view release on metacpan or  search on metacpan

lib/constant.pm  view on Meta::CPAN

package constant;
use 5.008;
use strict;
use warnings::register;

our $VERSION = '1.33';
our %declared;

#=======================================================================

# Some names are evil choices.
my %keywords = map +($_, 1), qw{ BEGIN INIT CHECK END DESTROY AUTOLOAD };
$keywords{UNITCHECK}++ if $] > 5.009;

my %forced_into_main = map +($_, 1),
    qw{ STDIN STDOUT STDERR ARGV ARGVOUT ENV INC SIG };

my %forbidden = (%keywords, %forced_into_main);

my $normal_constant_name = qr/^_?[^\W_0-9]\w*\z/;
my $tolerable = qr/^[A-Za-z_]\w*\z/;
my $boolean = qr/^[01]?\z/;

BEGIN {
    # We'd like to do use constant _CAN_PCS => $] > 5.009002
    # but that's a bit tricky before we load the constant module :-)
    # By doing this, we save several run time checks for *every* call
    # to import.
    my $const = $] > 5.009002;
    my $downgrade = $] < 5.015004; # && $] >= 5.008
    my $constarray = exists &_make_const;
    if ($const) {
	Internals::SvREADONLY($const, 1);
	Internals::SvREADONLY($downgrade, 1);
	$constant::{_CAN_PCS}   = \$const;
	$constant::{_DOWNGRADE} = \$downgrade;
	$constant::{_CAN_PCS_FOR_ARRAY} = \$constarray;
    }
    else {
	no strict 'refs';
	*{"_CAN_PCS"}   = sub () {$const};
	*{"_DOWNGRADE"} = sub () { $downgrade };
	*{"_CAN_PCS_FOR_ARRAY"} = sub () { $constarray };
    }
}

#=======================================================================
# import() - import symbols into user's namespace
#
# What we actually do is define a function in the caller's namespace
# which returns the value. The function we create will normally
# be inlined as a constant, thereby avoiding further sub calling 
# overhead.
#=======================================================================
sub import {
    my $class = shift;
    return unless @_;			# Ignore 'use constant;'
    my $constants;
    my $multiple  = ref $_[0];
    my $caller = caller;
    my $flush_mro;
    my $symtab;

    if (_CAN_PCS) {
	no strict 'refs';
	$symtab = \%{$caller . '::'};
    };

    if ( $multiple ) {
	if (ref $_[0] ne 'HASH') {
	    require Carp;
	    Carp::croak("Invalid reference type '".ref(shift)."' not 'HASH'");
	}