package Hash::FieldHash;
use 5.008_005;
use strict;
our $VERSION = '0.15';
use parent qw(Exporter);
our @EXPORT_OK = qw(fieldhash fieldhashes from_hash to_hash);
our %EXPORT_TAGS = (all => \@EXPORT_OK);
use XSLoader;
XSLoader::load(__PACKAGE__, $VERSION);
sub fieldhashes{
foreach my $hash_ref(@_){
&fieldhash($hash_ref);
}
}
1;
__END__
=for stopwords uvar CPAN rw-accessors chainable
[](https://travis-ci.org/gfx/p5-Hash-FieldHash)
=head1 NAME
Hash::FieldHash - Lightweight field hash for inside-out objects
=head1 VERSION
This document describes Hash::FieldHash version 0.15.
=head1 SYNOPSIS
use Hash::FieldHash qw(:all);
fieldhash my %foo;
fieldhashes \my(%bar, %baz);
{
my $o = Something->new();
$foo{$o} = 42;
print $foo{$o}; # => 42
}
# when $o is released, $foo{$o} is also deleted,
# so %foo is empty in here.
# in a class
{
package Foo;
use Hash::FieldHash qw(:all);
fieldhash my %bar, 'bar'; # make an accessor
}
my $obj = bless {}, 'Foo';
$obj->bar(10); # does $bar{$obj} = 10
=head1 DESCRIPTION
C<Hash::FieldHash> provides the field hash mechanism which supports
the inside-out technique.
You may know C<Hash::Util::FieldHash>. It's a very useful module,
but too complex to understand the functionality and only available in 5.10.
C<H::U::F::Compat> is available for pre-5.10, but it is too slow to use.
This is a better alternative to C<H::U::F> with following features:
=over 4
=item Simpler interface
C<Hash::FieldHash> provides a few functions: C<fieldhash()> and C<fieldhashes()>.
That's enough.
=item Higher performance
C<Hash::FieldHash> is faster than C<Hash::Util::FieldHash>, because
its internals use simpler structures.
=item Relic support
Although C<Hash::FieldHash> uses a new feature introduced in Perl 5.10,
I<the uvar magic for hashes> described in L<Hash::Util::Fieldhash/"GUTS">,
it supports Perl 5.8 using the traditional tie-hash layer.
=back
=head1 INTERFACE
=head2 Exportable functions
=over 4
=item C<< fieldhash(%hash, ?$name, ?$package) >>
Creates a field hash. The first argument must be a hash.
Optional I<$name> and I<$package> indicate the name of the field, which will
create rw-accessors, using the same name as I<$name>.
Returns nothing.
=item C<< fieldhashes(@hash_refs) >>
Creates a number of field hashes. All the arguments must be hash references.
Returns nothing.
=item C<< from_hash($object, \%fields) >>
Fills the named fields associated with I<$object> with I<%fields>.
The keys of I<%fields> can be simple or fully qualified.
Returns I<$object>.
=item C<< to_hash($object, ?-fully_qualify) >>
Serializes I<$object> into a hash reference.
If the C<-fully_qualify> option is supplied , field keys are fully qualified.
For example:
package MyClass;
use FieldHash qw(:all);
fieldhash my %foo => 'foo';
sub new{
my $class = shift;
my $self = bless {}, $class;
return from_hash($self, @_);
}
package MyDerivedClass;
use parent -norequire => 'MyClass';
use FieldHash qw(:all);
fieldhash my %bar => 'bar';
package main;
my $o = MyDerivedClass->new(foo => 10, bar => 20);
my $p = MyDerivedClass->new('MyClass::foo' => 10, 'MyDerivedClass::bar' => 20);
use Data::Dumper;
print Dumper($o->to_hash());
# $VAR1 = { foo => 10, bar => 20 }
print Dumper($o->to_hash(-fully_qualify));
# $VAR1 = { 'MyClass::foo' => 10, 'MyDerived::bar' => 20 }
=back
=head1 ROBUSTNESS
=head2 Thread support
As C<Hash::Util::FieldHash> does, C<Hash::FieldHash> fully supports threading
using the C<CLONE> method.
=head2 Memory leaks
C<Hash::FieldHash> itself does not leak memory, but it may leak memory when
you uses hash references as field hash keys because of an issue of perl 5.10.0.
=head1 NOTES
=head2 The type of field hash keys
C<Hash::FieldHash> accepts only references and registered addresses as its
keys, whereas C<Hash::Util::FieldHash> accepts any type of scalars.
According to L<Hash::Util::FieldHash/"The Generic Object">,
Non-reference keys in C<H::U::F> are used for class fields. That is,
all the fields defined by C<H::U::F> act as both object fields and class fields
by default. It seems confusing; if you do not want them to be class fields,
you must check the type of I<$self> explicitly. In addition,
these class fields are never inherited.
This behavior seems problematic, so C<Hash::FieldHash>
restricts the type of keys.
=head2 The ID of field hash keys
While C<Hash::Util::FieldHash> uses C<refaddr> as the IDs of field
hash keys, C<Hash::FieldHash> allocates arbitrary integers as the
IDs.
=head2 What accessors return
The accessors C<fieldhash()> creates are B<chainable> accessors.
That is, it returns the I<$object> (i.e. C<$self>) with a parameter,
where as it returns the I<$value> without it.
For example:
my $o = YourClass->new();
$o->foo(42); # returns $o itself
my $value = $o->foo(); # retuns 42
=head1 DEPENDENCIES
Perl 5.8.5 or later, and a C compiler.
=head1 BUGS
No bugs have been reported.
Please report any bugs or feature requests to the author.
=head1 SEE ALSO
L<Hash::Util::FieldHash>.
L<Hash::Util::FieldHash::Compat>.
L<perlguts/"Magic Virtual Tables">.
L<Class::Std> describes the inside-out technique.
=head1 AUTHOR
Fuji, Goro (gfx) E<lt>gfuji(at)cpan.orgE<gt>.
=head1 LICENSE AND COPYRIGHT
Copyright (c) 2009-2010, Fuji, Goro. All rights reserved.
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=cut