Commit | Line | Data |
---|---|---|
920dae64 AT |
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 | # replace *FOO{IO} handle but not $FOO, %FOO, etc. | |
19 | *FOO = geniosym; | |
20 | ||
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 | ||
29 | use strict refs; | |
30 | print { qualify_to_ref $fh } "foo!\n"; | |
31 | $ref = qualify_to_ref $name, $pkg; | |
32 | ||
33 | use Symbol qw(delete_package); | |
34 | delete_package('Foo::Bar'); | |
35 | print "deleted\n" unless exists $Foo::{'Bar::'}; | |
36 | ||
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 | ||
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 | ||
51 | C<Symbol::qualify> turns unqualified symbol names into qualified | |
52 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a | |
53 | second parameter, C<qualify> uses it as the default package; | |
54 | otherwise, it uses the package of its caller. Regardless, global | |
55 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with | |
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 | ||
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 | ||
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 | ||
70 | =head1 BUGS | |
71 | ||
72 | C<Symbol::delete_package> is a bit too powerful. It undefines every symbol that | |
73 | lives in the specified package. Since perl, for performance reasons, does not | |
74 | perform a symbol table lookup each time a function is called or a global | |
75 | variable is accessed, some code that has already been loaded and that makes use | |
76 | of symbols in package C<Foo> may stop working after you delete C<Foo>, even if | |
77 | you reload the C<Foo> module afterwards. | |
78 | ||
79 | =cut | |
80 | ||
81 | BEGIN { require 5.005; } | |
82 | ||
83 | require Exporter; | |
84 | @ISA = qw(Exporter); | |
85 | @EXPORT = qw(gensym ungensym qualify qualify_to_ref); | |
86 | @EXPORT_OK = qw(delete_package geniosym); | |
87 | ||
88 | $VERSION = '1.06'; | |
89 | ||
90 | my $genpkg = "Symbol::"; | |
91 | my $genseq = 0; | |
92 | ||
93 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); | |
94 | ||
95 | # | |
96 | # Note that we never _copy_ the glob; we just make a ref to it. | |
97 | # If we did copy it, then SVf_FAKE would be set on the copy, and | |
98 | # glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. | |
99 | # | |
100 | sub gensym () { | |
101 | my $name = "GEN" . $genseq++; | |
102 | my $ref = \*{$genpkg . $name}; | |
103 | delete $$genpkg{$name}; | |
104 | $ref; | |
105 | } | |
106 | ||
107 | sub geniosym () { | |
108 | my $sym = gensym(); | |
109 | # force the IO slot to be filled | |
110 | select(select $sym); | |
111 | *$sym{IO}; | |
112 | } | |
113 | ||
114 | sub ungensym ($) {} | |
115 | ||
116 | sub qualify ($;$) { | |
117 | my ($name) = @_; | |
118 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { | |
119 | my $pkg; | |
120 | # Global names: special character, "^xyz", or other. | |
121 | if ($name =~ /^(([^a-z])|(\^[a-z_]+))\z/i || $global{$name}) { | |
122 | # RGS 2001-11-05 : translate leading ^X to control-char | |
123 | $name =~ s/^\^([a-z_])/'qq(\c'.$1.')'/eei; | |
124 | $pkg = "main"; | |
125 | } | |
126 | else { | |
127 | $pkg = (@_ > 1) ? $_[1] : caller; | |
128 | } | |
129 | $name = $pkg . "::" . $name; | |
130 | } | |
131 | $name; | |
132 | } | |
133 | ||
134 | sub qualify_to_ref ($;$) { | |
135 | return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; | |
136 | } | |
137 | ||
138 | # | |
139 | # of Safe.pm lineage | |
140 | # | |
141 | sub delete_package ($) { | |
142 | my $pkg = shift; | |
143 | ||
144 | # expand to full symbol table name if needed | |
145 | ||
146 | unless ($pkg =~ /^main::.*::$/) { | |
147 | $pkg = "main$pkg" if $pkg =~ /^::/; | |
148 | $pkg = "main::$pkg" unless $pkg =~ /^main::/; | |
149 | $pkg .= '::' unless $pkg =~ /::$/; | |
150 | } | |
151 | ||
152 | my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; | |
153 | my $stem_symtab = *{$stem}{HASH}; | |
154 | return unless defined $stem_symtab and exists $stem_symtab->{$leaf}; | |
155 | ||
156 | ||
157 | # free all the symbols in the package | |
158 | ||
159 | my $leaf_symtab = *{$stem_symtab->{$leaf}}{HASH}; | |
160 | foreach my $name (keys %$leaf_symtab) { | |
161 | undef *{$pkg . $name}; | |
162 | } | |
163 | ||
164 | # delete the symbol table | |
165 | ||
166 | %$leaf_symtab = (); | |
167 | delete $stem_symtab->{$leaf}; | |
168 | } | |
169 | ||
170 | 1; |