说我有一个小对象,它引用了一个大对象:
package Tiny;
sub new {
my ($class, $tiny, $large) = @_;
return bless { tiny => $tiny, large => $large };
}
我想创建一个STORABLE_freeze
/ STORABLE_thaw
对,让我(递归)克隆$tiny
,但保持/保持对$large
的引用,而无需也克隆$ large。
我尝试临时删除$self->{large}
(请参见下文),并使用Scalar::Util::refaddr
键和对$large
的弱引用将其放入哈希中,从而序列化{{1} },然后立即将(弱)引用放回到原始对象和$self
中克隆的对象中,但这是一团糟,在每个克隆上,弱ref value 超出范围时会被删除,但是 key 永远保留在哈希中,永远泄漏内存,我需要一个全局类成员哈希(STORABLE_thaw
)来保存临时%largeWeakRefs
参考。有气味。
如何以更清洁的方式做到这一点?
这是我的解决方案,使用散列临时保存大引用:
$large
(是的,我知道我的示例仅处理克隆,而不处理直接冻结和解冻)
答案 0 :(得分:2)
您可以添加参考计数。
my %larges;
sub STORABLE_freeze {
my ( $self, $cloning ) = @_;
if ($cloning) {
my $large_key = pack('j', refaddr(self->{large}));
$larges{$large_key} //= [ $self->{large}, 0 ];
++$larges{$large_key}[1];
return ( $large_key, $self->{tiny} );
} else {
return ( "", $self->{tiny}, $self->{large} );
}
}
sub STORABLE_thaw {
my ( $self, $cloning, $serialized ) = splice(@_, 0, 3);
if ($cloning) {
my $large_key = $serialized;
$self->{ tiny } = shift;
$self->{ large } = $larges{$large_key}[0];
--$larges{$large_key}[1]
or delete($larges{$large_key});
} else {
$self->{ tiny } = shift;
$self->{ large } = shift;
}
}
未经测试。
如果克隆过程终止,则会发生内存泄漏。
或者,您可以避免对外部资源的需求,如下所示:
use Inline C => <<'__EOS__';
IV get_numeric_ref(SV *sv) {
SvGETMAGIC(sv);
if (!SvROK(sv))
croak("Argument not a reference");
sv = MUTABLE_SV(SvRV(sv));
SvREFCNT_inc(sv);
return PTR2IV(sv); /* Despite its name, can be used to convert pointer to IV */
}
SV* get_perl_ref_from_numeric_ref(IV iv) {
SV* sv = PTR2IV(iv);
return newRV_noinc(sv);
}
__EOS__
sub STORABLE_freeze {
my ( $self, $cloning ) = @_;
if ($cloning) {
return ( pack('j', get_numeric_ref($self->{large})), $self->{tiny} );
} else {
return ( "", $self->{tiny}, $self->{large} );
}
}
sub STORABLE_thaw {
my ( $self, $cloning, $serialized ) = splice(@_, 0, 3);
if ($cloning) {
$self->{ tiny } = shift;
$self->{ large } = get_perl_ref_from_numeric_ref(unpack('j', $serialized));
} else {
$self->{ tiny } = shift;
$self->{ large } = shift;
}
}
未测试STORABLE_freeze
和STORABLE_thaw
,但使用以下方法测试了C / XS代码:
use strict;
use warnings;
use feature qw( say state );
use Cpanel::JSON::XS qw( );
sub _dump {
state $encoder = Cpanel::JSON::XS->new->canonical->allow_nonref;
return $encoder->encode($_[0]);
}
{
my %h = ( a => 4, b => 5 );
say _dump(\%h); # {"a":4,"b":5}
say sprintf "0x%x", \%h; # 0x32cdbf8
say Internals::SvREFCNT(%h); # 1
my $i = get_numeric_ref(\%h);
say sprintf "0x%x", $i; # 0x32cdbf8
say Internals::SvREFCNT(%h); # 2
my $ref = get_perl_ref_from_numeric_ref($i);
say sprintf "0x%x", $ref; # 0x32cdbf8
say Internals::SvREFCNT(%h); # 2
say _dump($ref); # {"a":4,"b":5}
}
如果克隆过程终止,则将发生内存泄漏。我想在克隆过程中依靠“大”不会有任何问题是安全的,因此您可以删除SvREFCNT_inc
并将newRV_noinc
更改为newRV
,以避免潜在的内存泄漏。
为避免可能的内存泄漏,切勿在对象中存储“大”字。
my %larges;
sub new {
my $class = shift;
my $self = bless({}, $class);
return $self->_init(@_);
}
sub _init {
my ($self, $tiny, $large) = @_;
$self->{ tiny } = $tiny;
{
my $large_key = pack('j', refaddr($self));
$self->{ large_key } = $large_key;
$larges{ $large_key } = $large;
}
return $self;
}
sub DESTROY {
my ($self) = @_;
if (defined( my $large_key = $self->{ large_key } )) {
delete( $larges{ $large_key } );
}
}
sub STORABLE_freeze {
my ( $self, $cloning ) = @_;
if ($cloning) {
return ( $self->{large_key}, $self->{tiny} );
} else {
return ( "", $self->{tiny}, $larges{ $self->{large_key} } );
}
}
sub STORABLE_thaw {
my ( $self, $cloning, $serialized ) = splice(@_, 0, 3);
if ($cloning) {
my ($tiny) = @_;
my $large_key = $serialized;
$self->_init($tiny, $larges{ $large_key });
} else {
$self->_init(@_);
}
}
未经测试。
如果克隆过程终止,则不会发生内存泄漏。