=head1 VERSION
-Version 0.37
+Version 0.42
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.37';
+ $VERSION = '0.42';
}
=head1 SYNOPSIS
=head1 DESCRIPTION
-Magic is Perl way of enhancing objects.
-This mechanism lets the user add extra data to any variable and hook syntaxical operations (such as access, assignment or destruction) that can be applied to it.
+Magic is Perl's way of enhancing variables.
+This mechanism lets the user add extra data to any variable and hook syntactical operations (such as access, assignment or destruction) that can be applied to it.
With this module, you can add your own magic to any variable without having to write a single line of XS.
You'll realize that these magic variables look a lot like tied variables.
It doesn't replace the original semantics.
-Magic callbacks usually trigger before the original action take place, and can't prevent it to happen.
+Magic callbacks usually get triggered before the original action takes place, and can't prevent it from happening.
This also makes catching individual events easier than with C<tie>, where you have to provide fallbacks methods for all actions by usually inheriting from the correct C<Tie::Std*> class and overriding individual methods in your own class.
=item *
=item *
-C<sig>
-
-The numerical signature.
-If not specified or undefined, a random signature is generated.
-If the signature matches an already defined magic, then the existant magic object is returned.
-
-This option is B<deprecated> and will be removed in december 2009.
-
-=item *
-
C<data>
-A code reference to a private data constructor.
+A code (or string) reference to a private data constructor.
It is called each time this magic is cast on a variable, and the scalar returned is used as private data storage for it.
C<$_[0]> is a reference to the magic object and C<@_[1 .. @_-1]> are all extra arguments that were passed to L</cast>.
C<get>, C<set>, C<len>, C<clear>, C<free>, C<copy>, C<local>, C<fetch>, C<store>, C<exists> and C<delete>
-Code references to the corresponding magic callbacks.
+Code (or string) references to the corresponding magic callbacks.
You don't have to specify all of them : the magic associated with undefined entries simply won't be hooked.
In those callbacks, C<$_[0]> is always a reference to the magic object and C<$_[1]> is always the private data (or C<undef> when no private data constructor was supplied).
=back
+Each callback can be specified as a code or a string reference, in which case the function denoted by the string will be used as the callback.
+
+Note that C<free> callbacks are I<never> called during global destruction, as there's no way to ensure that the wizard and the C<free> callback weren't destroyed before the variable.
+
+Here's a simple usage example :
+
# A simple scalar tracer
my $wiz = wizard get => sub { print STDERR "got ${$_[0]}\n" },
set => sub { print STDERR "set to ${$_[0]}\n" },
free => sub { print STDERR "${$_[0]} was deleted\n" }
-Note that C<free> callbacks are I<never> called during global destruction, as there's no way to ensure that the wizard and the C<free> callback weren't destroyed before the variable.
-
=cut
sub wizard {
croak 'Wrong number of arguments for wizard()' if @_ % 2;
my %opts = @_;
- my @keys = qw/sig data op_info get set len clear free/;
+ my @keys = qw/data op_info get set len clear free/;
push @keys, 'copy' if MGf_COPY;
push @keys, 'dup' if MGf_DUP;
push @keys, 'local' if MGf_LOCAL;
return $ret;
}
-=head2 C<gensig>
-
-With this tool, you can manually generate random magic signature between SIG_MIN and SIG_MAX inclusive.
-That's the way L</wizard> creates them when no signature is supplied.
-
- # Generate a signature
- my $sig = gensig;
-
-This function is B<deprecated> and will be removed in december 2009.
-
-=head2 C<getsig>
-
- getsig $wiz
-
-This accessor returns the magic signature of this wizard.
-
- # Get $wiz signature
- my $sig = getsig $wiz;
-
-This function is B<deprecated> and will be removed in december 2009.
-
=head2 C<cast>
cast [$@%&*]var, $wiz, ...
If you want to overcome the possible deletion of the C<'TZ'> entry, you have no choice but to rely on C<store> uvar magic.
-C<cast> can be called from any magical callback, and in particular from C<data>.
-This allows you to recursively cast magic on datastructures :
-
- my $wiz;
- $wiz = wizard
- data => sub {
- my ($var, $depth) = @_;
- $depth ||= 0;
- my $r = ref $var;
- if ($r eq 'ARRAY') {
- &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for @$var;
- } elsif ($r eq 'HASH') {
- &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for values %$var;
- }
- return $depth;
- },
- free => sub {
- my ($var, $depth) = @_;
- my $r = ref $var;
- print "free $r at depth $depth\n";
- ();
- };
-
- {
- my %h = (
- a => [ 1, 2 ],
- b => { c => 3 }
- );
- cast %h, $wiz;
- }
-
-When C<%h> goes out of scope, this will print something among the lines of :
-
- free HASH at depth 0
- free HASH at depth 1
- free SCALAR at depth 2
- free ARRAY at depth 1
- free SCALAR at depth 3
- free SCALAR at depth 3
-
-Of course, this example does nothing with the values that are added after the C<cast>.
-
=head2 C<getdata>
getdata [$@%&*]var, $wiz
=head1 CONSTANTS
-=head2 C<SIG_MIN>
-
-The minimum integer used as a signature for user-defined magic.
-
-This constant is B<deprecated> and will be removed in december 2009.
-
-=head2 C<SIG_MAX>
-
-The maximum integer used as a signature for user-defined magic.
-
-This constant is B<deprecated> and will be removed in december 2009.
-
-=head2 C<SIG_NBR>
-
- SIG_NBR = SIG_MAX - SIG_MIN + 1
-
-This constant is B<deprecated> and will be removed in december 2009.
-
=head2 C<MGf_COPY>
Evaluates to true iff the 'copy' magic is available.
True for perls that don't call 'len' magic when taking the C<length> of a magical scalar.
+=head2 C<VMG_COMPAT_GLOB_GET>
+
+True for perls that call 'get' magic for operations on globs.
+
=head2 C<VMG_PERL_PATCHLEVEL>
The perl patchlevel this module was built with, or C<0> for non-debugging perls.
Value to pass with C<op_info> to get a C<B::OP> object representing the current op in the magic callbacks.
+=head1 COOKBOOK
+
+=head2 Associate an object to any perl variable
+
+This technique can be useful for passing user data through limited APIs.
+It is similar to using inside-out objects, but without the drawback of having to implement a complex destructor.
+
+ {
+ package Magical::UserData;
+
+ use Variable::Magic qw/wizard cast getdata/;
+
+ my $wiz = wizard data => sub { \$_[1] };
+
+ sub ud (\[$@%*&]) : lvalue {
+ my ($var) = @_;
+ my $data = &getdata($var, $wiz);
+ unless (defined $data) {
+ $data = \(my $slot);
+ &cast($var, $wiz, $slot)
+ or die "Couldn't cast UserData magic onto the variable";
+ }
+ $$data;
+ }
+ }
+
+ {
+ BEGIN { *ud = \&Magical::UserData::ud }
+
+ my $cb;
+ $cb = sub { print 'Hello, ', ud(&$cb), "!\n" };
+
+ ud(&$cb) = 'world';
+ $cb->(); # Hello, world!
+ }
+
+=head2 Recursively cast magic on datastructures
+
+C<cast> can be called from any magical callback, and in particular from C<data>.
+This allows you to recursively cast magic on datastructures :
+
+ my $wiz;
+ $wiz = wizard data => sub {
+ my ($var, $depth) = @_;
+ $depth ||= 0;
+ my $r = ref $var;
+ if ($r eq 'ARRAY') {
+ &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for @$var;
+ } elsif ($r eq 'HASH') {
+ &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for values %$var;
+ }
+ return $depth;
+ },
+ free => sub {
+ my ($var, $depth) = @_;
+ my $r = ref $var;
+ print "free $r at depth $depth\n";
+ ();
+ };
+
+ {
+ my %h = (
+ a => [ 1, 2 ],
+ b => { c => 3 }
+ );
+ cast %h, $wiz;
+ }
+
+When C<%h> goes out of scope, this will print something among the lines of :
+
+ free HASH at depth 0
+ free HASH at depth 1
+ free SCALAR at depth 2
+ free ARRAY at depth 1
+ free SCALAR at depth 3
+ free SCALAR at depth 3
+
+Of course, this example does nothing with the values that are added after the C<cast>.
+
=head1 PERL MAGIC HISTORY
The places where magic is invoked have changed a bit through perl history.
=head1 EXPORT
-The functions L</wizard>, L</gensig>, L</getsig>, L</cast>, L</getdata> and L</dispell> are only exported on request.
+The functions L</wizard>, L</cast>, L</getdata> and L</dispell> are only exported on request.
All of them are exported by the tags C<':funcs'> and C<':all'>.
All the constants are also only exported on request, either individually or by the tags C<':consts'> and C<':all'>.
our @EXPORT = ();
our %EXPORT_TAGS = (
- 'funcs' => [ qw/wizard gensig getsig cast getdata dispell/ ],
+ 'funcs' => [ qw/wizard cast getdata dispell/ ],
'consts' => [
- qw/SIG_MIN SIG_MAX SIG_NBR MGf_COPY MGf_DUP MGf_LOCAL VMG_UVAR/,
+ qw/MGf_COPY MGf_DUP MGf_LOCAL VMG_UVAR/,
qw/VMG_COMPAT_ARRAY_PUSH_NOLEN VMG_COMPAT_ARRAY_PUSH_NOLEN_VOID/,
qw/VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID/,
qw/VMG_COMPAT_ARRAY_UNDEF_CLEAR/,
qw/VMG_COMPAT_SCALAR_LENGTH_NOLEN/,
+ qw/VMG_COMPAT_GLOB_GET/,
qw/VMG_PERL_PATCHLEVEL/,
qw/VMG_THREADSAFE VMG_FORKSAFE/,
qw/VMG_OP_INFO_NAME VMG_OP_INFO_OBJECT/
=head1 COPYRIGHT & LICENSE
-Copyright 2007-2009 Vincent Pit, all rights reserved.
+Copyright 2007,2008,2009,2010 Vincent Pit, all rights reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
projects / perl / modules / Variable-Magic.git / blobdiff