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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 | |
26 | =head1 DESCRIPTION |
27 | |
28 | C<Symbol::gensym> creates an anonymous glob and returns a reference |
29 | to it. Such a glob reference can be used as a file or directory |
30 | handle. |
31 | |
32 | For backward compatibility with older implementations that didn't |
33 | support anonymous globs, C<Symbol::ungensym> is also provided. |
34 | But it doesn't do anything. |
35 | |
36 | C<Symbol::qualify> turns unqualified symbol names into qualified |
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37 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a |
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38 | second parameter, C<qualify> uses it as the default package; |
39 | otherwise, it uses the package of its caller. Regardless, global |
40 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualfied with |
41 | "main::". |
42 | |
43 | Qualification applies only to symbol names (strings). References are |
44 | left unchanged under the assumption that they are glob references, |
45 | which are qualified by their nature. |
46 | |
47 | =cut |
48 | |
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49 | BEGIN { require 5.002; } |
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50 | |
51 | require Exporter; |
52 | @ISA = qw(Exporter); |
53 | |
54 | @EXPORT = qw(gensym ungensym qualify); |
55 | |
56 | my $genpkg = "Symbol::"; |
57 | my $genseq = 0; |
58 | |
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59 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); |
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60 | |
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61 | # |
62 | # Note that we never _copy_ the glob; we just make a ref to it. |
63 | # If we did copy it, then SVf_FAKE would be set on the copy, and |
64 | # glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. |
65 | # |
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66 | sub gensym () { |
67 | my $name = "GEN" . $genseq++; |
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68 | my $ref = \*{$genpkg . $name}; |
69 | delete $$genpkg{$name}; |
70 | $ref; |
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71 | } |
72 | |
73 | sub ungensym ($) {} |
74 | |
75 | sub qualify ($;$) { |
76 | my ($name) = @_; |
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77 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { |
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78 | my $pkg; |
79 | # Global names: special character, "^x", or other. |
80 | if ($name =~ /^([^a-z])|(\^[a-z])$/i || $global{$name}) { |
81 | $pkg = "main"; |
82 | } |
83 | else { |
84 | $pkg = (@_ > 1) ? $_[1] : caller; |
85 | } |
86 | $name = $pkg . "::" . $name; |
87 | } |
88 | $name; |
89 | } |
90 | |
91 | 1; |