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1 | package Exporter; |
2 | |
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3 | require 5.001; |
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4 | |
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5 | use strict; |
6 | no strict 'refs'; |
7 | |
8 | our $Debug = 0; |
9 | our $ExportLevel = 0; |
10 | our $Verbose ||= 0; |
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11 | our $VERSION = '5.563'; |
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12 | |
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13 | sub export_to_level { |
14 | require Exporter::Heavy; |
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15 | goto &Exporter::Heavy::heavy_export_to_level; |
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16 | } |
17 | |
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18 | sub export { |
19 | require Exporter::Heavy; |
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20 | goto &Exporter::Heavy::heavy_export; |
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21 | } |
22 | |
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23 | sub export_tags { |
24 | require Exporter::Heavy; |
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25 | Exporter::Heavy::_push_tags((caller)[0], "EXPORT", \@_); |
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26 | } |
27 | |
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28 | sub export_ok_tags { |
29 | require Exporter::Heavy; |
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30 | Exporter::Heavy::_push_tags((caller)[0], "EXPORT_OK", \@_); |
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31 | } |
32 | |
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33 | sub import { |
34 | my $pkg = shift; |
35 | my $callpkg = caller($ExportLevel); |
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36 | |
37 | my($exports, $export_cache) = (\@{"$pkg\::EXPORT"}, |
38 | \%{"$pkg\::EXPORT"}); |
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39 | # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-( |
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40 | my($fail) = \@{"$pkg\::EXPORT_FAIL"}; |
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41 | return export $pkg, $callpkg, @_ |
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42 | if $Verbose or $Debug or @$fail > 1; |
43 | my $args = @_ or @_ = @$exports; |
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44 | |
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45 | if ($args and not %$export_cache) { |
46 | foreach my $sym (@$exports, @{"$pkg\::EXPORT_OK"}) { |
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47 | $sym =~ s/^&//; |
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48 | $export_cache->{$sym} = 1; |
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49 | } |
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50 | } |
51 | if ($Verbose or $Debug |
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52 | or grep {/\W/ or $args and not exists $export_cache->{$_} |
53 | or @$fail and $_ eq $fail->[0] |
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54 | or (@{"$pkg\::EXPORT_OK"} |
55 | and $_ eq ${"$pkg\::EXPORT_OK"}[0])} @_) { |
56 | return export $pkg, $callpkg, ($args ? @_ : ()); |
57 | } |
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58 | local $SIG{__WARN__} = |
59 | sub {require Carp; local $Carp::CarpLevel = 1; &Carp::carp}; |
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60 | foreach my $sym (@_) { |
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61 | # shortcut for the common case of no type character |
62 | *{"$callpkg\::$sym"} = \&{"$pkg\::$sym"}; |
63 | } |
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64 | } |
65 | |
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66 | |
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67 | # Default methods |
68 | |
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69 | sub export_fail { |
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70 | my $self = shift; |
71 | @_; |
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72 | } |
73 | |
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74 | |
75 | sub require_version { |
76 | require Exporter::Heavy; |
77 | goto &Exporter::Heavy::require_version; |
78 | } |
79 | |
80 | |
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81 | 1; |
82 | |
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83 | |
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84 | =head1 NAME |
85 | |
86 | Exporter - Implements default import method for modules |
87 | |
88 | =head1 SYNOPSIS |
89 | |
90 | In module ModuleName.pm: |
91 | |
92 | package ModuleName; |
93 | require Exporter; |
94 | @ISA = qw(Exporter); |
95 | |
96 | @EXPORT = qw(...); # symbols to export by default |
97 | @EXPORT_OK = qw(...); # symbols to export on request |
98 | %EXPORT_TAGS = tag => [...]; # define names for sets of symbols |
99 | |
100 | In other files which wish to use ModuleName: |
101 | |
102 | use ModuleName; # import default symbols into my package |
103 | |
104 | use ModuleName qw(...); # import listed symbols into my package |
105 | |
106 | use ModuleName (); # do not import any symbols |
107 | |
108 | =head1 DESCRIPTION |
109 | |
110 | The Exporter module implements a default C<import> method which |
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111 | many modules choose to inherit rather than implement their own. |
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112 | |
113 | Perl automatically calls the C<import> method when processing a |
114 | C<use> statement for a module. Modules and C<use> are documented |
115 | in L<perlfunc> and L<perlmod>. Understanding the concept of |
116 | modules and how the C<use> statement operates is important to |
117 | understanding the Exporter. |
118 | |
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119 | =head2 How to Export |
120 | |
121 | The arrays C<@EXPORT> and C<@EXPORT_OK> in a module hold lists of |
122 | symbols that are going to be exported into the users name space by |
123 | default, or which they can request to be exported, respectively. The |
124 | symbols can represent functions, scalars, arrays, hashes, or typeglobs. |
125 | The symbols must be given by full name with the exception that the |
126 | ampersand in front of a function is optional, e.g. |
127 | |
128 | @EXPORT = qw(afunc $scalar @array); # afunc is a function |
129 | @EXPORT_OK = qw(&bfunc %hash *typeglob); # explicit prefix on &bfunc |
130 | |
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131 | =head2 Selecting What To Export |
132 | |
133 | Do B<not> export method names! |
134 | |
135 | Do B<not> export anything else by default without a good reason! |
136 | |
137 | Exports pollute the namespace of the module user. If you must export |
138 | try to use @EXPORT_OK in preference to @EXPORT and avoid short or |
139 | common symbol names to reduce the risk of name clashes. |
140 | |
141 | Generally anything not exported is still accessible from outside the |
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142 | module using the ModuleName::item_name (or $blessed_ref-E<gt>method) |
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143 | syntax. By convention you can use a leading underscore on names to |
144 | informally indicate that they are 'internal' and not for public use. |
145 | |
146 | (It is actually possible to get private functions by saying: |
147 | |
148 | my $subref = sub { ... }; |
149 | &$subref; |
150 | |
151 | But there's no way to call that directly as a method, since a method |
152 | must have a name in the symbol table.) |
153 | |
154 | As a general rule, if the module is trying to be object oriented |
155 | then export nothing. If it's just a collection of functions then |
156 | @EXPORT_OK anything but use @EXPORT with caution. |
157 | |
158 | Other module design guidelines can be found in L<perlmod>. |
159 | |
160 | =head2 Specialised Import Lists |
161 | |
162 | If the first entry in an import list begins with !, : or / then the |
163 | list is treated as a series of specifications which either add to or |
164 | delete from the list of names to import. They are processed left to |
165 | right. Specifications are in the form: |
166 | |
167 | [!]name This name only |
168 | [!]:DEFAULT All names in @EXPORT |
169 | [!]:tag All names in $EXPORT_TAGS{tag} anonymous list |
170 | [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match |
171 | |
172 | A leading ! indicates that matching names should be deleted from the |
173 | list of names to import. If the first specification is a deletion it |
174 | is treated as though preceded by :DEFAULT. If you just want to import |
175 | extra names in addition to the default set you will still need to |
176 | include :DEFAULT explicitly. |
177 | |
178 | e.g., Module.pm defines: |
179 | |
180 | @EXPORT = qw(A1 A2 A3 A4 A5); |
181 | @EXPORT_OK = qw(B1 B2 B3 B4 B5); |
182 | %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]); |
183 | |
184 | Note that you cannot use tags in @EXPORT or @EXPORT_OK. |
185 | Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK. |
186 | |
187 | An application using Module can say something like: |
188 | |
189 | use Module qw(:DEFAULT :T2 !B3 A3); |
190 | |
191 | Other examples include: |
192 | |
193 | use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET); |
194 | use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/); |
195 | |
196 | Remember that most patterns (using //) will need to be anchored |
197 | with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>. |
198 | |
199 | You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the |
200 | specifications are being processed and what is actually being imported |
201 | into modules. |
202 | |
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203 | =head2 Exporting without using Export's import method |
204 | |
205 | Exporter has a special method, 'export_to_level' which is used in situations |
206 | where you can't directly call Export's import method. The export_to_level |
207 | method looks like: |
208 | |
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209 | MyPackage->export_to_level($where_to_export, $package, @what_to_export); |
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210 | |
211 | where $where_to_export is an integer telling how far up the calling stack |
212 | to export your symbols, and @what_to_export is an array telling what |
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213 | symbols *to* export (usually this is @_). The $package argument is |
214 | currently unused. |
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215 | |
216 | For example, suppose that you have a module, A, which already has an |
217 | import function: |
218 | |
219 | package A; |
220 | |
221 | @ISA = qw(Exporter); |
222 | @EXPORT_OK = qw ($b); |
223 | |
224 | sub import |
225 | { |
226 | $A::b = 1; # not a very useful import method |
227 | } |
228 | |
229 | and you want to Export symbol $A::b back to the module that called |
230 | package A. Since Exporter relies on the import method to work, via |
231 | inheritance, as it stands Exporter::import() will never get called. |
232 | Instead, say the following: |
233 | |
234 | package A; |
235 | @ISA = qw(Exporter); |
236 | @EXPORT_OK = qw ($b); |
237 | |
238 | sub import |
239 | { |
240 | $A::b = 1; |
241 | A->export_to_level(1, @_); |
242 | } |
243 | |
244 | This will export the symbols one level 'above' the current package - ie: to |
245 | the program or module that used package A. |
246 | |
247 | Note: Be careful not to modify '@_' at all before you call export_to_level |
248 | - or people using your package will get very unexplained results! |
249 | |
250 | |
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251 | =head2 Module Version Checking |
252 | |
253 | The Exporter module will convert an attempt to import a number from a |
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254 | module into a call to $module_name-E<gt>require_version($value). This can |
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255 | be used to validate that the version of the module being used is |
256 | greater than or equal to the required version. |
257 | |
258 | The Exporter module supplies a default require_version method which |
259 | checks the value of $VERSION in the exporting module. |
260 | |
261 | Since the default require_version method treats the $VERSION number as |
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262 | a simple numeric value it will regard version 1.10 as lower than |
263 | 1.9. For this reason it is strongly recommended that you use numbers |
264 | with at least two decimal places, e.g., 1.09. |
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265 | |
266 | =head2 Managing Unknown Symbols |
267 | |
268 | In some situations you may want to prevent certain symbols from being |
269 | exported. Typically this applies to extensions which have functions |
270 | or constants that may not exist on some systems. |
271 | |
272 | The names of any symbols that cannot be exported should be listed |
273 | in the C<@EXPORT_FAIL> array. |
274 | |
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275 | If a module attempts to import any of these symbols the Exporter |
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276 | will give the module an opportunity to handle the situation before |
277 | generating an error. The Exporter will call an export_fail method |
278 | with a list of the failed symbols: |
279 | |
280 | @failed_symbols = $module_name->export_fail(@failed_symbols); |
281 | |
282 | If the export_fail method returns an empty list then no error is |
283 | recorded and all the requested symbols are exported. If the returned |
284 | list is not empty then an error is generated for each symbol and the |
285 | export fails. The Exporter provides a default export_fail method which |
286 | simply returns the list unchanged. |
287 | |
288 | Uses for the export_fail method include giving better error messages |
289 | for some symbols and performing lazy architectural checks (put more |
290 | symbols into @EXPORT_FAIL by default and then take them out if someone |
291 | actually tries to use them and an expensive check shows that they are |
292 | usable on that platform). |
293 | |
294 | =head2 Tag Handling Utility Functions |
295 | |
296 | Since the symbols listed within %EXPORT_TAGS must also appear in either |
297 | @EXPORT or @EXPORT_OK, two utility functions are provided which allow |
298 | you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK: |
299 | |
300 | %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); |
301 | |
302 | Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT |
303 | Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK |
304 | |
305 | Any names which are not tags are added to @EXPORT or @EXPORT_OK |
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306 | unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags |
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307 | names being silently added to @EXPORT or @EXPORT_OK. Future versions |
308 | may make this a fatal error. |
309 | |
310 | =cut |