1package Symbol; 2 3=head1 NAME 4 5Symbol - manipulate Perl symbols and their names 6 7=head1 SYNOPSIS 8 9 use Symbol; 10 11 $sym = gensym; 12 open($sym, "filename"); 13 $_ = <$sym>; 14 # etc. 15 16 ungensym $sym; # no effect 17 18 # replace *FOO{IO} handle but not $FOO, %FOO, etc. 19 *FOO = geniosym; 20 21 print qualify("x"), "\n"; # "Test::x" 22 print qualify("x", "FOO"), "\n" # "FOO::x" 23 print qualify("BAR::x"), "\n"; # "BAR::x" 24 print qualify("BAR::x", "FOO"), "\n"; # "BAR::x" 25 print qualify("STDOUT", "FOO"), "\n"; # "main::STDOUT" (global) 26 print qualify(\*x), "\n"; # returns \*x 27 print qualify(\*x, "FOO"), "\n"; # returns \*x 28 29 use strict refs; 30 print { qualify_to_ref $fh } "foo!\n"; 31 $ref = qualify_to_ref $name, $pkg; 32 33 use Symbol qw(delete_package); 34 delete_package('Foo::Bar'); 35 print "deleted\n" unless exists $Foo::{'Bar::'}; 36 37 38=head1 DESCRIPTION 39 40C<Symbol::gensym> creates an anonymous glob and returns a reference 41to it. Such a glob reference can be used as a file or directory 42handle. 43 44For backward compatibility with older implementations that didn't 45support anonymous globs, C<Symbol::ungensym> is also provided. 46But it doesn't do anything. 47 48C<Symbol::geniosym> creates an anonymous IO handle. This can be 49assigned into an existing glob without affecting the non-IO portions 50of the glob. 51 52C<Symbol::qualify> turns unqualified symbol names into qualified 53variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a 54second parameter, C<qualify> uses it as the default package; 55otherwise, it uses the package of its caller. Regardless, global 56variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with 57"main::". 58 59Qualification applies only to symbol names (strings). References are 60left unchanged under the assumption that they are glob references, 61which are qualified by their nature. 62 63C<Symbol::qualify_to_ref> is just like C<Symbol::qualify> except that it 64returns a glob ref rather than a symbol name, so you can use the result 65even if C<use strict 'refs'> is in effect. 66 67C<Symbol::delete_package> wipes out a whole package namespace. Note 68this routine is not exported by default--you may want to import it 69explicitly. 70 71=cut 72 73BEGIN { require 5.005; } 74 75require Exporter; 76@ISA = qw(Exporter); 77@EXPORT = qw(gensym ungensym qualify qualify_to_ref); 78@EXPORT_OK = qw(delete_package geniosym); 79 80$VERSION = 1.04; 81 82my $genpkg = "Symbol::"; 83my $genseq = 0; 84 85my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); 86 87# 88# Note that we never _copy_ the glob; we just make a ref to it. 89# If we did copy it, then SVf_FAKE would be set on the copy, and 90# glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. 91# 92sub gensym () { 93 my $name = "GEN" . $genseq++; 94 my $ref = \*{$genpkg . $name}; 95 delete $$genpkg{$name}; 96 $ref; 97} 98 99sub geniosym () { 100 my $sym = gensym(); 101 # force the IO slot to be filled 102 select(select $sym); 103 *$sym{IO}; 104} 105 106sub ungensym ($) {} 107 108sub qualify ($;$) { 109 my ($name) = @_; 110 if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { 111 my $pkg; 112 # Global names: special character, "^xyz", or other. 113 if ($name =~ /^(([^a-z])|(\^[a-z_]+))\z/i || $global{$name}) { 114 # RGS 2001-11-05 : translate leading ^X to control-char 115 $name =~ s/^\^([a-z_])/'qq(\c'.$1.')'/eei; 116 $pkg = "main"; 117 } 118 else { 119 $pkg = (@_ > 1) ? $_[1] : caller; 120 } 121 $name = $pkg . "::" . $name; 122 } 123 $name; 124} 125 126sub qualify_to_ref ($;$) { 127 return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; 128} 129 130# 131# of Safe.pm lineage 132# 133sub delete_package ($) { 134 my $pkg = shift; 135 136 # expand to full symbol table name if needed 137 138 unless ($pkg =~ /^main::.*::$/) { 139 $pkg = "main$pkg" if $pkg =~ /^::/; 140 $pkg = "main::$pkg" unless $pkg =~ /^main::/; 141 $pkg .= '::' unless $pkg =~ /::$/; 142 } 143 144 my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; 145 my $stem_symtab = *{$stem}{HASH}; 146 return unless defined $stem_symtab and exists $stem_symtab->{$leaf}; 147 148 149 # free all the symbols in the package 150 151 my $leaf_symtab = *{$stem_symtab->{$leaf}}{HASH}; 152 foreach my $name (keys %$leaf_symtab) { 153 undef *{$pkg . $name}; 154 } 155 156 # delete the symbol table 157 158 %$leaf_symtab = (); 159 delete $stem_symtab->{$leaf}; 160} 161 1621; 163