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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 unless $Verbose; |
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7 | |
8 | require Carp; |
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9 | |
10 | sub export { |
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11 | |
12 | # First make import warnings look like they're coming from the "use". |
13 | local $SIG{__WARN__} = sub { |
14 | my $text = shift; |
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15 | $text =~ s/ at \S*Exporter.pm line \d+.*\n//; |
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16 | local $Carp::CarpLevel = 1; # ignore package calling us too. |
17 | Carp::carp($text); |
18 | }; |
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19 | local $SIG{__DIE__} = sub { |
20 | Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT") |
21 | if $_[0] =~ /^Unable to create sub named "(.*?)::"/; |
22 | }; |
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23 | |
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24 | my($pkg, $callpkg, @imports) = @_; |
25 | my($type, $sym, $oops); |
26 | *exports = *{"${pkg}::EXPORT"}; |
27 | |
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28 | if (@imports) { |
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29 | if (!%exports) { |
30 | grep(s/^&//, @exports); |
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31 | @exports{@exports} = (1) x @exports; |
32 | my $ok = \@{"${pkg}::EXPORT_OK"}; |
33 | if (@$ok) { |
34 | grep(s/^&//, @$ok); |
35 | @exports{@$ok} = (1) x @$ok; |
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36 | } |
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37 | } |
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38 | |
39 | if ($imports[0] =~ m#^[/!:]#){ |
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40 | my $tagsref = \%{"${pkg}::EXPORT_TAGS"}; |
41 | my $tagdata; |
42 | my %imports; |
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43 | my($remove, $spec, @names, @allexports); |
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44 | # negated first item implies starting with default set: |
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45 | unshift @imports, ':DEFAULT' if $imports[0] =~ m/^!/; |
46 | foreach $spec (@imports){ |
47 | $remove = $spec =~ s/^!//; |
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48 | |
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49 | if ($spec =~ s/^://){ |
50 | if ($spec eq 'DEFAULT'){ |
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51 | @names = @exports; |
52 | } |
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53 | elsif ($tagdata = $tagsref->{$spec}) { |
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54 | @names = @$tagdata; |
55 | } |
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56 | else { |
57 | warn qq["$spec" is not defined in %${pkg}::EXPORT_TAGS]; |
58 | ++$oops; |
59 | next; |
60 | } |
61 | } |
62 | elsif ($spec =~ m:^/(.*)/$:){ |
63 | my $patn = $1; |
64 | @allexports = keys %exports unless @allexports; # only do keys once |
65 | @names = grep(/$patn/, @allexports); # not anchored by default |
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66 | } |
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67 | else { |
68 | @names = ($spec); # is a normal symbol name |
69 | } |
70 | |
71 | warn "Import ".($remove ? "del":"add").": @names " |
72 | if $Verbose; |
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73 | |
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74 | if ($remove) { |
75 | foreach $sym (@names) { delete $imports{$sym} } |
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76 | } |
77 | else { |
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78 | @imports{@names} = (1) x @names; |
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79 | } |
80 | } |
81 | @imports = keys %imports; |
82 | } |
83 | |
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84 | foreach $sym (@imports) { |
85 | if (!$exports{$sym}) { |
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86 | if ($sym =~ m/^\d/) { |
87 | $pkg->require_version($sym); |
88 | # If the version number was the only thing specified |
89 | # then we should act as if nothing was specified: |
90 | if (@imports == 1) { |
91 | @imports = @exports; |
92 | last; |
93 | } |
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94 | # We need a way to emulate 'use Foo ()' but still |
95 | # allow an easy version check: "use Foo 1.23, ''"; |
96 | if (@imports == 2 and !$imports[1]) { |
97 | @imports = (); |
98 | last; |
99 | } |
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100 | } elsif ($sym !~ s/^&// || !$exports{$sym}) { |
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101 | warn qq["$sym" is not exported by the $pkg module]; |
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102 | $oops++; |
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103 | } |
104 | } |
105 | } |
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106 | Carp::croak("Can't continue after import errors") if $oops; |
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107 | } |
108 | else { |
109 | @imports = @exports; |
110 | } |
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111 | |
112 | *fail = *{"${pkg}::EXPORT_FAIL"}; |
113 | if (@fail) { |
114 | if (!%fail) { |
115 | # Build cache of symbols. Optimise the lookup by adding |
116 | # barewords twice... both with and without a leading &. |
117 | # (Technique could be applied to %exports cache at cost of memory) |
118 | my @expanded = map { /^\w/ ? ($_, '&'.$_) : $_ } @fail; |
119 | warn "${pkg}::EXPORT_FAIL cached: @expanded" if $Verbose; |
120 | @fail{@expanded} = (1) x @expanded; |
121 | } |
122 | my @failed; |
123 | foreach $sym (@imports) { push(@failed, $sym) if $fail{$sym} } |
124 | if (@failed) { |
125 | @failed = $pkg->export_fail(@failed); |
126 | foreach $sym (@failed) { |
127 | warn qq["$sym" is not implemented by the $pkg module ], |
128 | "on this architecture"; |
129 | } |
130 | Carp::croak("Can't continue after import errors") if @failed; |
131 | } |
132 | } |
133 | |
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134 | warn "Importing into $callpkg from $pkg: ", |
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135 | join(", ",sort @imports) if $Verbose; |
136 | |
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137 | foreach $sym (@imports) { |
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138 | # shortcut for the common case of no type character |
139 | (*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next) |
140 | unless $sym =~ s/^(\W)//; |
141 | $type = $1; |
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142 | *{"${callpkg}::$sym"} = |
143 | $type eq '&' ? \&{"${pkg}::$sym"} : |
144 | $type eq '$' ? \${"${pkg}::$sym"} : |
145 | $type eq '@' ? \@{"${pkg}::$sym"} : |
146 | $type eq '%' ? \%{"${pkg}::$sym"} : |
147 | $type eq '*' ? *{"${pkg}::$sym"} : |
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148 | Carp::croak("Can't export symbol: $type$sym"); |
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149 | } |
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150 | } |
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151 | |
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152 | sub import { |
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153 | my $pkg = shift; |
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154 | my $callpkg = caller($ExportLevel); |
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155 | export $pkg, $callpkg, @_; |
156 | } |
157 | |
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158 | |
159 | # Utility functions |
160 | |
161 | sub _push_tags { |
162 | my($pkg, $var, $syms) = @_; |
163 | my $nontag; |
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164 | *export_tags = \%{"${pkg}::EXPORT_TAGS"}; |
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165 | push(@{"${pkg}::$var"}, |
166 | map { $export_tags{$_} ? @{$export_tags{$_}} : scalar(++$nontag,$_) } |
167 | (@$syms) ? @$syms : keys %export_tags); |
168 | # This may change to a die one day |
169 | Carp::carp("Some names are not tags") if $nontag and $^W; |
170 | } |
171 | |
172 | sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) } |
173 | sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) } |
174 | |
175 | |
176 | # Default methods |
177 | |
178 | sub export_fail { |
179 | @_; |
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180 | } |
181 | |
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182 | sub require_version { |
183 | my($self, $wanted) = @_; |
184 | my $pkg = ref $self || $self; |
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185 | my $version = ${"${pkg}::VERSION"}; |
186 | if (!$version or $version < $wanted) { |
187 | $version ||= "(undef)"; |
188 | my $file = $INC{"$pkg.pm"}; |
189 | $file &&= " ($file)"; |
190 | Carp::croak("$pkg $wanted required--this is only version $version$file") |
191 | } |
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192 | $version; |
193 | } |
194 | |
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195 | 1; |
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196 | |
197 | # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing. |
198 | # package main; eval(join('',<DATA>)) or die $@ unless caller; |
199 | __END__ |
200 | package Test; |
201 | $INC{'Exporter.pm'} = 1; |
202 | @ISA = qw(Exporter); |
203 | @EXPORT = qw(A1 A2 A3 A4 A5); |
204 | @EXPORT_OK = qw(B1 B2 B3 B4 B5); |
205 | %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]); |
206 | @EXPORT_FAIL = qw(B4); |
207 | Exporter::export_ok_tags('T3', 'unknown_tag'); |
208 | sub export_fail { |
209 | map { "Test::$_" } @_ # edit symbols just as an example |
210 | } |
211 | |
212 | package main; |
213 | $Exporter::Verbose = 1; |
214 | #import Test; |
215 | #import Test qw(X3); # export ok via export_ok_tags() |
216 | #import Test qw(:T1 !A2 /5/ !/3/ B5); |
217 | import Test qw(:T2 !B4); |
218 | import Test qw(:T2); # should fail |
219 | 1; |
220 | |
221 | =head1 NAME |
222 | |
223 | Exporter - Implements default import method for modules |
224 | |
225 | =head1 SYNOPSIS |
226 | |
227 | In module ModuleName.pm: |
228 | |
229 | package ModuleName; |
230 | require Exporter; |
231 | @ISA = qw(Exporter); |
232 | |
233 | @EXPORT = qw(...); # symbols to export by default |
234 | @EXPORT_OK = qw(...); # symbols to export on request |
235 | %EXPORT_TAGS = tag => [...]; # define names for sets of symbols |
236 | |
237 | In other files which wish to use ModuleName: |
238 | |
239 | use ModuleName; # import default symbols into my package |
240 | |
241 | use ModuleName qw(...); # import listed symbols into my package |
242 | |
243 | use ModuleName (); # do not import any symbols |
244 | |
245 | =head1 DESCRIPTION |
246 | |
247 | The Exporter module implements a default C<import> method which |
248 | many modules choose inherit rather than implement their own. |
249 | |
250 | Perl automatically calls the C<import> method when processing a |
251 | C<use> statement for a module. Modules and C<use> are documented |
252 | in L<perlfunc> and L<perlmod>. Understanding the concept of |
253 | modules and how the C<use> statement operates is important to |
254 | understanding the Exporter. |
255 | |
256 | =head2 Selecting What To Export |
257 | |
258 | Do B<not> export method names! |
259 | |
260 | Do B<not> export anything else by default without a good reason! |
261 | |
262 | Exports pollute the namespace of the module user. If you must export |
263 | try to use @EXPORT_OK in preference to @EXPORT and avoid short or |
264 | common symbol names to reduce the risk of name clashes. |
265 | |
266 | Generally anything not exported is still accessible from outside the |
267 | module using the ModuleName::item_name (or $blessed_ref->method) |
268 | syntax. By convention you can use a leading underscore on names to |
269 | informally indicate that they are 'internal' and not for public use. |
270 | |
271 | (It is actually possible to get private functions by saying: |
272 | |
273 | my $subref = sub { ... }; |
274 | &$subref; |
275 | |
276 | But there's no way to call that directly as a method, since a method |
277 | must have a name in the symbol table.) |
278 | |
279 | As a general rule, if the module is trying to be object oriented |
280 | then export nothing. If it's just a collection of functions then |
281 | @EXPORT_OK anything but use @EXPORT with caution. |
282 | |
283 | Other module design guidelines can be found in L<perlmod>. |
284 | |
285 | =head2 Specialised Import Lists |
286 | |
287 | If the first entry in an import list begins with !, : or / then the |
288 | list is treated as a series of specifications which either add to or |
289 | delete from the list of names to import. They are processed left to |
290 | right. Specifications are in the form: |
291 | |
292 | [!]name This name only |
293 | [!]:DEFAULT All names in @EXPORT |
294 | [!]:tag All names in $EXPORT_TAGS{tag} anonymous list |
295 | [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match |
296 | |
297 | A leading ! indicates that matching names should be deleted from the |
298 | list of names to import. If the first specification is a deletion it |
299 | is treated as though preceded by :DEFAULT. If you just want to import |
300 | extra names in addition to the default set you will still need to |
301 | include :DEFAULT explicitly. |
302 | |
303 | e.g., Module.pm defines: |
304 | |
305 | @EXPORT = qw(A1 A2 A3 A4 A5); |
306 | @EXPORT_OK = qw(B1 B2 B3 B4 B5); |
307 | %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]); |
308 | |
309 | Note that you cannot use tags in @EXPORT or @EXPORT_OK. |
310 | Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK. |
311 | |
312 | An application using Module can say something like: |
313 | |
314 | use Module qw(:DEFAULT :T2 !B3 A3); |
315 | |
316 | Other examples include: |
317 | |
318 | use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET); |
319 | use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/); |
320 | |
321 | Remember that most patterns (using //) will need to be anchored |
322 | with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>. |
323 | |
324 | You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the |
325 | specifications are being processed and what is actually being imported |
326 | into modules. |
327 | |
328 | =head2 Module Version Checking |
329 | |
330 | The Exporter module will convert an attempt to import a number from a |
331 | module into a call to $module_name->require_version($value). This can |
332 | be used to validate that the version of the module being used is |
333 | greater than or equal to the required version. |
334 | |
335 | The Exporter module supplies a default require_version method which |
336 | checks the value of $VERSION in the exporting module. |
337 | |
338 | Since the default require_version method treats the $VERSION number as |
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339 | a simple numeric value it will regard version 1.10 as lower than |
340 | 1.9. For this reason it is strongly recommended that you use numbers |
341 | with at least two decimal places, e.g., 1.09. |
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342 | |
343 | =head2 Managing Unknown Symbols |
344 | |
345 | In some situations you may want to prevent certain symbols from being |
346 | exported. Typically this applies to extensions which have functions |
347 | or constants that may not exist on some systems. |
348 | |
349 | The names of any symbols that cannot be exported should be listed |
350 | in the C<@EXPORT_FAIL> array. |
351 | |
352 | If a module attempts to import any of these symbols the Exporter will |
353 | will give the module an opportunity to handle the situation before |
354 | generating an error. The Exporter will call an export_fail method |
355 | with a list of the failed symbols: |
356 | |
357 | @failed_symbols = $module_name->export_fail(@failed_symbols); |
358 | |
359 | If the export_fail method returns an empty list then no error is |
360 | recorded and all the requested symbols are exported. If the returned |
361 | list is not empty then an error is generated for each symbol and the |
362 | export fails. The Exporter provides a default export_fail method which |
363 | simply returns the list unchanged. |
364 | |
365 | Uses for the export_fail method include giving better error messages |
366 | for some symbols and performing lazy architectural checks (put more |
367 | symbols into @EXPORT_FAIL by default and then take them out if someone |
368 | actually tries to use them and an expensive check shows that they are |
369 | usable on that platform). |
370 | |
371 | =head2 Tag Handling Utility Functions |
372 | |
373 | Since the symbols listed within %EXPORT_TAGS must also appear in either |
374 | @EXPORT or @EXPORT_OK, two utility functions are provided which allow |
375 | you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK: |
376 | |
377 | %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); |
378 | |
379 | Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT |
380 | Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK |
381 | |
382 | Any names which are not tags are added to @EXPORT or @EXPORT_OK |
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383 | unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags |
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384 | names being silently added to @EXPORT or @EXPORT_OK. Future versions |
385 | may make this a fatal error. |
386 | |
387 | =cut |