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