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1 | package Symbol; |
2 | |
3 | =head1 NAME |
4 | |
5 | Symbol - 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 | |
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18 | # localize *FOO IO handle but not $FOO, %FOO, etc. |
19 | my $save_fooio = *FOO{IO} || geniosym; |
20 | *FOO = geniosym; |
21 | use_foo(); |
22 | *FOO{IO} = $save_fooio; |
23 | |
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24 | print qualify("x"), "\n"; # "Test::x" |
25 | print qualify("x", "FOO"), "\n" # "FOO::x" |
26 | print qualify("BAR::x"), "\n"; # "BAR::x" |
27 | print qualify("BAR::x", "FOO"), "\n"; # "BAR::x" |
28 | print qualify("STDOUT", "FOO"), "\n"; # "main::STDOUT" (global) |
29 | print qualify(\*x), "\n"; # returns \*x |
30 | print qualify(\*x, "FOO"), "\n"; # returns \*x |
31 | |
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32 | use strict refs; |
33 | print { qualify_to_ref $fh } "foo!\n"; |
34 | $ref = qualify_to_ref $name, $pkg; |
35 | |
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36 | use Symbol qw(delete_package); |
37 | delete_package('Foo::Bar'); |
38 | print "deleted\n" unless exists $Foo::{'Bar::'}; |
39 | |
40 | |
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41 | =head1 DESCRIPTION |
42 | |
43 | C<Symbol::gensym> creates an anonymous glob and returns a reference |
44 | to it. Such a glob reference can be used as a file or directory |
45 | handle. |
46 | |
47 | For backward compatibility with older implementations that didn't |
48 | support anonymous globs, C<Symbol::ungensym> is also provided. |
49 | But it doesn't do anything. |
50 | |
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51 | C<Symbol::geniosym> creates an anonymous IO handle. This can be |
52 | assigned into an existing glob without affecting the non-IO portions |
53 | of the glob. |
54 | |
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55 | C<Symbol::qualify> turns unqualified symbol names into qualified |
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56 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a |
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57 | second parameter, C<qualify> uses it as the default package; |
58 | otherwise, it uses the package of its caller. Regardless, global |
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59 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with |
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60 | "main::". |
61 | |
62 | Qualification applies only to symbol names (strings). References are |
63 | left unchanged under the assumption that they are glob references, |
64 | which are qualified by their nature. |
65 | |
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66 | C<Symbol::qualify_to_ref> is just like C<Symbol::qualify> except that it |
67 | returns a glob ref rather than a symbol name, so you can use the result |
68 | even if C<use strict 'refs'> is in effect. |
69 | |
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70 | C<Symbol::delete_package> wipes out a whole package namespace. Note |
71 | this routine is not exported by default--you may want to import it |
72 | explicitly. |
73 | |
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74 | =cut |
75 | |
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76 | BEGIN { require 5.005; } |
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77 | |
78 | require Exporter; |
79 | @ISA = qw(Exporter); |
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80 | @EXPORT = qw(gensym ungensym qualify qualify_to_ref); |
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81 | @EXPORT_OK = qw(delete_package geniosym); |
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82 | |
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83 | $VERSION = 1.04; |
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84 | |
85 | my $genpkg = "Symbol::"; |
86 | my $genseq = 0; |
87 | |
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88 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); |
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89 | |
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90 | # |
91 | # Note that we never _copy_ the glob; we just make a ref to it. |
92 | # If we did copy it, then SVf_FAKE would be set on the copy, and |
93 | # glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. |
94 | # |
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95 | sub gensym () { |
96 | my $name = "GEN" . $genseq++; |
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97 | my $ref = \*{$genpkg . $name}; |
98 | delete $$genpkg{$name}; |
99 | $ref; |
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100 | } |
101 | |
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102 | sub geniosym () { |
103 | my $sym = gensym(); |
104 | # force the IO slot to be filled |
105 | select(select $sym); |
106 | *$sym{IO}; |
107 | } |
108 | |
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109 | sub ungensym ($) {} |
110 | |
111 | sub qualify ($;$) { |
112 | my ($name) = @_; |
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113 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { |
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114 | my $pkg; |
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115 | # Global names: special character, "^xyz", or other. |
116 | if ($name =~ /^(([^a-z])|(\^[a-z_]+))\z/i || $global{$name}) { |
117 | # RGS 2001-11-05 : translate leading ^X to control-char |
118 | $name =~ s/^\^([a-z_])/'qq(\c'.$1.')'/eei; |
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119 | $pkg = "main"; |
120 | } |
121 | else { |
122 | $pkg = (@_ > 1) ? $_[1] : caller; |
123 | } |
124 | $name = $pkg . "::" . $name; |
125 | } |
126 | $name; |
127 | } |
128 | |
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129 | sub qualify_to_ref ($;$) { |
130 | return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; |
131 | } |
132 | |
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133 | # |
134 | # of Safe.pm lineage |
135 | # |
136 | sub delete_package ($) { |
137 | my $pkg = shift; |
138 | |
139 | # expand to full symbol table name if needed |
140 | |
141 | unless ($pkg =~ /^main::.*::$/) { |
142 | $pkg = "main$pkg" if $pkg =~ /^::/; |
143 | $pkg = "main::$pkg" unless $pkg =~ /^main::/; |
144 | $pkg .= '::' unless $pkg =~ /::$/; |
145 | } |
146 | |
147 | my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; |
148 | my $stem_symtab = *{$stem}{HASH}; |
149 | return unless defined $stem_symtab and exists $stem_symtab->{$leaf}; |
150 | |
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151 | |
152 | # free all the symbols in the package |
153 | |
154 | my $leaf_symtab = *{$stem_symtab->{$leaf}}{HASH}; |
155 | foreach my $name (keys %$leaf_symtab) { |
156 | undef *{$pkg . $name}; |
157 | } |
158 | |
159 | # delete the symbol table |
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160 | |
161 | %$leaf_symtab = (); |
162 | delete $stem_symtab->{$leaf}; |
163 | } |
164 | |
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165 | 1; |