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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 | # replace *FOO{IO} handle but not $FOO, %FOO, etc. |
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19 | *FOO = geniosym; |
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20 | |
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21 | print qualify("x"), "\n"; # "Test::x" |
22 | print qualify("x", "FOO"), "\n" # "FOO::x" |
23 | print qualify("BAR::x"), "\n"; # "BAR::x" |
24 | print qualify("BAR::x", "FOO"), "\n"; # "BAR::x" |
25 | print qualify("STDOUT", "FOO"), "\n"; # "main::STDOUT" (global) |
26 | print qualify(\*x), "\n"; # returns \*x |
27 | print qualify(\*x, "FOO"), "\n"; # returns \*x |
28 | |
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29 | use strict refs; |
30 | print { qualify_to_ref $fh } "foo!\n"; |
31 | $ref = qualify_to_ref $name, $pkg; |
32 | |
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33 | use Symbol qw(delete_package); |
34 | delete_package('Foo::Bar'); |
35 | print "deleted\n" unless exists $Foo::{'Bar::'}; |
36 | |
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37 | =head1 DESCRIPTION |
38 | |
39 | C<Symbol::gensym> creates an anonymous glob and returns a reference |
40 | to it. Such a glob reference can be used as a file or directory |
41 | handle. |
42 | |
43 | For backward compatibility with older implementations that didn't |
44 | support anonymous globs, C<Symbol::ungensym> is also provided. |
45 | But it doesn't do anything. |
46 | |
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47 | C<Symbol::geniosym> creates an anonymous IO handle. This can be |
48 | assigned into an existing glob without affecting the non-IO portions |
49 | of the glob. |
50 | |
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51 | C<Symbol::qualify> turns unqualified symbol names into qualified |
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52 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a |
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53 | second parameter, C<qualify> uses it as the default package; |
54 | otherwise, it uses the package of its caller. Regardless, global |
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55 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with |
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56 | "main::". |
57 | |
58 | Qualification applies only to symbol names (strings). References are |
59 | left unchanged under the assumption that they are glob references, |
60 | which are qualified by their nature. |
61 | |
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62 | C<Symbol::qualify_to_ref> is just like C<Symbol::qualify> except that it |
63 | returns a glob ref rather than a symbol name, so you can use the result |
64 | even if C<use strict 'refs'> is in effect. |
65 | |
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66 | C<Symbol::delete_package> wipes out a whole package namespace. Note |
67 | this routine is not exported by default--you may want to import it |
68 | explicitly. |
69 | |
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70 | =head1 BUGS |
71 | |
72 | C<Symbol::delete_package> is a bit too powerful. It undefines every symbol |
73 | that lives in the specified package and in its sub-packages. Since perl, |
74 | for performance reasons, does not perform a symbol table lookup each time |
75 | a function is called or a global variable is accessed, some code that has |
76 | already been loaded and that makes use of symbols in package C<Foo> may |
77 | stop working after you delete C<Foo>, even if you reload the C<Foo> module |
78 | afterwards. |
79 | |
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80 | =cut |
81 | |
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82 | BEGIN { require 5.005; } |
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83 | |
84 | require Exporter; |
85 | @ISA = qw(Exporter); |
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86 | @EXPORT = qw(gensym ungensym qualify qualify_to_ref); |
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87 | @EXPORT_OK = qw(delete_package geniosym); |
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88 | |
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89 | $VERSION = '1.05'; |
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90 | |
91 | my $genpkg = "Symbol::"; |
92 | my $genseq = 0; |
93 | |
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94 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); |
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95 | |
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96 | # |
97 | # Note that we never _copy_ the glob; we just make a ref to it. |
98 | # If we did copy it, then SVf_FAKE would be set on the copy, and |
99 | # glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. |
100 | # |
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101 | sub gensym () { |
102 | my $name = "GEN" . $genseq++; |
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103 | my $ref = \*{$genpkg . $name}; |
104 | delete $$genpkg{$name}; |
105 | $ref; |
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106 | } |
107 | |
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108 | sub geniosym () { |
109 | my $sym = gensym(); |
110 | # force the IO slot to be filled |
111 | select(select $sym); |
112 | *$sym{IO}; |
113 | } |
114 | |
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115 | sub ungensym ($) {} |
116 | |
117 | sub qualify ($;$) { |
118 | my ($name) = @_; |
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119 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { |
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120 | my $pkg; |
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121 | # Global names: special character, "^xyz", or other. |
122 | if ($name =~ /^(([^a-z])|(\^[a-z_]+))\z/i || $global{$name}) { |
123 | # RGS 2001-11-05 : translate leading ^X to control-char |
124 | $name =~ s/^\^([a-z_])/'qq(\c'.$1.')'/eei; |
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125 | $pkg = "main"; |
126 | } |
127 | else { |
128 | $pkg = (@_ > 1) ? $_[1] : caller; |
129 | } |
130 | $name = $pkg . "::" . $name; |
131 | } |
132 | $name; |
133 | } |
134 | |
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135 | sub qualify_to_ref ($;$) { |
136 | return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; |
137 | } |
138 | |
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139 | # |
140 | # of Safe.pm lineage |
141 | # |
142 | sub delete_package ($) { |
143 | my $pkg = shift; |
144 | |
145 | # expand to full symbol table name if needed |
146 | |
147 | unless ($pkg =~ /^main::.*::$/) { |
148 | $pkg = "main$pkg" if $pkg =~ /^::/; |
149 | $pkg = "main::$pkg" unless $pkg =~ /^main::/; |
150 | $pkg .= '::' unless $pkg =~ /::$/; |
151 | } |
152 | |
153 | my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; |
154 | my $stem_symtab = *{$stem}{HASH}; |
155 | return unless defined $stem_symtab and exists $stem_symtab->{$leaf}; |
156 | |
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157 | |
158 | # free all the symbols in the package |
159 | |
160 | my $leaf_symtab = *{$stem_symtab->{$leaf}}{HASH}; |
161 | foreach my $name (keys %$leaf_symtab) { |
162 | undef *{$pkg . $name}; |
163 | } |
164 | |
165 | # delete the symbol table |
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166 | |
167 | %$leaf_symtab = (); |
168 | delete $stem_symtab->{$leaf}; |
169 | } |
170 | |
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171 | 1; |