diff options
Diffstat (limited to 'Master/tlpkg/tlperl.straw/lib/Storable.pm')
| -rwxr-xr-x | Master/tlpkg/tlperl.straw/lib/Storable.pm | 1188 |
1 files changed, 1188 insertions, 0 deletions
diff --git a/Master/tlpkg/tlperl.straw/lib/Storable.pm b/Master/tlpkg/tlperl.straw/lib/Storable.pm new file mode 100755 index 00000000000..2b1acb4ea92 --- /dev/null +++ b/Master/tlpkg/tlperl.straw/lib/Storable.pm @@ -0,0 +1,1188 @@ +# +# Copyright (c) 1995-2000, Raphael Manfredi +# +# You may redistribute only under the same terms as Perl 5, as specified +# in the README file that comes with the distribution. +# + +require DynaLoader; +require Exporter; +package Storable; @ISA = qw(Exporter DynaLoader); + +@EXPORT = qw(store retrieve); +@EXPORT_OK = qw( + nstore store_fd nstore_fd fd_retrieve + freeze nfreeze thaw + dclone + retrieve_fd + lock_store lock_nstore lock_retrieve + file_magic read_magic +); + +use AutoLoader; +use FileHandle; +use vars qw($canonical $forgive_me $VERSION); + +$VERSION = '2.21'; +*AUTOLOAD = \&AutoLoader::AUTOLOAD; # Grrr... + +# +# Use of Log::Agent is optional +# + +{ + local $SIG{__DIE__}; + eval "use Log::Agent"; +} + +require Carp; + +# +# They might miss :flock in Fcntl +# + +BEGIN { + if (eval { require Fcntl; 1 } && exists $Fcntl::EXPORT_TAGS{'flock'}) { + Fcntl->import(':flock'); + } else { + eval q{ + sub LOCK_SH () {1} + sub LOCK_EX () {2} + }; + } +} + +sub CLONE { + # clone context under threads + Storable::init_perinterp(); +} + +# Can't Autoload cleanly as this clashes 8.3 with &retrieve +sub retrieve_fd { &fd_retrieve } # Backward compatibility + +# By default restricted hashes are downgraded on earlier perls. + +$Storable::downgrade_restricted = 1; +$Storable::accept_future_minor = 1; +bootstrap Storable; +1; +__END__ +# +# Use of Log::Agent is optional. If it hasn't imported these subs then +# Autoloader will kindly supply our fallback implementation. +# + +sub logcroak { + Carp::croak(@_); +} + +sub logcarp { + Carp::carp(@_); +} + +# +# Determine whether locking is possible, but only when needed. +# + +sub CAN_FLOCK; my $CAN_FLOCK; sub CAN_FLOCK { + return $CAN_FLOCK if defined $CAN_FLOCK; + require Config; import Config; + return $CAN_FLOCK = + $Config{'d_flock'} || + $Config{'d_fcntl_can_lock'} || + $Config{'d_lockf'}; +} + +sub show_file_magic { + print <<EOM; +# +# To recognize the data files of the Perl module Storable, +# the following lines need to be added to the local magic(5) file, +# usually either /usr/share/misc/magic or /etc/magic. +# +0 string perl-store perl Storable(v0.6) data +>4 byte >0 (net-order %d) +>>4 byte &01 (network-ordered) +>>4 byte =3 (major 1) +>>4 byte =2 (major 1) + +0 string pst0 perl Storable(v0.7) data +>4 byte >0 +>>4 byte &01 (network-ordered) +>>4 byte =5 (major 2) +>>4 byte =4 (major 2) +>>5 byte >0 (minor %d) +EOM +} + +sub file_magic { + my $file = shift; + my $fh = new FileHandle; + open($fh, "<". $file) || die "Can't open '$file': $!"; + binmode($fh); + defined(sysread($fh, my $buf, 32)) || die "Can't read from '$file': $!"; + close($fh); + + $file = "./$file" unless $file; # ensure TRUE value + + return read_magic($buf, $file); +} + +sub read_magic { + my($buf, $file) = @_; + my %info; + + my $buflen = length($buf); + my $magic; + if ($buf =~ s/^(pst0|perl-store)//) { + $magic = $1; + $info{file} = $file || 1; + } + else { + return undef if $file; + $magic = ""; + } + + return undef unless length($buf); + + my $net_order; + if ($magic eq "perl-store" && ord(substr($buf, 0, 1)) > 1) { + $info{version} = -1; + $net_order = 0; + } + else { + $net_order = ord(substr($buf, 0, 1, "")); + my $major = $net_order >> 1; + return undef if $major > 4; # sanity (assuming we never go that high) + $info{major} = $major; + $net_order &= 0x01; + if ($major > 1) { + return undef unless length($buf); + my $minor = ord(substr($buf, 0, 1, "")); + $info{minor} = $minor; + $info{version} = "$major.$minor"; + $info{version_nv} = sprintf "%d.%03d", $major, $minor; + } + else { + $info{version} = $major; + } + } + $info{version_nv} ||= $info{version}; + $info{netorder} = $net_order; + + unless ($net_order) { + return undef unless length($buf); + my $len = ord(substr($buf, 0, 1, "")); + return undef unless length($buf) >= $len; + return undef unless $len == 4 || $len == 8; # sanity + $info{byteorder} = substr($buf, 0, $len, ""); + $info{intsize} = ord(substr($buf, 0, 1, "")); + $info{longsize} = ord(substr($buf, 0, 1, "")); + $info{ptrsize} = ord(substr($buf, 0, 1, "")); + if ($info{version_nv} >= 2.002) { + return undef unless length($buf); + $info{nvsize} = ord(substr($buf, 0, 1, "")); + } + } + $info{hdrsize} = $buflen - length($buf); + + return \%info; +} + +sub BIN_VERSION_NV { + sprintf "%d.%03d", BIN_MAJOR(), BIN_MINOR(); +} + +sub BIN_WRITE_VERSION_NV { + sprintf "%d.%03d", BIN_MAJOR(), BIN_WRITE_MINOR(); +} + +# +# store +# +# Store target object hierarchy, identified by a reference to its root. +# The stored object tree may later be retrieved to memory via retrieve. +# Returns undef if an I/O error occurred, in which case the file is +# removed. +# +sub store { + return _store(\&pstore, @_, 0); +} + +# +# nstore +# +# Same as store, but in network order. +# +sub nstore { + return _store(\&net_pstore, @_, 0); +} + +# +# lock_store +# +# Same as store, but flock the file first (advisory locking). +# +sub lock_store { + return _store(\&pstore, @_, 1); +} + +# +# lock_nstore +# +# Same as nstore, but flock the file first (advisory locking). +# +sub lock_nstore { + return _store(\&net_pstore, @_, 1); +} + +# Internal store to file routine +sub _store { + my $xsptr = shift; + my $self = shift; + my ($file, $use_locking) = @_; + logcroak "not a reference" unless ref($self); + logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist + local *FILE; + if ($use_locking) { + open(FILE, ">>$file") || logcroak "can't write into $file: $!"; + unless (&CAN_FLOCK) { + logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; + return undef; + } + flock(FILE, LOCK_EX) || + logcroak "can't get exclusive lock on $file: $!"; + truncate FILE, 0; + # Unlocking will happen when FILE is closed + } else { + open(FILE, ">$file") || logcroak "can't create $file: $!"; + } + binmode FILE; # Archaic systems... + my $da = $@; # Don't mess if called from exception handler + my $ret; + # Call C routine nstore or pstore, depending on network order + eval { $ret = &$xsptr(*FILE, $self) }; + close(FILE) or $ret = undef; + unlink($file) or warn "Can't unlink $file: $!\n" if $@ || !defined $ret; + logcroak $@ if $@ =~ s/\.?\n$/,/; + $@ = $da; + return $ret ? $ret : undef; +} + +# +# store_fd +# +# Same as store, but perform on an already opened file descriptor instead. +# Returns undef if an I/O error occurred. +# +sub store_fd { + return _store_fd(\&pstore, @_); +} + +# +# nstore_fd +# +# Same as store_fd, but in network order. +# +sub nstore_fd { + my ($self, $file) = @_; + return _store_fd(\&net_pstore, @_); +} + +# Internal store routine on opened file descriptor +sub _store_fd { + my $xsptr = shift; + my $self = shift; + my ($file) = @_; + logcroak "not a reference" unless ref($self); + logcroak "too many arguments" unless @_ == 1; # No @foo in arglist + my $fd = fileno($file); + logcroak "not a valid file descriptor" unless defined $fd; + my $da = $@; # Don't mess if called from exception handler + my $ret; + # Call C routine nstore or pstore, depending on network order + eval { $ret = &$xsptr($file, $self) }; + logcroak $@ if $@ =~ s/\.?\n$/,/; + local $\; print $file ''; # Autoflush the file if wanted + $@ = $da; + return $ret ? $ret : undef; +} + +# +# freeze +# +# Store oject and its hierarchy in memory and return a scalar +# containing the result. +# +sub freeze { + _freeze(\&mstore, @_); +} + +# +# nfreeze +# +# Same as freeze but in network order. +# +sub nfreeze { + _freeze(\&net_mstore, @_); +} + +# Internal freeze routine +sub _freeze { + my $xsptr = shift; + my $self = shift; + logcroak "not a reference" unless ref($self); + logcroak "too many arguments" unless @_ == 0; # No @foo in arglist + my $da = $@; # Don't mess if called from exception handler + my $ret; + # Call C routine mstore or net_mstore, depending on network order + eval { $ret = &$xsptr($self) }; + logcroak $@ if $@ =~ s/\.?\n$/,/; + $@ = $da; + return $ret ? $ret : undef; +} + +# +# retrieve +# +# Retrieve object hierarchy from disk, returning a reference to the root +# object of that tree. +# +sub retrieve { + _retrieve($_[0], 0); +} + +# +# lock_retrieve +# +# Same as retrieve, but with advisory locking. +# +sub lock_retrieve { + _retrieve($_[0], 1); +} + +# Internal retrieve routine +sub _retrieve { + my ($file, $use_locking) = @_; + local *FILE; + open(FILE, $file) || logcroak "can't open $file: $!"; + binmode FILE; # Archaic systems... + my $self; + my $da = $@; # Could be from exception handler + if ($use_locking) { + unless (&CAN_FLOCK) { + logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; + return undef; + } + flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!"; + # Unlocking will happen when FILE is closed + } + eval { $self = pretrieve(*FILE) }; # Call C routine + close(FILE); + logcroak $@ if $@ =~ s/\.?\n$/,/; + $@ = $da; + return $self; +} + +# +# fd_retrieve +# +# Same as retrieve, but perform from an already opened file descriptor instead. +# +sub fd_retrieve { + my ($file) = @_; + my $fd = fileno($file); + logcroak "not a valid file descriptor" unless defined $fd; + my $self; + my $da = $@; # Could be from exception handler + eval { $self = pretrieve($file) }; # Call C routine + logcroak $@ if $@ =~ s/\.?\n$/,/; + $@ = $da; + return $self; +} + +# +# thaw +# +# Recreate objects in memory from an existing frozen image created +# by freeze. If the frozen image passed is undef, return undef. +# +sub thaw { + my ($frozen) = @_; + return undef unless defined $frozen; + my $self; + my $da = $@; # Could be from exception handler + eval { $self = mretrieve($frozen) }; # Call C routine + logcroak $@ if $@ =~ s/\.?\n$/,/; + $@ = $da; + return $self; +} + +1; +__END__ + +=head1 NAME + +Storable - persistence for Perl data structures + +=head1 SYNOPSIS + + use Storable; + store \%table, 'file'; + $hashref = retrieve('file'); + + use Storable qw(nstore store_fd nstore_fd freeze thaw dclone); + + # Network order + nstore \%table, 'file'; + $hashref = retrieve('file'); # There is NO nretrieve() + + # Storing to and retrieving from an already opened file + store_fd \@array, \*STDOUT; + nstore_fd \%table, \*STDOUT; + $aryref = fd_retrieve(\*SOCKET); + $hashref = fd_retrieve(\*SOCKET); + + # Serializing to memory + $serialized = freeze \%table; + %table_clone = %{ thaw($serialized) }; + + # Deep (recursive) cloning + $cloneref = dclone($ref); + + # Advisory locking + use Storable qw(lock_store lock_nstore lock_retrieve) + lock_store \%table, 'file'; + lock_nstore \%table, 'file'; + $hashref = lock_retrieve('file'); + +=head1 DESCRIPTION + +The Storable package brings persistence to your Perl data structures +containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be +conveniently stored to disk and retrieved at a later time. + +It can be used in the regular procedural way by calling C<store> with +a reference to the object to be stored, along with the file name where +the image should be written. + +The routine returns C<undef> for I/O problems or other internal error, +a true value otherwise. Serious errors are propagated as a C<die> exception. + +To retrieve data stored to disk, use C<retrieve> with a file name. +The objects stored into that file are recreated into memory for you, +and a I<reference> to the root object is returned. In case an I/O error +occurs while reading, C<undef> is returned instead. Other serious +errors are propagated via C<die>. + +Since storage is performed recursively, you might want to stuff references +to objects that share a lot of common data into a single array or hash +table, and then store that object. That way, when you retrieve back the +whole thing, the objects will continue to share what they originally shared. + +At the cost of a slight header overhead, you may store to an already +opened file descriptor using the C<store_fd> routine, and retrieve +from a file via C<fd_retrieve>. Those names aren't imported by default, +so you will have to do that explicitly if you need those routines. +The file descriptor you supply must be already opened, for read +if you're going to retrieve and for write if you wish to store. + + store_fd(\%table, *STDOUT) || die "can't store to stdout\n"; + $hashref = fd_retrieve(*STDIN); + +You can also store data in network order to allow easy sharing across +multiple platforms, or when storing on a socket known to be remotely +connected. The routines to call have an initial C<n> prefix for I<network>, +as in C<nstore> and C<nstore_fd>. At retrieval time, your data will be +correctly restored so you don't have to know whether you're restoring +from native or network ordered data. Double values are stored stringified +to ensure portability as well, at the slight risk of loosing some precision +in the last decimals. + +When using C<fd_retrieve>, objects are retrieved in sequence, one +object (i.e. one recursive tree) per associated C<store_fd>. + +If you're more from the object-oriented camp, you can inherit from +Storable and directly store your objects by invoking C<store> as +a method. The fact that the root of the to-be-stored tree is a +blessed reference (i.e. an object) is special-cased so that the +retrieve does not provide a reference to that object but rather the +blessed object reference itself. (Otherwise, you'd get a reference +to that blessed object). + +=head1 MEMORY STORE + +The Storable engine can also store data into a Perl scalar instead, to +later retrieve them. This is mainly used to freeze a complex structure in +some safe compact memory place (where it can possibly be sent to another +process via some IPC, since freezing the structure also serializes it in +effect). Later on, and maybe somewhere else, you can thaw the Perl scalar +out and recreate the original complex structure in memory. + +Surprisingly, the routines to be called are named C<freeze> and C<thaw>. +If you wish to send out the frozen scalar to another machine, use +C<nfreeze> instead to get a portable image. + +Note that freezing an object structure and immediately thawing it +actually achieves a deep cloning of that structure: + + dclone(.) = thaw(freeze(.)) + +Storable provides you with a C<dclone> interface which does not create +that intermediary scalar but instead freezes the structure in some +internal memory space and then immediately thaws it out. + +=head1 ADVISORY LOCKING + +The C<lock_store> and C<lock_nstore> routine are equivalent to +C<store> and C<nstore>, except that they get an exclusive lock on +the file before writing. Likewise, C<lock_retrieve> does the same +as C<retrieve>, but also gets a shared lock on the file before reading. + +As with any advisory locking scheme, the protection only works if you +systematically use C<lock_store> and C<lock_retrieve>. If one side of +your application uses C<store> whilst the other uses C<lock_retrieve>, +you will get no protection at all. + +The internal advisory locking is implemented using Perl's flock() +routine. If your system does not support any form of flock(), or if +you share your files across NFS, you might wish to use other forms +of locking by using modules such as LockFile::Simple which lock a +file using a filesystem entry, instead of locking the file descriptor. + +=head1 SPEED + +The heart of Storable is written in C for decent speed. Extra low-level +optimizations have been made when manipulating perl internals, to +sacrifice encapsulation for the benefit of greater speed. + +=head1 CANONICAL REPRESENTATION + +Normally, Storable stores elements of hashes in the order they are +stored internally by Perl, i.e. pseudo-randomly. If you set +C<$Storable::canonical> to some C<TRUE> value, Storable will store +hashes with the elements sorted by their key. This allows you to +compare data structures by comparing their frozen representations (or +even the compressed frozen representations), which can be useful for +creating lookup tables for complicated queries. + +Canonical order does not imply network order; those are two orthogonal +settings. + +=head1 CODE REFERENCES + +Since Storable version 2.05, CODE references may be serialized with +the help of L<B::Deparse>. To enable this feature, set +C<$Storable::Deparse> to a true value. To enable deserialization, +C<$Storable::Eval> should be set to a true value. Be aware that +deserialization is done through C<eval>, which is dangerous if the +Storable file contains malicious data. You can set C<$Storable::Eval> +to a subroutine reference which would be used instead of C<eval>. See +below for an example using a L<Safe> compartment for deserialization +of CODE references. + +If C<$Storable::Deparse> and/or C<$Storable::Eval> are set to false +values, then the value of C<$Storable::forgive_me> (see below) is +respected while serializing and deserializing. + +=head1 FORWARD COMPATIBILITY + +This release of Storable can be used on a newer version of Perl to +serialize data which is not supported by earlier Perls. By default, +Storable will attempt to do the right thing, by C<croak()>ing if it +encounters data that it cannot deserialize. However, the defaults +can be changed as follows: + +=over 4 + +=item utf8 data + +Perl 5.6 added support for Unicode characters with code points > 255, +and Perl 5.8 has full support for Unicode characters in hash keys. +Perl internally encodes strings with these characters using utf8, and +Storable serializes them as utf8. By default, if an older version of +Perl encounters a utf8 value it cannot represent, it will C<croak()>. +To change this behaviour so that Storable deserializes utf8 encoded +values as the string of bytes (effectively dropping the I<is_utf8> flag) +set C<$Storable::drop_utf8> to some C<TRUE> value. This is a form of +data loss, because with C<$drop_utf8> true, it becomes impossible to tell +whether the original data was the Unicode string, or a series of bytes +that happen to be valid utf8. + +=item restricted hashes + +Perl 5.8 adds support for restricted hashes, which have keys +restricted to a given set, and can have values locked to be read only. +By default, when Storable encounters a restricted hash on a perl +that doesn't support them, it will deserialize it as a normal hash, +silently discarding any placeholder keys and leaving the keys and +all values unlocked. To make Storable C<croak()> instead, set +C<$Storable::downgrade_restricted> to a C<FALSE> value. To restore +the default set it back to some C<TRUE> value. + +=item files from future versions of Storable + +Earlier versions of Storable would immediately croak if they encountered +a file with a higher internal version number than the reading Storable +knew about. Internal version numbers are increased each time new data +types (such as restricted hashes) are added to the vocabulary of the file +format. This meant that a newer Storable module had no way of writing a +file readable by an older Storable, even if the writer didn't store newer +data types. + +This version of Storable will defer croaking until it encounters a data +type in the file that it does not recognize. This means that it will +continue to read files generated by newer Storable modules which are careful +in what they write out, making it easier to upgrade Storable modules in a +mixed environment. + +The old behaviour of immediate croaking can be re-instated by setting +C<$Storable::accept_future_minor> to some C<FALSE> value. + +=back + +All these variables have no effect on a newer Perl which supports the +relevant feature. + +=head1 ERROR REPORTING + +Storable uses the "exception" paradigm, in that it does not try to workaround +failures: if something bad happens, an exception is generated from the +caller's perspective (see L<Carp> and C<croak()>). Use eval {} to trap +those exceptions. + +When Storable croaks, it tries to report the error via the C<logcroak()> +routine from the C<Log::Agent> package, if it is available. + +Normal errors are reported by having store() or retrieve() return C<undef>. +Such errors are usually I/O errors (or truncated stream errors at retrieval). + +=head1 WIZARDS ONLY + +=head2 Hooks + +Any class may define hooks that will be called during the serialization +and deserialization process on objects that are instances of that class. +Those hooks can redefine the way serialization is performed (and therefore, +how the symmetrical deserialization should be conducted). + +Since we said earlier: + + dclone(.) = thaw(freeze(.)) + +everything we say about hooks should also hold for deep cloning. However, +hooks get to know whether the operation is a mere serialization, or a cloning. + +Therefore, when serializing hooks are involved, + + dclone(.) <> thaw(freeze(.)) + +Well, you could keep them in sync, but there's no guarantee it will always +hold on classes somebody else wrote. Besides, there is little to gain in +doing so: a serializing hook could keep only one attribute of an object, +which is probably not what should happen during a deep cloning of that +same object. + +Here is the hooking interface: + +=over 4 + +=item C<STORABLE_freeze> I<obj>, I<cloning> + +The serializing hook, called on the object during serialization. It can be +inherited, or defined in the class itself, like any other method. + +Arguments: I<obj> is the object to serialize, I<cloning> is a flag indicating +whether we're in a dclone() or a regular serialization via store() or freeze(). + +Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized +is the serialized form to be used, and the optional $ref1, $ref2, etc... are +extra references that you wish to let the Storable engine serialize. + +At deserialization time, you will be given back the same LIST, but all the +extra references will be pointing into the deserialized structure. + +The B<first time> the hook is hit in a serialization flow, you may have it +return an empty list. That will signal the Storable engine to further +discard that hook for this class and to therefore revert to the default +serialization of the underlying Perl data. The hook will again be normally +processed in the next serialization. + +Unless you know better, serializing hook should always say: + + sub STORABLE_freeze { + my ($self, $cloning) = @_; + return if $cloning; # Regular default serialization + .... + } + +in order to keep reasonable dclone() semantics. + +=item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ... + +The deserializing hook called on the object during deserialization. +But wait: if we're deserializing, there's no object yet... right? + +Wrong: the Storable engine creates an empty one for you. If you know Eiffel, +you can view C<STORABLE_thaw> as an alternate creation routine. + +This means the hook can be inherited like any other method, and that +I<obj> is your blessed reference for this particular instance. + +The other arguments should look familiar if you know C<STORABLE_freeze>: +I<cloning> is true when we're part of a deep clone operation, I<serialized> +is the serialized string you returned to the engine in C<STORABLE_freeze>, +and there may be an optional list of references, in the same order you gave +them at serialization time, pointing to the deserialized objects (which +have been processed courtesy of the Storable engine). + +When the Storable engine does not find any C<STORABLE_thaw> hook routine, +it tries to load the class by requiring the package dynamically (using +the blessed package name), and then re-attempts the lookup. If at that +time the hook cannot be located, the engine croaks. Note that this mechanism +will fail if you define several classes in the same file, but L<perlmod> +warned you. + +It is up to you to use this information to populate I<obj> the way you want. + +Returned value: none. + +=item C<STORABLE_attach> I<class>, I<cloning>, I<serialized> + +While C<STORABLE_freeze> and C<STORABLE_thaw> are useful for classes where +each instance is independent, this mechanism has difficulty (or is +incompatible) with objects that exist as common process-level or +system-level resources, such as singleton objects, database pools, caches +or memoized objects. + +The alternative C<STORABLE_attach> method provides a solution for these +shared objects. Instead of C<STORABLE_freeze> --E<gt> C<STORABLE_thaw>, +you implement C<STORABLE_freeze> --E<gt> C<STORABLE_attach> instead. + +Arguments: I<class> is the class we are attaching to, I<cloning> is a flag +indicating whether we're in a dclone() or a regular de-serialization via +thaw(), and I<serialized> is the stored string for the resource object. + +Because these resource objects are considered to be owned by the entire +process/system, and not the "property" of whatever is being serialized, +no references underneath the object should be included in the serialized +string. Thus, in any class that implements C<STORABLE_attach>, the +C<STORABLE_freeze> method cannot return any references, and C<Storable> +will throw an error if C<STORABLE_freeze> tries to return references. + +All information required to "attach" back to the shared resource object +B<must> be contained B<only> in the C<STORABLE_freeze> return string. +Otherwise, C<STORABLE_freeze> behaves as normal for C<STORABLE_attach> +classes. + +Because C<STORABLE_attach> is passed the class (rather than an object), +it also returns the object directly, rather than modifying the passed +object. + +Returned value: object of type C<class> + +=back + +=head2 Predicates + +Predicates are not exportable. They must be called by explicitly prefixing +them with the Storable package name. + +=over 4 + +=item C<Storable::last_op_in_netorder> + +The C<Storable::last_op_in_netorder()> predicate will tell you whether +network order was used in the last store or retrieve operation. If you +don't know how to use this, just forget about it. + +=item C<Storable::is_storing> + +Returns true if within a store operation (via STORABLE_freeze hook). + +=item C<Storable::is_retrieving> + +Returns true if within a retrieve operation (via STORABLE_thaw hook). + +=back + +=head2 Recursion + +With hooks comes the ability to recurse back to the Storable engine. +Indeed, hooks are regular Perl code, and Storable is convenient when +it comes to serializing and deserializing things, so why not use it +to handle the serialization string? + +There are a few things you need to know, however: + +=over 4 + +=item * + +You can create endless loops if the things you serialize via freeze() +(for instance) point back to the object we're trying to serialize in +the hook. + +=item * + +Shared references among objects will not stay shared: if we're serializing +the list of object [A, C] where both object A and C refer to the SAME object +B, and if there is a serializing hook in A that says freeze(B), then when +deserializing, we'll get [A', C'] where A' refers to B', but C' refers to D, +a deep clone of B'. The topology was not preserved. + +=back + +That's why C<STORABLE_freeze> lets you provide a list of references +to serialize. The engine guarantees that those will be serialized in the +same context as the other objects, and therefore that shared objects will +stay shared. + +In the above [A, C] example, the C<STORABLE_freeze> hook could return: + + ("something", $self->{B}) + +and the B part would be serialized by the engine. In C<STORABLE_thaw>, you +would get back the reference to the B' object, deserialized for you. + +Therefore, recursion should normally be avoided, but is nonetheless supported. + +=head2 Deep Cloning + +There is a Clone module available on CPAN which implements deep cloning +natively, i.e. without freezing to memory and thawing the result. It is +aimed to replace Storable's dclone() some day. However, it does not currently +support Storable hooks to redefine the way deep cloning is performed. + +=head1 Storable magic + +Yes, there's a lot of that :-) But more precisely, in UNIX systems +there's a utility called C<file>, which recognizes data files based on +their contents (usually their first few bytes). For this to work, +a certain file called F<magic> needs to taught about the I<signature> +of the data. Where that configuration file lives depends on the UNIX +flavour; often it's something like F</usr/share/misc/magic> or +F</etc/magic>. Your system administrator needs to do the updating of +the F<magic> file. The necessary signature information is output to +STDOUT by invoking Storable::show_file_magic(). Note that the GNU +implementation of the C<file> utility, version 3.38 or later, +is expected to contain support for recognising Storable files +out-of-the-box, in addition to other kinds of Perl files. + +You can also use the following functions to extract the file header +information from Storable images: + +=over + +=item $info = Storable::file_magic( $filename ) + +If the given file is a Storable image return a hash describing it. If +the file is readable, but not a Storable image return C<undef>. If +the file does not exist or is unreadable then croak. + +The hash returned has the following elements: + +=over + +=item C<version> + +This returns the file format version. It is a string like "2.7". + +Note that this version number is not the same as the version number of +the Storable module itself. For instance Storable v0.7 create files +in format v2.0 and Storable v2.15 create files in format v2.7. The +file format version number only increment when additional features +that would confuse older versions of the module are added. + +Files older than v2.0 will have the one of the version numbers "-1", +"0" or "1". No minor number was used at that time. + +=item C<version_nv> + +This returns the file format version as number. It is a string like +"2.007". This value is suitable for numeric comparisons. + +The constant function C<Storable::BIN_VERSION_NV> returns a comparable +number that represent the highest file version number that this +version of Storable fully support (but see discussion of +C<$Storable::accept_future_minor> above). The constant +C<Storable::BIN_WRITE_VERSION_NV> function returns what file version +is written and might be less than C<Storable::BIN_VERSION_NV> in some +configuations. + +=item C<major>, C<minor> + +This also returns the file format version. If the version is "2.7" +then major would be 2 and minor would be 7. The minor element is +missing for when major is less than 2. + +=item C<hdrsize> + +The is the number of bytes that the Storable header occupies. + +=item C<netorder> + +This is TRUE if the image store data in network order. This means +that it was created with nstore() or similar. + +=item C<byteorder> + +This is only present when C<netorder> is FALSE. It is the +$Config{byteorder} string of the perl that created this image. It is +a string like "1234" (32 bit little endian) or "87654321" (64 bit big +endian). This must match the current perl for the image to be +readable by Storable. + +=item C<intsize>, C<longsize>, C<ptrsize>, C<nvsize> + +These are only present when C<netorder> is FALSE. These are the sizes of +various C datatypes of the perl that created this image. These must +match the current perl for the image to be readable by Storable. + +The C<nvsize> element is only present for file format v2.2 and +higher. + +=item C<file> + +The name of the file. + +=back + +=item $info = Storable::read_magic( $buffer ) + +=item $info = Storable::read_magic( $buffer, $must_be_file ) + +The $buffer should be a Storable image or the first few bytes of it. +If $buffer starts with a Storable header, then a hash describing the +image is returned, otherwise C<undef> is returned. + +The hash has the same structure as the one returned by +Storable::file_magic(). The C<file> element is true if the image is a +file image. + +If the $must_be_file argument is provided and is TRUE, then return +C<undef> unless the image looks like it belongs to a file dump. + +The maximum size of a Storable header is currently 21 bytes. If the +provided $buffer is only the first part of a Storable image it should +at least be this long to ensure that read_magic() will recognize it as +such. + +=back + +=head1 EXAMPLES + +Here are some code samples showing a possible usage of Storable: + + use Storable qw(store retrieve freeze thaw dclone); + + %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1); + + store(\%color, 'mycolors') or die "Can't store %a in mycolors!\n"; + + $colref = retrieve('mycolors'); + die "Unable to retrieve from mycolors!\n" unless defined $colref; + printf "Blue is still %lf\n", $colref->{'Blue'}; + + $colref2 = dclone(\%color); + + $str = freeze(\%color); + printf "Serialization of %%color is %d bytes long.\n", length($str); + $colref3 = thaw($str); + +which prints (on my machine): + + Blue is still 0.100000 + Serialization of %color is 102 bytes long. + +Serialization of CODE references and deserialization in a safe +compartment: + +=for example begin + + use Storable qw(freeze thaw); + use Safe; + use strict; + my $safe = new Safe; + # because of opcodes used in "use strict": + $safe->permit(qw(:default require)); + local $Storable::Deparse = 1; + local $Storable::Eval = sub { $safe->reval($_[0]) }; + my $serialized = freeze(sub { 42 }); + my $code = thaw($serialized); + $code->() == 42; + +=for example end + +=for example_testing + is( $code->(), 42 ); + +=head1 WARNING + +If you're using references as keys within your hash tables, you're bound +to be disappointed when retrieving your data. Indeed, Perl stringifies +references used as hash table keys. If you later wish to access the +items via another reference stringification (i.e. using the same +reference that was used for the key originally to record the value into +the hash table), it will work because both references stringify to the +same string. + +It won't work across a sequence of C<store> and C<retrieve> operations, +however, because the addresses in the retrieved objects, which are +part of the stringified references, will probably differ from the +original addresses. The topology of your structure is preserved, +but not hidden semantics like those. + +On platforms where it matters, be sure to call C<binmode()> on the +descriptors that you pass to Storable functions. + +Storing data canonically that contains large hashes can be +significantly slower than storing the same data normally, as +temporary arrays to hold the keys for each hash have to be allocated, +populated, sorted and freed. Some tests have shown a halving of the +speed of storing -- the exact penalty will depend on the complexity of +your data. There is no slowdown on retrieval. + +=head1 BUGS + +You can't store GLOB, FORMLINE, etc.... If you can define semantics +for those operations, feel free to enhance Storable so that it can +deal with them. + +The store functions will C<croak> if they run into such references +unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that +case, the fatal message is turned in a warning and some +meaningless string is stored instead. + +Setting C<$Storable::canonical> may not yield frozen strings that +compare equal due to possible stringification of numbers. When the +string version of a scalar exists, it is the form stored; therefore, +if you happen to use your numbers as strings between two freezing +operations on the same data structures, you will get different +results. + +When storing doubles in network order, their value is stored as text. +However, you should also not expect non-numeric floating-point values +such as infinity and "not a number" to pass successfully through a +nstore()/retrieve() pair. + +As Storable neither knows nor cares about character sets (although it +does know that characters may be more than eight bits wide), any difference +in the interpretation of character codes between a host and a target +system is your problem. In particular, if host and target use different +code points to represent the characters used in the text representation +of floating-point numbers, you will not be able be able to exchange +floating-point data, even with nstore(). + +C<Storable::drop_utf8> is a blunt tool. There is no facility either to +return B<all> strings as utf8 sequences, or to attempt to convert utf8 +data back to 8 bit and C<croak()> if the conversion fails. + +Prior to Storable 2.01, no distinction was made between signed and +unsigned integers on storing. By default Storable prefers to store a +scalars string representation (if it has one) so this would only cause +problems when storing large unsigned integers that had never been converted +to string or floating point. In other words values that had been generated +by integer operations such as logic ops and then not used in any string or +arithmetic context before storing. + +=head2 64 bit data in perl 5.6.0 and 5.6.1 + +This section only applies to you if you have existing data written out +by Storable 2.02 or earlier on perl 5.6.0 or 5.6.1 on Unix or Linux which +has been configured with 64 bit integer support (not the default) +If you got a precompiled perl, rather than running Configure to build +your own perl from source, then it almost certainly does not affect you, +and you can stop reading now (unless you're curious). If you're using perl +on Windows it does not affect you. + +Storable writes a file header which contains the sizes of various C +language types for the C compiler that built Storable (when not writing in +network order), and will refuse to load files written by a Storable not +on the same (or compatible) architecture. This check and a check on +machine byteorder is needed because the size of various fields in the file +are given by the sizes of the C language types, and so files written on +different architectures are incompatible. This is done for increased speed. +(When writing in network order, all fields are written out as standard +lengths, which allows full interworking, but takes longer to read and write) + +Perl 5.6.x introduced the ability to optional configure the perl interpreter +to use C's C<long long> type to allow scalars to store 64 bit integers on 32 +bit systems. However, due to the way the Perl configuration system +generated the C configuration files on non-Windows platforms, and the way +Storable generates its header, nothing in the Storable file header reflected +whether the perl writing was using 32 or 64 bit integers, despite the fact +that Storable was storing some data differently in the file. Hence Storable +running on perl with 64 bit integers will read the header from a file +written by a 32 bit perl, not realise that the data is actually in a subtly +incompatible format, and then go horribly wrong (possibly crashing) if it +encountered a stored integer. This is a design failure. + +Storable has now been changed to write out and read in a file header with +information about the size of integers. It's impossible to detect whether +an old file being read in was written with 32 or 64 bit integers (they have +the same header) so it's impossible to automatically switch to a correct +backwards compatibility mode. Hence this Storable defaults to the new, +correct behaviour. + +What this means is that if you have data written by Storable 1.x running +on perl 5.6.0 or 5.6.1 configured with 64 bit integers on Unix or Linux +then by default this Storable will refuse to read it, giving the error +I<Byte order is not compatible>. If you have such data then you you +should set C<$Storable::interwork_56_64bit> to a true value to make this +Storable read and write files with the old header. You should also +migrate your data, or any older perl you are communicating with, to this +current version of Storable. + +If you don't have data written with specific configuration of perl described +above, then you do not and should not do anything. Don't set the flag - +not only will Storable on an identically configured perl refuse to load them, +but Storable a differently configured perl will load them believing them +to be correct for it, and then may well fail or crash part way through +reading them. + +=head1 CREDITS + +Thank you to (in chronological order): + + Jarkko Hietaniemi <jhi@iki.fi> + Ulrich Pfeifer <pfeifer@charly.informatik.uni-dortmund.de> + Benjamin A. Holzman <bah@ecnvantage.com> + Andrew Ford <A.Ford@ford-mason.co.uk> + Gisle Aas <gisle@aas.no> + Jeff Gresham <gresham_jeffrey@jpmorgan.com> + Murray Nesbitt <murray@activestate.com> + Marc Lehmann <pcg@opengroup.org> + Justin Banks <justinb@wamnet.com> + Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!) + Salvador Ortiz Garcia <sog@msg.com.mx> + Dominic Dunlop <domo@computer.org> + Erik Haugan <erik@solbors.no> + +for their bug reports, suggestions and contributions. + +Benjamin Holzman contributed the tied variable support, Andrew Ford +contributed the canonical order for hashes, and Gisle Aas fixed +a few misunderstandings of mine regarding the perl internals, +and optimized the emission of "tags" in the output streams by +simply counting the objects instead of tagging them (leading to +a binary incompatibility for the Storable image starting at version +0.6--older images are, of course, still properly understood). +Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading +and references to tied items support. + +=head1 AUTHOR + +Storable was written by Raphael Manfredi F<E<lt>Raphael_Manfredi@pobox.comE<gt>> +Maintenance is now done by the perl5-porters F<E<lt>perl5-porters@perl.orgE<gt>> + +Please e-mail us with problems, bug fixes, comments and complaints, +although if you have compliments you should send them to Raphael. +Please don't e-mail Raphael with problems, as he no longer works on +Storable, and your message will be delayed while he forwards it to us. + +=head1 SEE ALSO + +L<Clone>. + +=cut |