package Variable::Magic;
+use 5.007003;
+
use strict;
use warnings;
=head1 VERSION
-Version 0.01
+Version 0.21_01
=cut
-our $VERSION = '0.01';
+our $VERSION;
+BEGIN {
+ $VERSION = '0.21_01';
+}
=head1 SYNOPSIS
use Variable::Magic qw/wizard cast dispell/;
- my $wiz = wizard set => sub { print STDERR "now set to $_[0]!\n" };
+ my $wiz = wizard set => sub { print STDERR "now set to ${$_[0]}!\n" };
my $a = 1;
cast $a, $wiz;
$a = 2; # "now set to 2!"
=over 4
-=item C<get>
+=item *
+
+C<get>
This magic is invoked when the variable is evaluated (does not include array/hash subscripts and slices).
-=item C<set>
+=item *
+
+C<set>
This one is triggered each time the value of the variable changes (includes array/hash subscripts and slices).
-=item C<len>
+=item *
+
+C<len>
This magic is a little special : it is called when the 'size' or the 'length' of the variable has to be known by Perl. Typically, it's the magic involved when an array is evaluated in scalar context, but also on array assignation and loops (C<for>, C<map> or C<grep>). The callback has then to return the length as an integer.
-=item C<clear>
+=item *
+
+C<clear>
+
+This magic is invoked when the variable is reset, such as when an array is emptied. Please note that this is different from undefining the variable, even though the magic is called when the clearing is a result of the undefine (e.g. for an array, but actually a bug prevent it to work before perl 5.9.5 - see the L<history|/PERL MAGIC HISTORY>).
+
+=item *
+
+C<free>
+
+This one can be considered as an object destructor. It happens when the variable goes out of scope (with the exception of global scope), but not when it is undefined.
+
+=item *
+
+C<copy>
+
+This magic only applies to tied arrays and hashes. It fires when you try to access or change their elements. It is available on your perl iff C<MGf_COPY> is true.
-This magic is invoked when the variable is reset, such as when an array is emptied. Please note that this is different from undefining the variable, even though the magic is called when the reset is a result of the undefine (e.g. for an array).
+=item *
-=item C<free>
+C<dup>
-This last one can be considered as an object destructor. It happens when the variable goes out of scope (with the exception of global scope), but not when it is undefined.
+Invoked when the variable is cloned across threads. Currently not available.
+
+=item *
+
+C<local>
+
+When this magic is set on a variable, all subsequent localizations of the variable will trigger the callback. It is available on your perl iff C<MGf_LOCAL> is true.
=back
+The following actions only apply to hashes and are available iff C<VMG_UVAR> is true. They are referred to as C<uvar> magics.
+
+=over 4
+
+=item *
+
+C<fetch>
+
+This magic happens each time an element is fetched from the hash.
+
+=item *
+
+C<store>
+
+This one is called when an element is stored into the hash.
+
+=item *
+
+C<exists>
+
+This magic fires when a key is tested for existence in the hash.
+
+=item *
+
+C<delete>
+
+This last one triggers when a key is deleted in the hash, regardless of whether the key actually exists in it.
+
+=back
+
+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).
+=head1 PERL MAGIC HISTORY
+
+The places where magic is invoked have changed a bit through perl history. Here's a little list of the most recent ones.
+
+=over 4
+
+=item *
+
+B<5.6.x>
+
+I<p14416> : 'copy' and 'dup' magic.
+
+=item *
+
+B<5.9.3>
+
+I<p25854> : 'len' magic is no longer called when pushing an element into a magic array.
+
+I<p26569> : 'local' magic.
+
+=item *
+
+B<5.9.5>
+
+I<p31064> : Meaningful 'uvar' magic.
+
+I<p31473> : 'clear' magic wasn't invoked when undefining an array. The bug is fixed as of this version.
+
+=item *
+
+B<5.10.0>
+
+Since C<PERL_MAGIC_uvar> is uppercased, C<hv_magic_check()> triggers 'copy' magic on hash stores for (non-tied) hashes that also have 'uvar' magic.
+
+=item *
+
+B<5.11.x>
+
+I<p32969> : 'len' magic is no longer invoked when calling C<length> with a magical scalar.
+
+=back
+
=head1 CONSTANTS
=head2 C<SIG_MIN>
The minimum integer used as a signature for user-defined magic.
-=cut
-
-use constant SIG_MIN => 2 ** 8;
-
=head2 C<SIG_MAX>
The maximum integer used as a signature for user-defined magic.
-=cut
-
-use constant SIG_MAX => 2 ** 16 - 1;
-
=head2 C<SIG_NBR>
SIG_NBR = SIG_MAX - SIG_MIN + 1
-=cut
+=head2 C<MGf_COPY>
-use constant SIG_NBR => SIG_MAX - SIG_MIN + 1;
+Evaluates to true iff the 'copy' magic is available.
-=head1 FUNCTIONS
+=head2 C<MGf_DUP>
-=cut
+Evaluates to true iff the 'dup' magic is available.
+
+=head2 C<MGf_LOCAL>
+
+Evaluates to true iff the 'local' magic is available.
+
+=head2 C<VMG_UVAR>
+
+When this constant is true, you can use the C<fetch,store,exists,delete> callbacks on hashes.
+
+=head2 C<VMG_COMPAT_ARRAY_PUSH_NOLEN>
+
+True for perls that don't call 'len' magic when you push an element in a magical array.
+
+=head2 C<VMG_COMPAT_ARRAY_UNDEF_CLEAR>
+
+True for perls that call 'clear' magic when undefining magical arrays.
+
+=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.
-require XSLoader;
+=head2 C<VMG_PERL_PATCHLEVEL>
-XSLoader::load(__PACKAGE__, $VERSION);
+The perl patchlevel this module was built with, or C<0> for non-debugging perls.
-my %wizz;
+=head2 C<VMG_THREADSAFE>
+
+True iff this module could have been built with thread-safety features enabled.
+
+=head1 FUNCTIONS
+
+=cut
+
+BEGIN {
+ require XSLoader;
+ XSLoader::load(__PACKAGE__, $VERSION);
+}
=head2 C<wizard>
- wizard sig => .., data => ..., get => .., set => .., len => .., clear => .., free => ..
+ wizard sig => ...,
+ data => sub { ... },
+ get => sub { my ($ref, $data) = @_; ... },
+ set => sub { my ($ref, $data) = @_; ... },
+ len => sub { my ($ref, $data, $len) = @_; ... ; return $newlen; },
+ clear => sub { my ($ref, $data) = @_; ... },
+ free => sub { my ($ref, $data) = @_, ... },
+ copy => sub { my ($ref, $data, $key, $elt) = @_; ... },
+ local => sub { my ($ref, $data) = @_; ... },
+ fetch => sub { my ($ref, $data, $key) = @_; ... },
+ store => sub { my ($ref, $data, $key) = @_; ... },
+ exists => sub { my ($ref, $data, $key) = @_; ... },
+ delete => sub { my ($ref, $data, $key) = @_; ... }
This function creates a 'wizard', an opaque type that holds the magic information. It takes a list of keys / values as argument, whose keys can be :
=over 4
-=item C<'sig'>
+=item *
-The numerical signature. If not specified or undefined, a random signature is generated.
+C<sig>
-=item C<'data'>
+The numerical signature. If not specified or undefined, a random signature is generated. If the signature matches an already defined magic, then the existant magic object is returned.
-A code reference to a private data constructor. It will be called each time this magic is cast on a variable, and the scalar returned will be used as private data storage for it.
+=item *
-=item C<'get'>, C<'set'>, C<'len'>, C<'clear'> and C<'free'>
+C<data>
-Code references to corresponding magic callbacks. You don't have to specify all of them : the magic associated with undefined entries simply won't be hooked. When the magic variable is an array or a hash, C<$_[0]> is a reference to it, but directly references it otherwise. C<$_[1]> is the private data (or C<undef> when no private data constructor was supplied). In the special case of C<len> magic and when the variable is an array, C<$_[2]> contains its normal length.
+A code 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<$_[0]> is a reference to the magic object and C<@_[1 .. @_-1]> are all extra arguments that were passed to L</cast>.
+
+=item *
+
+C<get>, C<set>, C<len>, C<clear>, C<free>, C<copy>, C<local>, C<fetch>, C<store>, C<exists> and C<delete>
+
+Code references to corresponding magic callbacks. You don't have to specify all of them : the magic associated with undefined entries simply won't be hooked. In those callbacks, C<$_[0]> is always a reference to the magic object and C<$_[1]> is always the private data (or C<undef> when no private data constructor was supplied). In the special case of C<len> magic and when the variable is an array, C<$_[2]> contains its normal length. C<$_[2]> is the current key in C<copy>, C<fetch>, C<store>, C<exists> and C<delete> callbacks, although for C<copy> it may just be a copy of the actual key so it's useless to (for example) cast magic on it. C<copy> magic also receives the current element (i.e. the value) in C<$_[3]>.
=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" }
+ 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" }
=cut
sub wizard {
croak 'Wrong number of arguments for wizard()' if @_ % 2;
my %opts = @_;
- my $sig;
- if (defined $opts{sig}) {
- $sig = int $opts{sig};
- $sig += SIG_MIN if $sig < SIG_MIN;
- $sig %= SIG_MAX + 1 if $sig > SIG_MAX;
- } else {
- $sig = gensig();
+ my @cbs = qw/sig data get set len clear free/;
+ push @cbs, 'copy' if MGf_COPY;
+ push @cbs, 'dup' if MGf_DUP;
+ push @cbs, 'local' if MGf_LOCAL;
+ push @cbs, qw/fetch store exists delete/ if VMG_UVAR;
+ my $ret = eval { _wizard(map $opts{$_}, @cbs) };
+ if (my $err = $@) {
+ $err =~ s/\sat\s+.*?\n//;
+ croak $err;
}
- return _wizard($sig, map { $opts{$_} } qw/get set len clear free data/);
+ return $ret;
}
=head2 C<gensig>
# Generate a signature
my $sig = gensig;
-=cut
-
-sub gensig {
- my $sig;
- my $used = ~~keys %wizz;
- croak 'Too many magic signatures used' if $used == SIG_NBR;
- do { $sig = SIG_MIN + int(rand(SIG_NBR)) } while $wizz{$sig};
- return $sig;
-}
-
=head2 C<getsig>
getsig $wiz
=head2 C<cast>
- cast [$@%&*]var, $wiz
+ cast [$@%&*]var, [$wiz|$sig], ...
-This function associates C<$wiz> magic to the variable supplied, without overwriting any other kind of magic. It returns true on success or when C<$wiz> magic is already present, and false on error.
+This function associates C<$wiz> magic to the variable supplied, without overwriting any other kind of magic. You can also supply the numeric signature C<$sig> instead of C<$wiz>. It returns true on success or when C<$wiz> magic is already present, C<0> on error, and C<undef> when no magic corresponds to the given signature (in case C<$sig> was supplied). All extra arguments specified after C<$wiz> are passed to the private data constructor. If the variable isn't a hash, any C<uvar> callback of the wizard is safely ignored.
- # Casts $wiz to $x
+ # Casts $wiz onto $x. If $wiz isn't a signature, undef can't be returned.
my $x;
die 'error' unless cast $x, $wiz;
=head2 C<getdata>
- getdata [$@%&*]var, $wiz
+ getdata [$@%&*]var, [$wiz|$sig]
+
+This accessor fetches the private data associated with the magic C<$wiz> (or the signature C<$sig>) in the variable. C<undef> is returned when no such magic or data is found, or when C<$sig> does not represent a current valid magic object.
-This accessor fetches the private data associated with the magic C<$wiz> in the variable. C<undef> is returned when no such magic or data is found.
+ # Get the attached data.
+ my $data = getdata $x, $wiz or die 'no such magic or magic has no data';
=head2 C<dispell>
- dispell [$@%&*]variable, $wiz
- dispell [$@%&*]variable, $sig
+ dispell [$@%&*]variable, [$wiz|$sig]
-The exact opposite of L</cast> : it dissociates C<$wiz> magic from the variable. You can also pass the magic signature as the second argument. True is returned on success, and false on error or when no magic represented by C<$wiz> could be found in the variable.
+The exact opposite of L</cast> : it dissociates C<$wiz> magic from the variable. You can also pass the magic signature C<$sig> as the second argument. True is returned on success, C<0> on error or when no magic represented by C<$wiz> could be found in the variable, and C<undef> when no magic corresponds to the given signature (in case C<$sig> was supplied).
- # Dispell now
+ # Dispell now. If $wiz isn't a signature, undef can't be returned.
die 'no such magic or error' unless dispell $x, $wiz;
=head1 EXPORT
The functions L</wizard>, L</gensig>, L</getsig>, L</cast>, L</getdata> and L</dispell> are only exported on request. All of them are exported by the tags C<':funcs'> and C<':all'>.
-The constants L</SIG_MIN>, L</SIG_MAX> and L</SIG_NBR> are also only exported on request. They are all exported by the tags C<':consts'> and C<':all'>.
+The constants L</SIG_MIN>, L</SIG_MAX>, L</SIG_NBR>, L</MGf_COPY>, L</MGf_DUP>, L</MGf_LOCAL> and L</VMG_UVAR> are also only exported on request. They are all exported by the tags C<':consts'> and C<':all'>.
=cut
our @EXPORT = ();
our %EXPORT_TAGS = (
'funcs' => [ qw/wizard gensig getsig cast getdata dispell/ ],
- 'consts' => [ qw/SIG_MIN SIG_MAX SIG_NBR/ ]
+ 'consts' => [ qw/SIG_MIN SIG_MAX SIG_NBR MGf_COPY MGf_DUP MGf_LOCAL VMG_UVAR/,
+ qw/VMG_COMPAT_ARRAY_PUSH_NOLEN VMG_COMPAT_ARRAY_UNDEF_CLEAR/,
+ qw/VMG_COMPAT_SCALAR_LENGTH_NOLEN/,
+ qw/VMG_PERL_PATCHLEVEL/,
+ qw/VMG_THREADSAFE/ ]
);
our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
-$EXPORT_TAGS{'all'} = \@EXPORT_OK;
+$EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
+
+=head1 CAVEATS
+
+If you store a magic object in the private data slot, the magic won't be accessible by L</getdata> since it's not copied by assignation. The only way to address this would be to return a reference.
+
+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.
=head1 DEPENDENCIES
+L<perl> 5.7.3.
+
L<Carp> (standard since perl 5), L<XSLoader> (standard since perl 5.006).
-Tests use L<Symbol> (standard since perl 5.002).
+Copy tests need L<Tie::Array> (standard since perl 5.005) and L<Tie::Hash> (since 5.002).
+
+Some uvar tests need L<Hash::Util::FieldHash> (standard since perl 5.009004).
+
+Glob tests need L<Symbol> (standard since perl 5.002).
+
+Threads tests need L<threads> and L<threads::shared>.
=head1 SEE ALSO
L<perlguts> and L<perlapi> for internal information about magic.
+L<perltie> and L<overload> for other ways of enhancing objects.
+
=head1 AUTHOR
-Vincent Pit, C<< <perl at profvince.com> >>
+Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
+
+You can contact me by mail or on #perl @ FreeNode (vincent or Prof_Vince).
=head1 BUGS
-Please report any bugs or feature requests to
-C<bug-variable-magic at rt.cpan.org>, or through the web interface at
-L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Variable-Magic>.
-I will be notified, and then you'll automatically be notified of progress on
-your bug as I make changes.
+Please report any bugs or feature requests to C<bug-variable-magic at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Variable-Magic>. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
=head1 SUPPORT
perldoc Variable::Magic
+Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Variable-Magic>.
+
=head1 COPYRIGHT & LICENSE
-Copyright 2007 Vincent Pit, all rights reserved.
+Copyright 2007-2008 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