6 # The following bit of eval-magic is necessary to make this work on
8 use vars qw/$AttrList/;
12 use 5.009005; # due to new regexp features
13 # allow checking for valid ': attrlist' attachments
21 (?<nested> \( (?: [^()]++ | (?&nested)++ )*+ \) ) ?
23 (?: \s* : \s* | \s+ (?! :) )
31 # allow checking for valid ': attrlist' attachments
32 # (we use 'our' rather than 'my' here, due to the rather complex and buggy
33 # behaviour of lexicals with qr// and (??{$lex}) )
35 $nested = qr{ \( (?: (?> [^()]+ ) | (??{ $nested }) )* \) }x;
36 our $one_attr = qr{ (?> (?! \d) \w+ (?:$nested)? ) (?:\s*\:\s*|\s+(?!\:)) }x;
37 $AttrList = qr{ \s* : \s* (?: $one_attr )* }x;
42 our @ISA = qw(Exporter);
43 our @EXPORT = qw(AUTOLOAD);
44 sub Version {$VERSION}
47 my %Cache; # private cache for all SelfLoader's client packages
49 # in croak and carp, protect $@ from "require Carp;" RT #40216
51 sub croak { { local $@; require Carp; } goto &Carp::croak }
52 sub carp { { local $@; require Carp; } goto &Carp::carp }
56 print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if DEBUG;
57 my $SL_code = $Cache{$AUTOLOAD};
58 my $save = $@; # evals in both AUTOLOAD and _load_stubs can corrupt $@
60 # Maybe this pack had stubs before __DATA__, and never initialized.
61 # Or, this maybe an automatic DESTROY method call when none exists.
62 $AUTOLOAD =~ m/^(.*)::/;
63 SelfLoader->_load_stubs($1) unless exists $Cache{"${1}::<DATA"};
64 $SL_code = $Cache{$AUTOLOAD};
65 $SL_code = "sub $AUTOLOAD { }"
66 if (!$SL_code and $AUTOLOAD =~ m/::DESTROY$/);
67 croak "Undefined subroutine $AUTOLOAD" unless $SL_code;
69 print STDERR "SelfLoader::AUTOLOAD eval: $SL_code\n" if DEBUG;
80 defined(&$AUTOLOAD) || die "SelfLoader inconsistency error";
81 delete $Cache{$AUTOLOAD};
85 sub load_stubs { shift->_load_stubs((caller)[0]) }
88 # $endlines is used by Devel::SelfStubber to capture lines after __END__
89 my($self, $callpack, $endlines) = @_;
91 my $fh = \*{"${callpack}::DATA"};
93 my $currpack = $callpack;
94 my($line,$name,@lines, @stubs, $protoype);
96 print STDERR "SelfLoader::load_stubs($callpack)\n" if DEBUG;
97 croak("$callpack doesn't contain an __DATA__ token")
98 unless defined fileno($fh);
99 # Protect: fork() shares the file pointer between the parent and the kid
100 if(sysseek($fh, tell($fh), 0)) {
101 open my $nfh, '<&', $fh or croak "reopen: $!";# dup() the fd
102 close $fh or die "close: $!"; # autocloses, but be paranoid
103 open $fh, '<&', $nfh or croak "reopen2: $!"; # dup() the fd "back"
104 close $nfh or die "close after reopen: $!"; # autocloses, but be paranoid
106 $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached
109 while(defined($line = <$fh>) and $line !~ m/^__END__/) {
110 if ($line =~ m/^\s*sub\s+([\w:]+)\s*((?:\([\\\$\@\%\&\*\;]*\))?(?:$AttrList)?)/) {
111 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
114 if (index($1,'::') == -1) { # simple sub name
115 $name = "${currpack}::$1";
116 } else { # sub name with package
119 if (defined(&{"${1}::AUTOLOAD"})) {
120 \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD ||
121 die 'SelfLoader Error: attempt to specify Selfloading',
122 " sub $name in non-selfloading module $1";
124 $self->export($1,'AUTOLOAD');
127 } elsif ($line =~ m/^package\s+([\w:]+)/) { # A package declared
128 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
129 $self->_package_defined($line);
133 $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached
134 if (defined(&{"${1}::AUTOLOAD"})) {
135 \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD ||
136 die 'SelfLoader Error: attempt to specify Selfloading',
137 " package $currpack which already has AUTOLOAD";
139 $self->export($currpack,'AUTOLOAD');
145 if (defined($line) && $line =~ /^__END__/) { # __END__
146 unless ($line =~ /^__END__\s*DATA/) {
148 # Devel::SelfStubber would like us to capture the lines after
149 # __END__ so it can write out the entire file
155 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
157 eval join('', @stubs) if @stubs;
162 my($self,$fullname,$pack,$lines, $protoype) = @_;
163 return () unless $fullname;
164 carp("Redefining sub $fullname")
165 if exists $Cache{$fullname};
166 $Cache{$fullname} = join('', "\n\#line 1 \"sub $fullname\"\npackage $pack; ", @$lines);
167 #$Cache{$fullname} = join('', "package $pack; ",@$lines);
168 print STDERR "SelfLoader cached $fullname: $Cache{$fullname}" if DEBUG;
169 # return stub to be eval'd
170 defined($protoype) ? "sub $fullname $protoype;" : "sub $fullname;"
173 sub _package_defined {}
180 SelfLoader - load functions only on demand
187 ... (initializing code)
195 This module tells its users that functions in the FOOBAR package are to be
196 autoloaded from after the C<__DATA__> token. See also
197 L<perlsub/"Autoloading">.
199 =head2 The __DATA__ token
201 The C<__DATA__> token tells the perl compiler that the perl code
202 for compilation is finished. Everything after the C<__DATA__> token
203 is available for reading via the filehandle FOOBAR::DATA,
204 where FOOBAR is the name of the current package when the C<__DATA__>
205 token is reached. This works just the same as C<__END__> does in
206 package 'main', but for other modules data after C<__END__> is not
207 automatically retrievable, whereas data after C<__DATA__> is.
208 The C<__DATA__> token is not recognized in versions of perl prior to
211 Note that it is possible to have C<__DATA__> tokens in the same package
212 in multiple files, and that the last C<__DATA__> token in a given
213 package that is encountered by the compiler is the one accessible
214 by the filehandle. This also applies to C<__END__> and main, i.e. if
215 the 'main' program has an C<__END__>, but a module 'require'd (_not_ 'use'd)
216 by that program has a 'package main;' declaration followed by an 'C<__DATA__>',
217 then the C<DATA> filehandle is set to access the data after the C<__DATA__>
218 in the module, _not_ the data after the C<__END__> token in the 'main'
219 program, since the compiler encounters the 'require'd file later.
221 =head2 SelfLoader autoloading
223 The B<SelfLoader> works by the user placing the C<__DATA__>
224 token I<after> perl code which needs to be compiled and
225 run at 'require' time, but I<before> subroutine declarations
226 that can be loaded in later - usually because they may never
229 The B<SelfLoader> will read from the FOOBAR::DATA filehandle to
230 load in the data after C<__DATA__>, and load in any subroutine
231 when it is called. The costs are the one-time parsing of the
232 data after C<__DATA__>, and a load delay for the _first_
233 call of any autoloaded function. The benefits (hopefully)
234 are a speeded up compilation phase, with no need to load
235 functions which are never used.
237 The B<SelfLoader> will stop reading from C<__DATA__> if
238 it encounters the C<__END__> token - just as you would expect.
239 If the C<__END__> token is present, and is followed by the
240 token DATA, then the B<SelfLoader> leaves the FOOBAR::DATA
241 filehandle open on the line after that token.
243 The B<SelfLoader> exports the C<AUTOLOAD> subroutine to the
244 package using the B<SelfLoader>, and this loads the called
245 subroutine when it is first called.
247 There is no advantage to putting subroutines which will _always_
248 be called after the C<__DATA__> token.
250 =head2 Autoloading and package lexicals
252 A 'my $pack_lexical' statement makes the variable $pack_lexical
253 local _only_ to the file up to the C<__DATA__> token. Subroutines
254 declared elsewhere _cannot_ see these types of variables,
255 just as if you declared subroutines in the package but in another
256 file, they cannot see these variables.
258 So specifically, autoloaded functions cannot see package
259 lexicals (this applies to both the B<SelfLoader> and the Autoloader).
260 The C<vars> pragma provides an alternative to defining package-level
261 globals that will be visible to autoloaded routines. See the documentation
262 on B<vars> in the pragma section of L<perlmod>.
264 =head2 SelfLoader and AutoLoader
266 The B<SelfLoader> can replace the AutoLoader - just change 'use AutoLoader'
267 to 'use SelfLoader' (though note that the B<SelfLoader> exports
268 the AUTOLOAD function - but if you have your own AUTOLOAD and
269 are using the AutoLoader too, you probably know what you're doing),
270 and the C<__END__> token to C<__DATA__>. You will need perl version 5.001m
271 or later to use this (version 5.001 with all patches up to patch m).
273 There is no need to inherit from the B<SelfLoader>.
275 The B<SelfLoader> works similarly to the AutoLoader, but picks up the
276 subs from after the C<__DATA__> instead of in the 'lib/auto' directory.
277 There is a maintenance gain in not needing to run AutoSplit on the module
278 at installation, and a runtime gain in not needing to keep opening and
279 closing files to load subs. There is a runtime loss in needing
280 to parse the code after the C<__DATA__>. Details of the B<AutoLoader> and
281 another view of these distinctions can be found in that module's
284 =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle.
286 This section is only relevant if you want to use
287 the C<FOOBAR::DATA> together with the B<SelfLoader>.
289 Data after the C<__DATA__> token in a module is read using the
290 FOOBAR::DATA filehandle. C<__END__> can still be used to denote the end
291 of the C<__DATA__> section if followed by the token DATA - this is supported
292 by the B<SelfLoader>. The C<FOOBAR::DATA> filehandle is left open if an
293 C<__END__> followed by a DATA is found, with the filehandle positioned at
294 the start of the line after the C<__END__> token. If no C<__END__> token is
295 present, or an C<__END__> token with no DATA token on the same line, then
296 the filehandle is closed.
298 The B<SelfLoader> reads from wherever the current
299 position of the C<FOOBAR::DATA> filehandle is, until the
300 EOF or C<__END__>. This means that if you want to use
301 that filehandle (and ONLY if you want to), you should either
303 1. Put all your subroutine declarations immediately after
304 the C<__DATA__> token and put your own data after those
305 declarations, using the C<__END__> token to mark the end
306 of subroutine declarations. You must also ensure that the B<SelfLoader>
307 reads first by calling 'SelfLoader-E<gt>load_stubs();', or by using a
308 function which is selfloaded;
312 2. You should read the C<FOOBAR::DATA> filehandle first, leaving
313 the handle open and positioned at the first line of subroutine
316 You could conceivably do both.
318 =head2 Classes and inherited methods.
320 For modules which are not classes, this section is not relevant.
321 This section is only relevant if you have methods which could
324 A subroutine stub (or forward declaration) looks like
328 i.e. it is a subroutine declaration without the body of the
329 subroutine. For modules which are not classes, there is no real
330 need for stubs as far as autoloading is concerned.
332 For modules which ARE classes, and need to handle inherited methods,
333 stubs are needed to ensure that the method inheritance mechanism works
334 properly. You can load the stubs into the module at 'require' time, by
335 adding the statement 'SelfLoader-E<gt>load_stubs();' to the module to do
338 The alternative is to put the stubs in before the C<__DATA__> token BEFORE
339 releasing the module, and for this purpose the C<Devel::SelfStubber>
340 module is available. However this does require the extra step of ensuring
341 that the stubs are in the module. If this is done I strongly recommend
342 that this is done BEFORE releasing the module - it should NOT be done
343 at install time in general.
345 =head1 Multiple packages and fully qualified subroutine names
347 Subroutines in multiple packages within the same file are supported - but you
348 should note that this requires exporting the C<SelfLoader::AUTOLOAD> to
349 every package which requires it. This is done automatically by the
350 B<SelfLoader> when it first loads the subs into the cache, but you should
351 really specify it in the initialization before the C<__DATA__> by putting
352 a 'use SelfLoader' statement in each package.
354 Fully qualified subroutine names are also supported. For example,
361 will all be loaded correctly by the B<SelfLoader>, and the B<SelfLoader>
362 will ensure that the packages 'foo' and 'baz' correctly have the
363 B<SelfLoader> C<AUTOLOAD> method when the data after C<__DATA__> is first
368 C<SelfLoader> is maintained by the perl5-porters. Please direct
369 any questions to the canonical mailing list. Anything that
370 is applicable to the CPAN release can be sent to its maintainer,
373 Author and Maintainer: The Perl5-Porters <perl5-porters@perl.org>
375 Maintainer of the CPAN release: Steffen Mueller <smueller@cpan.org>
377 =head1 COPYRIGHT AND LICENSE
379 This package has been part of the perl core since the first release
380 of perl5. It has been released separately to CPAN so older installations
381 can benefit from bug fixes.
383 This package has the same copyright and license as the perl core:
385 Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999,
386 2000, 2001, 2002, 2003, 2004, 2005, 2006 by Larry Wall and others
390 This program is free software; you can redistribute it and/or modify
391 it under the terms of either:
393 a) the GNU General Public License as published by the Free
394 Software Foundation; either version 1, or (at your option) any
397 b) the "Artistic License" which comes with this Kit.
399 This program is distributed in the hope that it will be useful,
400 but WITHOUT ANY WARRANTY; without even the implied warranty of
401 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either
402 the GNU General Public License or the Artistic License for more details.
404 You should have received a copy of the Artistic License with this
405 Kit, in the file named "Artistic". If not, I'll be glad to provide one.
407 You should also have received a copy of the GNU General Public License
408 along with this program in the file named "Copying". If not, write to the
409 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
410 02111-1307, USA or visit their web page on the internet at
411 http://www.gnu.org/copyleft/gpl.html.
413 For those of you that choose to use the GNU General Public License,
414 my interpretation of the GNU General Public License is that no Perl
415 script falls under the terms of the GPL unless you explicitly put
416 said script under the terms of the GPL yourself. Furthermore, any
417 object code linked with perl does not automatically fall under the
418 terms of the GPL, provided such object code only adds definitions
419 of subroutines and variables, and does not otherwise impair the
420 resulting interpreter from executing any standard Perl script. I
421 consider linking in C subroutines in this manner to be the moral
422 equivalent of defining subroutines in the Perl language itself. You
423 may sell such an object file as proprietary provided that you provide
424 or offer to provide the Perl source, as specified by the GNU General
425 Public License. (This is merely an alternate way of specifying input
426 to the program.) You may also sell a binary produced by the dumping of
427 a running Perl script that belongs to you, provided that you provide or
428 offer to provide the Perl source as specified by the GPL. (The
429 fact that a Perl interpreter and your code are in the same binary file
430 is, in this case, a form of mere aggregation.) This is my interpretation
431 of the GPL. If you still have concerns or difficulties understanding
432 my intent, feel free to contact me. Of course, the Artistic License
433 spells all this out for your protection, so you may prefer to use that.