You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
441 lines
14 KiB
441 lines
14 KiB
package Exporter;
|
|
|
|
require 5.006;
|
|
|
|
# Be lean.
|
|
#use strict;
|
|
#no strict 'refs';
|
|
|
|
our $Debug = 0;
|
|
our $ExportLevel = 0;
|
|
our $Verbose ||= 0;
|
|
our $VERSION = '5.60';
|
|
our (%Cache);
|
|
# Carp does this now for us, so we can finally live w/o Carp
|
|
#$Carp::Internal{Exporter} = 1;
|
|
|
|
sub as_heavy {
|
|
require Exporter::Heavy;
|
|
# 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 {
|
|
goto &{as_heavy()};
|
|
}
|
|
|
|
sub import {
|
|
my $pkg = shift;
|
|
my $callpkg = caller($ExportLevel);
|
|
|
|
if ($pkg eq "Exporter" and @_ and $_[0] eq "import") {
|
|
*{$callpkg."::import"} = \&import;
|
|
return;
|
|
}
|
|
|
|
# We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-(
|
|
my($exports, $fail) = (\@{"$pkg\::EXPORT"}, \@{"$pkg\::EXPORT_FAIL"});
|
|
return export $pkg, $callpkg, @_
|
|
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"});
|
|
}
|
|
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 (@_);
|
|
}
|
|
return export $pkg, $callpkg, ($args ? @_ : ()) if $heavy;
|
|
local $SIG{__WARN__} =
|
|
sub {require Carp; &Carp::carp};
|
|
# shortcut for the common case of no type character
|
|
*{"$callpkg\::$_"} = \&{"$pkg\::$_"} foreach @_;
|
|
}
|
|
|
|
# Default methods
|
|
|
|
sub export_fail {
|
|
my $self = shift;
|
|
@_;
|
|
}
|
|
|
|
# Unfortunately, caller(1)[3] "does not work" if the caller is aliased as
|
|
# *name = \&foo. Thus the need to create a lot of identical subroutines
|
|
# Otherwise we could have aliased them to export().
|
|
|
|
sub export_to_level {
|
|
goto &{as_heavy()};
|
|
}
|
|
|
|
sub export_tags {
|
|
goto &{as_heavy()};
|
|
}
|
|
|
|
sub export_ok_tags {
|
|
goto &{as_heavy()};
|
|
}
|
|
|
|
sub require_version {
|
|
goto &{as_heavy()};
|
|
}
|
|
|
|
1;
|
|
__END__
|
|
|
|
=head1 NAME
|
|
|
|
Exporter - Implements default import method for modules
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
In module YourModule.pm:
|
|
|
|
package YourModule;
|
|
require Exporter;
|
|
@ISA = qw(Exporter);
|
|
@EXPORT_OK = qw(munge frobnicate); # symbols to export on request
|
|
|
|
or
|
|
|
|
package YourModule;
|
|
use Exporter 'import'; # gives you Exporter's import() method directly
|
|
@EXPORT_OK = qw(munge frobnicate); # symbols to export on request
|
|
|
|
In other files which wish to use YourModule:
|
|
|
|
use ModuleName qw(frobnicate); # import listed symbols
|
|
frobnicate ($left, $right) # calls YourModule::frobnicate
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
The Exporter module implements an C<import> method which allows a module
|
|
to export functions and variables to its users' namespaces. Many modules
|
|
use Exporter rather than implementing their own C<import> method because
|
|
Exporter provides a highly flexible interface, with an implementation optimised
|
|
for the common case.
|
|
|
|
Perl automatically calls the C<import> method when processing a
|
|
C<use> statement for a module. Modules and C<use> are documented
|
|
in L<perlfunc> and L<perlmod>. Understanding the concept of
|
|
modules and how the C<use> statement operates is important to
|
|
understanding the Exporter.
|
|
|
|
=head2 How to Export
|
|
|
|
The arrays C<@EXPORT> and C<@EXPORT_OK> in a module hold lists of
|
|
symbols that are going to be exported into the users name space by
|
|
default, or which they can request to be exported, respectively. The
|
|
symbols can represent functions, scalars, arrays, hashes, or typeglobs.
|
|
The symbols must be given by full name with the exception that the
|
|
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<not> export method names!
|
|
|
|
Do B<not> export anything else by default without a good reason!
|
|
|
|
Exports pollute the namespace of the module user. If you must export
|
|
try to use @EXPORT_OK in preference to @EXPORT and avoid short or
|
|
common symbol names to reduce the risk of name clashes.
|
|
|
|
Generally anything not exported is still accessible from outside the
|
|
module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
|
|
syntax. By convention you can use a leading underscore on names to
|
|
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->(@args); # Call it as a function
|
|
$obj->$subref(@args); # Use it as a method
|
|
|
|
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. 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<perlmod>.
|
|
|
|
=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<use ModuleName;>
|
|
|
|
This imports all the symbols from ModuleName's @EXPORT into the namespace
|
|
of the C<use> statement.
|
|
|
|
=item C<use ModuleName ();>
|
|
|
|
This causes perl to load your module but does not import any symbols.
|
|
|
|
=item C<use ModuleName qw(...);>
|
|
|
|
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 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
|
|
[!]:DEFAULT All names in @EXPORT
|
|
[!]:tag All names in $EXPORT_TAGS{tag} anonymous list
|
|
[!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
|
|
|
|
A leading ! indicates that matching names should be deleted from the
|
|
list of names to import. If the first specification is a deletion it
|
|
is treated as though preceded by :DEFAULT. If you just want to import
|
|
extra names in addition to the default set you will still need to
|
|
include :DEFAULT explicitly.
|
|
|
|
e.g., Module.pm defines:
|
|
|
|
@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)]);
|
|
|
|
Note that you cannot use tags in @EXPORT or @EXPORT_OK.
|
|
Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
|
|
|
|
An application using Module can say something like:
|
|
|
|
use Module qw(:DEFAULT :T2 !B3 A3);
|
|
|
|
Other examples include:
|
|
|
|
use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
|
|
use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
|
|
|
|
Remember that most patterns (using //) will need to be anchored
|
|
with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
|
|
|
|
You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
|
|
specifications are being processed and what is actually being imported
|
|
into modules.
|
|
|
|
=head2 Exporting without using Exporter's import method
|
|
|
|
Exporter has a special method, 'export_to_level' which is used in situations
|
|
where you can't directly call Exporter's import method. The export_to_level
|
|
method looks like:
|
|
|
|
MyPackage->export_to_level($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
|
|
symbols *to* export (usually this is @_). The $package argument is
|
|
currently unused.
|
|
|
|
For example, suppose that you have a module, A, which already has an
|
|
import function:
|
|
|
|
package A;
|
|
|
|
@ISA = qw(Exporter);
|
|
@EXPORT_OK = qw ($b);
|
|
|
|
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);
|
|
|
|
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 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
|
|
|
|
The Exporter module will convert an attempt to import a number from a
|
|
module into a call to $module_name-E<gt>require_version($value). This can
|
|
be used to validate that the version of the module being used is
|
|
greater than or equal to the required version.
|
|
|
|
The Exporter module supplies a default require_version method which
|
|
checks the value of $VERSION in the exporting module.
|
|
|
|
Since the default require_version method treats the $VERSION number as
|
|
a simple numeric value it will regard version 1.10 as lower than
|
|
1.9. For this reason it is strongly recommended that you use numbers
|
|
with at least two decimal places, e.g., 1.09.
|
|
|
|
=head2 Managing Unknown Symbols
|
|
|
|
In some situations you may want to prevent certain symbols from being
|
|
exported. Typically this applies to extensions which have functions
|
|
or constants that may not exist on some systems.
|
|
|
|
The names of any symbols that cannot be exported should be listed
|
|
in the C<@EXPORT_FAIL> array.
|
|
|
|
If a module attempts to import any of these symbols the Exporter
|
|
will give the module an opportunity to handle the situation before
|
|
generating an error. The Exporter will call an export_fail method
|
|
with a list of the failed symbols:
|
|
|
|
@failed_symbols = $module_name->export_fail(@failed_symbols);
|
|
|
|
If the export_fail method returns an empty list then no error is
|
|
recorded and all the requested symbols are exported. If the returned
|
|
list is not empty then an error is generated for each symbol and the
|
|
export fails. The Exporter provides a default export_fail method which
|
|
simply returns the list unchanged.
|
|
|
|
Uses for the export_fail method include giving better error messages
|
|
for some symbols and performing lazy architectural checks (put more
|
|
symbols into @EXPORT_FAIL by default and then take them out if someone
|
|
actually tries to use them and an expensive check shows that they are
|
|
usable on that platform).
|
|
|
|
=head2 Tag Handling Utility Functions
|
|
|
|
Since the symbols listed within %EXPORT_TAGS must also appear in either
|
|
@EXPORT or @EXPORT_OK, two utility functions are provided which allow
|
|
you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
|
|
|
|
%EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
|
|
|
|
Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
|
|
Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
|
|
|
|
Any names which are not tags are added to @EXPORT or @EXPORT_OK
|
|
unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
|
|
names being silently added to @EXPORT or @EXPORT_OK. Future versions
|
|
may make this a fatal error.
|
|
|
|
=head2 Generating combined tags
|
|
|
|
If several symbol categories exist in %EXPORT_TAGS, it's usually
|
|
useful to create the utility ":all" to simplify "use" statements.
|
|
|
|
The simplest way to do this is:
|
|
|
|
%EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
|
|
|
|
# add all the other ":class" tags to the ":all" class,
|
|
# deleting duplicates
|
|
{
|
|
my %seen;
|
|
|
|
push @{$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 C<AUTOLOAD>ed Constants
|
|
|
|
Many modules make use of C<AUTOLOAD>ing for constant subroutines to
|
|
avoid having to compile and waste memory on rarely used values (see
|
|
L<perlsub> 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 C<AUTOLOAD>ed 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<BEGIN> 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<AUTOLOAD> for C<SO_LINGER> to take place before
|
|
SO_LINGER is encountered later in C<My> package.
|
|
|
|
If you are writing a package that C<AUTOLOAD>s, consider forcing
|
|
an C<AUTOLOAD> for any constants explicitly imported by other packages
|
|
or which are usually used when your package is C<use>d.
|
|
|
|
=cut
|