2 # Copyright (c) 1995-2000, Raphael Manfredi
4 # You may redistribute only under the same terms as Perl 5, as specified
5 # in the README file that comes with the distribution.
10 package Storable; @ISA = qw(Exporter DynaLoader);
12 @EXPORT = qw(store retrieve);
14 nstore store_fd nstore_fd fd_retrieve
18 lock_store lock_nstore lock_retrieve
22 use vars qw($canonical $forgive_me $VERSION);
25 *AUTOLOAD = \&AutoLoader::AUTOLOAD; # Grrr...
28 # Use of Log::Agent is optional
31 eval "use Log::Agent";
36 # They might miss :flock in Fcntl
40 if (eval { require Fcntl; 1 } && exists $Fcntl::EXPORT_TAGS{'flock'}) {
41 Fcntl->import(':flock');
51 # clone context under threads
52 Storable::init_perinterp();
55 # Can't Autoload cleanly as this clashes 8.3 with &retrieve
56 sub retrieve_fd { &fd_retrieve } # Backward compatibility
58 # By default restricted hashes are downgraded on earlier perls.
60 $Storable::downgrade_restricted = 1;
61 $Storable::accept_future_minor = 1;
66 # Use of Log::Agent is optional. If it hasn't imported these subs then
67 # Autoloader will kindly supply our fallback implementation.
79 # Determine whether locking is possible, but only when needed.
82 sub CAN_FLOCK; my $CAN_FLOCK; sub CAN_FLOCK {
83 return $CAN_FLOCK if defined $CAN_FLOCK;
84 require Config; import Config;
87 $Config{'d_fcntl_can_lock'} ||
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.
98 0 string perl-store perl Storable(v0.6) data
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)
104 0 string pst0 perl Storable(v0.7) data
106 >>4 byte &01 (network-ordered)
107 >>4 byte =5 (major 2)
108 >>4 byte =4 (major 2)
109 >>5 byte >0 (minor %d)
115 return unless defined $header and length $header > 11;
117 if ($header =~ s/^perl-store//) {
118 die "Can't deal with version 0 headers";
119 } elsif ($header =~ s/^pst0//) {
122 # Assume it's a string.
123 my ($major, $minor, $bytelen) = unpack "C3", $header;
125 my $net_order = $major & 1;
127 @$result{qw(major minor netorder)} = ($major, $minor, $net_order);
129 return $result if $net_order;
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.
134 delete $result->{minor};
135 $header = '.' . $header;
139 @$result{qw(byteorder intsize longsize ptrsize)} =
140 unpack "x3 A$bytelen C3", $header;
142 if ($major >= 2 and $minor >= 2) {
143 $result->{nvsize} = unpack "x6 x$bytelen C", $header;
151 # Store target object hierarchy, identified by a reference to its root.
152 # The stored object tree may later be retrieved to memory via retrieve.
153 # Returns undef if an I/O error occurred, in which case the file is
157 return _store(\&pstore, @_, 0);
163 # Same as store, but in network order.
166 return _store(\&net_pstore, @_, 0);
172 # Same as store, but flock the file first (advisory locking).
175 return _store(\&pstore, @_, 1);
181 # Same as nstore, but flock the file first (advisory locking).
184 return _store(\&net_pstore, @_, 1);
187 # Internal store to file routine
191 my ($file, $use_locking) = @_;
192 logcroak "not a reference" unless ref($self);
193 logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist
196 open(FILE, ">>$file") || logcroak "can't write into $file: $!";
197 unless (&CAN_FLOCK) {
198 logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O";
201 flock(FILE, LOCK_EX) ||
202 logcroak "can't get exclusive lock on $file: $!";
204 # Unlocking will happen when FILE is closed
206 open(FILE, ">$file") || logcroak "can't create $file: $!";
208 binmode FILE; # Archaic systems...
209 my $da = $@; # Don't mess if called from exception handler
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 $@ =~ s/\.?\n$/,/;
217 return $ret ? $ret : undef;
223 # Same as store, but perform on an already opened file descriptor instead.
224 # Returns undef if an I/O error occurred.
227 return _store_fd(\&pstore, @_);
233 # Same as store_fd, but in network order.
236 my ($self, $file) = @_;
237 return _store_fd(\&net_pstore, @_);
240 # Internal store routine on opened file descriptor
245 logcroak "not a reference" unless ref($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
251 # Call C routine nstore or pstore, depending on network order
252 eval { $ret = &$xsptr($file, $self) };
253 logcroak $@ if $@ =~ s/\.?\n$/,/;
254 local $\; print $file ''; # Autoflush the file if wanted
256 return $ret ? $ret : undef;
262 # Store oject and its hierarchy in memory and return a scalar
263 # containing the result.
266 _freeze(\&mstore, @_);
272 # Same as freeze but in network order.
275 _freeze(\&net_mstore, @_);
278 # Internal freeze routine
282 logcroak "not a reference" unless ref($self);
283 logcroak "too many arguments" unless @_ == 0; # No @foo in arglist
284 my $da = $@; # Don't mess if called from exception handler
286 # Call C routine mstore or net_mstore, depending on network order
287 eval { $ret = &$xsptr($self) };
288 logcroak $@ if $@ =~ s/\.?\n$/,/;
290 return $ret ? $ret : undef;
296 # Retrieve object hierarchy from disk, returning a reference to the root
297 # object of that tree.
306 # Same as retrieve, but with advisory locking.
312 # Internal retrieve routine
314 my ($file, $use_locking) = @_;
316 open(FILE, $file) || logcroak "can't open $file: $!";
317 binmode FILE; # Archaic systems...
319 my $da = $@; # Could be from exception handler
321 unless (&CAN_FLOCK) {
322 logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O";
325 flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!";
326 # Unlocking will happen when FILE is closed
328 eval { $self = pretrieve(*FILE) }; # Call C routine
330 logcroak $@ if $@ =~ s/\.?\n$/,/;
338 # Same as retrieve, but perform from an already opened file descriptor instead.
342 my $fd = fileno($file);
343 logcroak "not a valid file descriptor" unless defined $fd;
345 my $da = $@; # Could be from exception handler
346 eval { $self = pretrieve($file) }; # Call C routine
347 logcroak $@ if $@ =~ s/\.?\n$/,/;
355 # Recreate objects in memory from an existing frozen image created
356 # by freeze. If the frozen image passed is undef, return undef.
360 return undef unless defined $frozen;
362 my $da = $@; # Could be from exception handler
363 eval { $self = mretrieve($frozen) }; # Call C routine
364 logcroak $@ if $@ =~ s/\.?\n$/,/;
374 Storable - persistence for Perl data structures
379 store \%table, 'file';
380 $hashref = retrieve('file');
382 use Storable qw(nstore store_fd nstore_fd freeze thaw dclone);
385 nstore \%table, 'file';
386 $hashref = retrieve('file'); # There is NO nretrieve()
388 # Storing to and retrieving from an already opened file
389 store_fd \@array, \*STDOUT;
390 nstore_fd \%table, \*STDOUT;
391 $aryref = fd_retrieve(\*SOCKET);
392 $hashref = fd_retrieve(\*SOCKET);
394 # Serializing to memory
395 $serialized = freeze \%table;
396 %table_clone = %{ thaw($serialized) };
398 # Deep (recursive) cloning
399 $cloneref = dclone($ref);
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');
409 The Storable package brings persistence to your Perl data structures
410 containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be
411 conveniently stored to disk and retrieved at a later time.
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.
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.
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
423 occurs while reading, C<undef> is returned instead. Other serious
424 errors are propagated via C<die>.
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.
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
433 from a file via C<fd_retrieve>. Those names aren't imported by default,
434 so you will have to do that explicitly if you need those routines.
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.
438 store_fd(\%table, *STDOUT) || die "can't store to stdout\n";
439 $hashref = fd_retrieve(*STDIN);
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
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.
450 When using C<fd_retrieve>, objects are retrieved in sequence, one
451 object (i.e. one recursive tree) per associated C<store_fd>.
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).
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.
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.
474 Note that freezing an object structure and immediately thawing it
475 actually achieves a deep cloning of that structure:
477 dclone(.) = thaw(freeze(.))
479 Storable provides you with a C<dclone> interface which does not create
480 that intermediary scalar but instead freezes the structure in some
481 internal memory space and then immediately thaws it out.
483 =head1 ADVISORY LOCKING
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.
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>,
493 you will get no protection at all.
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.
503 The heart of Storable is written in C for decent speed. Extra low-level
504 optimizations have been made when manipulating perl internals, to
505 sacrifice encapsulation for the benefit of greater speed.
507 =head1 CANONICAL REPRESENTATION
509 Normally, Storable stores elements of hashes in the order they are
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.
517 Canonical order does not imply network order; those are two orthogonal
520 =head1 CODE REFERENCES
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<$Storable::Eval>
528 to a subroutine reference which would be used instead of C<eval>. See
529 below for an example using a L<Safe> compartment for deserialization
532 If C<$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.
536 =head1 FORWARD COMPATIBILITY
538 This release of Storable can be used on a newer version of Perl to
539 serialize data which is not supported by earlier Perls. By default,
540 Storable will attempt to do the right thing, by C<croak()>ing if it
541 encounters data that it cannot deserialize. However, the defaults
542 can be changed as follows:
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.
560 =item restricted hashes
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<$Storable::downgrade_restricted> to a C<FALSE> value. To restore
569 the default set it back to some C<TRUE> value.
571 =item files from future versions of Storable
573 Earlier versions of Storable would immediately croak if they encountered
574 a file with a higher internal version number than the reading Storable
575 knew about. Internal version numbers are increased each time new data
576 types (such as restricted hashes) are added to the vocabulary of the file
577 format. This meant that a newer Storable module had no way of writing a
578 file readable by an older Storable, even if the writer didn't store newer
581 This version of Storable will defer croaking until it encounters a data
582 type in the file that it does not recognize. This means that it will
583 continue to read files generated by newer Storable modules which are careful
584 in what they write out, making it easier to upgrade Storable modules in a
587 The old behaviour of immediate croaking can be re-instated by setting
588 C<$Storable::accept_future_minor> to some C<FALSE> value.
592 All these variables have no effect on a newer Perl which supports the
595 =head1 ERROR REPORTING
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
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.
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).
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,
615 how the symmetrical deserialization should be conducted).
617 Since we said earlier:
619 dclone(.) = thaw(freeze(.))
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.
624 Therefore, when serializing hooks are involved,
626 dclone(.) <> thaw(freeze(.))
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
630 doing so: a serializing hook could keep only one attribute of an object,
631 which is probably not what should happen during a deep cloning of that
634 Here is the hooking interface:
638 =item C<STORABLE_freeze> I<obj>, I<cloning>
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.
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().
646 Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized
647 is the serialized form to be used, and the optional $ref1, $ref2, etc... are
648 extra references that you wish to let the Storable engine serialize.
650 At deserialization time, you will be given back the same LIST, but all the
651 extra references will be pointing into the deserialized structure.
653 The B<first time> the hook is hit in a serialization flow, you may have it
654 return an empty list. That will signal the Storable engine to further
655 discard that hook for this class and to therefore revert to the default
656 serialization of the underlying Perl data. The hook will again be normally
657 processed in the next serialization.
659 Unless you know better, serializing hook should always say:
661 sub STORABLE_freeze {
662 my ($self, $cloning) = @_;
663 return if $cloning; # Regular default serialization
667 in order to keep reasonable dclone() semantics.
669 =item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ...
671 The deserializing hook called on the object during deserialization.
672 But wait: if we're deserializing, there's no object yet... right?
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.
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.
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).
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
691 will fail if you define several classes in the same file, but L<perlmod>
694 It is up to you to use this information to populate I<obj> the way you want.
696 Returned value: none.
702 Predicates are not exportable. They must be called by explicitly prefixing
703 them with the Storable package name.
707 =item C<Storable::last_op_in_netorder>
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.
713 =item C<Storable::is_storing>
715 Returns true if within a store operation (via STORABLE_freeze hook).
717 =item C<Storable::is_retrieving>
719 Returns true if within a retrieve operation (via STORABLE_thaw hook).
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?
730 There are a few things you need to know, however:
736 You can create endless loops if the things you serialize via freeze()
737 (for instance) point back to the object we're trying to serialize in
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.
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
755 In the above [A, C] example, the C<STORABLE_freeze> hook could return:
757 ("something", $self->{B})
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.
762 Therefore, recursion should normally be avoided, but is nonetheless supported.
766 There is a Clone module available on CPAN which implements deep cloning
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.
771 =head1 Storable magic
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,
776 a certain file called F<magic> needs to taught about the I<signature>
777 of the data. Where that configuration file lives depends on the UNIX
778 flavour; often it's something like F</usr/share/misc/magic> or
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
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.
788 Here are some code samples showing a possible usage of Storable:
790 use Storable qw(store retrieve freeze thaw dclone);
792 %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1);
794 store(\%color, '/tmp/colors') or die "Can't store %a in /tmp/colors!\n";
796 $colref = retrieve('/tmp/colors');
797 die "Unable to retrieve from /tmp/colors!\n" unless defined $colref;
798 printf "Blue is still %lf\n", $colref->{'Blue'};
800 $colref2 = dclone(\%color);
802 $str = freeze(\%color);
803 printf "Serialization of %%color is %d bytes long.\n", length($str);
804 $colref3 = thaw($str);
806 which prints (on my machine):
808 Blue is still 0.100000
809 Serialization of %color is 102 bytes long.
811 Serialization of CODE references and deserialization in a safe
816 use Storable qw(freeze thaw);
820 # because of opcodes used in "use strict":
821 $safe->permit(qw(:default require));
822 local $Storable::Deparse = 1;
823 local $Storable::Eval = sub { $safe->reval($_[0]) };
824 my $serialized = freeze(sub { 42 });
825 my $code = thaw($serialized);
835 If you're using references as keys within your hash tables, you're bound
836 to be disappointed when retrieving your data. Indeed, Perl stringifies
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
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.
849 On platforms where it matters, be sure to call C<binmode()> on the
850 descriptors that you pass to Storable functions.
852 Storing data canonically that contains large hashes can be
853 significantly slower than storing the same data normally, as
854 temporary arrays to hold the keys for each hash have to be allocated,
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.
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
865 The store functions will C<croak> if they run into such references
866 unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that
867 case, the fatal message is turned in a warning and some
868 meaningless string is stored instead.
870 Setting C<$Storable::canonical> may not yield frozen strings that
871 compare equal due to possible stringification of numbers. When the
872 string version of a scalar exists, it is the form stored; therefore,
873 if you happen to use your numbers as strings between two freezing
874 operations on the same data structures, you will get different
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.
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().
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.
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.
902 =head2 64 bit data in perl 5.6.0 and 5.6.1
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.
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)
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.
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,
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.
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
959 Thank you to (in chronological order):
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>
969 Justin Banks <justinb@wamnet.com>
970 Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!)
971 Salvador Ortiz Garcia <sog@msg.com.mx>
972 Dominic Dunlop <domo@computer.org>
973 Erik Haugan <erik@solbors.no>
975 for their bug reports, suggestions and contributions.
977 Benjamin Holzman contributed the tied variable support, Andrew Ford
978 contributed the canonical order for hashes, and Gisle Aas fixed
979 a few misunderstandings of mine regarding the perl internals,
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
983 0.6--older images are, of course, still properly understood).
984 Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading
985 and references to tied items support.
989 Storable was written by Raphael Manfredi F<E<lt>Raphael_Manfredi@pobox.comE<gt>>
990 Maintenance is now done by the perl5-porters F<E<lt>perl5-porters@perl.orgE<gt>>
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.