FreezeThaw - converting Perl structures to strings and back.
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NAME
FreezeThaw - converting Perl structures to strings and back.
SYNOPSIS
use FreezeThaw qw(freeze thaw cmpStr safeFreeze cmpStrHard);
$string = freeze $data1, $data2, $data3;
...
($olddata1, $olddata2, $olddata3) = thaw $string;
if (cmpStr($olddata2,$data2) == 0) {print "OK!"}
DESCRIPTION
Converts data to/from stringified form, appropriate for
saving-to/reading-from permanent storage.
Deals with objects, circular lists, repeated appearence of the same
refence. Does not deal with overloaded stringify operator yet.
EXPORT
- Default
-
None.
- Exportable
-
freeze thaw cmpStr cmpStrHard safeFreeze.
User API
cmpStr-
analogue of cmp for data. Takes two arguments and compares them as
separate entities.
cmpStrHard-
analogue of cmp for data. Takes two arguments and compares them
considered as a group.
freeze-
returns a string that encupsulates its arguments (considered as a
group). thawing this string leads to a fatal error if arguments to
freeze contained references to GLOBs and CODEs.
safeFreeze-
returns a string that encupsulates its arguments (considered as a
group). The result is thawable in the same process. thawing the
result in a different process should result in a fatal error if
arguments to safeFreeze contained references to GLOBs and
CODEs.
thaw-
takes one string argument and returns an array. The elements of the
array are "equivalent" to arguments of the freeze command that
created the string. Can result in a fatal error (see above).
Developer API
FreezeThaw freezes and thaws data blessed in some package by
calling methods Freeze and Thaw in the package. The fallback
methods are provided by the FreezeThaw itself. The fallback
Freeze freezes the "content" of blessed object (from Perl point of
view). The fallback Thaw blesses the thawed data back into the package.
So the package needs to define its own methods only if the fallback
methods will fail (for example, for a lot of data the "content" of an
object is an address of some C data). The methods are called like
$newcooky = $obj->Freeze($cooky);
$obj = Package->Thaw($content,$cooky);
To save and restore the data the following method are applicable:
$cooky->FreezeScalar($data,$ignorePackage,$noduplicate);
during Freeze()ing, and
$data = $cooky->ThawScalar;
Two optional arguments $ignorePackage and $noduplicate regulate
whether the freezing should not call the methods even if $data is a
reference to a blessed object, and whether the data should not be
marked as seen already even if it was seen before. The default methods
sub UNIVERSAL::Freeze {
my ($obj, $cooky) = (shift, shift);
$cooky->FreezeScalar($obj,1,1);
}
sub UNIVERSAL::Thaw {
my ($package, $cooky) = (shift, shift);
my $obj = $cooky->ThawScalar;
bless $obj, $package;
}
call the FreezeScalar method of the $cooky since the freezing
engine will see the data the second time during this call. Indeed, it
is the freezing engine who calls UNIVERSAL::Freeze(), and it calls it
because it needs to freeze $obj. The above call to
$cooky->FreezeScalar() handles the same data back to engine, but
because flags are different, the code does not cycle.
Freezing and thawing $cooky also allows the following additional methods:
$cooky->isSafe;
to find out whether the current freeze was initiated by freeze or
safeFreeze command. Analogous method for thaw $cooky returns
whether the current thaw operation is considered safe (i.e., either
does not contain cached elsewhere data, or comes from the same
application). You can use
$cooky->makeSafe;
to prohibit cached data for the duration of the rest of freezing or
thawing of current object.
Two methods
$value = $cooky->repeatedOK;
$cooky->noRepeated; # Now repeated are prohibited
allow to find out/change the current setting for allowing repeated
references.
If you want to flush the cache of saved objects you can use
FreezeThaw->flushCache;
this can invalidate some frozen string, so that thawing them will
result in fatal error.
Instantiating
Sometimes, when an object from a package is recreated in presense of
repeated references, it is not safe to recreate the internal structure
of an object in one step. In such a situation recreation of an object
is carried out in two steps: in the first the object is allocated,
in the second it is instantiated.
The restriction is that during the allocation step you cannot use any
reference to any Perl object that can be referenced from any other
place. This restriction is applied since that object may not exist yet.
Correspondingly, during instantiation step the previosly allocated
object should be filled, i.e., it can be changed in any way such
that the references to this object remain valid.
The methods are called like this:
$pre_object_ref = Package->Allocate($pre_pre_object_ref);
# Returns reference
Package->Instantiate($pre_object_ref,$cooky);
# Converts into reference to blessed object
The reverse operations are
$object_ref->FreezeEmpty($cooky);
$object_ref->FreezeInstance($cooky);
during these calls object can freezeScalar some information (in a
usual way) that will be used during Allocate and Instantiate
calls (via thawScalar). Note that the return value of
FreezeEmpty is cached during the phase of creation of uninialized
objects. This must be used like this: the return value is the
reference to the created object, so it is not destructed until other
objects are created, thus the frozen values of the different objects
will not share the same references. Example of bad result:
$o1->FreezeEmpty($cooky)
freezes {}, and $o2->FreezeEmpty($cooky) makes the same. Now
nobody guaranties that that these two copies of {} are different,
unless a reference to the first one is preserved during the call to
$o2->FreezeEmpty($cooky). If $o1->FreezeEmpty($cooky)
returns the value of {} it uses, it will be preserved by the
engine.
The helper function FreezeThaw::copyContents is provided for
simplification of instantiation. The syntax is
FreezeThaw::copyContents $to, $from;
The function copies contents the object $from point to into what the
object $to points to (including package for blessed references). Both
arguments should be references.
The default methods are provided. They do the following:
FreezeEmpty-
Freezes an empty object of underlying type.
FreezeInstance-
Calls Freeze.
Allocate-
Thaws what was frozen by FreezeEmpty.
Instantiate-
Thaws what was frozen by FreezeInstance, uses copyContents to
transfer this to the $pre_object.
BUGS and LIMITATIONS
A lot of objects are blessed in some obscure packages by XSUB
typemaps. It is not clear how to (automatically) prevent the
UNIVERSAL methods to be called for objects in these packages.
The objects which can survive freeze()/thaw() cycle must also survive a
change of a "member" to an equal member. Say, after
$a = [a => 3];
$a->{b} = \ $a->{a};
$a satisfies
$a->{b} == \ $a->{a}
This property will be broken by freeze()/thaw(), but it is also broken by
$a->{a} = delete $a->{a};
require 5.002; # defined ref stuff...
# Different line noise chars:
#
# $567| next 567 chars form a scalar
#
# @34| next 34 scalars form an array
#
# %34| next 34 scalars form a hash
#
# ? next scalar is a safe-stamp at beginning
#
# ? next scalar is a stringified data
#
# ! repeated array follows (after a scalar denoting array $#),
# (possibly?) followed by instantiation array. At beginning
#
# <45| ordinal of element in repeated array
#
# * stringified glob follows
#
# & stringified coderef follows
#
# \\ stringified defererenced data follows
#
# / stringified REx follows
#
# > stringified package name follows, then frozen data
#
# { stringified package name follows, then allocation data
#
# } stringified package name follows, then instantiation data
#
# _ frozen form of undef
package FreezeThaw;
use Exporter;
@ISA = qw(Exporter);
$VERSION = '0.5001';
@EXPORT_OK = qw(freeze thaw cmpStr cmpStrHard safeFreeze);
use strict;
use Carp;
my $lock = (reverse time) ^ $$ ^ \&freezeString; # To distingush processes
use vars qw( @multiple
%seen_packages
$seen_packages
%seen_packages
%count
%address
$string
$unsafe
$noCache
$cooky
$secondpass
), # Localized in freeze()
qw( $norepeated ), # Localized in freezeScalar()
qw( $uninitOK ), # Localized in thawScalar()
qw( @uninit ), # Localized in thaw()
qw($safe); # Localized in safeFreeze()
BEGIN { # allow optimization away
my $haveIsRex = defined &re::is_regexp;
my $RexIsREGEXP = ($haveIsRex and # 'REGEXP' eq ref qr/1/); # First-class REX
$] >= 5.011); # Code like above requires Scalar::Utils::reftype
eval <<EOE or die;
sub haveIsRex () {$haveIsRex}
sub RexIsREGEXP () {$RexIsREGEXP}
1
EOE
}
my (%saved);
my %Empty = ( ARRAY => sub {[]}, HASH => sub {{}},
SCALAR => sub {my $undef; \$undef},
REF => sub {my $undef; \$undef},
CODE => 1, # 1 means atomic
GLOB => 1,
(RexIsREGEXP
? (Regexp => sub {my $qr = qr//})
: (Regexp => 0)),
);
# This should better be done via pos() and \G, but apparently \G is not
# optimized (bug in the REx optimizer???)
BEGIN {
my $pointer_size = length pack 'p', 0;
#my $max_dig0 = 3*$pointer_size; # 8bits take less than 3 decimals
# Now calculate the exact value:
#my $max_pointer = sprintf "%.${max_dig0}g", 0x100**$pointer_size;
my $max_pointer = sprintf "%.0f", 0x100**$pointer_size;
die "Panic" if $max_pointer =~ /\D/;
my $max_pointer_l = length $max_pointer;
warn "Max pointer_l=$max_pointer_l" if $ENV{FREEZE_THAW_WARN};
eval "sub max_strlen_l () {$max_pointer_l}; 1" or die;
}
sub flushCache {$lock ^= rand; undef %saved;}
sub getref ($) {
my $ref = ref $_[0];
return $ref if not $ref or defined $Empty{$ref}; # Optimization _and_ Regexp
my $str;
if (defined &overload::StrVal) {
$str = overload::StrVal($_[0]);
} else {
$str = "$_[0]";
}
$ref = $1 if $str =~ /=(\w+)/;
$ref;
}
sub freezeString {$string .= "\$" . length($_[0]) . '|' . $_[0]}
sub freezeNumber {$string .= $_[0] . '|'}
sub freezeREx {$string .= '/' . length($_[0]) . '|' . $_[0]}
sub thawString { # Returns list: a string and offset of rest
substr($string, $_[0], 2+max_strlen_l) =~ /^\$(\d+)\|/
or confess "Wrong format of frozen string: " . substr($string, $_[0]);
length($string) - $_[0] > length($1) + 1 + $1
or confess "Frozen string too short: `" .
substr($string, $_[0]) . "', expect " . (length($1) + 2 + $1);
(substr($string, $_[0] + length($1) + 2, $1), $_[0] + length($1) + 2 + $1);
}
sub thawNumber { # Returns list: a number and offset of rest
substr($string, $_[0], 1+max_strlen_l) =~ /^(\d+)\|/
or confess "Wrong format of frozen string: " . substr($string, $_[0]);
($1, $_[0] + length($1) + 1);
}
sub _2rex ($);
if (eval 'ref qr/1/') {
eval 'sub _2rex ($) {my $r = shift; qr/$r/} 1' or die;
} else {
eval 'sub _2rex ($) { shift } 1' or die;
}
sub thawREx { # Returns list: a REx and offset of rest
substr($string, $_[0], 2+max_strlen_l) =~ m,^/(\d+)\|,
or confess "Wrong format of frozen REx: " . substr($string, $_[0]);
length($string) - $_[0] > length($1) + 1 + $1
or confess "Frozen string too short: `" .
substr($string, $_[0]) . "', expect " . (length($1) + 2 + $1);
(_2rex substr($string, $_[0] + length($1) + 2, $1),
$_[0] + length($1) + 2 + $1);
}
sub freezeArray {
$string .= '@' . @{$_[0]} . '|';
for (@{$_[0]}) {
freezeScalar($_);
}
}
sub thawArray {
substr($string, $_[0], 2+max_strlen_l) =~ /^[\@%](\d+)\|/ # % To make it possible thaw hashes
or confess "Wrong format of frozen array: \n$_[0]";
my $count = $1;
my $off = $_[0] + 2 + length $count;
my (@res, $res);
while ($count and length $string > $off) {
($res,$off) = thawScalar($off);
push(@res,$res);
--$count;
}
confess "Wrong length of data in thawing Array: $count left" if $count;
(\@res, $off);
}
sub freezeHash {
my @arr = sort keys %{$_[0]};
$string .= '%' . (2*@arr) . '|';
for (@arr, @{$_[0]}{@arr}) {
freezeScalar($_);
}
}
sub thawHash {
my ($arr, $rest) = &thawArray;
my %hash;
my $l = @$arr/2;
foreach (0 .. $l - 1) {
$hash{$arr->[$_]} = $arr->[$l + $_];
}
(\%hash,$rest);
}
# Second optional argument: ignore the package
# Third optional one: do not check for duplicates on outer level
sub freezeScalar {
$string .= '_', return unless defined $_[0];
return &freezeString unless ref $_[0];
my $ref = ref $_[0];
my $str;
if ($_[1] and $ref) { # Similar to getref()
if (defined &overload::StrVal) {
$str = overload::StrVal($_[0]);
} else {
$str = "$_[0]";
}
$ref = $1 if $str =~ /=(\w+)/;
} else {
$str = "$_[0]";
}
# Die if a) repeated prohibited, b) met, c) not explicitely requested to ingore.
confess "Repeated reference met when prohibited"
if $norepeated && !$_[2] && defined $count{$str};
if ($secondpass and !$_[2]) {
$string .= "<$address{$str}|", return
if defined $count{$str} and $count{$str} > 1;
} elsif (!$_[2]) {
# $count{$str} is defined if we have seen it on this pass.
$address{$str} = @multiple, push(@multiple, $_[0])
if defined $count{$str} and not exists $address{$str};
# This is for debugging and shortening thrown-away output (also
# internal data in arrays and hashes is not duplicated).
$string .= "<$address{$str}|", ++$count{$str}, return
if defined $count{$str};
++$count{$str};
}
return &freezeArray if $ref eq 'ARRAY';
return &freezeHash if $ref eq 'HASH';
return &freezeREx if haveIsRex ? re::is_regexp($_[0])
: ($ref eq 'Regexp' and not defined ${$_[0]});
$string .= "*", return &freezeString
if $ref eq 'GLOB' and !$safe;
$string .= "&", return &freezeString
if $ref eq 'CODE' and !$safe;
$string .= '\\', return &freezeScalar( $ {shift()} )
if $ref eq 'REF' or $ref eq 'SCALAR';
if ($noCache and (($ref eq 'CODE') or $ref eq 'GLOB')) {
confess "CODE and GLOB references prohibited now";
}
if ($safe and (($ref eq 'CODE') or $ref eq 'GLOB')) {
$unsafe = 1;
$saved{$str} = $_[0] unless defined $saved{$str};
$string .= "?";
return &freezeString;
}
$string .= '>';
local $norepeated = $norepeated;
local $noCache = $noCache;
freezePackage(ref $_[0]);
$_[0]->Freeze($cooky);
}
sub freezePackage {
my $packageid = $seen_packages{$_[0]};
if (defined $packageid) {
$string .= ')';
&freezeNumber( $packageid );
} else {
$string .= '>';
&freezeNumber( $seen_packages );
&freezeScalar( $_[0] );
$seen_packages{ $_[0] } = $seen_packages++;
}
}
sub thawPackage { # First argument: offset
my $key = substr($string,$_[0],1);
my ($get, $rest, $id);
($id, $rest) = &thawNumber($_[0] + 1);
if ($key eq ')') {
$get = $seen_packages{$id};
} else {
($get, $rest) = &thawString($rest);
$seen_packages{$id} = $get;
}
($get, $rest);
}
# First argument: offset; Optional other: index in the @uninit array
sub thawScalar {
my $key = substr($string,$_[0],1);
if ($key eq "\$") {&thawString}
elsif ($key eq '@') {&thawArray}
elsif ($key eq '%') {&thawHash}
elsif ($key eq '/') {&thawREx}
elsif ($key eq '\\') {
my ($out,$rest) = &thawScalar( $_[0]+1 ) ;
(\$out,$rest);
}
elsif ($key eq '_') { (undef, $_[0]+1) }
elsif ($key eq '&') {confess "Do not know how to thaw CODE"}
elsif ($key eq '*') {confess "Do not know how to thaw GLOB"}
elsif ($key eq '?') {
my ($address,$rest) = &thawScalar( $_[0]+1 ) ;
confess "The saved data accessed in unprotected thaw" unless $unsafe;
confess "The saved data disappeared somewhere"
unless defined $saved{$address};
($saved{$address},$rest);
} elsif ($key eq '<') {
confess "Repeated data prohibited at this moment" unless $uninitOK;
my ($off,$end) = &thawNumber ($_[0]+1);
($uninit[$off],$end);
} elsif ($key eq '>' or $key eq '{' or $key eq '}') {
my ($package,$rest) = &thawPackage( $_[0]+1 );
my $cooky = bless \$rest, 'FreezeThaw::TCooky';
local $uninitOK = $uninitOK;
local $unsafe = $unsafe;
if ($key eq '{') {
my $res = $package->Allocate($cooky);
($res, $rest);
} elsif ($key eq '}') {
warn "Here it is undef!" unless defined $_[1];
$package->Instantiate($uninit[$_[1]],$cooky);
(undef, $rest);
} else {
($package->Thaw($cooky),$rest);
}
} else {
confess "Do not know how to thaw data with code `$key'";
}
}
sub freezeEmpty { # Takes a type, freezes ref to empty object
my $e = $Empty{ref $_[0]};
if (ref $e) {
my $cache = &$e;
freezeScalar $cache;
$cache;
} elsif ($e) {
my $cache = shift;
freezeScalar($cache,1,1); # Atomic
$cache;
} else {
$string .= "{";
freezePackage ref $_[0];
$_[0]->FreezeEmpty($cooky);
}
}
sub freeze {
local @multiple;
local %seen_packages;
local $seen_packages = 0;
local %seen_packages;
# local @seentypes;
local %count;
local %address;
local $string = 'FrT;';
local $unsafe;
local $noCache;
local $cooky = bless \$cooky, 'FreezeThaw::FCooky'; # Just something fake
local $secondpass;
freezeScalar(\@_);
if (@multiple) {
# Now repeated structures are enumerated with order of *second* time
# they appear in the what we freeze.
# What we want is to have them enumerated with respect to the first time
#### $string = ''; # Start again
#### @multiple = ();
#### %address = ();
#### for (keys %count) {
#### $count{$_} = undef if $count{$_} <= 1; # As at start
#### $count{$_} = 0 if $count{$_}; # As at start
#### }
#### $seen_packages = 0;
#### %seen_packages = ();
#### freezeScalar(\@_);
# Now repeated structures are enumerated with order of first time
# they appear in the what we freeze
#### my $oldstring = substr $string, 4;
$string = 'FrT;!'; # Start again
$seen_packages = 0;
%seen_packages = (); # XXXX We reshuffle parts of the
# string, so the order of packages may
# be wrong...
freezeNumber($#multiple);
{
my @cache; # Force different values for different
# empty objects.
foreach (@multiple) {
push @cache, freezeEmpty $_;
}
}
# for (keys %count) {
# $count{$_} = undef
# if !(defined $count{$_}) or $count{$_} <= 1; # As at start
# }
# $string .= '@' . @multiple . '|';
$secondpass = 1;
for (@multiple) {
freezeScalar($_,0,1,1), next if $Empty{ref $_};
$string .= "}";
freezePackage ref $_;
$_->FreezeInstance($cooky);
}
#### $string .= $oldstring;
freezeScalar(\@_);
}
return "FrT;?\$" . length($lock) . "|" . $lock . substr $string, 4
if $unsafe;
$string;
}
sub safeFreeze {
local $safe = 1;
&freeze;
}
sub copyContents { # Given two references, copies contents of the
# second one to the first one, provided they have
# the same basic type. The package is copied too.
my($first,$second) = @_;
my $ref = getref $second;
if ($ref eq 'SCALAR' or $ref eq 'REF') {
$$first = $$second;
} elsif ($ref eq 'ARRAY') {
@$first = @$second;
} elsif ($ref eq 'HASH') {
%$first = %$second;
} elsif (haveIsRex ? re::is_regexp($second)
: ($ref eq 'Regexp' and not defined $$second)) {
$first = qr/$second/;
} else {
croak "Don't know how to copyContents of type `$ref'";
}
if (ref $second ne ref $first) { # Rebless
# SvAMAGIC() is a property of a reference, not of a referent!
# Thus we cannot use $first here if $second was overloaded...
bless $_[0], ref $second;
}
$first;
}
sub thaw {
confess "thaw requires one argument" unless @_ ==1;
local $string = shift;
local %seen_packages;
my $initoff = 0;
#print STDERR "Thawing `$string'", substr ($string, 0, 4), "\n";
if (substr($string, 0, 4) ne 'FrT;') {
warn "Signature not present, continuing anyway" if $^W;
} else {
$initoff = 4;
}
local $unsafe = $initoff + (substr($string, $initoff, 1) eq "?" ? 1 : 0);
if ($unsafe != $initoff) {
my $key;
($key,$unsafe) = thawScalar($unsafe);
confess "The lock in frozen data does not match the key"
unless $key eq $lock;
}
local @multiple;
local $uninitOK = 1; # The methods can change it.
my $repeated = substr($string,$unsafe,1) eq '!' ? 1 : 0;
my ($res, $off);
if ($repeated) {
($res, $off) = thawNumber($repeated + $unsafe);
} else {
($res, $off) = thawScalar($repeated + $unsafe);
}
my $cooky = bless \$off, 'FreezeThaw::TCooky';
if ($repeated) {
local @uninit;
my $lst = $res;
foreach (0..$lst) {
($res, $off) = thawScalar($off, $_);
push(@uninit, $res);
}
my @init;
foreach (0..$lst) {
($res, $off) = thawScalar($off, $_);
push(@init, $res);
}
#($init, $off) = thawScalar($off);
#print "Instantiating...\n";
#my $ref;
for (0..$#uninit) {
copyContents $uninit[$_], $init[$_] if ref $init[$_];
}
($res, $off) = thawScalar($off);
}
croak "Extra elements in frozen structure: `" . substr($string,$off) . "'"
if $off != length $string;
return @$res;
}
sub cmpStr {
confess "Compare requires two arguments" unless @_ == 2;
freeze(shift) cmp freeze(shift);
}
sub cmpStrHard {
confess "Compare requires two arguments" unless @_ == 2;
local @multiple;
# local @seentypes;
local %count;
local %address;
local $string = 'FrT;';
local $unsafe;
local $noCache;
local $cooky = bless \$cooky, 'FreezeThaw::FCooky'; # Just something fake
freezeScalar($_[0]);
my %cnt1 = %count;
freezeScalar($_[1]);
my %cnt2 = %count;
%count = ();
# Now all the caches are filled, delete the entries for guys which
# are in one argument only.
my ($elt, $val);
while (($elt, $val) = each %cnt1) {
$count{$elt}++ if $cnt2{$elt} > $cnt1{$elt};
}
$string = '';
freezeScalar($_[0]);
my $str1 = $string;
$string = '';
freezeScalar($_[1]);
$str1 cmp $string;
}
# local $string = freeze(shift,shift);
# local $uninitOK = 1;
# #print "$string\n";
# my $off = 7; # Hardwired offset after @2|
# if (substr($string,4,1) eq '!') {
# $off = 5; # Hardwired offset after !
# my ($uninit, $len);
# ($len,$off) = thawScalar $off;
# local @uninit;
# foreach (0..$len) {
# ($uninit,$off) = thawScalar $off, $_;
# }
# $off += 3; # Hardwired offset after @2|
# }
# croak "Unknown format of frozen array: " . substr($string,$off-3)
# unless substr($string,$off-3,1) eq '@';
# my ($first,$off2) = thawScalar $off;
# my $off3;
# ($first,$off3) = thawScalar $off2;
# substr($string, $off, $off2-$off) cmp substr($string,$off2,$off3-$off2);
# }
sub FreezeThaw::FCooky::FreezeScalar {
shift;
&freezeScalar;
}
sub FreezeThaw::FCooky::isSafe {
$safe || $noCache;
}
sub FreezeThaw::FCooky::makeSafe {
$noCache = 1;
}
sub FreezeThaw::FCooky::repeatedOK {
!$norepeated;
}
sub FreezeThaw::FCooky::noRepeated {
$norepeated = 1;
}
sub FreezeThaw::TCooky::repeatedOK {
$uninitOK;
}
sub FreezeThaw::TCooky::noRepeated {
undef $uninitOK;
}
sub FreezeThaw::TCooky::isSafe {
!$unsafe;
}
sub FreezeThaw::TCooky::makeSafe {
undef $unsafe;
}
sub FreezeThaw::TCooky::ThawScalar {
my $self = shift;
my ($res,$off) = &thawScalar($$self);
$$self = $off;
$res;
}
sub UNIVERSAL::Freeze {
my ($obj, $cooky) = (shift, shift);
$cooky->FreezeScalar($obj,1,1);
}
sub UNIVERSAL::Thaw {
my ($package, $cooky) = (shift, shift);
my $obj = $cooky->ThawScalar;
bless $obj, $package;
}
sub UNIVERSAL::FreezeInstance {
my($obj,$cooky) = @_;
return if !RexIsREGEXP # Special-case non-1st-class RExes
and ref $obj and (haveIsRex ? re::is_regexp($obj)
: (ref $obj eq 'Regexp' and not defined $$obj)); # Regexp
$obj->Freeze($cooky);
}
sub UNIVERSAL::Instantiate {
my($package,$pre,$cooky) = @_;
return if !RexIsREGEXP and $package eq 'Regexp';
my $obj = $package->Thaw($cooky);
# SvAMAGIC() is a property of a reference, not of a referent!
# Thus we cannot use $pre here if $obj was overloaded...
copyContents $_[1], $obj;
}
sub UNIVERSAL::Allocate {
my($package,$cooky) = @_;
$cooky->ThawScalar;
}
sub UNIVERSAL::FreezeEmpty {
my $obj = shift;
my $type = getref $obj;
my $e = $Empty{$type};
if (ref $e) {
my $ref = &$e;
freezeScalar $ref;
$ref; # Put into cache.
} elsif ($e) {
freezeScalar($obj,1,1); # Atomic
undef;
} elsif (!RexIsREGEXP and defined $e and not defined $$obj) { # REx pre-5.11
freezeREx($obj);
undef;
} else {
die "Do not know how to FreezeEmpty $type";
}
}
1;