=head1 NAME

ModPerl::RegistryCooker - Cook mod_perl 2.0 Registry Modules

=head1 Synopsis

  # shouldn't be used as-is but sub-classed first
  # see ModPerl::Registry for an example

=head1 Description

C<ModPerl::RegistryCooker> is used to create flexible and overridable
registry modules which emulate mod_cgi for Perl scripts. The concepts
are discussed in the manpage of the following modules:
C<L<ModPerl::Registry>>, C<L<ModPerl::Registry>> and
C<L<ModPerl::RegistryBB>>.

C<ModPerl::RegistryCooker> has two purposes:

=over

=item *

Provide ingredients that can be used by registry sub-classes

=item *

Provide a default behavior, which can be overriden in sub-classed

META: in the future this functionality may move into a separate class.

=back

Here are the current overridable methods:

META: these are all documented in RegistryCooker.pm, though not using
pod. please help to port these to pod and move the descriptions here.

=over

=item * new()

create the class's object, bless it and return it

  my $obj = $class->new($r);

C<$class> -- the registry class, usually C<__PACKAGE__> can be used.

C<$r> -- C<Apache2::Request> object.

default: new()

=item * init()

initializes the data object's fields: C<REQ>, C<FILENAME>,
C<URI>. Called from the new().

default: init()

=item * default_handler()

default:  default_handler()

=item * run()

default: run()

=item * can_compile()

default: can_compile()

=item * make_namespace()

default: make_namespace()

=item * namespace_root()

default: namespace_root()


=item * namespace_from()

If C<namespace_from_uri> is used and the script is called from the
virtual host, by default the virtual host name is prepended to the uri
when package name for the compiled script is created. Sometimes this
behavior is undesirable, e.g., when the same (physical) script is
accessed using the same path_info but different virtual hosts. In that
case you can make the script compiled only once for all vhosts, by
specifying:

  $ModPerl::RegistryCooker::NameWithVirtualHost = 0;

The drawback is that it affects the global environment and all other
scripts will be compiled ignoring virtual hosts.

default: namespace_from()

=item * is_cached()

default: is_cached()

=item * should_compile()

default: should_compile()

=item * flush_namespace()

default: flush_namespace()


=item * cache_table()

default: cache_table()

=item * cache_it()

default: cache_it()

=item * read_script()

default: read_script()

=item * shebang_to_perl()

default: shebang_to_perl()

=item * get_script_name()

default: get_script_name()

=item * chdir_file()

default: chdir_file()

=item * get_mark_line()

default: get_mark_line()

=item * compile()

default: compile()


=item * error_check()

default: error_check()

=item * strip_end_data_segment()

default: strip_end_data_segment()

=item * convert_script_to_compiled_handler()

default: convert_script_to_compiled_handler()

=back




=head2 Special Predefined Functions

The following functions are implemented as constants.

=over

=item * NOP()

Use when the function shouldn't do anything.

=item * TRUE()

Use when a function should always return a true value.

=item * FALSE()

Use when a function should always return a false value.

=back




=head1 Sub-classing Techniques

To override the default C<ModPerl::RegistryCooker> methods, first,
sub-class C<ModPerl::RegistryCooker> or one of its existing
sub-classes, using C<use base>. Second, override the methods.

Those methods that weren't overridden will be resolved at run time
when used for the first time and cached for the future requests. One
way to to shortcut this first run resolution is to use the symbol
aliasing feature. For example to alias C<ModPerl::MyRegistry::flush_namespace>
as C<ModPerl::RegistryCooker::flush_namespace>, you can do:

  package ModPerl::MyRegistry;
  use base qw(ModPerl::RegistryCooker);
  *ModPerl::MyRegistry::flush_namespace =
      \&ModPerl::RegistryCooker::flush_namespace;
  1;

In fact, it's a good idea to explicitly alias all the methods so you
know exactly what functions are used, rather then relying on the
defaults. For that purpose C<ModPerl::RegistryCooker> class method
install_aliases() can be used. Simply prepare a hash with method names
in the current package as keys and corresponding fully qualified
methods to be aliased for as values and pass it to
install_aliases(). Continuing our example we could do:

  package ModPerl::MyRegistry;
  use base qw(ModPerl::RegistryCooker);
  my %aliases = (
      flush_namespace => 'ModPerl::RegistryCooker::flush_namespace',
  );
  __PACKAGE__->install_aliases(\%aliases);
  1;

The values use fully qualified packages so you can mix methods from
different classes.

=head1 Examples

The best examples are existing core registry modules:
C<L<ModPerl::Registry>>, C<L<ModPerl::Registry>> and
C<L<ModPerl::RegistryBB>>. Look at the source code and their manpages
to see how they subclass C<ModPerl::RegistryCooker>.

For example by default C<L<ModPerl::Registry>> uses the script's path
when creating a package's namespace. If for example you want to use a
uri instead you can override it with:

  *ModPerl::MyRegistry::namespace_from =
      \&ModPerl::RegistryCooker::namespace_from_uri;
  1;

Since the C<namespace_from_uri> component already exists in
C<ModPerl::RegistryCooker>. If you want to write your own method,
e.g., that creates a namespace based on the inode, you can do:

  sub namespace_from_inode {
      my $self = shift;
      return (stat $self->[FILENAME])[1];
  }

META: when $r-E<gt>finfo will be ported it'll be more effecient. 
(stat $r-E<gt>finfo)[1]


=head1 Authors

Doug MacEachern

Stas Bekman

=head1 See Also

C<L<ModPerl::Registry|docs::2.0::api::ModPerl::Registry>>,
C<L<ModPerl::RegistryBB|docs::2.0::api::ModPerl::RegistryBB>> and
C<L<ModPerl::PerlRun|docs::2.0::api::ModPerl::PerlRun>>.

=cut
