Rework constant.pm to take advantage of the space savings of proxy

constant subroutines whenever it can.

p4raw-id: //depot/perl@26487

diff --git a/lib/constant.pm b/lib/constant.pm
index 0a866aa..d6c8a09 100644 (file)
--- a/lib/constant.pm
+++ b/lib/constant.pm
@@ -5,7 +5,7 @@ use 5.006_00;
 use warnings::register;
 
 our($VERSION, %declared);
-$VERSION = '1.06';
+$VERSION = '1.07';
 
 #=======================================================================
 
@@ -31,6 +31,12 @@ sub import {
     my $constants;
     my $multiple  = ref $_[0];
     my $pkg = caller;
+    my $symtab;
+
+    if ($] > 5.009002) {
+       no strict 'refs';
+       $symtab = \%{$pkg . '::'};
+    };
 
     if ( $multiple ) {
        if (ref $_[0] ne 'HASH') {
@@ -94,19 +100,26 @@ sub import {
            no strict 'refs';
            my $full_name = "${pkg}::$name";
            $declared{$full_name}++;
-           if ($multiple) {
-               my $scalar = $constants->{$name};
-               *$full_name = sub () { $scalar };
-           } else {
-               if (@_ == 1) {
-                   my $scalar = $_[0];
-                   *$full_name = sub () { $scalar };
-               } elsif (@_) {
-                   my @list = @_;
-                   *$full_name = sub () { @list };
+           if ($multiple || @_ == 1) {
+               my $scalar = $multiple ? $constants->{$name} : $_[0];
+               if ($symtab && !exists $symtab->{$name}) {
+                   # No typeglob yet, so we can use a reference as space-
+                   # efficient proxy for a constant subroutine
+                   # The check in Perl_ck_rvconst knows that inlinable
+                   # constants from cv_const_sv are read only. So we have to:
+                   Internals::SvREADONLY($scalar, 1);
+                   $symtab->{$name} = \$scalar;
                } else {
-                   *$full_name = sub () { };
+                   if(!exists $symtab->{$name}) {
+                       print STDERR "$name $scalar\n";
+                   }
+                   *$full_name = sub () { $scalar };
                }
+           } elsif (@_) {
+               my @list = @_;
+               *$full_name = sub () { @list };
+           } else {
+               *$full_name = sub () { };
            }
        }
     }