use strict;
use warnings;
-use Carp qw/croak/;
-
=head1 NAME
Variable::Magic - Associate user-defined magic to variables from Perl.
=head1 VERSION
-Version 0.37
+Version 0.47
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.37';
+ $VERSION = '0.47';
}
=head1 SYNOPSIS
- use Variable::Magic qw/wizard cast VMG_OP_INFO_NAME/;
+ use Variable::Magic qw<wizard cast VMG_OP_INFO_NAME>;
{ # A variable tracer
- my $wiz = wizard set => sub { print "now set to ${$_[0]}!\n" },
- free => sub { print "destroyed!\n" };
+ my $wiz = wizard(
+ set => sub { print "now set to ${$_[0]}!\n" },
+ free => sub { print "destroyed!\n" },
+ );
my $a = 1;
cast $a, $wiz;
} # "destroyed!"
{ # A hash with a default value
- my $wiz = wizard data => sub { $_[1] },
- fetch => sub { $_[2] = $_[1] unless exists $_[0]->{$_[2]}; () },
- store => sub { print "key $_[2] stored in $_[-1]\n" },
- copy_key => 1,
- op_info => VMG_OP_INFO_NAME;
+ my $wiz = wizard(
+ data => sub { $_[1] },
+ fetch => sub { $_[2] = $_[1] unless exists $_[0]->{$_[2]}; () },
+ store => sub { print "key $_[2] stored in $_[-1]\n" },
+ copy_key => 1,
+ op_info => VMG_OP_INFO_NAME,
+ );
my %h = (_default => 0, apple => 2);
cast %h, $wiz, '_default';
- print $h{banana}, "\n"; # "0", because the 'banana' key doesn't exist in %h
+ print $h{banana}, "\n"; # "0" (there is no 'banana' key in %h)
$h{pear} = 1; # "key pear stored in helem"
}
=head1 DESCRIPTION
-Magic is Perl way of enhancing objects.
-This mechanism lets the user add extra data to any variable and hook syntaxical operations (such as access, assignment or destruction) that can be applied to it.
+Magic is Perl's way of enhancing variables.
+This mechanism lets the user add extra data to any variable and hook syntactical operations (such as access, assignment or destruction) that can be applied to it.
With this module, you can add your own magic to any variable without having to write a single line of XS.
You'll realize that these magic variables look a lot like tied variables.
It doesn't replace the original semantics.
-Magic callbacks usually trigger before the original action take place, and can't prevent it to happen.
+Magic callbacks usually get triggered before the original action takes place, and can't prevent it from happening.
This also makes catching individual events easier than with C<tie>, where you have to provide fallbacks methods for all actions by usually inheriting from the correct C<Tie::Std*> class and overriding individual methods in your own class.
=item *
=back
-The following actions only apply to hashes and are available iff C<VMG_UVAR> is true.
+The following actions only apply to hashes and are available iff L</VMG_UVAR> is true.
They are referred to as C<uvar> magics.
=over 4
You can refer to the tests to have more insight of where the different magics are invoked.
-To prevent any clash between different magics defined with this module, an unique numerical signature is attached to each kind of magic (i.e. each set of callbacks for magic operations).
-At the C level, magic tokens owned by magic created by this module have their C<< mg->mg_private >> field set to C<0x3891> or C<0x3892>, so please don't use these magic (sic) numbers in other extensions.
-
=head1 FUNCTIONS
=cut
=head2 C<wizard>
- wizard data => sub { ... },
- get => sub { my ($ref, $data [, $op]) = @_; ... },
- set => sub { my ($ref, $data [, $op]) = @_; ... },
- len => sub { my ($ref, $data, $len [, $op]) = @_; ... ; return $newlen; },
- clear => sub { my ($ref, $data [, $op]) = @_; ... },
- free => sub { my ($ref, $data [, $op]) = @_, ... },
- copy => sub { my ($ref, $data, $key, $elt [, $op]) = @_; ... },
- local => sub { my ($ref, $data [, $op]) = @_; ... },
- fetch => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- store => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- exists => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- delete => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- copy_key => $bool,
- op_info => [ 0 | VMG_OP_INFO_NAME | VMG_OP_INFO_OBJECT ]
+ wizard(
+ data => sub { ... },
+ get => sub { my ($ref, $data [, $op]) = @_; ... },
+ set => sub { my ($ref, $data [, $op]) = @_; ... },
+ len => sub {
+ my ($ref, $data, $len [, $op]) = @_; ... ; return $newlen
+ },
+ clear => sub { my ($ref, $data [, $op]) = @_; ... },
+ free => sub { my ($ref, $data [, $op]) = @_, ... },
+ copy => sub { my ($ref, $data, $key, $elt [, $op]) = @_; ... },
+ local => sub { my ($ref, $data [, $op]) = @_; ... },
+ fetch => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ store => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ exists => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ delete => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ copy_key => $bool,
+ op_info => [ 0 | VMG_OP_INFO_NAME | VMG_OP_INFO_OBJECT ],
+ )
This function creates a 'wizard', an opaque type that holds the magic information.
It takes a list of keys / values as argument, whose keys can be :
=item *
-C<sig>
-
-The numerical signature.
-If not specified or undefined, a random signature is generated.
-If the signature matches an already defined magic, then the existant magic object is returned.
-
-This option is B<deprecated> and will be removed in december 2009.
-
-=item *
-
C<data>
-A code reference to a private data constructor.
+A code (or string) reference to a private data constructor.
It is called each time this magic is cast on a variable, and the scalar returned is used as private data storage for it.
C<$_[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
- # 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" }
+Each callback can be specified as :
-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.
+=over 4
-=cut
+=item *
-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/;
- push @keys, 'copy' if MGf_COPY;
- push @keys, 'dup' if MGf_DUP;
- push @keys, 'local' if MGf_LOCAL;
- push @keys, qw/fetch store exists delete copy_key/ if VMG_UVAR;
- my $ret = eval { _wizard(map $opts{$_}, @keys) };
- if (my $err = $@) {
- $err =~ s/\sat\s+.*?\n//;
- croak $err;
- }
- return $ret;
-}
+a code reference, which will be called as a subroutine.
+
+=item *
-=head2 C<gensig>
+a string reference, where the string denotes which subroutine is to be called when magic is triggered.
+If the subroutine name is not fully qualified, then the current package at the time the magic is invoked will be used instead.
+
+=item *
+
+a reference to C<undef>, in which case a no-op magic callback is installed instead of the default one.
+This may especially be helpful for 'local' magic, where an empty callback prevents magic from being copied during localization.
+
+=back
+
+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.
-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.
+Here's a simple usage example :
- # Generate a signature
- my $sig = gensig;
+ # 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" },
+ );
-This function is B<deprecated> and will be removed in december 2009.
+=cut
-=head2 C<getsig>
+sub wizard {
+ if (@_ % 2) {
+ require Carp;
+ Carp::croak('Wrong number of arguments for wizard()');
+ }
- getsig $wiz
+ my %opts = @_;
-This accessor returns the magic signature of this wizard.
+ my @keys = qw<op_info data get set len clear free copy dup>;
+ push @keys, 'local' if MGf_LOCAL;
+ push @keys, qw<fetch store exists delete copy_key> if VMG_UVAR;
- # Get $wiz signature
- my $sig = getsig $wiz;
+ my ($wiz, $err);
+ {
+ local $@;
+ $wiz = eval { _wizard(map $opts{$_}, @keys) };
+ $err = $@;
+ }
+ if ($err) {
+ $err =~ s/\sat\s+.*?\n//;
+ require Carp;
+ Carp::croak($err);
+ }
-This function is B<deprecated> and will be removed in december 2009.
+ return $wiz;
+}
=head2 C<cast>
=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.
=head2 C<VMG_UVAR>
When this constant is true, you can use the C<fetch,store,exists,delete> callbacks on hashes.
+Initial VMG_UVAR capability was introduced in perl 5.9.5, with a fully functional implementation
+shipped with perl 5.10.0.
+
+=head2 C<VMG_COMPAT_SCALAR_LENGTH_NOLEN>
+
+True for perls that don't call 'len' magic when taking the C<length> of a magical scalar.
=head2 C<VMG_COMPAT_ARRAY_PUSH_NOLEN>
True for perls that call 'clear' magic when undefining magical arrays.
-=head2 C<VMG_COMPAT_SCALAR_LENGTH_NOLEN>
+=head2 C<VMG_COMPAT_HASH_DELETE_NOUVAR_VOID>
-True for perls that don't call 'len' magic when taking the C<length> of a magical scalar.
+True for perls that don't call 'delete' uvar magic when you delete an element from a hash in void context.
+
+=head2 C<VMG_COMPAT_GLOB_GET>
+
+True for perls that call 'get' magic for operations on globs.
=head2 C<VMG_PERL_PATCHLEVEL>
=head2 Associate an object to any perl variable
-This can be useful for passing user data through limited APIs.
+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/;
+ use Variable::Magic qw<wizard cast getdata>;
my $wiz = wizard data => sub { \$_[1] };
my ($var) = @_;
my $data = &getdata($var, $wiz);
unless (defined $data) {
- &cast($var, $wiz);
- $data = &getdata($var, $wiz);
- die "Couldn't cast UserData magic onto the variable" unless defined $data;
+ $data = \(my $slot);
+ &cast($var, $wiz, $slot)
+ or die "Couldn't cast UserData magic onto the variable";
}
$$data;
}
=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'>.
=cut
-use base qw/Exporter/;
+use base qw<Exporter>;
our @EXPORT = ();
our %EXPORT_TAGS = (
- 'funcs' => [ qw/wizard gensig getsig cast getdata dispell/ ],
- 'consts' => [
- qw/SIG_MIN SIG_MAX SIG_NBR 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_PERL_PATCHLEVEL/,
- qw/VMG_THREADSAFE VMG_FORKSAFE/,
- qw/VMG_OP_INFO_NAME VMG_OP_INFO_OBJECT/
- ]
+ 'funcs' => [ qw<wizard cast getdata dispell> ],
+ 'consts' => [ qw<
+ MGf_COPY MGf_DUP MGf_LOCAL VMG_UVAR
+ VMG_COMPAT_SCALAR_LENGTH_NOLEN
+ VMG_COMPAT_ARRAY_PUSH_NOLEN VMG_COMPAT_ARRAY_PUSH_NOLEN_VOID
+ VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID
+ VMG_COMPAT_ARRAY_UNDEF_CLEAR
+ VMG_COMPAT_HASH_DELETE_NOUVAR_VOID
+ VMG_COMPAT_GLOB_GET
+ VMG_PERL_PATCHLEVEL
+ VMG_THREADSAFE VMG_FORKSAFE
+ VMG_OP_INFO_NAME VMG_OP_INFO_OBJECT
+ > ],
);
our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
$EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
If you define a wizard with a C<free> callback and cast it on itself, this destructor won't be called because the wizard will be destroyed first.
+In order to define magic on hash members, you need at least L<perl> 5.10.0 (see L</VMG_UVAR>)
+
=head1 DEPENDENCIES
L<perl> 5.8.
+A C compiler.
+This module may happen to build with a C++ compiler as well, but don't rely on it, as no guarantee is made in this regard.
+
L<Carp> (standard since perl 5), L<XSLoader> (standard since perl 5.006).
Copy tests need L<Tie::Array> (standard since perl 5.005) and L<Tie::Hash> (since 5.002).
=head1 COPYRIGHT & LICENSE
-Copyright 2007-2009 Vincent Pit, all rights reserved.
+Copyright 2007,2008,2009,2010,2011 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