6 # We go to a lot of trouble not to 'require Carp' at file scope,
7 # because Carp requires Exporter, and something has to give.
11 $Verbose = 0 unless $Verbose;
15 # First make import warnings look like they're coming from the "use".
16 local $SIG{__WARN__} = sub {
18 if ($text =~ s/ at \S*Exporter.pm line \d+.*\n//) {
20 local $Carp::CarpLevel = 1; # ignore package calling us too.
27 local $SIG{__DIE__} = sub {
29 local $Carp::CarpLevel = 1; # ignore package calling us too.
30 Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT")
31 if $_[0] =~ /^Unable to create sub named "(.*?)::"/;
34 my($pkg, $callpkg, @imports) = @_;
35 my($type, $sym, $oops);
36 *exports = *{"${pkg}::EXPORT"};
40 grep(s/^&//, @exports);
41 @exports{@exports} = (1) x @exports;
42 my $ok = \@{"${pkg}::EXPORT_OK"};
45 @exports{@$ok} = (1) x @$ok;
49 if ($imports[0] =~ m#^[/!:]#){
50 my $tagsref = \%{"${pkg}::EXPORT_TAGS"};
53 my($remove, $spec, @names, @allexports);
54 # negated first item implies starting with default set:
55 unshift @imports, ':DEFAULT' if $imports[0] =~ m/^!/;
56 foreach $spec (@imports){
57 $remove = $spec =~ s/^!//;
60 if ($spec eq 'DEFAULT'){
63 elsif ($tagdata = $tagsref->{$spec}) {
67 warn qq["$spec" is not defined in %${pkg}::EXPORT_TAGS];
72 elsif ($spec =~ m:^/(.*)/$:){
74 @allexports = keys %exports unless @allexports; # only do keys once
75 @names = grep(/$patn/, @allexports); # not anchored by default
78 @names = ($spec); # is a normal symbol name
81 warn "Import ".($remove ? "del":"add").": @names "
85 foreach $sym (@names) { delete $imports{$sym} }
88 @imports{@names} = (1) x @names;
91 @imports = keys %imports;
94 foreach $sym (@imports) {
95 if (!$exports{$sym}) {
97 $pkg->require_version($sym);
98 # If the version number was the only thing specified
99 # then we should act as if nothing was specified:
104 # We need a way to emulate 'use Foo ()' but still
105 # allow an easy version check: "use Foo 1.23, ''";
106 if (@imports == 2 and !$imports[1]) {
110 } elsif ($sym !~ s/^&// || !$exports{$sym}) {
112 Carp::carp(qq["$sym" is not exported by the $pkg module]);
119 Carp::croak("Can't continue after import errors");
126 *fail = *{"${pkg}::EXPORT_FAIL"};
129 # Build cache of symbols. Optimise the lookup by adding
130 # barewords twice... both with and without a leading &.
131 # (Technique could be applied to %exports cache at cost of memory)
132 my @expanded = map { /^\w/ ? ($_, '&'.$_) : $_ } @fail;
133 warn "${pkg}::EXPORT_FAIL cached: @expanded" if $Verbose;
134 @fail{@expanded} = (1) x @expanded;
137 foreach $sym (@imports) { push(@failed, $sym) if $fail{$sym} }
139 @failed = $pkg->export_fail(@failed);
140 foreach $sym (@failed) {
142 Carp::carp(qq["$sym" is not implemented by the $pkg module ],
143 "on this architecture");
147 Carp::croak("Can't continue after import errors");
152 warn "Importing into $callpkg from $pkg: ",
153 join(", ",sort @imports) if $Verbose;
155 foreach $sym (@imports) {
156 # shortcut for the common case of no type character
157 (*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next)
158 unless $sym =~ s/^(\W)//;
160 *{"${callpkg}::$sym"} =
161 $type eq '&' ? \&{"${pkg}::$sym"} :
162 $type eq '$' ? \${"${pkg}::$sym"} :
163 $type eq '@' ? \@{"${pkg}::$sym"} :
164 $type eq '%' ? \%{"${pkg}::$sym"} :
165 $type eq '*' ? *{"${pkg}::$sym"} :
166 do { require Carp; Carp::croak("Can't export symbol: $type$sym") };
173 my ($level, $junk) = (shift, shift); # need to get rid of first arg
174 # we know it already.
175 my $callpkg = caller($level);
176 $pkg->export($callpkg, @_);
181 my $callpkg = caller($ExportLevel);
182 export $pkg, $callpkg, @_;
190 my($pkg, $var, $syms) = @_;
192 *export_tags = \%{"${pkg}::EXPORT_TAGS"};
193 push(@{"${pkg}::$var"},
194 map { $export_tags{$_} ? @{$export_tags{$_}} : scalar(++$nontag,$_) }
195 (@$syms) ? @$syms : keys %export_tags);
196 if ($nontag and $^W) {
197 # This may change to a die one day
199 Carp::carp("Some names are not tags");
203 sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) }
204 sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) }
214 sub require_version {
215 my($self, $wanted) = @_;
216 my $pkg = ref $self || $self;
217 my $version = ${"${pkg}::VERSION"};
218 if (!$version or $version < $wanted) {
219 $version ||= "(undef)";
220 my $file = $INC{"$pkg.pm"};
221 $file &&= " ($file)";
223 Carp::croak("$pkg $wanted required--this is only version $version$file")
230 # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
231 # package main; eval(join('',<DATA>)) or die $@ unless caller;
234 $INC{'Exporter.pm'} = 1;
236 @EXPORT = qw(A1 A2 A3 A4 A5);
237 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
238 %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
239 @EXPORT_FAIL = qw(B4);
240 Exporter::export_ok_tags('T3', 'unknown_tag');
242 map { "Test::$_" } @_ # edit symbols just as an example
246 $Exporter::Verbose = 1;
248 #import Test qw(X3); # export ok via export_ok_tags()
249 #import Test qw(:T1 !A2 /5/ !/3/ B5);
250 import Test qw(:T2 !B4);
251 import Test qw(:T2); # should fail
256 Exporter - Implements default import method for modules
260 In module ModuleName.pm:
266 @EXPORT = qw(...); # symbols to export by default
267 @EXPORT_OK = qw(...); # symbols to export on request
268 %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
270 In other files which wish to use ModuleName:
272 use ModuleName; # import default symbols into my package
274 use ModuleName qw(...); # import listed symbols into my package
276 use ModuleName (); # do not import any symbols
280 The Exporter module implements a default C<import> method which
281 many modules choose to inherit rather than implement their own.
283 Perl automatically calls the C<import> method when processing a
284 C<use> statement for a module. Modules and C<use> are documented
285 in L<perlfunc> and L<perlmod>. Understanding the concept of
286 modules and how the C<use> statement operates is important to
287 understanding the Exporter.
289 =head2 Selecting What To Export
291 Do B<not> export method names!
293 Do B<not> export anything else by default without a good reason!
295 Exports pollute the namespace of the module user. If you must export
296 try to use @EXPORT_OK in preference to @EXPORT and avoid short or
297 common symbol names to reduce the risk of name clashes.
299 Generally anything not exported is still accessible from outside the
300 module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
301 syntax. By convention you can use a leading underscore on names to
302 informally indicate that they are 'internal' and not for public use.
304 (It is actually possible to get private functions by saying:
306 my $subref = sub { ... };
309 But there's no way to call that directly as a method, since a method
310 must have a name in the symbol table.)
312 As a general rule, if the module is trying to be object oriented
313 then export nothing. If it's just a collection of functions then
314 @EXPORT_OK anything but use @EXPORT with caution.
316 Other module design guidelines can be found in L<perlmod>.
318 =head2 Specialised Import Lists
320 If the first entry in an import list begins with !, : or / then the
321 list is treated as a series of specifications which either add to or
322 delete from the list of names to import. They are processed left to
323 right. Specifications are in the form:
325 [!]name This name only
326 [!]:DEFAULT All names in @EXPORT
327 [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
328 [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
330 A leading ! indicates that matching names should be deleted from the
331 list of names to import. If the first specification is a deletion it
332 is treated as though preceded by :DEFAULT. If you just want to import
333 extra names in addition to the default set you will still need to
334 include :DEFAULT explicitly.
336 e.g., Module.pm defines:
338 @EXPORT = qw(A1 A2 A3 A4 A5);
339 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
340 %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
342 Note that you cannot use tags in @EXPORT or @EXPORT_OK.
343 Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
345 An application using Module can say something like:
347 use Module qw(:DEFAULT :T2 !B3 A3);
349 Other examples include:
351 use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
352 use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
354 Remember that most patterns (using //) will need to be anchored
355 with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
357 You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
358 specifications are being processed and what is actually being imported
361 =head2 Exporting without using Export's import method
363 Exporter has a special method, 'export_to_level' which is used in situations
364 where you can't directly call Export's import method. The export_to_level
367 MyPackage->export_to_level($where_to_export, @what_to_export);
369 where $where_to_export is an integer telling how far up the calling stack
370 to export your symbols, and @what_to_export is an array telling what
371 symbols *to* export (usually this is @_).
373 For example, suppose that you have a module, A, which already has an
379 @EXPORT_OK = qw ($b);
383 $A::b = 1; # not a very useful import method
386 and you want to Export symbol $A::b back to the module that called
387 package A. Since Exporter relies on the import method to work, via
388 inheritance, as it stands Exporter::import() will never get called.
389 Instead, say the following:
393 @EXPORT_OK = qw ($b);
398 A->export_to_level(1, @_);
401 This will export the symbols one level 'above' the current package - ie: to
402 the program or module that used package A.
404 Note: Be careful not to modify '@_' at all before you call export_to_level
405 - or people using your package will get very unexplained results!
408 =head2 Module Version Checking
410 The Exporter module will convert an attempt to import a number from a
411 module into a call to $module_name-E<gt>require_version($value). This can
412 be used to validate that the version of the module being used is
413 greater than or equal to the required version.
415 The Exporter module supplies a default require_version method which
416 checks the value of $VERSION in the exporting module.
418 Since the default require_version method treats the $VERSION number as
419 a simple numeric value it will regard version 1.10 as lower than
420 1.9. For this reason it is strongly recommended that you use numbers
421 with at least two decimal places, e.g., 1.09.
423 =head2 Managing Unknown Symbols
425 In some situations you may want to prevent certain symbols from being
426 exported. Typically this applies to extensions which have functions
427 or constants that may not exist on some systems.
429 The names of any symbols that cannot be exported should be listed
430 in the C<@EXPORT_FAIL> array.
432 If a module attempts to import any of these symbols the Exporter
433 will give the module an opportunity to handle the situation before
434 generating an error. The Exporter will call an export_fail method
435 with a list of the failed symbols:
437 @failed_symbols = $module_name->export_fail(@failed_symbols);
439 If the export_fail method returns an empty list then no error is
440 recorded and all the requested symbols are exported. If the returned
441 list is not empty then an error is generated for each symbol and the
442 export fails. The Exporter provides a default export_fail method which
443 simply returns the list unchanged.
445 Uses for the export_fail method include giving better error messages
446 for some symbols and performing lazy architectural checks (put more
447 symbols into @EXPORT_FAIL by default and then take them out if someone
448 actually tries to use them and an expensive check shows that they are
449 usable on that platform).
451 =head2 Tag Handling Utility Functions
453 Since the symbols listed within %EXPORT_TAGS must also appear in either
454 @EXPORT or @EXPORT_OK, two utility functions are provided which allow
455 you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
457 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
459 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
460 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
462 Any names which are not tags are added to @EXPORT or @EXPORT_OK
463 unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
464 names being silently added to @EXPORT or @EXPORT_OK. Future versions
465 may make this a fatal error.