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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 | =head1 DESCRIPTION |
31 | |
32 | C<Symbol::gensym> creates an anonymous glob and returns a reference |
33 | to it. Such a glob reference can be used as a file or directory |
34 | handle. |
35 | |
36 | For backward compatibility with older implementations that didn't |
37 | support anonymous globs, C<Symbol::ungensym> is also provided. |
38 | But it doesn't do anything. |
39 | |
40 | C<Symbol::qualify> turns unqualified symbol names into qualified |
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41 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a |
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42 | second parameter, C<qualify> uses it as the default package; |
43 | otherwise, it uses the package of its caller. Regardless, global |
44 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualfied with |
45 | "main::". |
46 | |
47 | Qualification applies only to symbol names (strings). References are |
48 | left unchanged under the assumption that they are glob references, |
49 | which are qualified by their nature. |
50 | |
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51 | C<Symbol::qualify_to_ref> is just like C<Symbol::qualify> except that it |
52 | returns a glob ref rather than a symbol name, so you can use the result |
53 | even if C<use strict 'refs'> is in effect. |
54 | |
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55 | =cut |
56 | |
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57 | BEGIN { require 5.002; } |
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58 | |
59 | require Exporter; |
60 | @ISA = qw(Exporter); |
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61 | @EXPORT = qw(gensym ungensym qualify qualify_to_ref); |
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62 | |
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63 | $VERSION = 1.02; |
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64 | |
65 | my $genpkg = "Symbol::"; |
66 | my $genseq = 0; |
67 | |
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68 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); |
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69 | |
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70 | # |
71 | # Note that we never _copy_ the glob; we just make a ref to it. |
72 | # If we did copy it, then SVf_FAKE would be set on the copy, and |
73 | # glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. |
74 | # |
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75 | sub gensym () { |
76 | my $name = "GEN" . $genseq++; |
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77 | my $ref = \*{$genpkg . $name}; |
78 | delete $$genpkg{$name}; |
79 | $ref; |
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80 | } |
81 | |
82 | sub ungensym ($) {} |
83 | |
84 | sub qualify ($;$) { |
85 | my ($name) = @_; |
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86 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { |
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87 | my $pkg; |
88 | # Global names: special character, "^x", or other. |
89 | if ($name =~ /^([^a-z])|(\^[a-z])$/i || $global{$name}) { |
90 | $pkg = "main"; |
91 | } |
92 | else { |
93 | $pkg = (@_ > 1) ? $_[1] : caller; |
94 | } |
95 | $name = $pkg . "::" . $name; |
96 | } |
97 | $name; |
98 | } |
99 | |
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100 | sub qualify_to_ref ($;$) { |
101 | return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; |
102 | } |
103 | |
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104 | 1; |