.02 or earlier on perl 5.6.0 or 5.6.1 on Unix or Linux which | |
906 | has been configured with 64 bit integer support (not the default) | |
907 | If you got a precompiled perl, rather than running Configure to build | |
908 | your own perl from source, then it almost certainly does not affect you, | |
909 | and you can stop reading now (unless you're curious). If you're using perl | |
910 | on Windows it does not affect you. | |
911 | ||
912 | Storable writes a file header which contains the sizes of various C | |
913 | language types for the C compiler that built Storable (when not writing in | |
914 | network order), and will refuse to load files written by a Storable not | |
915 | on the same (or compatible) architecture. This check and a check on | |
916 | machine byteorder is needed because the size of various fields in the file | |
917 | are given by the sizes of the C language types, and so files written on | |
918 | different architectures are incompatible. This is done for increased speed. | |
919 | (When writing in network order, all fields are written out as standard | |
920 | lengths, which allows full interworking, but takes longer to read and write) | |
921 | ||
922 | Perl 5.6.x introduced the ability to optional configure the perl interpreter | |
923 | to use C's C<long long> type to allow scalars to store 64 bit integers on 32 | |
924 | bit systems. However, due to the way the Perl configuration system | |
925 | generated the C configuration files on non-Windows platforms, and the way | |
926 | Storable generates its header, nothing in the Storable file header reflected | |
927 | whether the perl writing was using 32 or 64 bit integers, despite the fact | |
928 | that Storable was storing some data differently in the file. Hence Storable | |
929 | running on perl with 64 bit integers will read the header from a file | |
930 | written by a 32 bit perl, not realise that the data is actually in a subtly | |
931 | incompatible format, and then go horribly wrong (possibly crashing) if it | |
932 | encountered a stored integer. This is a design failure. | |
933 | ||
934 | Storable has now been changed to write out and read in a file header with | |
935 | information about the size of integers. It's impossible to detect whether | |
936 | an old file being read in was written with 32 or 64 bit integers (they have | |
937 | the same header) so it's impossible to automatically switch to a correct | |
938 | backwards compatibility mode. Hence this Storable defaults to the new, | |
939 | correct behaviour. | |
940 | ||
941 | What this means is that if you have data written by Storable 1.x running | |
942 | on perl 5.6.0 or 5.6.1 configured with 64 bit integers on Unix or Linux | |
943 | then by default this Storable will refuse to read it, giving the error | |
944 | I<Byte order is not compatible>. If you have such data then you you | |
945 | should set C<$Storable::interwork_56_64bit> to a true value to make this | |
946 | Storable read and write files with the old header. You should also | |
947 | migrate your data, or any older perl you are communicating with, to this | |
948 | current version of Storable. | |
949 | ||
950 | If you don't have data written with specific configuration of perl described | |
951 | above, then you do not and should not do anything. Don't set the flag - | |
952 | not only will Storable on an identically configured perl refuse to load them, | |
953 | but Storable a differently configured perl will load them believing them | |
954 | to be correct for it, and then may well fail or crash part way through | |
955 | reading them. | |
956 | ||
7a6a85bf RG |
957 | =head1 CREDITS |
958 | ||
959 | Thank you to (in chronological order): | |
960 | ||
961 | Jarkko Hietaniemi <jhi@iki.fi> | |
962 | Ulrich Pfeifer <pfeifer@charly.informatik.uni-dortmund.de> | |
963 | Benjamin A. Holzman <bah@ecnvantage.com> | |
964 | Andrew Ford <A.Ford@ford-mason.co.uk> | |
965 | Gisle Aas <gisle@aas.no> | |
966 | Jeff Gresham <gresham_jeffrey@jpmorgan.com> | |
967 | Murray Nesbitt <murray@activestate.com> | |
968 | Marc Lehmann <pcg@opengroup.org> | |
9e21b3d0 JH |
969 | Justin Banks <justinb@wamnet.com> |
970 | Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!) | |
dd19458b JH |
971 | Salvador Ortiz Garcia <sog@msg.com.mx> |
972 | Dominic Dunlop <domo@computer.org> | |
973 | Erik Haugan <erik@solbors.no> | |
7a6a85bf RG |
974 | |
975 | for their bug reports, suggestions and contributions. | |
976 | ||
977 | Benjamin Holzman contributed the tied variable support, Andrew Ford | |
978 | contributed the canonical order for hashes, and Gisle Aas fixed | |
f062ea6c | 979 | a few misunderstandings of mine regarding the perl internals, |
7a6a85bf RG |
980 | and optimized the emission of "tags" in the output streams by |
981 | simply counting the objects instead of tagging them (leading to | |
982 | a binary incompatibility for the Storable image starting at version | |
f062ea6c | 983 | 0.6--older images are, of course, still properly understood). |
7a6a85bf | 984 | Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading |
f062ea6c | 985 | and references to tied items support. |
7a6a85bf | 986 | |
7a6a85bf RG |
987 | =head1 AUTHOR |
988 | ||
0ba8809e | 989 | Storable was written by Raphael Manfredi F<E<lt>Raphael_Manfredi@pobox.comE<gt>> |
775ecd75 | 990 | Maintenance is now done by the perl5-porters F<E<lt>perl5-porters@perl.orgE<gt>> |
0ba8809e NC |
991 | |
992 | Please e-mail us with problems, bug fixes, comments and complaints, | |
993 | although if you have complements you should send them to Raphael. | |
994 | Please don't e-mail Raphael with problems, as he no longer works on | |
995 | Storable, and your message will be delayed while he forwards it to us. | |
7a6a85bf RG |
996 | |
997 | =head1 SEE ALSO | |
998 | ||
c261f00e | 999 | L<Clone>. |
7a6a85bf RG |
1000 | |
1001 | =cut |