+Hash tied to provide additional keys/values than the original.

diff --git a/Hash/Makefile.am b/Hash/Makefile.am
index e1e05a3..10b3bf4 100644 (file)
--- a/Hash/Makefile.am
+++ b/Hash/Makefile.am
@@ -23,5 +23,6 @@ EXTRA_DIST+= \
                Sub.pm \
                Readonly.pm \
                RestrictTo.pm \
-               RecordKeys.pm
+               RecordKeys.pm \
+               Merge.pm
 

diff --git a/Hash/Merge.pm b/Hash/Merge.pm
new file mode 100644 (file)
index 0000000..376cb18
--- /dev/null
+++ b/Hash/Merge.pm
@@ -0,0 +1,122 @@
+# $Id$
+# Hash tied to provide additional keys/values than the original.
+# Copyright (C) 2005 Jan Kratochvil <project-www.jankratochvil.net@jankratochvil.net>
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; exactly version 2 of June 1991 is required
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+
+package My::Hash::Merge;
+our $VERSION=do { my @r=(q$Revision$=~/\d+/g); sprintf "%d.".("%03d"x$#r),@r; };
+our $CVS_ID=q$Id$;
+use strict;
+use warnings;
+use My::Web;   # for &Wrequire
+Wrequire 'My::Hash';
+our @ISA=qw(My::Hash);
+use Carp qw(cluck confess);
+
+
+sub TIEHASH($@)
+{
+my($class,@parents)=@_;
+
+       my $self=bless {},$class;
+       for my $parent (@parents) {
+               # Possibly upgrade unref("HASH")es:
+               $parent=$class->SUPER::TIEHASH($parent)->{"parent"};
+               push @{$self->{"parents"}},$parent;
+               }
+       return $self;
+}
+
+sub key_find($$)
+{
+my($self,$key)=@_;
+
+       my $count=0;
+       my $first;
+       for my $parent (@{$self->{"parents"}}) {
+               next if !exists $parent->{$key};
+               $count++;
+               $first||=$parent;
+               }
+       # 0 IS allowed here.
+       cluck "Duplicity ($count-icity) for key: $key" if $count>=2;
+       $first||=$self->{"parents"}[0];
+       return $first;
+}
+
+sub STORE($$$)
+{
+my($this,$key,$value)=@_;
+
+       my $first=$this->key_find($key);
+       $first->{$key}=$value;
+}
+
+sub FETCH($$)
+{
+my($this,$key)=@_;
+
+       my $first=$this->key_find($key);
+       return if !$first;
+       return $first->{$key};
+}
+
+sub FIRSTKEY($)
+{
+my($this)=@_;
+
+confess "TODO: Not yet implemented.";
+}
+
+sub NEXTKEY($$)
+{
+my($this,$lastkey)=@_;
+
+confess "TODO: Not yet implemented.";
+}
+
+sub EXISTS($$)
+{
+my($this,$key)=@_;
+
+       my $first=$this->key_find($key);
+       $first||={};
+       return exists $first->{$key};
+}
+
+sub DELETE($$)
+{
+my($this,$key)=@_;
+
+       my $first=$this->key_find($key);
+       delete $first->{$key};
+}
+
+sub CLEAR($)
+{
+my($this)=@_;
+
+confess "TODO: Not yet implemented.";
+}
+
+sub SCALAR
+{
+my($this)=@_;
+
+confess "TODO: Not yet implemented.";
+}
+
+1;