X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/90564d9841a592d4954f5fb3ef7a8ffd42cd7c65..f34d064265539eae4e15437b48bf9db7bfe04ff9:/lib/Exporter.pm diff --git a/lib/Exporter.pm b/lib/Exporter.pm index 585109e..2b860f3 100644 --- a/lib/Exporter.pm +++ b/lib/Exporter.pm @@ -1,88 +1,100 @@ package Exporter; -require 5.001; +require 5.006; -$ExportLevel = 0; -$Verbose ||= 0; -$VERSION = '5.562'; +# Be lean. +#use strict; +#no strict 'refs'; -sub export_to_level { - require Exporter::Heavy; - goto &heavy_export_to_level; -} - -sub export { - require Exporter::Heavy; - goto &heavy_export; -} +our $Debug = 0; +our $ExportLevel = 0; +our $Verbose ||= 0; +our $VERSION = '5.59'; +our (%Cache); +# Carp does this now for us, so we can finally live w/o Carp +#$Carp::Internal{Exporter} = 1; -sub export_tags { +sub as_heavy { require Exporter::Heavy; - _push_tags((caller)[0], "EXPORT", \@_); + # Unfortunately, this does not work if the caller is aliased as *name = \&foo + # Thus the need to create a lot of identical subroutines + my $c = (caller(1))[3]; + $c =~ s/.*:://; + \&{"Exporter::Heavy::heavy_$c"}; } -sub export_ok_tags { - require Exporter::Heavy; - _push_tags((caller)[0], "EXPORT_OK", \@_); +sub export { + goto &{as_heavy()}; } sub import { my $pkg = shift; my $callpkg = caller($ExportLevel); - *exports = *{"$pkg\::EXPORT"}; + + if ($pkg eq "Exporter" and @_ and $_[0] eq "import") { + *{$callpkg."::import"} = \&import; + return; + } + # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-( - *fail = *{"$pkg\::EXPORT_FAIL"}; + my($exports, $fail) = (\@{"$pkg\::EXPORT"}, \@{"$pkg\::EXPORT_FAIL"}); return export $pkg, $callpkg, @_ - if $Verbose or $Debug or @fail > 1; - my $args = @_ or @_ = @exports; - - if ($args and not %exports) { - foreach my $sym (@exports, @{"$pkg\::EXPORT_OK"}) { - $sym =~ s/^&//; - $exports{$sym} = 1; - } + if $Verbose or $Debug or @$fail > 1; + my $export_cache = ($Cache{$pkg} ||= {}); + my $args = @_ or @_ = @$exports; + + local $_; + if ($args and not %$export_cache) { + s/^&//, $export_cache->{$_} = 1 + foreach (@$exports, @{"$pkg\::EXPORT_OK"}); } - if ($Verbose or $Debug - or grep {/\W/ or $args and not exists $exports{$_} - or @fail and $_ eq $fail[0] - or (@{"$pkg\::EXPORT_OK"} - and $_ eq ${"$pkg\::EXPORT_OK"}[0])} @_) { - return export $pkg, $callpkg, ($args ? @_ : ()); + my $heavy; + # Try very hard not to use {} and hence have to enter scope on the foreach + # We bomb out of the loop with last as soon as heavy is set. + if ($args or $fail) { + ($heavy = (/\W/ or $args and not exists $export_cache->{$_} + or @$fail and $_ eq $fail->[0])) and last + foreach (@_); + } else { + ($heavy = /\W/) and last + foreach (@_); } - #local $SIG{__WARN__} = sub {require Carp; goto &Carp::carp}; + return export $pkg, $callpkg, ($args ? @_ : ()) if $heavy; local $SIG{__WARN__} = - sub {require Carp; local $Carp::CarpLevel = 1; &Carp::carp}; - foreach $sym (@_) { - # shortcut for the common case of no type character - *{"$callpkg\::$sym"} = \&{"$pkg\::$sym"}; - } + sub {require Carp; &Carp::carp}; + # shortcut for the common case of no type character + *{"$callpkg\::$_"} = \&{"$pkg\::$_"} foreach @_; } -1; +# Default methods -# A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing. -# package main; eval(join('',)) or die $@ unless caller; -__END__ -package Test; -$INC{'Exporter.pm'} = 1; -@ISA = qw(Exporter); -@EXPORT = qw(A1 A2 A3 A4 A5); -@EXPORT_OK = qw(B1 B2 B3 B4 B5); -%EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]); -@EXPORT_FAIL = qw(B4); -Exporter::export_ok_tags('T3', 'unknown_tag'); sub export_fail { - map { "Test::$_" } @_ # edit symbols just as an example + my $self = shift; + @_; +} + +# Unfortunately, caller(1)[3] "does not work" if the caller is aliased as +# *name = \&foo. Thus the need to create a lot of identical subroutines +# Otherwise we could have aliased them to export(). + +sub export_to_level { + goto &{as_heavy()}; +} + +sub export_tags { + goto &{as_heavy()}; +} + +sub export_ok_tags { + goto &{as_heavy()}; +} + +sub require_version { + goto &{as_heavy()}; } -package main; -$Exporter::Verbose = 1; -#import Test; -#import Test qw(X3); # export ok via export_ok_tags() -#import Test qw(:T1 !A2 /5/ !/3/ B5); -import Test qw(:T2 !B4); -import Test qw(:T2); # should fail 1; +__END__ =head1 NAME @@ -90,28 +102,31 @@ Exporter - Implements default import method for modules =head1 SYNOPSIS -In module ModuleName.pm: +In module YourModule.pm: - package ModuleName; + package YourModule; require Exporter; @ISA = qw(Exporter); + @EXPORT_OK = qw(munge frobnicate); # symbols to export on request - @EXPORT = qw(...); # symbols to export by default - @EXPORT_OK = qw(...); # symbols to export on request - %EXPORT_TAGS = tag => [...]; # define names for sets of symbols +or -In other files which wish to use ModuleName: + package YourModule; + use Exporter 'import'; # gives you Exporter's import() method directly + @EXPORT_OK = qw(munge frobnicate); # symbols to export on request - use ModuleName; # import default symbols into my package +In other files which wish to use YourModule: - use ModuleName qw(...); # import listed symbols into my package - - use ModuleName (); # do not import any symbols + use ModuleName qw(frobnicate); # import listed symbols + frobnicate ($left, $right) # calls YourModule::frobnicate =head1 DESCRIPTION -The Exporter module implements a default C method which -many modules choose to inherit rather than implement their own. +The Exporter module implements an C method which allows a module +to export functions and variables to its users' namespaces. Many modules +use Exporter rather than implementing their own C method because +Exporter provides a highly flexible interface, with an implementation optimised +for the common case. Perl automatically calls the C method when processing a C statement for a module. Modules and C are documented @@ -131,6 +146,9 @@ ampersand in front of a function is optional, e.g. @EXPORT = qw(afunc $scalar @array); # afunc is a function @EXPORT_OK = qw(&bfunc %hash *typeglob); # explicit prefix on &bfunc +If you are only exporting function names it is recommended to omit the +ampersand, as the implementation is faster this way. + =head2 Selecting What To Export Do B export method names! @@ -149,22 +167,55 @@ informally indicate that they are 'internal' and not for public use. (It is actually possible to get private functions by saying: my $subref = sub { ... }; - &$subref; + $subref->(@args); # Call it as a function + $obj->$subref(@args); # Use it as a method -But there's no way to call that directly as a method, since a method -must have a name in the symbol table.) +However if you use them for methods it is up to you to figure out +how to make inheritance work.) As a general rule, if the module is trying to be object oriented then export nothing. If it's just a collection of functions then -@EXPORT_OK anything but use @EXPORT with caution. +@EXPORT_OK anything but use @EXPORT with caution. For function and +method names use barewords in preference to names prefixed with +ampersands for the export lists. Other module design guidelines can be found in L. +=head2 How to Import + +In other files which wish to use your module there are three basic ways for +them to load your module and import its symbols: + +=over 4 + +=item C + +This imports all the symbols from ModuleName's @EXPORT into the namespace +of the C statement. + +=item C + +This causes perl to load your module but does not import any symbols. + +=item C + +This imports only the symbols listed by the caller into their namespace. +All listed symbols must be in your @EXPORT or @EXPORT_OK, else an error +occurs. The advanced export features of Exporter are accessed like this, +but with list entries that are syntactically distinct from symbol names. + +=back + +Unless you want to use its advanced features, this is probably all you +need to know to use Exporter. + +=head1 Advanced features + =head2 Specialised Import Lists -If the first entry in an import list begins with !, : or / then the -list is treated as a series of specifications which either add to or -delete from the list of names to import. They are processed left to +If any of the entries in an import list begins with !, : or / then +the list is treated as a series of specifications which either add to +or delete from the list of names to import. They are processed left to right. Specifications are in the form: [!]name This name only @@ -203,13 +254,13 @@ You can say C to see how the specifications are being processed and what is actually being imported into modules. -=head2 Exporting without using Export's import method +=head2 Exporting without using Exporter's import method Exporter has a special method, 'export_to_level' which is used in situations -where you can't directly call Export's import method. The export_to_level +where you can't directly call Exporter's import method. The export_to_level method looks like: -MyPackage->export_to_level($where_to_export, $package, @what_to_export); + MyPackage->export_to_level($where_to_export, $package, @what_to_export); where $where_to_export is an integer telling how far up the calling stack to export your symbols, and @what_to_export is an array telling what @@ -219,37 +270,49 @@ currently unused. For example, suppose that you have a module, A, which already has an import function: -package A; + package A; -@ISA = qw(Exporter); -@EXPORT_OK = qw ($b); + @ISA = qw(Exporter); + @EXPORT_OK = qw ($b); -sub import -{ - $A::b = 1; # not a very useful import method -} + sub import + { + $A::b = 1; # not a very useful import method + } and you want to Export symbol $A::b back to the module that called package A. Since Exporter relies on the import method to work, via inheritance, as it stands Exporter::import() will never get called. Instead, say the following: -package A; -@ISA = qw(Exporter); -@EXPORT_OK = qw ($b); + package A; + @ISA = qw(Exporter); + @EXPORT_OK = qw ($b); -sub import -{ - $A::b = 1; - A->export_to_level(1, @_); -} + sub import + { + $A::b = 1; + A->export_to_level(1, @_); + } This will export the symbols one level 'above' the current package - ie: to the program or module that used package A. -Note: Be careful not to modify '@_' at all before you call export_to_level +Note: Be careful not to modify C<@_> at all before you call export_to_level - or people using your package will get very unexplained results! +=head2 Exporting without inheriting from Exporter + +By including Exporter in your @ISA you inherit an Exporter's import() method +but you also inherit several other helper methods which you probably don't +want. To avoid this you can do + + package YourModule; + use Exporter qw( import ); + +which will export Exporter's own import() method into YourModule. +Everything will work as before but you won't need to include Exporter in +@YourModule::ISA. =head2 Module Version Checking @@ -310,4 +373,69 @@ unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags names being silently added to @EXPORT or @EXPORT_OK. Future versions may make this a fatal error. +=head2 Generating combined tags + +If several symbol categories exist in %EXPORT_TAGS, it's usually +useful to create the utility ":all" to simplify "use" statements. + +The simplest way to do this is: + + %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); + + # add all the other ":class" tags to the ":all" class, + # deleting duplicates + { + my %seen; + + push @{$EXPORT_TAGS{all}}, + grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} foreach keys %EXPORT_TAGS; + } + +CGI.pm creates an ":all" tag which contains some (but not really +all) of its categories. That could be done with one small +change: + + # add some of the other ":class" tags to the ":all" class, + # deleting duplicates + { + my %seen; + + push @{$EXPORT_TAGS{all}}, + grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} + foreach qw/html2 html3 netscape form cgi internal/; + } + +Note that the tag names in %EXPORT_TAGS don't have the leading ':'. + +=head2 Ced Constants + +Many modules make use of Cing for constant subroutines to +avoid having to compile and waste memory on rarely used values (see +L for details on constant subroutines). Calls to such +constant subroutines are not optimized away at compile time because +they can't be checked at compile time for constancy. + +Even if a prototype is available at compile time, the body of the +subroutine is not (it hasn't been Ced yet). perl needs to +examine both the C<()> prototype and the body of a subroutine at +compile time to detect that it can safely replace calls to that +subroutine with the constant value. + +A workaround for this is to call the constants once in a C block: + + package My ; + + use Socket ; + + foo( SO_LINGER ); ## SO_LINGER NOT optimized away; called at runtime + BEGIN { SO_LINGER } + foo( SO_LINGER ); ## SO_LINGER optimized away at compile time. + +This forces the C for C to take place before +SO_LINGER is encountered later in C package. + +If you are writing a package that Cs, consider forcing +an C for any constants explicitly imported by other packages +or which are usually used when your package is Cd. + =cut