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Diffstat (limited to 'Master/tlpkg/tlperl0/lib/Symbol.pm')
| -rwxr-xr-x | Master/tlpkg/tlperl0/lib/Symbol.pm | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/Master/tlpkg/tlperl0/lib/Symbol.pm b/Master/tlpkg/tlperl0/lib/Symbol.pm new file mode 100755 index 00000000000..1e408b59f71 --- /dev/null +++ b/Master/tlpkg/tlperl0/lib/Symbol.pm @@ -0,0 +1,170 @@ +package Symbol; + +=head1 NAME + +Symbol - manipulate Perl symbols and their names + +=head1 SYNOPSIS + + use Symbol; + + $sym = gensym; + open($sym, "filename"); + $_ = <$sym>; + # etc. + + ungensym $sym; # no effect + + # replace *FOO{IO} handle but not $FOO, %FOO, etc. + *FOO = geniosym; + + print qualify("x"), "\n"; # "main::x" + print qualify("x", "FOO"), "\n"; # "FOO::x" + print qualify("BAR::x"), "\n"; # "BAR::x" + print qualify("BAR::x", "FOO"), "\n"; # "BAR::x" + print qualify("STDOUT", "FOO"), "\n"; # "main::STDOUT" (global) + print qualify(\*x), "\n"; # returns \*x + print qualify(\*x, "FOO"), "\n"; # returns \*x + + use strict refs; + print { qualify_to_ref $fh } "foo!\n"; + $ref = qualify_to_ref $name, $pkg; + + use Symbol qw(delete_package); + delete_package('Foo::Bar'); + print "deleted\n" unless exists $Foo::{'Bar::'}; + +=head1 DESCRIPTION + +C<Symbol::gensym> creates an anonymous glob and returns a reference +to it. Such a glob reference can be used as a file or directory +handle. + +For backward compatibility with older implementations that didn't +support anonymous globs, C<Symbol::ungensym> is also provided. +But it doesn't do anything. + +C<Symbol::geniosym> creates an anonymous IO handle. This can be +assigned into an existing glob without affecting the non-IO portions +of the glob. + +C<Symbol::qualify> turns unqualified symbol names into qualified +variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a +second parameter, C<qualify> uses it as the default package; +otherwise, it uses the package of its caller. Regardless, global +variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with +"main::". + +Qualification applies only to symbol names (strings). References are +left unchanged under the assumption that they are glob references, +which are qualified by their nature. + +C<Symbol::qualify_to_ref> is just like C<Symbol::qualify> except that it +returns a glob ref rather than a symbol name, so you can use the result +even if C<use strict 'refs'> is in effect. + +C<Symbol::delete_package> wipes out a whole package namespace. Note +this routine is not exported by default--you may want to import it +explicitly. + +=head1 BUGS + +C<Symbol::delete_package> is a bit too powerful. It undefines every symbol that +lives in the specified package. Since perl, for performance reasons, does not +perform a symbol table lookup each time a function is called or a global +variable is accessed, some code that has already been loaded and that makes use +of symbols in package C<Foo> may stop working after you delete C<Foo>, even if +you reload the C<Foo> module afterwards. + +=cut + +BEGIN { require 5.005; } + +require Exporter; +@ISA = qw(Exporter); +@EXPORT = qw(gensym ungensym qualify qualify_to_ref); +@EXPORT_OK = qw(delete_package geniosym); + +$VERSION = '1.07'; + +my $genpkg = "Symbol::"; +my $genseq = 0; + +my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); + +# +# Note that we never _copy_ the glob; we just make a ref to it. +# If we did copy it, then SVf_FAKE would be set on the copy, and +# glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. +# +sub gensym () { + my $name = "GEN" . $genseq++; + my $ref = \*{$genpkg . $name}; + delete $$genpkg{$name}; + $ref; +} + +sub geniosym () { + my $sym = gensym(); + # force the IO slot to be filled + select(select $sym); + *$sym{IO}; +} + +sub ungensym ($) {} + +sub qualify ($;$) { + my ($name) = @_; + if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { + my $pkg; + # Global names: special character, "^xyz", or other. + if ($name =~ /^(([^a-z])|(\^[a-z_]+))\z/i || $global{$name}) { + # RGS 2001-11-05 : translate leading ^X to control-char + $name =~ s/^\^([a-z_])/'qq(\c'.$1.')'/eei; + $pkg = "main"; + } + else { + $pkg = (@_ > 1) ? $_[1] : caller; + } + $name = $pkg . "::" . $name; + } + $name; +} + +sub qualify_to_ref ($;$) { + return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; +} + +# +# of Safe.pm lineage +# +sub delete_package ($) { + my $pkg = shift; + + # expand to full symbol table name if needed + + unless ($pkg =~ /^main::.*::$/) { + $pkg = "main$pkg" if $pkg =~ /^::/; + $pkg = "main::$pkg" unless $pkg =~ /^main::/; + $pkg .= '::' unless $pkg =~ /::$/; + } + + my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; + my $stem_symtab = *{$stem}{HASH}; + return unless defined $stem_symtab and exists $stem_symtab->{$leaf}; + + + # free all the symbols in the package + + my $leaf_symtab = *{$stem_symtab->{$leaf}}{HASH}; + foreach my $name (keys %$leaf_symtab) { + undef *{$pkg . $name}; + } + + # delete the symbol table + + %$leaf_symtab = (); + delete $stem_symtab->{$leaf}; +} + +1; |