2 # Copyright (c) 1995-2001, Raphael Manfredi
3 # Copyright (c) 2002-2014 by the Perl 5 Porters
5 # You may redistribute only under the same terms as Perl 5, as specified
6 # in the README file that comes with the distribution.
11 package Storable; @ISA = qw(Exporter);
13 @EXPORT = qw(store retrieve);
15 nstore store_fd nstore_fd fd_retrieve
19 lock_store lock_nstore lock_retrieve
23 use vars qw($canonical $forgive_me $VERSION);
31 pop @INC if $INC[-1] eq '.';
38 # Use of Log::Agent is optional. If it hasn't imported these subs then
39 # provide a fallback implementation.
41 unless ($Storable::{logcroak} && *{$Storable::{logcroak}}{CODE}) {
47 unless ($Storable::{logcarp} && *{$Storable::{logcarp}}{CODE}) {
56 # They might miss :flock in Fcntl
60 if (eval { require Fcntl; 1 } && exists $Fcntl::EXPORT_TAGS{'flock'}) {
61 Fcntl->import(':flock');
71 # clone context under threads
72 Storable::init_perinterp();
75 # By default restricted hashes are downgraded on earlier perls.
77 $Storable::downgrade_restricted = 1;
78 $Storable::accept_future_minor = 1;
80 XSLoader::load('Storable', $Storable::VERSION);
83 # Determine whether locking is possible, but only when needed.
86 sub CAN_FLOCK; my $CAN_FLOCK; sub CAN_FLOCK {
87 return $CAN_FLOCK if defined $CAN_FLOCK;
88 require Config; import Config;
91 $Config{'d_fcntl_can_lock'} ||
98 # To recognize the data files of the Perl module Storable,
99 # the following lines need to be added to the local magic(5) file,
100 # usually either /usr/share/misc/magic or /etc/magic.
102 0 string perl-store perl Storable(v0.6) data
103 >4 byte >0 (net-order %d)
104 >>4 byte &01 (network-ordered)
105 >>4 byte =3 (major 1)
106 >>4 byte =2 (major 1)
108 0 string pst0 perl Storable(v0.7) data
110 >>4 byte &01 (network-ordered)
111 >>4 byte =5 (major 2)
112 >>4 byte =4 (major 2)
113 >>5 byte >0 (minor %d)
121 my $fh = IO::File->new;
122 open($fh, "<". $file) || die "Can't open '$file': $!";
124 defined(sysread($fh, my $buf, 32)) || die "Can't read from '$file': $!";
127 $file = "./$file" unless $file; # ensure TRUE value
129 return read_magic($buf, $file);
133 my($buf, $file) = @_;
136 my $buflen = length($buf);
138 if ($buf =~ s/^(pst0|perl-store)//) {
140 $info{file} = $file || 1;
143 return undef if $file;
147 return undef unless length($buf);
150 if ($magic eq "perl-store" && ord(substr($buf, 0, 1)) > 1) {
156 my $major = (ord $1) >> 1;
157 return undef if $major > 4; # sanity (assuming we never go that high)
158 $info{major} = $major;
159 $net_order = (ord $1) & 0x01;
161 return undef unless $buf =~ s/(.)//s;
163 $info{minor} = $minor;
164 $info{version} = "$major.$minor";
165 $info{version_nv} = sprintf "%d.%03d", $major, $minor;
168 $info{version} = $major;
171 $info{version_nv} ||= $info{version};
172 $info{netorder} = $net_order;
174 unless ($net_order) {
175 return undef unless $buf =~ s/(.)//s;
177 return undef unless length($buf) >= $len;
178 return undef unless $len == 4 || $len == 8; # sanity
179 @info{qw(byteorder intsize longsize ptrsize)}
180 = unpack "a${len}CCC", $buf;
181 (substr $buf, 0, $len + 3) = '';
182 if ($info{version_nv} >= 2.002) {
183 return undef unless $buf =~ s/(.)//s;
184 $info{nvsize} = ord $1;
187 $info{hdrsize} = $buflen - length($buf);
193 sprintf "%d.%03d", BIN_MAJOR(), BIN_MINOR();
196 sub BIN_WRITE_VERSION_NV {
197 sprintf "%d.%03d", BIN_MAJOR(), BIN_WRITE_MINOR();
203 # Store target object hierarchy, identified by a reference to its root.
204 # The stored object tree may later be retrieved to memory via retrieve.
205 # Returns undef if an I/O error occurred, in which case the file is
209 return _store(\&pstore, @_, 0);
215 # Same as store, but in network order.
218 return _store(\&net_pstore, @_, 0);
224 # Same as store, but flock the file first (advisory locking).
227 return _store(\&pstore, @_, 1);
233 # Same as nstore, but flock the file first (advisory locking).
236 return _store(\&net_pstore, @_, 1);
239 # Internal store to file routine
243 my ($file, $use_locking) = @_;
244 logcroak "not a reference" unless ref($self);
245 logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist
248 open(FILE, ">>$file") || logcroak "can't write into $file: $!";
249 unless (&CAN_FLOCK) {
251 "Storable::lock_store: fcntl/flock emulation broken on $^O";
254 flock(FILE, LOCK_EX) ||
255 logcroak "can't get exclusive lock on $file: $!";
257 # Unlocking will happen when FILE is closed
259 open(FILE, ">$file") || logcroak "can't create $file: $!";
261 binmode FILE; # Archaic systems...
262 my $da = $@; # Don't mess if called from exception handler
264 # Call C routine nstore or pstore, depending on network order
265 eval { $ret = &$xsptr(*FILE, $self) };
266 # close will return true on success, so the or short-circuits, the ()
267 # expression is true, and for that case the block will only be entered
268 # if $@ is true (ie eval failed)
269 # if close fails, it returns false, $ret is altered, *that* is (also)
270 # false, so the () expression is false, !() is true, and the block is
272 if (!(close(FILE) or undef $ret) || $@) {
273 unlink($file) or warn "Can't unlink $file: $!\n";
275 logcroak $@ if $@ =~ s/\.?\n$/,/;
283 # Same as store, but perform on an already opened file descriptor instead.
284 # Returns undef if an I/O error occurred.
287 return _store_fd(\&pstore, @_);
293 # Same as store_fd, but in network order.
296 my ($self, $file) = @_;
297 return _store_fd(\&net_pstore, @_);
300 # Internal store routine on opened file descriptor
305 logcroak "not a reference" unless ref($self);
306 logcroak "too many arguments" unless @_ == 1; # No @foo in arglist
307 my $fd = fileno($file);
308 logcroak "not a valid file descriptor" unless defined $fd;
309 my $da = $@; # Don't mess if called from exception handler
311 # Call C routine nstore or pstore, depending on network order
312 eval { $ret = &$xsptr($file, $self) };
313 logcroak $@ if $@ =~ s/\.?\n$/,/;
314 local $\; print $file ''; # Autoflush the file if wanted
322 # Store object and its hierarchy in memory and return a scalar
323 # containing the result.
326 _freeze(\&mstore, @_);
332 # Same as freeze but in network order.
335 _freeze(\&net_mstore, @_);
338 # Internal freeze routine
342 logcroak "not a reference" unless ref($self);
343 logcroak "too many arguments" unless @_ == 0; # No @foo in arglist
344 my $da = $@; # Don't mess if called from exception handler
346 # Call C routine mstore or net_mstore, depending on network order
347 eval { $ret = &$xsptr($self) };
348 logcroak $@ if $@ =~ s/\.?\n$/,/;
350 return $ret ? $ret : undef;
356 # Retrieve object hierarchy from disk, returning a reference to the root
357 # object of that tree.
366 # Same as retrieve, but with advisory locking.
372 # Internal retrieve routine
374 my ($file, $use_locking) = @_;
376 open(FILE, $file) || logcroak "can't open $file: $!";
377 binmode FILE; # Archaic systems...
379 my $da = $@; # Could be from exception handler
381 unless (&CAN_FLOCK) {
383 "Storable::lock_store: fcntl/flock emulation broken on $^O";
386 flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!";
387 # Unlocking will happen when FILE is closed
389 eval { $self = pretrieve(*FILE) }; # Call C routine
391 logcroak $@ if $@ =~ s/\.?\n$/,/;
399 # Same as retrieve, but perform from an already opened file descriptor instead.
403 my $fd = fileno($file);
404 logcroak "not a valid file descriptor" unless defined $fd;
406 my $da = $@; # Could be from exception handler
407 eval { $self = pretrieve($file) }; # Call C routine
408 logcroak $@ if $@ =~ s/\.?\n$/,/;
413 sub retrieve_fd { &fd_retrieve } # Backward compatibility
418 # Recreate objects in memory from an existing frozen image created
419 # by freeze. If the frozen image passed is undef, return undef.
423 return undef unless defined $frozen;
425 my $da = $@; # Could be from exception handler
426 eval { $self = mretrieve($frozen) }; # Call C routine
427 logcroak $@ if $@ =~ s/\.?\n$/,/;
437 Storable - persistence for Perl data structures
442 store \%table, 'file';
443 $hashref = retrieve('file');
445 use Storable qw(nstore store_fd nstore_fd freeze thaw dclone);
448 nstore \%table, 'file';
449 $hashref = retrieve('file'); # There is NO nretrieve()
451 # Storing to and retrieving from an already opened file
452 store_fd \@array, \*STDOUT;
453 nstore_fd \%table, \*STDOUT;
454 $aryref = fd_retrieve(\*SOCKET);
455 $hashref = fd_retrieve(\*SOCKET);
457 # Serializing to memory
458 $serialized = freeze \%table;
459 %table_clone = %{ thaw($serialized) };
461 # Deep (recursive) cloning
462 $cloneref = dclone($ref);
465 use Storable qw(lock_store lock_nstore lock_retrieve)
466 lock_store \%table, 'file';
467 lock_nstore \%table, 'file';
468 $hashref = lock_retrieve('file');
472 The Storable package brings persistence to your Perl data structures
473 containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be
474 conveniently stored to disk and retrieved at a later time.
476 It can be used in the regular procedural way by calling C<store> with
477 a reference to the object to be stored, along with the file name where
478 the image should be written.
480 The routine returns C<undef> for I/O problems or other internal error,
481 a true value otherwise. Serious errors are propagated as a C<die> exception.
483 To retrieve data stored to disk, use C<retrieve> with a file name.
484 The objects stored into that file are recreated into memory for you,
485 and a I<reference> to the root object is returned. In case an I/O error
486 occurs while reading, C<undef> is returned instead. Other serious
487 errors are propagated via C<die>.
489 Since storage is performed recursively, you might want to stuff references
490 to objects that share a lot of common data into a single array or hash
491 table, and then store that object. That way, when you retrieve back the
492 whole thing, the objects will continue to share what they originally shared.
494 At the cost of a slight header overhead, you may store to an already
495 opened file descriptor using the C<store_fd> routine, and retrieve
496 from a file via C<fd_retrieve>. Those names aren't imported by default,
497 so you will have to do that explicitly if you need those routines.
498 The file descriptor you supply must be already opened, for read
499 if you're going to retrieve and for write if you wish to store.
501 store_fd(\%table, *STDOUT) || die "can't store to stdout\n";
502 $hashref = fd_retrieve(*STDIN);
504 You can also store data in network order to allow easy sharing across
505 multiple platforms, or when storing on a socket known to be remotely
506 connected. The routines to call have an initial C<n> prefix for I<network>,
507 as in C<nstore> and C<nstore_fd>. At retrieval time, your data will be
508 correctly restored so you don't have to know whether you're restoring
509 from native or network ordered data. Double values are stored stringified
510 to ensure portability as well, at the slight risk of loosing some precision
511 in the last decimals.
513 When using C<fd_retrieve>, objects are retrieved in sequence, one
514 object (i.e. one recursive tree) per associated C<store_fd>.
516 If you're more from the object-oriented camp, you can inherit from
517 Storable and directly store your objects by invoking C<store> as
518 a method. The fact that the root of the to-be-stored tree is a
519 blessed reference (i.e. an object) is special-cased so that the
520 retrieve does not provide a reference to that object but rather the
521 blessed object reference itself. (Otherwise, you'd get a reference
522 to that blessed object).
526 The Storable engine can also store data into a Perl scalar instead, to
527 later retrieve them. This is mainly used to freeze a complex structure in
528 some safe compact memory place (where it can possibly be sent to another
529 process via some IPC, since freezing the structure also serializes it in
530 effect). Later on, and maybe somewhere else, you can thaw the Perl scalar
531 out and recreate the original complex structure in memory.
533 Surprisingly, the routines to be called are named C<freeze> and C<thaw>.
534 If you wish to send out the frozen scalar to another machine, use
535 C<nfreeze> instead to get a portable image.
537 Note that freezing an object structure and immediately thawing it
538 actually achieves a deep cloning of that structure:
540 dclone(.) = thaw(freeze(.))
542 Storable provides you with a C<dclone> interface which does not create
543 that intermediary scalar but instead freezes the structure in some
544 internal memory space and then immediately thaws it out.
546 =head1 ADVISORY LOCKING
548 The C<lock_store> and C<lock_nstore> routine are equivalent to
549 C<store> and C<nstore>, except that they get an exclusive lock on
550 the file before writing. Likewise, C<lock_retrieve> does the same
551 as C<retrieve>, but also gets a shared lock on the file before reading.
553 As with any advisory locking scheme, the protection only works if you
554 systematically use C<lock_store> and C<lock_retrieve>. If one side of
555 your application uses C<store> whilst the other uses C<lock_retrieve>,
556 you will get no protection at all.
558 The internal advisory locking is implemented using Perl's flock()
559 routine. If your system does not support any form of flock(), or if
560 you share your files across NFS, you might wish to use other forms
561 of locking by using modules such as LockFile::Simple which lock a
562 file using a filesystem entry, instead of locking the file descriptor.
566 The heart of Storable is written in C for decent speed. Extra low-level
567 optimizations have been made when manipulating perl internals, to
568 sacrifice encapsulation for the benefit of greater speed.
570 =head1 CANONICAL REPRESENTATION
572 Normally, Storable stores elements of hashes in the order they are
573 stored internally by Perl, i.e. pseudo-randomly. If you set
574 C<$Storable::canonical> to some C<TRUE> value, Storable will store
575 hashes with the elements sorted by their key. This allows you to
576 compare data structures by comparing their frozen representations (or
577 even the compressed frozen representations), which can be useful for
578 creating lookup tables for complicated queries.
580 Canonical order does not imply network order; those are two orthogonal
583 =head1 CODE REFERENCES
585 Since Storable version 2.05, CODE references may be serialized with
586 the help of L<B::Deparse>. To enable this feature, set
587 C<$Storable::Deparse> to a true value. To enable deserialization,
588 C<$Storable::Eval> should be set to a true value. Be aware that
589 deserialization is done through C<eval>, which is dangerous if the
590 Storable file contains malicious data. You can set C<$Storable::Eval>
591 to a subroutine reference which would be used instead of C<eval>. See
592 below for an example using a L<Safe> compartment for deserialization
595 If C<$Storable::Deparse> and/or C<$Storable::Eval> are set to false
596 values, then the value of C<$Storable::forgive_me> (see below) is
597 respected while serializing and deserializing.
599 =head1 FORWARD COMPATIBILITY
601 This release of Storable can be used on a newer version of Perl to
602 serialize data which is not supported by earlier Perls. By default,
603 Storable will attempt to do the right thing, by C<croak()>ing if it
604 encounters data that it cannot deserialize. However, the defaults
605 can be changed as follows:
611 Perl 5.6 added support for Unicode characters with code points > 255,
612 and Perl 5.8 has full support for Unicode characters in hash keys.
613 Perl internally encodes strings with these characters using utf8, and
614 Storable serializes them as utf8. By default, if an older version of
615 Perl encounters a utf8 value it cannot represent, it will C<croak()>.
616 To change this behaviour so that Storable deserializes utf8 encoded
617 values as the string of bytes (effectively dropping the I<is_utf8> flag)
618 set C<$Storable::drop_utf8> to some C<TRUE> value. This is a form of
619 data loss, because with C<$drop_utf8> true, it becomes impossible to tell
620 whether the original data was the Unicode string, or a series of bytes
621 that happen to be valid utf8.
623 =item restricted hashes
625 Perl 5.8 adds support for restricted hashes, which have keys
626 restricted to a given set, and can have values locked to be read only.
627 By default, when Storable encounters a restricted hash on a perl
628 that doesn't support them, it will deserialize it as a normal hash,
629 silently discarding any placeholder keys and leaving the keys and
630 all values unlocked. To make Storable C<croak()> instead, set
631 C<$Storable::downgrade_restricted> to a C<FALSE> value. To restore
632 the default set it back to some C<TRUE> value.
634 =item files from future versions of Storable
636 Earlier versions of Storable would immediately croak if they encountered
637 a file with a higher internal version number than the reading Storable
638 knew about. Internal version numbers are increased each time new data
639 types (such as restricted hashes) are added to the vocabulary of the file
640 format. This meant that a newer Storable module had no way of writing a
641 file readable by an older Storable, even if the writer didn't store newer
644 This version of Storable will defer croaking until it encounters a data
645 type in the file that it does not recognize. This means that it will
646 continue to read files generated by newer Storable modules which are careful
647 in what they write out, making it easier to upgrade Storable modules in a
650 The old behaviour of immediate croaking can be re-instated by setting
651 C<$Storable::accept_future_minor> to some C<FALSE> value.
655 All these variables have no effect on a newer Perl which supports the
658 =head1 ERROR REPORTING
660 Storable uses the "exception" paradigm, in that it does not try to workaround
661 failures: if something bad happens, an exception is generated from the
662 caller's perspective (see L<Carp> and C<croak()>). Use eval {} to trap
665 When Storable croaks, it tries to report the error via the C<logcroak()>
666 routine from the C<Log::Agent> package, if it is available.
668 Normal errors are reported by having store() or retrieve() return C<undef>.
669 Such errors are usually I/O errors (or truncated stream errors at retrieval).
675 Any class may define hooks that will be called during the serialization
676 and deserialization process on objects that are instances of that class.
677 Those hooks can redefine the way serialization is performed (and therefore,
678 how the symmetrical deserialization should be conducted).
680 Since we said earlier:
682 dclone(.) = thaw(freeze(.))
684 everything we say about hooks should also hold for deep cloning. However,
685 hooks get to know whether the operation is a mere serialization, or a cloning.
687 Therefore, when serializing hooks are involved,
689 dclone(.) <> thaw(freeze(.))
691 Well, you could keep them in sync, but there's no guarantee it will always
692 hold on classes somebody else wrote. Besides, there is little to gain in
693 doing so: a serializing hook could keep only one attribute of an object,
694 which is probably not what should happen during a deep cloning of that
697 Here is the hooking interface:
701 =item C<STORABLE_freeze> I<obj>, I<cloning>
703 The serializing hook, called on the object during serialization. It can be
704 inherited, or defined in the class itself, like any other method.
706 Arguments: I<obj> is the object to serialize, I<cloning> is a flag indicating
707 whether we're in a dclone() or a regular serialization via store() or freeze().
709 Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized
710 is the serialized form to be used, and the optional $ref1, $ref2, etc... are
711 extra references that you wish to let the Storable engine serialize.
713 At deserialization time, you will be given back the same LIST, but all the
714 extra references will be pointing into the deserialized structure.
716 The B<first time> the hook is hit in a serialization flow, you may have it
717 return an empty list. That will signal the Storable engine to further
718 discard that hook for this class and to therefore revert to the default
719 serialization of the underlying Perl data. The hook will again be normally
720 processed in the next serialization.
722 Unless you know better, serializing hook should always say:
724 sub STORABLE_freeze {
725 my ($self, $cloning) = @_;
726 return if $cloning; # Regular default serialization
730 in order to keep reasonable dclone() semantics.
732 =item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ...
734 The deserializing hook called on the object during deserialization.
735 But wait: if we're deserializing, there's no object yet... right?
737 Wrong: the Storable engine creates an empty one for you. If you know Eiffel,
738 you can view C<STORABLE_thaw> as an alternate creation routine.
740 This means the hook can be inherited like any other method, and that
741 I<obj> is your blessed reference for this particular instance.
743 The other arguments should look familiar if you know C<STORABLE_freeze>:
744 I<cloning> is true when we're part of a deep clone operation, I<serialized>
745 is the serialized string you returned to the engine in C<STORABLE_freeze>,
746 and there may be an optional list of references, in the same order you gave
747 them at serialization time, pointing to the deserialized objects (which
748 have been processed courtesy of the Storable engine).
750 When the Storable engine does not find any C<STORABLE_thaw> hook routine,
751 it tries to load the class by requiring the package dynamically (using
752 the blessed package name), and then re-attempts the lookup. If at that
753 time the hook cannot be located, the engine croaks. Note that this mechanism
754 will fail if you define several classes in the same file, but L<perlmod>
757 It is up to you to use this information to populate I<obj> the way you want.
759 Returned value: none.
761 =item C<STORABLE_attach> I<class>, I<cloning>, I<serialized>
763 While C<STORABLE_freeze> and C<STORABLE_thaw> are useful for classes where
764 each instance is independent, this mechanism has difficulty (or is
765 incompatible) with objects that exist as common process-level or
766 system-level resources, such as singleton objects, database pools, caches
769 The alternative C<STORABLE_attach> method provides a solution for these
770 shared objects. Instead of C<STORABLE_freeze> --E<gt> C<STORABLE_thaw>,
771 you implement C<STORABLE_freeze> --E<gt> C<STORABLE_attach> instead.
773 Arguments: I<class> is the class we are attaching to, I<cloning> is a flag
774 indicating whether we're in a dclone() or a regular de-serialization via
775 thaw(), and I<serialized> is the stored string for the resource object.
777 Because these resource objects are considered to be owned by the entire
778 process/system, and not the "property" of whatever is being serialized,
779 no references underneath the object should be included in the serialized
780 string. Thus, in any class that implements C<STORABLE_attach>, the
781 C<STORABLE_freeze> method cannot return any references, and C<Storable>
782 will throw an error if C<STORABLE_freeze> tries to return references.
784 All information required to "attach" back to the shared resource object
785 B<must> be contained B<only> in the C<STORABLE_freeze> return string.
786 Otherwise, C<STORABLE_freeze> behaves as normal for C<STORABLE_attach>
789 Because C<STORABLE_attach> is passed the class (rather than an object),
790 it also returns the object directly, rather than modifying the passed
793 Returned value: object of type C<class>
799 Predicates are not exportable. They must be called by explicitly prefixing
800 them with the Storable package name.
804 =item C<Storable::last_op_in_netorder>
806 The C<Storable::last_op_in_netorder()> predicate will tell you whether
807 network order was used in the last store or retrieve operation. If you
808 don't know how to use this, just forget about it.
810 =item C<Storable::is_storing>
812 Returns true if within a store operation (via STORABLE_freeze hook).
814 =item C<Storable::is_retrieving>
816 Returns true if within a retrieve operation (via STORABLE_thaw hook).
822 With hooks comes the ability to recurse back to the Storable engine.
823 Indeed, hooks are regular Perl code, and Storable is convenient when
824 it comes to serializing and deserializing things, so why not use it
825 to handle the serialization string?
827 There are a few things you need to know, however:
833 You can create endless loops if the things you serialize via freeze()
834 (for instance) point back to the object we're trying to serialize in
839 Shared references among objects will not stay shared: if we're serializing
840 the list of object [A, C] where both object A and C refer to the SAME object
841 B, and if there is a serializing hook in A that says freeze(B), then when
842 deserializing, we'll get [A', C'] where A' refers to B', but C' refers to D,
843 a deep clone of B'. The topology was not preserved.
847 That's why C<STORABLE_freeze> lets you provide a list of references
848 to serialize. The engine guarantees that those will be serialized in the
849 same context as the other objects, and therefore that shared objects will
852 In the above [A, C] example, the C<STORABLE_freeze> hook could return:
854 ("something", $self->{B})
856 and the B part would be serialized by the engine. In C<STORABLE_thaw>, you
857 would get back the reference to the B' object, deserialized for you.
859 Therefore, recursion should normally be avoided, but is nonetheless supported.
863 There is a Clone module available on CPAN which implements deep cloning
864 natively, i.e. without freezing to memory and thawing the result. It is
865 aimed to replace Storable's dclone() some day. However, it does not currently
866 support Storable hooks to redefine the way deep cloning is performed.
868 =head1 Storable magic
870 Yes, there's a lot of that :-) But more precisely, in UNIX systems
871 there's a utility called C<file>, which recognizes data files based on
872 their contents (usually their first few bytes). For this to work,
873 a certain file called F<magic> needs to taught about the I<signature>
874 of the data. Where that configuration file lives depends on the UNIX
875 flavour; often it's something like F</usr/share/misc/magic> or
876 F</etc/magic>. Your system administrator needs to do the updating of
877 the F<magic> file. The necessary signature information is output to
878 STDOUT by invoking Storable::show_file_magic(). Note that the GNU
879 implementation of the C<file> utility, version 3.38 or later,
880 is expected to contain support for recognising Storable files
881 out-of-the-box, in addition to other kinds of Perl files.
883 You can also use the following functions to extract the file header
884 information from Storable images:
888 =item $info = Storable::file_magic( $filename )
890 If the given file is a Storable image return a hash describing it. If
891 the file is readable, but not a Storable image return C<undef>. If
892 the file does not exist or is unreadable then croak.
894 The hash returned has the following elements:
900 This returns the file format version. It is a string like "2.7".
902 Note that this version number is not the same as the version number of
903 the Storable module itself. For instance Storable v0.7 create files
904 in format v2.0 and Storable v2.15 create files in format v2.7. The
905 file format version number only increment when additional features
906 that would confuse older versions of the module are added.
908 Files older than v2.0 will have the one of the version numbers "-1",
909 "0" or "1". No minor number was used at that time.
913 This returns the file format version as number. It is a string like
914 "2.007". This value is suitable for numeric comparisons.
916 The constant function C<Storable::BIN_VERSION_NV> returns a comparable
917 number that represents the highest file version number that this
918 version of Storable fully supports (but see discussion of
919 C<$Storable::accept_future_minor> above). The constant
920 C<Storable::BIN_WRITE_VERSION_NV> function returns what file version
921 is written and might be less than C<Storable::BIN_VERSION_NV> in some
924 =item C<major>, C<minor>
926 This also returns the file format version. If the version is "2.7"
927 then major would be 2 and minor would be 7. The minor element is
928 missing for when major is less than 2.
932 The is the number of bytes that the Storable header occupies.
936 This is TRUE if the image store data in network order. This means
937 that it was created with nstore() or similar.
941 This is only present when C<netorder> is FALSE. It is the
942 $Config{byteorder} string of the perl that created this image. It is
943 a string like "1234" (32 bit little endian) or "87654321" (64 bit big
944 endian). This must match the current perl for the image to be
945 readable by Storable.
947 =item C<intsize>, C<longsize>, C<ptrsize>, C<nvsize>
949 These are only present when C<netorder> is FALSE. These are the sizes of
950 various C datatypes of the perl that created this image. These must
951 match the current perl for the image to be readable by Storable.
953 The C<nvsize> element is only present for file format v2.2 and
958 The name of the file.
962 =item $info = Storable::read_magic( $buffer )
964 =item $info = Storable::read_magic( $buffer, $must_be_file )
966 The $buffer should be a Storable image or the first few bytes of it.
967 If $buffer starts with a Storable header, then a hash describing the
968 image is returned, otherwise C<undef> is returned.
970 The hash has the same structure as the one returned by
971 Storable::file_magic(). The C<file> element is true if the image is a
974 If the $must_be_file argument is provided and is TRUE, then return
975 C<undef> unless the image looks like it belongs to a file dump.
977 The maximum size of a Storable header is currently 21 bytes. If the
978 provided $buffer is only the first part of a Storable image it should
979 at least be this long to ensure that read_magic() will recognize it as
986 Here are some code samples showing a possible usage of Storable:
988 use Storable qw(store retrieve freeze thaw dclone);
990 %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1);
992 store(\%color, 'mycolors') or die "Can't store %a in mycolors!\n";
994 $colref = retrieve('mycolors');
995 die "Unable to retrieve from mycolors!\n" unless defined $colref;
996 printf "Blue is still %lf\n", $colref->{'Blue'};
998 $colref2 = dclone(\%color);
1000 $str = freeze(\%color);
1001 printf "Serialization of %%color is %d bytes long.\n", length($str);
1002 $colref3 = thaw($str);
1004 which prints (on my machine):
1006 Blue is still 0.100000
1007 Serialization of %color is 102 bytes long.
1009 Serialization of CODE references and deserialization in a safe
1014 use Storable qw(freeze thaw);
1017 my $safe = new Safe;
1018 # because of opcodes used in "use strict":
1019 $safe->permit(qw(:default require));
1020 local $Storable::Deparse = 1;
1021 local $Storable::Eval = sub { $safe->reval($_[0]) };
1022 my $serialized = freeze(sub { 42 });
1023 my $code = thaw($serialized);
1028 =for example_testing
1029 is( $code->(), 42 );
1031 =head1 SECURITY WARNING
1033 B<Do not accept Storable documents from untrusted sources!>
1035 Some features of Storable can lead to security vulnerabilities if you
1036 accept Storable documents from untrusted sources. Most obviously, the
1037 optional (off by default) CODE reference serialization feature allows
1038 transfer of code to the deserializing process. Furthermore, any
1039 serialized object will cause Storable to helpfully load the module
1040 corresponding to the class of the object in the deserializing module.
1041 For manipulated module names, this can load almost arbitrary code.
1042 Finally, the deserialized object's destructors will be invoked when
1043 the objects get destroyed in the deserializing process. Maliciously
1044 crafted Storable documents may put such objects in the value of
1045 a hash key that is overridden by another key/value pair in the
1046 same hash, thus causing immediate destructor execution.
1048 In a future version of Storable, we intend to provide options to disable
1049 loading modules for classes and to disable deserializing objects
1050 altogether. I<Nonetheless, Storable deserializing documents from
1051 untrusted sources is expected to have other, yet undiscovered,
1052 security concerns such as allowing an attacker to cause the deserializer
1055 B<Therefore, let me repeat: Do not accept Storable documents from
1058 If your application requires accepting data from untrusted sources, you
1059 are best off with a less powerful and more-likely safe serialization format
1060 and implementation. If your data is sufficiently simple, JSON is a good
1061 choice and offers maximum interoperability.
1065 If you're using references as keys within your hash tables, you're bound
1066 to be disappointed when retrieving your data. Indeed, Perl stringifies
1067 references used as hash table keys. If you later wish to access the
1068 items via another reference stringification (i.e. using the same
1069 reference that was used for the key originally to record the value into
1070 the hash table), it will work because both references stringify to the
1073 It won't work across a sequence of C<store> and C<retrieve> operations,
1074 however, because the addresses in the retrieved objects, which are
1075 part of the stringified references, will probably differ from the
1076 original addresses. The topology of your structure is preserved,
1077 but not hidden semantics like those.
1079 On platforms where it matters, be sure to call C<binmode()> on the
1080 descriptors that you pass to Storable functions.
1082 Storing data canonically that contains large hashes can be
1083 significantly slower than storing the same data normally, as
1084 temporary arrays to hold the keys for each hash have to be allocated,
1085 populated, sorted and freed. Some tests have shown a halving of the
1086 speed of storing -- the exact penalty will depend on the complexity of
1087 your data. There is no slowdown on retrieval.
1091 You can't store GLOB, FORMLINE, REGEXP, etc.... If you can define semantics
1092 for those operations, feel free to enhance Storable so that it can
1095 The store functions will C<croak> if they run into such references
1096 unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that
1097 case, the fatal message is converted to a warning and some meaningless
1098 string is stored instead.
1100 Setting C<$Storable::canonical> may not yield frozen strings that
1101 compare equal due to possible stringification of numbers. When the
1102 string version of a scalar exists, it is the form stored; therefore,
1103 if you happen to use your numbers as strings between two freezing
1104 operations on the same data structures, you will get different
1107 When storing doubles in network order, their value is stored as text.
1108 However, you should also not expect non-numeric floating-point values
1109 such as infinity and "not a number" to pass successfully through a
1110 nstore()/retrieve() pair.
1112 As Storable neither knows nor cares about character sets (although it
1113 does know that characters may be more than eight bits wide), any difference
1114 in the interpretation of character codes between a host and a target
1115 system is your problem. In particular, if host and target use different
1116 code points to represent the characters used in the text representation
1117 of floating-point numbers, you will not be able be able to exchange
1118 floating-point data, even with nstore().
1120 C<Storable::drop_utf8> is a blunt tool. There is no facility either to
1121 return B<all> strings as utf8 sequences, or to attempt to convert utf8
1122 data back to 8 bit and C<croak()> if the conversion fails.
1124 Prior to Storable 2.01, no distinction was made between signed and
1125 unsigned integers on storing. By default Storable prefers to store a
1126 scalars string representation (if it has one) so this would only cause
1127 problems when storing large unsigned integers that had never been converted
1128 to string or floating point. In other words values that had been generated
1129 by integer operations such as logic ops and then not used in any string or
1130 arithmetic context before storing.
1132 =head2 64 bit data in perl 5.6.0 and 5.6.1
1134 This section only applies to you if you have existing data written out
1135 by Storable 2.02 or earlier on perl 5.6.0 or 5.6.1 on Unix or Linux which
1136 has been configured with 64 bit integer support (not the default)
1137 If you got a precompiled perl, rather than running Configure to build
1138 your own perl from source, then it almost certainly does not affect you,
1139 and you can stop reading now (unless you're curious). If you're using perl
1140 on Windows it does not affect you.
1142 Storable writes a file header which contains the sizes of various C
1143 language types for the C compiler that built Storable (when not writing in
1144 network order), and will refuse to load files written by a Storable not
1145 on the same (or compatible) architecture. This check and a check on
1146 machine byteorder is needed because the size of various fields in the file
1147 are given by the sizes of the C language types, and so files written on
1148 different architectures are incompatible. This is done for increased speed.
1149 (When writing in network order, all fields are written out as standard
1150 lengths, which allows full interworking, but takes longer to read and write)
1152 Perl 5.6.x introduced the ability to optional configure the perl interpreter
1153 to use C's C<long long> type to allow scalars to store 64 bit integers on 32
1154 bit systems. However, due to the way the Perl configuration system
1155 generated the C configuration files on non-Windows platforms, and the way
1156 Storable generates its header, nothing in the Storable file header reflected
1157 whether the perl writing was using 32 or 64 bit integers, despite the fact
1158 that Storable was storing some data differently in the file. Hence Storable
1159 running on perl with 64 bit integers will read the header from a file
1160 written by a 32 bit perl, not realise that the data is actually in a subtly
1161 incompatible format, and then go horribly wrong (possibly crashing) if it
1162 encountered a stored integer. This is a design failure.
1164 Storable has now been changed to write out and read in a file header with
1165 information about the size of integers. It's impossible to detect whether
1166 an old file being read in was written with 32 or 64 bit integers (they have
1167 the same header) so it's impossible to automatically switch to a correct
1168 backwards compatibility mode. Hence this Storable defaults to the new,
1171 What this means is that if you have data written by Storable 1.x running
1172 on perl 5.6.0 or 5.6.1 configured with 64 bit integers on Unix or Linux
1173 then by default this Storable will refuse to read it, giving the error
1174 I<Byte order is not compatible>. If you have such data then you
1175 should set C<$Storable::interwork_56_64bit> to a true value to make this
1176 Storable read and write files with the old header. You should also
1177 migrate your data, or any older perl you are communicating with, to this
1178 current version of Storable.
1180 If you don't have data written with specific configuration of perl described
1181 above, then you do not and should not do anything. Don't set the flag -
1182 not only will Storable on an identically configured perl refuse to load them,
1183 but Storable a differently configured perl will load them believing them
1184 to be correct for it, and then may well fail or crash part way through
1189 Thank you to (in chronological order):
1191 Jarkko Hietaniemi <jhi@iki.fi>
1192 Ulrich Pfeifer <pfeifer@charly.informatik.uni-dortmund.de>
1193 Benjamin A. Holzman <bholzman@earthlink.net>
1194 Andrew Ford <A.Ford@ford-mason.co.uk>
1195 Gisle Aas <gisle@aas.no>
1196 Jeff Gresham <gresham_jeffrey@jpmorgan.com>
1197 Murray Nesbitt <murray@activestate.com>
1198 Marc Lehmann <pcg@opengroup.org>
1199 Justin Banks <justinb@wamnet.com>
1200 Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!)
1201 Salvador Ortiz Garcia <sog@msg.com.mx>
1202 Dominic Dunlop <domo@computer.org>
1203 Erik Haugan <erik@solbors.no>
1204 Benjamin A. Holzman <ben.holzman@grantstreet.com>
1205 Reini Urban <rurban@cpanel.net>
1207 for their bug reports, suggestions and contributions.
1209 Benjamin Holzman contributed the tied variable support, Andrew Ford
1210 contributed the canonical order for hashes, and Gisle Aas fixed
1211 a few misunderstandings of mine regarding the perl internals,
1212 and optimized the emission of "tags" in the output streams by
1213 simply counting the objects instead of tagging them (leading to
1214 a binary incompatibility for the Storable image starting at version
1215 0.6--older images are, of course, still properly understood).
1216 Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading
1217 and references to tied items support. Benjamin Holzman added a performance
1218 improvement for overloaded classes; thanks to Grant Street Group for footing
1223 Storable was written by Raphael Manfredi
1224 F<E<lt>Raphael_Manfredi@pobox.comE<gt>>
1225 Maintenance is now done by the perl5-porters
1226 F<E<lt>perl5-porters@perl.orgE<gt>>
1228 Please e-mail us with problems, bug fixes, comments and complaints,
1229 although if you have compliments you should send them to Raphael.
1230 Please don't e-mail Raphael with problems, as he no longer works on
1231 Storable, and your message will be delayed while he forwards it to us.