Commit | Line | Data |
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920dae64 AT |
1 | package base; |
2 | ||
3 | use strict 'vars'; | |
4 | use vars qw($VERSION); | |
5 | $VERSION = '2.07'; | |
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}; | |
21 | return( ($fglob && *$fglob{HASH}) ? 1 : 0 ); | |
22 | } | |
23 | ||
24 | sub has_version { | |
25 | my($base) = shift; | |
26 | my $vglob = ${$base.'::'}{VERSION}; | |
27 | return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 ); | |
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 | ||
41 | if ($] < 5.009) { | |
42 | *get_fields = sub { | |
43 | # Shut up a possible typo warning. | |
44 | () = \%{$_[0].'::FIELDS'}; | |
45 | my $f = \%{$_[0].'::FIELDS'}; | |
46 | ||
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'); | |
51 | ||
52 | return $f; | |
53 | } | |
54 | } | |
55 | else { | |
56 | *get_fields = sub { | |
57 | # Shut up a possible typo warning. | |
58 | () = \%{$_[0].'::FIELDS'}; | |
59 | return \%{$_[0].'::FIELDS'}; | |
60 | } | |
61 | } | |
62 | ||
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); | |
72 | ||
73 | foreach my $base (@_) { | |
74 | next if $inheritor->isa($base); | |
75 | ||
76 | if (has_version($base)) { | |
77 | ${$base.'::VERSION'} = '-1, set by base.pm' | |
78 | unless defined ${$base.'::VERSION'}; | |
79 | } | |
80 | else { | |
81 | local $SIG{__DIE__}; | |
82 | eval "require $base"; | |
83 | # Only ignore "Can't locate" errors from our eval require. | |
84 | # Other fatal errors (syntax etc) must be reported. | |
85 | die if $@ && $@ !~ /^Can't locate .*? at \(eval /; | |
86 | unless (%{"$base\::"}) { | |
87 | require Carp; | |
88 | Carp::croak(<<ERROR); | |
89 | Base class package "$base" is empty. | |
90 | (Perhaps you need to 'use' the module which defines that package first.) | |
91 | ERROR | |
92 | ||
93 | } | |
94 | ${$base.'::VERSION'} = "-1, set by base.pm" | |
95 | unless defined ${$base.'::VERSION'}; | |
96 | } | |
97 | push @{"$inheritor\::ISA"}, $base; | |
98 | ||
99 | if ( has_fields($base) || has_attr($base) ) { | |
100 | # No multiple fields inheritence *suck* | |
101 | if ($fields_base) { | |
102 | require Carp; | |
103 | Carp::croak("Can't multiply inherit %FIELDS"); | |
104 | } else { | |
105 | $fields_base = $base; | |
106 | } | |
107 | } | |
108 | } | |
109 | ||
110 | if( defined $fields_base ) { | |
111 | inherit_fields($inheritor, $fields_base); | |
112 | } | |
113 | } | |
114 | ||
115 | ||
116 | sub inherit_fields { | |
117 | my($derived, $base) = @_; | |
118 | ||
119 | return SUCCESS unless $base; | |
120 | ||
121 | my $battr = get_attr($base); | |
122 | my $dattr = get_attr($derived); | |
123 | my $dfields = get_fields($derived); | |
124 | my $bfields = get_fields($base); | |
125 | ||
126 | $dattr->[0] = @$battr; | |
127 | ||
128 | if( keys %$dfields ) { | |
129 | warn "$derived is inheriting from $base but already has its own ". | |
130 | "fields!\n". | |
131 | "This will cause problems.\n". | |
132 | "Be sure you use base BEFORE declaring fields\n"; | |
133 | } | |
134 | ||
135 | # Iterate through the base's fields adding all the non-private | |
136 | # ones to the derived class. Hang on to the original attribute | |
137 | # (Public, Private, etc...) and add Inherited. | |
138 | # This is all too complicated to do efficiently with add_fields(). | |
139 | while (my($k,$v) = each %$bfields) { | |
140 | my $fno; | |
141 | if ($fno = $dfields->{$k} and $fno != $v) { | |
142 | require Carp; | |
143 | Carp::croak ("Inherited %FIELDS can't override existing %FIELDS"); | |
144 | } | |
145 | ||
146 | if( $battr->[$v] & PRIVATE ) { | |
147 | $dattr->[$v] = PRIVATE | INHERITED; | |
148 | } | |
149 | else { | |
150 | $dattr->[$v] = INHERITED | $battr->[$v]; | |
151 | $dfields->{$k} = $v; | |
152 | } | |
153 | } | |
154 | ||
155 | foreach my $idx (1..$#{$battr}) { | |
156 | next if defined $dattr->[$idx]; | |
157 | $dattr->[$idx] = $battr->[$idx] & INHERITED; | |
158 | } | |
159 | } | |
160 | ||
161 | ||
162 | 1; | |
163 | ||
164 | __END__ | |
165 | ||
166 | =head1 NAME | |
167 | ||
168 | base - Establish IS-A relationship with base classes at compile time | |
169 | ||
170 | =head1 SYNOPSIS | |
171 | ||
172 | package Baz; | |
173 | use base qw(Foo Bar); | |
174 | ||
175 | =head1 DESCRIPTION | |
176 | ||
177 | Allows you to both load one or more modules, while setting up inheritance from | |
178 | those modules at the same time. Roughly similar in effect to | |
179 | ||
180 | package Baz; | |
181 | BEGIN { | |
182 | require Foo; | |
183 | require Bar; | |
184 | push @ISA, qw(Foo Bar); | |
185 | } | |
186 | ||
187 | If any of the listed modules are not loaded yet, I<base> silently attempts to | |
188 | C<require> them (and silently continues if the C<require> failed). Whether to | |
189 | C<require> a base class module is determined by the absence of a global variable | |
190 | $VERSION in the base package. If $VERSION is not detected even after loading | |
191 | it, <base> will define $VERSION in the base package, setting it to the string | |
192 | C<-1, set by base.pm>. | |
193 | ||
194 | Will also initialize the fields if one of the base classes has it. | |
195 | Multiple inheritence of fields is B<NOT> supported, if two or more | |
196 | base classes each have inheritable fields the 'base' pragma will | |
197 | croak. See L<fields>, L<public> and L<protected> for a description of | |
198 | this feature. | |
199 | ||
200 | =head1 DIAGNOSTICS | |
201 | ||
202 | =over 4 | |
203 | ||
204 | =item Base class package "%s" is empty. | |
205 | ||
206 | base.pm was unable to require the base package, because it was not | |
207 | found in your path. | |
208 | ||
209 | =back | |
210 | ||
211 | =head1 HISTORY | |
212 | ||
213 | This module was introduced with Perl 5.004_04. | |
214 | ||
215 | ||
216 | =head1 CAVEATS | |
217 | ||
218 | Due to the limitations of the implementation, you must use | |
219 | base I<before> you declare any of your own fields. | |
220 | ||
221 | ||
222 | =head1 SEE ALSO | |
223 | ||
224 | L<fields> | |
225 | ||
226 | =cut |