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by mr.nick (Chaplain)
on Mar 26, 2001 at 20:32 UTC ( [id://67227]=note: print w/replies, xml ) Need Help??

in reply to A (kinda) Circular Cache

As I said to Tilly when asked why I didn't use the tried and true method of link lists, "Oh yeah, link lists. Perl's auto-hash made me forget them."

So, in that vein, I present the Reinvent the Wheel Cache #2 (I believe it works under all cases). I plan to do some benchmarking later on ... (even though nobody will probably see this node)

package cache2; use strict; ## okay, a second shot at this sub new { my $self=bless {},shift; ## we keep track of lots of things $self->{size}=shift || 30; $self->{count}=0; $self->{head}=undef; $self->{tail}=undef; $self->{hash}={}; $self; } sub ins { my $self=shift; my $key=shift; my $val=shift; ## put it at the head (we walk down -- next is further down the chai +n) ## create the hash ref my $new={ prev => undef, next => $self->{head}, key => $key, value => $val, }; ## tack it on $self->{head}=$new; ## and the hash for quick lookup $self->{hash}->{$key}=$new; $self->{count}++; ## do our size checking if ($self->{count}==$self->{size}+1) { $self->del($self->{tail}->{key}); } } sub del { my $self=shift; my $key=shift; my $item=$self->{hash}->{$key}; return unless defined $item; ## reattach it's prev/next $item->{prev}->{next}=$item->{next} if defined $item->{prev}; $item->{next}->{prev}=$item->{prev} if defined $item->{next}; ## head/tail handling $self->{head}=$item->{next} if $self->{head}==$item; $self->{tail}=$item->{prev} if $self->{tail}==$item; ## and the hash delete $self->{hash}->{$key}; ## and the count $self->{count}--; } sub get { my $self=shift; my $key=shift; my $item=$self->{hash}->{$key}; return unless defined $item; ## move it to the front by ## delete it $self->del($key); ## and add it $self->ins($key,$item->{value}); $item->{value}; } sub show { my $self=shift; my $item=$self->{head}; while (defined $item) { print "$item: "; print "key $item->{key} " if defined $item->{key}; print "value $item->{value} " if defined $item->{value}; print "\n"; $item=$item->{next}; } } 1;

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