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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 | $ExportLevel = 0; |
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6 | $Verbose ||= 0; |
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7 | |
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8 | sub export_to_level { |
9 | require Exporter::Heavy; |
10 | goto &heavy_export_to_level; |
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11 | } |
12 | |
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13 | sub export { |
14 | require Exporter::Heavy; |
15 | goto &heavy_export; |
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16 | } |
17 | |
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18 | sub export_tags { |
19 | require Exporter::Heavy; |
20 | _push_tags((caller)[0], "EXPORT", \@_); |
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21 | } |
22 | |
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23 | sub export_ok_tags { |
24 | require Exporter::Heavy; |
25 | _push_tags((caller)[0], "EXPORT_OK", \@_); |
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26 | } |
27 | |
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28 | sub import { |
29 | my $pkg = shift; |
30 | my $callpkg = caller($ExportLevel); |
31 | *exports = *{"$pkg\::EXPORT"}; |
32 | # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-( |
33 | *fail = *{"$pkg\::EXPORT_FAIL"}; |
34 | return export $pkg, $callpkg, @_ |
35 | if $Verbose or $Debug or @fail > 1; |
36 | my $args = @_ or @_ = @exports; |
37 | |
38 | if ($args and not %exports) { |
39 | foreach my $sym (@exports, @{"$pkg\::EXPORT_OK"}) { |
40 | $sym =~ s/^&//; |
41 | $exports{$sym} = 1; |
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42 | } |
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43 | } |
44 | if ($Verbose or $Debug |
45 | or grep {/\W/ or $args and not exists $exports{$_} |
46 | or @fail and $_ eq $fail[0] |
47 | or (@{"$pkg\::EXPORT_OK"} |
48 | and $_ eq ${"$pkg\::EXPORT_OK"}[0])} @_) { |
49 | return export $pkg, $callpkg, ($args ? @_ : ()); |
50 | } |
51 | #local $SIG{__WARN__} = sub {require Carp; goto &Carp::carp}; |
52 | local $SIG{__WARN__} = |
53 | sub {require Carp; local $Carp::CarpLevel = 1; &Carp::carp}; |
54 | foreach $sym (@_) { |
55 | # shortcut for the common case of no type character |
56 | *{"$callpkg\::$sym"} = \&{"$pkg\::$sym"}; |
57 | } |
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58 | } |
59 | |
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60 | 1; |
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61 | |
62 | # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing. |
63 | # package main; eval(join('',<DATA>)) or die $@ unless caller; |
64 | __END__ |
65 | package Test; |
66 | $INC{'Exporter.pm'} = 1; |
67 | @ISA = qw(Exporter); |
68 | @EXPORT = qw(A1 A2 A3 A4 A5); |
69 | @EXPORT_OK = qw(B1 B2 B3 B4 B5); |
70 | %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]); |
71 | @EXPORT_FAIL = qw(B4); |
72 | Exporter::export_ok_tags('T3', 'unknown_tag'); |
73 | sub export_fail { |
74 | map { "Test::$_" } @_ # edit symbols just as an example |
75 | } |
76 | |
77 | package main; |
78 | $Exporter::Verbose = 1; |
79 | #import Test; |
80 | #import Test qw(X3); # export ok via export_ok_tags() |
81 | #import Test qw(:T1 !A2 /5/ !/3/ B5); |
82 | import Test qw(:T2 !B4); |
83 | import Test qw(:T2); # should fail |
84 | 1; |
85 | |
86 | =head1 NAME |
87 | |
88 | Exporter - Implements default import method for modules |
89 | |
90 | =head1 SYNOPSIS |
91 | |
92 | In module ModuleName.pm: |
93 | |
94 | package ModuleName; |
95 | require Exporter; |
96 | @ISA = qw(Exporter); |
97 | |
98 | @EXPORT = qw(...); # symbols to export by default |
99 | @EXPORT_OK = qw(...); # symbols to export on request |
100 | %EXPORT_TAGS = tag => [...]; # define names for sets of symbols |
101 | |
102 | In other files which wish to use ModuleName: |
103 | |
104 | use ModuleName; # import default symbols into my package |
105 | |
106 | use ModuleName qw(...); # import listed symbols into my package |
107 | |
108 | use ModuleName (); # do not import any symbols |
109 | |
110 | =head1 DESCRIPTION |
111 | |
112 | The Exporter module implements a default C<import> method which |
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113 | many modules choose to inherit rather than implement their own. |
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114 | |
115 | Perl automatically calls the C<import> method when processing a |
116 | C<use> statement for a module. Modules and C<use> are documented |
117 | in L<perlfunc> and L<perlmod>. Understanding the concept of |
118 | modules and how the C<use> statement operates is important to |
119 | understanding the Exporter. |
120 | |
121 | =head2 Selecting What To Export |
122 | |
123 | Do B<not> export method names! |
124 | |
125 | Do B<not> export anything else by default without a good reason! |
126 | |
127 | Exports pollute the namespace of the module user. If you must export |
128 | try to use @EXPORT_OK in preference to @EXPORT and avoid short or |
129 | common symbol names to reduce the risk of name clashes. |
130 | |
131 | Generally anything not exported is still accessible from outside the |
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132 | module using the ModuleName::item_name (or $blessed_ref-E<gt>method) |
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133 | syntax. By convention you can use a leading underscore on names to |
134 | informally indicate that they are 'internal' and not for public use. |
135 | |
136 | (It is actually possible to get private functions by saying: |
137 | |
138 | my $subref = sub { ... }; |
139 | &$subref; |
140 | |
141 | But there's no way to call that directly as a method, since a method |
142 | must have a name in the symbol table.) |
143 | |
144 | As a general rule, if the module is trying to be object oriented |
145 | then export nothing. If it's just a collection of functions then |
146 | @EXPORT_OK anything but use @EXPORT with caution. |
147 | |
148 | Other module design guidelines can be found in L<perlmod>. |
149 | |
150 | =head2 Specialised Import Lists |
151 | |
152 | If the first entry in an import list begins with !, : or / then the |
153 | list is treated as a series of specifications which either add to or |
154 | delete from the list of names to import. They are processed left to |
155 | right. Specifications are in the form: |
156 | |
157 | [!]name This name only |
158 | [!]:DEFAULT All names in @EXPORT |
159 | [!]:tag All names in $EXPORT_TAGS{tag} anonymous list |
160 | [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match |
161 | |
162 | A leading ! indicates that matching names should be deleted from the |
163 | list of names to import. If the first specification is a deletion it |
164 | is treated as though preceded by :DEFAULT. If you just want to import |
165 | extra names in addition to the default set you will still need to |
166 | include :DEFAULT explicitly. |
167 | |
168 | e.g., Module.pm defines: |
169 | |
170 | @EXPORT = qw(A1 A2 A3 A4 A5); |
171 | @EXPORT_OK = qw(B1 B2 B3 B4 B5); |
172 | %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]); |
173 | |
174 | Note that you cannot use tags in @EXPORT or @EXPORT_OK. |
175 | Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK. |
176 | |
177 | An application using Module can say something like: |
178 | |
179 | use Module qw(:DEFAULT :T2 !B3 A3); |
180 | |
181 | Other examples include: |
182 | |
183 | use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET); |
184 | use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/); |
185 | |
186 | Remember that most patterns (using //) will need to be anchored |
187 | with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>. |
188 | |
189 | You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the |
190 | specifications are being processed and what is actually being imported |
191 | into modules. |
192 | |
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193 | =head2 Exporting without using Export's import method |
194 | |
195 | Exporter has a special method, 'export_to_level' which is used in situations |
196 | where you can't directly call Export's import method. The export_to_level |
197 | method looks like: |
198 | |
199 | MyPackage->export_to_level($where_to_export, @what_to_export); |
200 | |
201 | where $where_to_export is an integer telling how far up the calling stack |
202 | to export your symbols, and @what_to_export is an array telling what |
203 | symbols *to* export (usually this is @_). |
204 | |
205 | For example, suppose that you have a module, A, which already has an |
206 | import function: |
207 | |
208 | package A; |
209 | |
210 | @ISA = qw(Exporter); |
211 | @EXPORT_OK = qw ($b); |
212 | |
213 | sub import |
214 | { |
215 | $A::b = 1; # not a very useful import method |
216 | } |
217 | |
218 | and you want to Export symbol $A::b back to the module that called |
219 | package A. Since Exporter relies on the import method to work, via |
220 | inheritance, as it stands Exporter::import() will never get called. |
221 | Instead, say the following: |
222 | |
223 | package A; |
224 | @ISA = qw(Exporter); |
225 | @EXPORT_OK = qw ($b); |
226 | |
227 | sub import |
228 | { |
229 | $A::b = 1; |
230 | A->export_to_level(1, @_); |
231 | } |
232 | |
233 | This will export the symbols one level 'above' the current package - ie: to |
234 | the program or module that used package A. |
235 | |
236 | Note: Be careful not to modify '@_' at all before you call export_to_level |
237 | - or people using your package will get very unexplained results! |
238 | |
239 | |
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240 | =head2 Module Version Checking |
241 | |
242 | The Exporter module will convert an attempt to import a number from a |
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243 | module into a call to $module_name-E<gt>require_version($value). This can |
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244 | be used to validate that the version of the module being used is |
245 | greater than or equal to the required version. |
246 | |
247 | The Exporter module supplies a default require_version method which |
248 | checks the value of $VERSION in the exporting module. |
249 | |
250 | Since the default require_version method treats the $VERSION number as |
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251 | a simple numeric value it will regard version 1.10 as lower than |
252 | 1.9. For this reason it is strongly recommended that you use numbers |
253 | with at least two decimal places, e.g., 1.09. |
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254 | |
255 | =head2 Managing Unknown Symbols |
256 | |
257 | In some situations you may want to prevent certain symbols from being |
258 | exported. Typically this applies to extensions which have functions |
259 | or constants that may not exist on some systems. |
260 | |
261 | The names of any symbols that cannot be exported should be listed |
262 | in the C<@EXPORT_FAIL> array. |
263 | |
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264 | If a module attempts to import any of these symbols the Exporter |
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265 | will give the module an opportunity to handle the situation before |
266 | generating an error. The Exporter will call an export_fail method |
267 | with a list of the failed symbols: |
268 | |
269 | @failed_symbols = $module_name->export_fail(@failed_symbols); |
270 | |
271 | If the export_fail method returns an empty list then no error is |
272 | recorded and all the requested symbols are exported. If the returned |
273 | list is not empty then an error is generated for each symbol and the |
274 | export fails. The Exporter provides a default export_fail method which |
275 | simply returns the list unchanged. |
276 | |
277 | Uses for the export_fail method include giving better error messages |
278 | for some symbols and performing lazy architectural checks (put more |
279 | symbols into @EXPORT_FAIL by default and then take them out if someone |
280 | actually tries to use them and an expensive check shows that they are |
281 | usable on that platform). |
282 | |
283 | =head2 Tag Handling Utility Functions |
284 | |
285 | Since the symbols listed within %EXPORT_TAGS must also appear in either |
286 | @EXPORT or @EXPORT_OK, two utility functions are provided which allow |
287 | you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK: |
288 | |
289 | %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); |
290 | |
291 | Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT |
292 | Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK |
293 | |
294 | Any names which are not tags are added to @EXPORT or @EXPORT_OK |
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295 | unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags |
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296 | names being silently added to @EXPORT or @EXPORT_OK. Future versions |
297 | may make this a fatal error. |
298 | |
299 | =cut |