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');
50 # Can't Autoload cleanly as this clashes 8.3 with &retrieve
51 sub retrieve_fd { &fd_retrieve } # Backward compatibility
53 # By default restricted hashes are downgraded on earlier perls.
55 $Storable::downgrade_restricted = 1;
56 $Storable::accept_future_minor = 1;
61 # Use of Log::Agent is optional. If it hasn't imported these subs then
62 # Autoloader will kindly supply our fallback implementation.
74 # Determine whether locking is possible, but only when needed.
77 sub CAN_FLOCK; my $CAN_FLOCK; sub CAN_FLOCK {
78 return $CAN_FLOCK if defined $CAN_FLOCK;
79 require Config; import Config;
82 $Config{'d_fcntl_can_lock'} ||
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.
93 0 string perl-store perl Storable(v0.6) data
94 >4 byte >0 (net-order %d)
95 >>4 byte &01 (network-ordered)
99 0 string pst0 perl Storable(v0.7) data
101 >>4 byte &01 (network-ordered)
102 >>4 byte =5 (major 2)
103 >>4 byte =4 (major 2)
104 >>5 byte >0 (minor %d)
110 return unless defined $header and length $header > 11;
112 if ($header =~ s/^perl-store//) {
113 die "Can't deal with version 0 headers";
114 } elsif ($header =~ s/^pst0//) {
117 # Assume it's a string.
118 my ($major, $minor, $bytelen) = unpack "C3", $header;
120 my $net_order = $major & 1;
122 @$result{qw(major minor netorder)} = ($major, $minor, $net_order);
124 return $result if $net_order;
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.
129 delete $result->{minor};
130 $header = '.' . $header;
134 @$result{qw(byteorder intsize longsize ptrsize)} =
135 unpack "x3 A$bytelen C3", $header;
137 if ($major >= 2 and $minor >= 2) {
138 $result->{nvsize} = unpack "x6 x$bytelen C", $header;
146 # Store target object hierarchy, identified by a reference to its root.
147 # The stored object tree may later be retrieved to memory via retrieve.
148 # Returns undef if an I/O error occurred, in which case the file is
152 return _store(\&pstore, @_, 0);
158 # Same as store, but in network order.
161 return _store(\&net_pstore, @_, 0);
167 # Same as store, but flock the file first (advisory locking).
170 return _store(\&pstore, @_, 1);
176 # Same as nstore, but flock the file first (advisory locking).
179 return _store(\&net_pstore, @_, 1);
182 # Internal store to file routine
186 my ($file, $use_locking) = @_;
187 logcroak "not a reference" unless ref($self);
188 logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist
191 open(FILE, ">>$file") || logcroak "can't write into $file: $!";
192 unless (&CAN_FLOCK) {
193 logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O";
196 flock(FILE, LOCK_EX) ||
197 logcroak "can't get exclusive lock on $file: $!";
199 # Unlocking will happen when FILE is closed
201 open(FILE, ">$file") || logcroak "can't create $file: $!";
203 binmode FILE; # Archaic systems...
204 my $da = $@; # Don't mess if called from exception handler
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 $@ =~ s/\.?\n$/,/;
212 return $ret ? $ret : undef;
218 # Same as store, but perform on an already opened file descriptor instead.
219 # Returns undef if an I/O error occurred.
222 return _store_fd(\&pstore, @_);
228 # Same as store_fd, but in network order.
231 my ($self, $file) = @_;
232 return _store_fd(\&net_pstore, @_);
235 # Internal store routine on opened file descriptor
240 logcroak "not a reference" unless ref($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
246 # Call C routine nstore or pstore, depending on network order
247 eval { $ret = &$xsptr($file, $self) };
248 logcroak $@ if $@ =~ s/\.?\n$/,/;
249 local $\; print $file ''; # Autoflush the file if wanted
251 return $ret ? $ret : undef;
257 # Store oject and its hierarchy in memory and return a scalar
258 # containing the result.
261 _freeze(\&mstore, @_);
267 # Same as freeze but in network order.
270 _freeze(\&net_mstore, @_);
273 # Internal freeze routine
277 logcroak "not a reference" unless ref($self);
278 logcroak "too many arguments" unless @_ == 0; # No @foo in arglist
279 my $da = $@; # Don't mess if called from exception handler
281 # Call C routine mstore or net_mstore, depending on network order
282 eval { $ret = &$xsptr($self) };
283 logcroak $@ if $@ =~ s/\.?\n$/,/;
285 return $ret ? $ret : undef;
291 # Retrieve object hierarchy from disk, returning a reference to the root
292 # object of that tree.
301 # Same as retrieve, but with advisory locking.
307 # Internal retrieve routine
309 my ($file, $use_locking) = @_;
311 open(FILE, $file) || logcroak "can't open $file: $!";
312 binmode FILE; # Archaic systems...
314 my $da = $@; # Could be from exception handler
316 unless (&CAN_FLOCK) {
317 logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O";
320 flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!";
321 # Unlocking will happen when FILE is closed
323 eval { $self = pretrieve(*FILE) }; # Call C routine
325 logcroak $@ if $@ =~ s/\.?\n$/,/;
333 # Same as retrieve, but perform from an already opened file descriptor instead.
337 my $fd = fileno($file);
338 logcroak "not a valid file descriptor" unless defined $fd;
340 my $da = $@; # Could be from exception handler
341 eval { $self = pretrieve($file) }; # Call C routine
342 logcroak $@ if $@ =~ s/\.?\n$/,/;
350 # Recreate objects in memory from an existing frozen image created
351 # by freeze. If the frozen image passed is undef, return undef.
355 return undef unless defined $frozen;
357 my $da = $@; # Could be from exception handler
358 eval { $self = mretrieve($frozen) }; # Call C routine
359 logcroak $@ if $@ =~ s/\.?\n$/,/;
366 Storable - persistence for Perl data structures
371 store \%table, 'file';
372 $hashref = retrieve('file');
374 use Storable qw(nstore store_fd nstore_fd freeze thaw dclone);
377 nstore \%table, 'file';
378 $hashref = retrieve('file'); # There is NO nretrieve()
380 # Storing to and retrieving from an already opened file
381 store_fd \@array, \*STDOUT;
382 nstore_fd \%table, \*STDOUT;
383 $aryref = fd_retrieve(\*SOCKET);
384 $hashref = fd_retrieve(\*SOCKET);
386 # Serializing to memory
387 $serialized = freeze \%table;
388 %table_clone = %{ thaw($serialized) };
390 # Deep (recursive) cloning
391 $cloneref = dclone($ref);
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');
401 The Storable package brings persistence to your Perl data structures
402 containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be
403 conveniently stored to disk and retrieved at a later time.
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.
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.
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
415 occurs while reading, C<undef> is returned instead. Other serious
416 errors are propagated via C<die>.
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.
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
425 from a file via C<fd_retrieve>. Those names aren't imported by default,
426 so you will have to do that explicitly if you need those routines.
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.
430 store_fd(\%table, *STDOUT) || die "can't store to stdout\n";
431 $hashref = fd_retrieve(*STDIN);
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
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.
442 When using C<fd_retrieve>, objects are retrieved in sequence, one
443 object (i.e. one recursive tree) per associated C<store_fd>.
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).
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.
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.
466 Note that freezing an object structure and immediately thawing it
467 actually achieves a deep cloning of that structure:
469 dclone(.) = thaw(freeze(.))
471 Storable provides you with a C<dclone> interface which does not create
472 that intermediary scalar but instead freezes the structure in some
473 internal memory space and then immediately thaws it out.
475 =head1 ADVISORY LOCKING
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.
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>,
485 you will get no protection at all.
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.
495 The heart of Storable is written in C for decent speed. Extra low-level
496 optimizations have been made when manipulating perl internals, to
497 sacrifice encapsulation for the benefit of greater speed.
499 =head1 CANONICAL REPRESENTATION
501 Normally, Storable stores elements of hashes in the order they are
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.
509 Canonical order does not imply network order; those are two orthogonal
512 =head1 CODE REFERENCES
514 Since Storable version 2.05, CODE references may be serialized with
515 the help of L<B::Deparse>. To enable this feature, set
516 C<$Storable::Deparse> to a true value. To enable deserializazion,
517 C<$Storable::Eval> should be set to a true value. Be aware that
518 deserialization is done through C<eval>, which is dangerous if the
519 Storable file contains malicious data. You can set C<$Storable::Eval>
520 to a subroutine reference which would be used instead of C<eval>. See
521 below for an example using a L<Safe> compartment for deserialization
524 If C<$Storable::Deparse> and/or C<$Storable::Eval> are set to false
525 values, then the value of C<$Storable::forgive_me> (see below) is
526 respected while serializing and deserializing.
528 =head1 FORWARD COMPATIBILITY
530 This release of Storable can be used on a newer version of Perl to
531 serialize data which is not supported by earlier Perls. By default,
532 Storable will attempt to do the right thing, by C<croak()>ing if it
533 encounters data that it cannot deserialize. However, the defaults
534 can be changed as follows:
540 Perl 5.6 added support for Unicode characters with code points > 255,
541 and Perl 5.8 has full support for Unicode characters in hash keys.
542 Perl internally encodes strings with these characters using utf8, and
543 Storable serializes them as utf8. By default, if an older version of
544 Perl encounters a utf8 value it cannot represent, it will C<croak()>.
545 To change this behaviour so that Storable deserializes utf8 encoded
546 values as the string of bytes (effectively dropping the I<is_utf8> flag)
547 set C<$Storable::drop_utf8> to some C<TRUE> value. This is a form of
548 data loss, because with C<$drop_utf8> true, it becomes impossible to tell
549 whether the original data was the Unicode string, or a series of bytes
550 that happen to be valid utf8.
552 =item restricted hashes
554 Perl 5.8 adds support for restricted hashes, which have keys
555 restricted to a given set, and can have values locked to be read only.
556 By default, when Storable encounters a restricted hash on a perl
557 that doesn't support them, it will deserialize it as a normal hash,
558 silently discarding any placeholder keys and leaving the keys and
559 all values unlocked. To make Storable C<croak()> instead, set
560 C<$Storable::downgrade_restricted> to a C<FALSE> value. To restore
561 the default set it back to some C<TRUE> value.
563 =item files from future versions of Storable
565 Earlier versions of Storable would immediately croak if they encountered
566 a file with a higher internal version number than the reading Storable
567 knew about. Internal version numbers are increased each time new data
568 types (such as restricted hashes) are added to the vocabulary of the file
569 format. This meant that a newer Storable module had no way of writing a
570 file readable by an older Storable, even if the writer didn't store newer
573 This version of Storable will defer croaking until it encounters a data
574 type in the file that it does not recognize. This means that it will
575 continue to read files generated by newer Storable modules which are careful
576 in what they write out, making it easier to upgrade Storable modules in a
579 The old behaviour of immediate croaking can be re-instated by setting
580 C<$Storable::accept_future_minor> to some C<FALSE> value.
584 All these variables have no effect on a newer Perl which supports the
587 =head1 ERROR REPORTING
589 Storable uses the "exception" paradigm, in that it does not try to workaround
590 failures: if something bad happens, an exception is generated from the
591 caller's perspective (see L<Carp> and C<croak()>). Use eval {} to trap
594 When Storable croaks, it tries to report the error via the C<logcroak()>
595 routine from the C<Log::Agent> package, if it is available.
597 Normal errors are reported by having store() or retrieve() return C<undef>.
598 Such errors are usually I/O errors (or truncated stream errors at retrieval).
604 Any class may define hooks that will be called during the serialization
605 and deserialization process on objects that are instances of that class.
606 Those hooks can redefine the way serialization is performed (and therefore,
607 how the symmetrical deserialization should be conducted).
609 Since we said earlier:
611 dclone(.) = thaw(freeze(.))
613 everything we say about hooks should also hold for deep cloning. However,
614 hooks get to know whether the operation is a mere serialization, or a cloning.
616 Therefore, when serializing hooks are involved,
618 dclone(.) <> thaw(freeze(.))
620 Well, you could keep them in sync, but there's no guarantee it will always
621 hold on classes somebody else wrote. Besides, there is little to gain in
622 doing so: a serializing hook could keep only one attribute of an object,
623 which is probably not what should happen during a deep cloning of that
626 Here is the hooking interface:
630 =item C<STORABLE_freeze> I<obj>, I<cloning>
632 The serializing hook, called on the object during serialization. It can be
633 inherited, or defined in the class itself, like any other method.
635 Arguments: I<obj> is the object to serialize, I<cloning> is a flag indicating
636 whether we're in a dclone() or a regular serialization via store() or freeze().
638 Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized
639 is the serialized form to be used, and the optional $ref1, $ref2, etc... are
640 extra references that you wish to let the Storable engine serialize.
642 At deserialization time, you will be given back the same LIST, but all the
643 extra references will be pointing into the deserialized structure.
645 The B<first time> the hook is hit in a serialization flow, you may have it
646 return an empty list. That will signal the Storable engine to further
647 discard that hook for this class and to therefore revert to the default
648 serialization of the underlying Perl data. The hook will again be normally
649 processed in the next serialization.
651 Unless you know better, serializing hook should always say:
653 sub STORABLE_freeze {
654 my ($self, $cloning) = @_;
655 return if $cloning; # Regular default serialization
659 in order to keep reasonable dclone() semantics.
661 =item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ...
663 The deserializing hook called on the object during deserialization.
664 But wait: if we're deserializing, there's no object yet... right?
666 Wrong: the Storable engine creates an empty one for you. If you know Eiffel,
667 you can view C<STORABLE_thaw> as an alternate creation routine.
669 This means the hook can be inherited like any other method, and that
670 I<obj> is your blessed reference for this particular instance.
672 The other arguments should look familiar if you know C<STORABLE_freeze>:
673 I<cloning> is true when we're part of a deep clone operation, I<serialized>
674 is the serialized string you returned to the engine in C<STORABLE_freeze>,
675 and there may be an optional list of references, in the same order you gave
676 them at serialization time, pointing to the deserialized objects (which
677 have been processed courtesy of the Storable engine).
679 When the Storable engine does not find any C<STORABLE_thaw> hook routine,
680 it tries to load the class by requiring the package dynamically (using
681 the blessed package name), and then re-attempts the lookup. If at that
682 time the hook cannot be located, the engine croaks. Note that this mechanism
683 will fail if you define several classes in the same file, but L<perlmod>
686 It is up to you to use this information to populate I<obj> the way you want.
688 Returned value: none.
694 Predicates are not exportable. They must be called by explicitly prefixing
695 them with the Storable package name.
699 =item C<Storable::last_op_in_netorder>
701 The C<Storable::last_op_in_netorder()> predicate will tell you whether
702 network order was used in the last store or retrieve operation. If you
703 don't know how to use this, just forget about it.
705 =item C<Storable::is_storing>
707 Returns true if within a store operation (via STORABLE_freeze hook).
709 =item C<Storable::is_retrieving>
711 Returns true if within a retrieve operation (via STORABLE_thaw hook).
717 With hooks comes the ability to recurse back to the Storable engine.
718 Indeed, hooks are regular Perl code, and Storable is convenient when
719 it comes to serializing and deserializing things, so why not use it
720 to handle the serialization string?
722 There are a few things you need to know, however:
728 You can create endless loops if the things you serialize via freeze()
729 (for instance) point back to the object we're trying to serialize in
734 Shared references among objects will not stay shared: if we're serializing
735 the list of object [A, C] where both object A and C refer to the SAME object
736 B, and if there is a serializing hook in A that says freeze(B), then when
737 deserializing, we'll get [A', C'] where A' refers to B', but C' refers to D,
738 a deep clone of B'. The topology was not preserved.
742 That's why C<STORABLE_freeze> lets you provide a list of references
743 to serialize. The engine guarantees that those will be serialized in the
744 same context as the other objects, and therefore that shared objects will
747 In the above [A, C] example, the C<STORABLE_freeze> hook could return:
749 ("something", $self->{B})
751 and the B part would be serialized by the engine. In C<STORABLE_thaw>, you
752 would get back the reference to the B' object, deserialized for you.
754 Therefore, recursion should normally be avoided, but is nonetheless supported.
758 There is a Clone module available on CPAN which implements deep cloning
759 natively, i.e. without freezing to memory and thawing the result. It is
760 aimed to replace Storable's dclone() some day. However, it does not currently
761 support Storable hooks to redefine the way deep cloning is performed.
763 =head1 Storable magic
765 Yes, there's a lot of that :-) But more precisely, in UNIX systems
766 there's a utility called C<file>, which recognizes data files based on
767 their contents (usually their first few bytes). For this to work,
768 a certain file called F<magic> needs to taught about the I<signature>
769 of the data. Where that configuration file lives depends on the UNIX
770 flavour; often it's something like F</usr/share/misc/magic> or
771 F</etc/magic>. Your system administrator needs to do the updating of
772 the F<magic> file. The necessary signature information is output to
773 STDOUT by invoking Storable::show_file_magic(). Note that the GNU
774 implementation of the C<file> utility, version 3.38 or later,
775 is expected to contain support for recognising Storable files
776 out-of-the-box, in addition to other kinds of Perl files.
780 Here are some code samples showing a possible usage of Storable:
782 use Storable qw(store retrieve freeze thaw dclone);
784 %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1);
786 store(\%color, '/tmp/colors') or die "Can't store %a in /tmp/colors!\n";
788 $colref = retrieve('/tmp/colors');
789 die "Unable to retrieve from /tmp/colors!\n" unless defined $colref;
790 printf "Blue is still %lf\n", $colref->{'Blue'};
792 $colref2 = dclone(\%color);
794 $str = freeze(\%color);
795 printf "Serialization of %%color is %d bytes long.\n", length($str);
796 $colref3 = thaw($str);
798 which prints (on my machine):
800 Blue is still 0.100000
801 Serialization of %color is 102 bytes long.
803 Serialization of CODE references and deserialization in a safe
808 use Storable qw(freeze thaw);
812 # because of opcodes used in "use strict":
813 $safe->permit(qw(:default require caller));
814 local $Storable::Deparse = 1;
815 local $Storable::Eval = sub { $safe->reval($_[0]) };
816 my $serialized = freeze(sub { 42 });
817 my $code = thaw($serialized);
827 If you're using references as keys within your hash tables, you're bound
828 to be disappointed when retrieving your data. Indeed, Perl stringifies
829 references used as hash table keys. If you later wish to access the
830 items via another reference stringification (i.e. using the same
831 reference that was used for the key originally to record the value into
832 the hash table), it will work because both references stringify to the
835 It won't work across a sequence of C<store> and C<retrieve> operations,
836 however, because the addresses in the retrieved objects, which are
837 part of the stringified references, will probably differ from the
838 original addresses. The topology of your structure is preserved,
839 but not hidden semantics like those.
841 On platforms where it matters, be sure to call C<binmode()> on the
842 descriptors that you pass to Storable functions.
844 Storing data canonically that contains large hashes can be
845 significantly slower than storing the same data normally, as
846 temporary arrays to hold the keys for each hash have to be allocated,
847 populated, sorted and freed. Some tests have shown a halving of the
848 speed of storing -- the exact penalty will depend on the complexity of
849 your data. There is no slowdown on retrieval.
853 You can't store GLOB, FORMLINE, etc.... If you can define semantics
854 for those operations, feel free to enhance Storable so that it can
857 The store functions will C<croak> if they run into such references
858 unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that
859 case, the fatal message is turned in a warning and some
860 meaningless string is stored instead.
862 Setting C<$Storable::canonical> may not yield frozen strings that
863 compare equal due to possible stringification of numbers. When the
864 string version of a scalar exists, it is the form stored; therefore,
865 if you happen to use your numbers as strings between two freezing
866 operations on the same data structures, you will get different
869 When storing doubles in network order, their value is stored as text.
870 However, you should also not expect non-numeric floating-point values
871 such as infinity and "not a number" to pass successfully through a
872 nstore()/retrieve() pair.
874 As Storable neither knows nor cares about character sets (although it
875 does know that characters may be more than eight bits wide), any difference
876 in the interpretation of character codes between a host and a target
877 system is your problem. In particular, if host and target use different
878 code points to represent the characters used in the text representation
879 of floating-point numbers, you will not be able be able to exchange
880 floating-point data, even with nstore().
882 C<Storable::drop_utf8> is a blunt tool. There is no facility either to
883 return B<all> strings as utf8 sequences, or to attempt to convert utf8
884 data back to 8 bit and C<croak()> if the conversion fails.
886 Prior to Storable 2.01, no distinction was made between signed and
887 unsigned integers on storing. By default Storable prefers to store a
888 scalars string representation (if it has one) so this would only cause
889 problems when storing large unsigned integers that had never been coverted
890 to string or floating point. In other words values that had been generated
891 by integer operations such as logic ops and then not used in any string or
892 arithmetic context before storing.
894 =head2 64 bit data in perl 5.6.0 and 5.6.1
896 This section only applies to you if you have existing data written out
897 by Storable 2.02 or earlier on perl 5.6.0 or 5.6.1 on Unix or Linux which
898 has been configured with 64 bit integer support (not the default)
899 If you got a precompiled perl, rather than running Configure to build
900 your own perl from source, then it almost certainly does not affect you,
901 and you can stop reading now (unless you're curious). If you're using perl
902 on Windows it does not affect you.
904 Storable writes a file header which contains the sizes of various C
905 language types for the C compiler that built Storable (when not writing in
906 network order), and will refuse to load files written by a Storable not
907 on the same (or compatible) architecture. This check and a check on
908 machine byteorder is needed because the size of various fields in the file
909 are given by the sizes of the C language types, and so files written on
910 different architectures are incompatible. This is done for increased speed.
911 (When writing in network order, all fields are written out as standard
912 lengths, which allows full interworking, but takes longer to read and write)
914 Perl 5.6.x introduced the ability to optional configure the perl interpreter
915 to use C's C<long long> type to allow scalars to store 64 bit integers on 32
916 bit systems. However, due to the way the Perl configuration system
917 generated the C configuration files on non-Windows platforms, and the way
918 Storable generates its header, nothing in the Storable file header reflected
919 whether the perl writing was using 32 or 64 bit integers, despite the fact
920 that Storable was storing some data differently in the file. Hence Storable
921 running on perl with 64 bit integers will read the header from a file
922 written by a 32 bit perl, not realise that the data is actually in a subtly
923 incompatible format, and then go horribly wrong (possibly crashing) if it
924 encountered a stored integer. This is a design failure.
926 Storable has now been changed to write out and read in a file header with
927 information about the size of integers. It's impossible to detect whether
928 an old file being read in was written with 32 or 64 bit integers (they have
929 the same header) so it's impossible to automatically switch to a correct
930 backwards compatibility mode. Hence this Storable defaults to the new,
933 What this means is that if you have data written by Storable 1.x running
934 on perl 5.6.0 or 5.6.1 configured with 64 bit integers on Unix or Linux
935 then by default this Storable will refuse to read it, giving the error
936 I<Byte order is not compatible>. If you have such data then you you
937 should set C<$Storable::interwork_56_64bit> to a true value to make this
938 Storable read and write files with the old header. You should also
939 migrate your data, or any older perl you are communicating with, to this
940 current version of Storable.
942 If you don't have data written with specific configuration of perl described
943 above, then you do not and should not do anything. Don't set the flag -
944 not only will Storable on an identically configured perl refuse to load them,
945 but Storable a differently configured perl will load them believing them
946 to be correct for it, and then may well fail or crash part way through
951 Thank you to (in chronological order):
953 Jarkko Hietaniemi <jhi@iki.fi>
954 Ulrich Pfeifer <pfeifer@charly.informatik.uni-dortmund.de>
955 Benjamin A. Holzman <bah@ecnvantage.com>
956 Andrew Ford <A.Ford@ford-mason.co.uk>
957 Gisle Aas <gisle@aas.no>
958 Jeff Gresham <gresham_jeffrey@jpmorgan.com>
959 Murray Nesbitt <murray@activestate.com>
960 Marc Lehmann <pcg@opengroup.org>
961 Justin Banks <justinb@wamnet.com>
962 Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!)
963 Salvador Ortiz Garcia <sog@msg.com.mx>
964 Dominic Dunlop <domo@computer.org>
965 Erik Haugan <erik@solbors.no>
967 for their bug reports, suggestions and contributions.
969 Benjamin Holzman contributed the tied variable support, Andrew Ford
970 contributed the canonical order for hashes, and Gisle Aas fixed
971 a few misunderstandings of mine regarding the perl internals,
972 and optimized the emission of "tags" in the output streams by
973 simply counting the objects instead of tagging them (leading to
974 a binary incompatibility for the Storable image starting at version
975 0.6--older images are, of course, still properly understood).
976 Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading
977 and references to tied items support.
981 Storable was written by Raphael Manfredi F<E<lt>Raphael_Manfredi@pobox.comE<gt>>
982 Maintenance is now done by the perl5-porters F<E<lt>perl5-porters@perl.orgE<gt>>
984 Please e-mail us with problems, bug fixes, comments and complaints,
985 although if you have complements you should send them to Raphael.
986 Please don't e-mail Raphael with problems, as he no longer works on
987 Storable, and your message will be delayed while he forwards it to us.