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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 | |
18 | print qualify("x"), "\n"; # "Test::x" |
19 | print qualify("x", "FOO"), "\n" # "FOO::x" |
20 | print qualify("BAR::x"), "\n"; # "BAR::x" |
21 | print qualify("BAR::x", "FOO"), "\n"; # "BAR::x" |
22 | print qualify("STDOUT", "FOO"), "\n"; # "main::STDOUT" (global) |
23 | print qualify(\*x), "\n"; # returns \*x |
24 | print qualify(\*x, "FOO"), "\n"; # returns \*x |
25 | |
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26 | use strict refs; |
27 | print { qualify_to_ref $fh } "foo!\n"; |
28 | $ref = qualify_to_ref $name, $pkg; |
29 | |
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30 | use Symbol qw(delete_package); |
31 | delete_package('Foo::Bar'); |
32 | print "deleted\n" unless exists $Foo::{'Bar::'}; |
33 | |
34 | |
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35 | =head1 DESCRIPTION |
36 | |
37 | C<Symbol::gensym> creates an anonymous glob and returns a reference |
38 | to it. Such a glob reference can be used as a file or directory |
39 | handle. |
40 | |
41 | For backward compatibility with older implementations that didn't |
42 | support anonymous globs, C<Symbol::ungensym> is also provided. |
43 | But it doesn't do anything. |
44 | |
45 | C<Symbol::qualify> turns unqualified symbol names into qualified |
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46 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a |
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47 | second parameter, C<qualify> uses it as the default package; |
48 | otherwise, it uses the package of its caller. Regardless, global |
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49 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with |
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50 | "main::". |
51 | |
52 | Qualification applies only to symbol names (strings). References are |
53 | left unchanged under the assumption that they are glob references, |
54 | which are qualified by their nature. |
55 | |
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56 | C<Symbol::qualify_to_ref> is just like C<Symbol::qualify> except that it |
57 | returns a glob ref rather than a symbol name, so you can use the result |
58 | even if C<use strict 'refs'> is in effect. |
59 | |
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60 | C<Symbol::delete_package> wipes out a whole package namespace. Note |
61 | this routine is not exported by default--you may want to import it |
62 | explicitly. |
63 | |
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64 | =cut |
65 | |
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66 | BEGIN { require 5.002; } |
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67 | |
68 | require Exporter; |
69 | @ISA = qw(Exporter); |
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70 | @EXPORT = qw(gensym ungensym qualify qualify_to_ref); |
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71 | @EXPORT_OK = qw(delete_package); |
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72 | |
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73 | $VERSION = 1.03; |
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74 | |
75 | my $genpkg = "Symbol::"; |
76 | my $genseq = 0; |
77 | |
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78 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); |
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79 | |
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80 | # |
81 | # Note that we never _copy_ the glob; we just make a ref to it. |
82 | # If we did copy it, then SVf_FAKE would be set on the copy, and |
83 | # glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. |
84 | # |
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85 | sub gensym () { |
86 | my $name = "GEN" . $genseq++; |
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87 | my $ref = \*{$genpkg . $name}; |
88 | delete $$genpkg{$name}; |
89 | $ref; |
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90 | } |
91 | |
92 | sub ungensym ($) {} |
93 | |
94 | sub qualify ($;$) { |
95 | my ($name) = @_; |
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96 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { |
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97 | my $pkg; |
98 | # Global names: special character, "^x", or other. |
99 | if ($name =~ /^([^a-z])|(\^[a-z])$/i || $global{$name}) { |
100 | $pkg = "main"; |
101 | } |
102 | else { |
103 | $pkg = (@_ > 1) ? $_[1] : caller; |
104 | } |
105 | $name = $pkg . "::" . $name; |
106 | } |
107 | $name; |
108 | } |
109 | |
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110 | sub qualify_to_ref ($;$) { |
111 | return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; |
112 | } |
113 | |
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114 | # |
115 | # of Safe.pm lineage |
116 | # |
117 | sub delete_package ($) { |
118 | my $pkg = shift; |
119 | |
120 | # expand to full symbol table name if needed |
121 | |
122 | unless ($pkg =~ /^main::.*::$/) { |
123 | $pkg = "main$pkg" if $pkg =~ /^::/; |
124 | $pkg = "main::$pkg" unless $pkg =~ /^main::/; |
125 | $pkg .= '::' unless $pkg =~ /::$/; |
126 | } |
127 | |
128 | my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; |
129 | my $stem_symtab = *{$stem}{HASH}; |
130 | return unless defined $stem_symtab and exists $stem_symtab->{$leaf}; |
131 | |
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132 | |
133 | # free all the symbols in the package |
134 | |
135 | my $leaf_symtab = *{$stem_symtab->{$leaf}}{HASH}; |
136 | foreach my $name (keys %$leaf_symtab) { |
137 | undef *{$pkg . $name}; |
138 | } |
139 | |
140 | # delete the symbol table |
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141 | |
142 | %$leaf_symtab = (); |
143 | delete $stem_symtab->{$leaf}; |
144 | } |
145 | |
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146 | 1; |