1 | package Symbol; |
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2 | |
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3 | =head1 NAME |
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4 | |
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5 | Symbol - manipulate Perl symbols and their names |
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6 | |
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7 | =head1 SYNOPSIS |
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8 | |
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9 | use Symbol; |
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10 | |
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11 | $sym = gensym; |
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12 | open($sym, "filename"); |
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13 | $_ = <$sym>; |
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14 | # etc. |
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15 | |
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16 | ungensym $sym; # no effect |
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17 | |
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18 | print qualify("x"), "\n"; # "Test::x" |
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19 | print qualify("x", "FOO"), "\n" # "FOO::x" |
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20 | print qualify("BAR::x"), "\n"; # "BAR::x" |
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21 | print qualify("BAR::x", "FOO"), "\n"; # "BAR::x" |
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22 | print qualify("STDOUT", "FOO"), "\n"; # "main::STDOUT" (global) |
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23 | print qualify(\*x), "\n"; # returns \*x |
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24 | print qualify(\*x, "FOO"), "\n"; # returns \*x |
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25 | |
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26 | use strict refs; |
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27 | print { qualify_to_ref $fh } "foo!\n"; |
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28 | $ref = qualify_to_ref $name, $pkg; |
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29 | |
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30 | use Symbol qw(delete_package); |
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31 | delete_package('Foo::Bar'); |
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32 | print "deleted\n" unless exists $Foo::{'Bar::'}; |
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33 | |
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34 | |
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35 | =head1 DESCRIPTION |
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36 | |
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37 | C<Symbol::gensym> creates an anonymous glob and returns a reference |
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38 | to it. Such a glob reference can be used as a file or directory |
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39 | handle. |
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40 | |
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41 | For backward compatibility with older implementations that didn't |
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42 | support anonymous globs, C<Symbol::ungensym> is also provided. |
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43 | But it doesn't do anything. |
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44 | |
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45 | C<Symbol::qualify> turns unqualified symbol names into qualified |
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46 | variable names (e.g. "myvar" -E<gt> "MyPackage::myvar"). If it is given a |
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47 | second parameter, C<qualify> uses it as the default package; |
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48 | otherwise, it uses the package of its caller. Regardless, global |
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49 | variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with |
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50 | "main::". |
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51 | |
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52 | Qualification applies only to symbol names (strings). References are |
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53 | left unchanged under the assumption that they are glob references, |
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54 | which are qualified by their nature. |
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55 | |
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56 | C<Symbol::qualify_to_ref> is just like C<Symbol::qualify> except that it |
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57 | returns a glob ref rather than a symbol name, so you can use the result |
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58 | even if C<use strict 'refs'> is in effect. |
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59 | |
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60 | C<Symbol::delete_package> wipes out a whole package namespace. Note |
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61 | this routine is not exported by default--you may want to import it |
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62 | explicitly. |
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63 | |
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64 | =cut |
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65 | |
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66 | BEGIN { require 5.002; } |
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67 | |
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68 | require Exporter; |
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69 | @ISA = qw(Exporter); |
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70 | @EXPORT = qw(gensym ungensym qualify qualify_to_ref); |
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71 | @EXPORT_OK = qw(delete_package); |
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72 | |
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73 | $VERSION = 1.02; |
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74 | |
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75 | my $genpkg = "Symbol::"; |
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76 | my $genseq = 0; |
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77 | |
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78 | my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT); |
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79 | |
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80 | # |
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81 | # Note that we never _copy_ the glob; we just make a ref to it. |
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82 | # If we did copy it, then SVf_FAKE would be set on the copy, and |
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83 | # glob-specific behaviors (e.g. C<*$ref = \&func>) wouldn't work. |
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84 | # |
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85 | sub gensym () { |
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86 | my $name = "GEN" . $genseq++; |
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87 | my $ref = \*{$genpkg . $name}; |
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88 | delete $$genpkg{$name}; |
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89 | $ref; |
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90 | } |
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91 | |
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92 | sub ungensym ($) {} |
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93 | |
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94 | sub qualify ($;$) { |
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95 | my ($name) = @_; |
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96 | if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) { |
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97 | my $pkg; |
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98 | # Global names: special character, "^x", or other. |
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99 | if ($name =~ /^([^a-z])|(\^[a-z])$/i || $global{$name}) { |
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100 | $pkg = "main"; |
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101 | } |
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102 | else { |
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103 | $pkg = (@_ > 1) ? $_[1] : caller; |
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104 | } |
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105 | $name = $pkg . "::" . $name; |
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106 | } |
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107 | $name; |
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108 | } |
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109 | |
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110 | sub qualify_to_ref ($;$) { |
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111 | return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller }; |
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112 | } |
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113 | |
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114 | # |
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115 | # of Safe.pm lineage |
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116 | # |
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117 | sub delete_package ($) { |
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118 | my $pkg = shift; |
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119 | |
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120 | # expand to full symbol table name if needed |
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121 | |
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122 | unless ($pkg =~ /^main::.*::$/) { |
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123 | $pkg = "main$pkg" if $pkg =~ /^::/; |
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124 | $pkg = "main::$pkg" unless $pkg =~ /^main::/; |
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125 | $pkg .= '::' unless $pkg =~ /::$/; |
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126 | } |
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127 | |
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128 | my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; |
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129 | my $stem_symtab = *{$stem}{HASH}; |
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130 | return unless defined $stem_symtab and exists $stem_symtab->{$leaf}; |
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131 | |
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132 | my $leaf_glob = $stem_symtab->{$leaf}; |
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133 | my $leaf_symtab = *{$leaf_glob}{HASH}; |
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134 | |
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135 | %$leaf_symtab = (); |
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136 | delete $stem_symtab->{$leaf}; |
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137 | } |
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138 | |
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139 | 1; |
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