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c07a80fd | 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 | ||
4379a6f8 | 18 | # replace *FOO{IO} handle but not $FOO, %FOO, etc. |
ae716a98 | 19 | *FOO = geniosym; |
ae716a98 | 20 | |
c07a80fd | 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 | ||
b42fedfb CS |
29 | use strict refs; |
30 | print { qualify_to_ref $fh } "foo!\n"; | |
31 | $ref = qualify_to_ref $name, $pkg; | |
32 | ||
1ee082b7 GS |
33 | use Symbol qw(delete_package); |
34 | delete_package('Foo::Bar'); | |
35 | print "deleted\n" unless exists $Foo::{'Bar::'}; | |
36 | ||
c07a80fd | 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 | ||
ae716a98 YST |
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 | ||
c07a80fd | 51 | C<Symbol::qualify> turns unqualified symbol names into qualified |
7c584b33 | 52 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a |
c07a80fd | 53 | second parameter, C<qualify> uses it as the default package; |
54 | otherwise, it uses the package of its caller. Regardless, global | |
f610777f | 55 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with |
c07a80fd | 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 | ||
b42fedfb CS |
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 | ||
1ee082b7 GS |
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 | ||
83628169 RGS |
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 | ||
c07a80fd | 80 | =cut |
81 | ||
c74f62b5 | 82 | BEGIN { require 5.005; } |
c07a80fd | 83 | |
84 | require Exporter; | |
85 | @ISA = qw(Exporter); | |
b42fedfb | 86 | @EXPORT = qw(gensym ungensym qualify qualify_to_ref); |
ae716a98 | 87 | @EXPORT_OK = qw(delete_package geniosym); |
c07a80fd | 88 | |
83628169 | 89 | $VERSION = '1.05'; |
c07a80fd | 90 | |
91 | my $genpkg = "Symbol::"; | |
92 | my $genseq = 0; | |
93 | ||
7c584b33 | 94 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); |
c07a80fd | 95 | |
6adf1df6 JH |
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 | # | |
c07a80fd | 101 | sub gensym () { |
102 | my $name = "GEN" . $genseq++; | |
6adf1df6 JH |
103 | my $ref = \*{$genpkg . $name}; |
104 | delete $$genpkg{$name}; | |
105 | $ref; | |
c07a80fd | 106 | } |
107 | ||
ae716a98 YST |
108 | sub geniosym () { |
109 | my $sym = gensym(); | |
110 | # force the IO slot to be filled | |
111 | select(select $sym); | |
112 | *$sym{IO}; | |
113 | } | |
114 | ||
c07a80fd | 115 | sub ungensym ($) {} |
116 | ||
117 | sub qualify ($;$) { | |
118 | my ($name) = @_; | |
49da0595 | 119 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { |
c07a80fd | 120 | my $pkg; |
c74f62b5 RGS |
121 | # Global names: special character, "^xyz", or other. |
122 | if ($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; | |
c07a80fd | 125 | $pkg = "main"; |
126 | } | |
127 | else { | |
128 | $pkg = (@_ > 1) ? $_[1] : caller; | |
129 | } | |
130 | $name = $pkg . "::" . $name; | |
131 | } | |
132 | $name; | |
133 | } | |
134 | ||
b42fedfb CS |
135 | sub qualify_to_ref ($;$) { |
136 | return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; | |
137 | } | |
138 | ||
1ee082b7 GS |
139 | # |
140 | # of Safe.pm lineage | |
141 | # | |
142 | sub delete_package ($) { | |
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 | ||
c2e66d9e GS |
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 . $name}; | |
163 | } | |
164 | ||
165 | # delete the symbol table | |
1ee082b7 GS |
166 | |
167 | %$leaf_symtab = (); | |
168 | delete $stem_symtab->{$leaf}; | |
169 | } | |
170 | ||
c07a80fd | 171 | 1; |