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1 | package base; |
2 | |
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3 | use strict 'vars'; |
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4 | use vars qw($VERSION); |
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5 | $VERSION = '2.13'; |
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6 | |
7 | # constant.pm is slow |
8 | sub SUCCESS () { 1 } |
9 | |
10 | sub PUBLIC () { 2**0 } |
11 | sub PRIVATE () { 2**1 } |
12 | sub INHERITED () { 2**2 } |
13 | sub PROTECTED () { 2**3 } |
14 | |
15 | |
16 | my $Fattr = \%fields::attr; |
17 | |
18 | sub has_fields { |
19 | my($base) = shift; |
20 | my $fglob = ${"$base\::"}{FIELDS}; |
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21 | return( ($fglob && 'GLOB' eq ref($fglob) && *$fglob{HASH}) ? 1 : 0 ); |
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22 | } |
23 | |
24 | sub has_version { |
25 | my($base) = shift; |
26 | my $vglob = ${$base.'::'}{VERSION}; |
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27 | return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 ); |
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28 | } |
29 | |
30 | sub has_attr { |
31 | my($proto) = shift; |
32 | my($class) = ref $proto || $proto; |
33 | return exists $Fattr->{$class}; |
34 | } |
35 | |
36 | sub get_attr { |
37 | $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]}; |
38 | return $Fattr->{$_[0]}; |
39 | } |
40 | |
8731c5d9 |
41 | if ($] < 5.009) { |
42 | *get_fields = sub { |
9e998a43 |
43 | # Shut up a possible typo warning. |
44 | () = \%{$_[0].'::FIELDS'}; |
45 | my $f = \%{$_[0].'::FIELDS'}; |
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46 | |
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47 | # should be centralized in fields? perhaps |
48 | # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' } |
49 | # is used here anyway, it doesn't matter. |
50 | bless $f, 'pseudohash' if (ref($f) ne 'pseudohash'); |
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51 | |
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52 | return $f; |
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53 | } |
54 | } |
55 | else { |
56 | *get_fields = sub { |
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57 | # Shut up a possible typo warning. |
58 | () = \%{$_[0].'::FIELDS'}; |
59 | return \%{$_[0].'::FIELDS'}; |
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60 | } |
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61 | } |
62 | |
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63 | sub import { |
64 | my $class = shift; |
65 | |
66 | return SUCCESS unless @_; |
67 | |
68 | # List of base classes from which we will inherit %FIELDS. |
69 | my $fields_base; |
70 | |
71 | my $inheritor = caller(0); |
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72 | my @isa_classes; |
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73 | |
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74 | my @bases; |
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75 | foreach my $base (@_) { |
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76 | if ( $inheritor eq $base ) { |
77 | warn "Class '$inheritor' tried to inherit from itself\n"; |
78 | } |
79 | |
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80 | next if grep $_->isa($base), ($inheritor, @bases); |
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81 | |
82 | if (has_version($base)) { |
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83 | ${$base.'::VERSION'} = '-1, set by base.pm' |
84 | unless defined ${$base.'::VERSION'}; |
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85 | } |
86 | else { |
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87 | my $sigdie; |
88 | { |
89 | local $SIG{__DIE__}; |
90 | eval "require $base"; |
91 | # Only ignore "Can't locate" errors from our eval require. |
92 | # Other fatal errors (syntax etc) must be reported. |
93 | die if $@ && $@ !~ /^Can't locate .*? at \(eval /; |
94 | unless (%{"$base\::"}) { |
95 | require Carp; |
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96 | local $" = " "; |
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97 | Carp::croak(<<ERROR); |
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98 | Base class package "$base" is empty. |
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99 | (Perhaps you need to 'use' the module which defines that package first, |
100 | or make that module available in \@INC (\@INC contains: @INC). |
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101 | ERROR |
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102 | } |
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103 | $sigdie = $SIG{__DIE__} || undef; |
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104 | } |
105 | # Make sure a global $SIG{__DIE__} makes it out of the localization. |
106 | $SIG{__DIE__} = $sigdie if defined $sigdie; |
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107 | ${$base.'::VERSION'} = "-1, set by base.pm" |
108 | unless defined ${$base.'::VERSION'}; |
109 | } |
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110 | push @bases, $base; |
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111 | |
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112 | if ( has_fields($base) || has_attr($base) ) { |
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113 | # No multiple fields inheritance *suck* |
114 | if ($fields_base) { |
115 | require Carp; |
116 | Carp::croak("Can't multiply inherit fields"); |
117 | } else { |
118 | $fields_base = $base; |
119 | } |
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120 | } |
121 | } |
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122 | # Save this until the end so it's all or nothing if the above loop croaks. |
123 | push @{"$inheritor\::ISA"}, @isa_classes; |
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124 | |
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125 | push @{"$inheritor\::ISA"}, @bases; |
126 | |
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127 | if( defined $fields_base ) { |
128 | inherit_fields($inheritor, $fields_base); |
129 | } |
130 | } |
131 | |
132 | |
133 | sub inherit_fields { |
134 | my($derived, $base) = @_; |
135 | |
136 | return SUCCESS unless $base; |
137 | |
138 | my $battr = get_attr($base); |
139 | my $dattr = get_attr($derived); |
140 | my $dfields = get_fields($derived); |
141 | my $bfields = get_fields($base); |
142 | |
143 | $dattr->[0] = @$battr; |
144 | |
145 | if( keys %$dfields ) { |
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146 | warn <<"END"; |
147 | $derived is inheriting from $base but already has its own fields! |
148 | This will cause problems. Be sure you use base BEFORE declaring fields. |
149 | END |
150 | |
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151 | } |
152 | |
153 | # Iterate through the base's fields adding all the non-private |
154 | # ones to the derived class. Hang on to the original attribute |
155 | # (Public, Private, etc...) and add Inherited. |
156 | # This is all too complicated to do efficiently with add_fields(). |
157 | while (my($k,$v) = each %$bfields) { |
158 | my $fno; |
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159 | if ($fno = $dfields->{$k} and $fno != $v) { |
160 | require Carp; |
161 | Carp::croak ("Inherited fields can't override existing fields"); |
162 | } |
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163 | |
164 | if( $battr->[$v] & PRIVATE ) { |
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165 | $dattr->[$v] = PRIVATE | INHERITED; |
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166 | } |
167 | else { |
168 | $dattr->[$v] = INHERITED | $battr->[$v]; |
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169 | $dfields->{$k} = $v; |
170 | } |
171 | } |
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172 | |
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173 | foreach my $idx (1..$#{$battr}) { |
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174 | next if defined $dattr->[$idx]; |
175 | $dattr->[$idx] = $battr->[$idx] & INHERITED; |
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176 | } |
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177 | } |
178 | |
179 | |
180 | 1; |
181 | |
182 | __END__ |
183 | |
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184 | =head1 NAME |
185 | |
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186 | base - Establish an ISA relationship with base classes at compile time |
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187 | |
188 | =head1 SYNOPSIS |
189 | |
190 | package Baz; |
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191 | use base qw(Foo Bar); |
192 | |
193 | =head1 DESCRIPTION |
194 | |
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195 | Allows you to both load one or more modules, while setting up inheritance from |
196 | those modules at the same time. Roughly similar in effect to |
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197 | |
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198 | package Baz; |
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199 | BEGIN { |
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200 | require Foo; |
201 | require Bar; |
202 | push @ISA, qw(Foo Bar); |
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203 | } |
204 | |
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205 | C<base> employs some heuristics to determine if a module has already been |
206 | loaded, if it has it doesn't try again. If C<base> tries to C<require> the |
207 | module it will not die if it cannot find the module's file, but will die on any |
208 | other error. After all this, should your base class be empty, containing no |
209 | symbols, it will die. This is useful for inheriting from classes in the same |
210 | file as yourself, like so: |
211 | |
212 | package Foo; |
213 | sub exclaim { "I can have such a thing?!" } |
214 | |
215 | package Bar; |
216 | use base "Foo"; |
217 | |
218 | If $VERSION is not detected even after loading it, <base> will define $VERSION |
219 | in the base package, setting it to the string C<-1, set by base.pm>. |
220 | |
221 | C<base> will also initialize the fields if one of the base classes has it. |
222 | Multiple inheritance of fields is B<NOT> supported, if two or more base classes |
223 | each have inheritable fields the 'base' pragma will croak. See L<fields>, |
224 | L<public> and L<protected> for a description of this feature. |
225 | |
226 | The base class' C<import> method is B<not> called. |
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227 | |
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228 | |
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229 | =head1 DIAGNOSTICS |
230 | |
231 | =over 4 |
232 | |
233 | =item Base class package "%s" is empty. |
234 | |
235 | base.pm was unable to require the base package, because it was not |
236 | found in your path. |
237 | |
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238 | =item Class 'Foo' tried to inherit from itself |
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239 | |
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240 | Attempting to inherit from yourself generates a warning. |
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241 | |
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242 | use Foo; |
243 | use base 'Foo'; |
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244 | |
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245 | =back |
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246 | |
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247 | =head1 HISTORY |
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248 | |
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249 | This module was introduced with Perl 5.004_04. |
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250 | |
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251 | =head1 CAVEATS |
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252 | |
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253 | Due to the limitations of the implementation, you must use |
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254 | base I<before> you declare any of your own fields. |
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255 | |
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256 | |
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257 | =head1 SEE ALSO |
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258 | |
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259 | L<fields> |
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260 | |
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261 | =cut |