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#================================================================= -*-Perl-*-
#
# Template::Namespace::Constants
#
# DESCRIPTION
# Plugin compiler module for performing constant folding at compile time
# on variables in a particular namespace.
#
# AUTHOR
# Andy Wardley <abw@wardley.org>
#
# COPYRIGHT
# Copyright (C) 1996-2022 Andy Wardley. All Rights Reserved.
#
# This module is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
#============================================================================
package Template::Namespace::Constants;
use strict;
use warnings;
use base 'Template::Base';
use Template::Config;
use Template::Directive;
use Template::Exception;
our $VERSION = '3.100';
our $DEBUG = 0 unless defined $DEBUG;
sub _init {
my ($self, $config) = @_;
$self->{ STASH } = Template::Config->stash($config)
|| return $self->error(Template::Config->error());
return $self;
}
#------------------------------------------------------------------------
# ident(\@ident) foo.bar(baz)
#------------------------------------------------------------------------
sub ident {
my ($self, $ident) = @_;
my @save = @$ident;
# discard first node indicating constants namespace
splice(@$ident, 0, 2);
my $nelems = @$ident / 2;
my ($e, $result);
local $" = ', ';
print STDERR "constant ident [ @$ident ] " if $DEBUG;
foreach $e (0..$nelems-1) {
# node name must be a constant
unless ($ident->[$e * 2] =~ s/^'(.+)'$/$1/s) {
$self->DEBUG(" * deferred (non-constant item: ", $ident->[$e * 2], ")\n")
if $DEBUG;
return Template::Directive->ident(\@save);
}
# if args is non-zero then it must be eval'ed
if ($ident->[$e * 2 + 1]) {
my $args = $ident->[$e * 2 + 1];
my $comp = eval "$args";
if ($@) {
$self->DEBUG(" * deferred (non-constant args: $args)\n") if $DEBUG;
return Template::Directive->ident(\@save);
}
$self->DEBUG("($args) ") if $comp && $DEBUG;
$ident->[$e * 2 + 1] = $comp;
}
}
$result = $self->{ STASH }->get($ident);
if (! length $result || ref $result) {
my $reason = length $result ? 'reference' : 'no result';
$self->DEBUG(" * deferred ($reason)\n") if $DEBUG;
return Template::Directive->ident(\@save);
}
$result =~ s/'/\\'/g;
$self->DEBUG(" * resolved => '$result'\n") if $DEBUG;
return "'$result'";
}
1;
__END__
=head1 NAME
Template::Namespace::Constants - Compile time constant folding
=head1 SYNOPSIS
# easy way to define constants
use Template;
my $tt = Template->new({
CONSTANTS => {
pi => 3.14,
e => 2.718,
},
});
# nitty-gritty, hands-dirty way
use Template::Namespace::Constants;
my $tt = Template->new({
NAMESPACE => {
constants => Template::Namespace::Constants->new({
pi => 3.14,
e => 2.718,
},
},
});
=head1 DESCRIPTION
The C<Template::Namespace::Constants> module implements a namespace handler
which is plugged into the C<Template::Directive> compiler module. This then
performs compile time constant folding of variables in a particular namespace.
=head1 METHODS
=head2 new(\%constants)
The new() constructor method creates and returns a reference to a new
Template::Namespace::Constants object. This creates an internal stash
to store the constant variable definitions passed as arguments.
my $handler = Template::Namespace::Constants->new({
pi => 3.14,
e => 2.718,
});
=head2 ident(\@ident)
Method called to resolve a variable identifier into a compiled form. In this
case, the method fetches the corresponding constant value from its internal
stash and returns it.
=head1 AUTHOR
Andy Wardley E<lt>abw@wardley.orgE<gt> L<http://wardley.org/>
=head1 COPYRIGHT
Copyright (C) 1996-2022 Andy Wardley. All Rights Reserved.
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
=head1 SEE ALSO
L<Template::Directive>
=cut
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