4 @EXPORT = qw(AUTOLOAD);
9 my %Cache; # private cache for all SelfLoader's client packages
11 # allow checking for valid ': attrlist' attachments
12 # (we use 'our' rather than 'my' here, due to the rather complex and buggy
13 # behaviour of lexicals with qr// and (??{$lex}) )
15 $nested = qr{ \( (?: (?> [^()]+ ) | (??{ $nested }) )* \) }x;
16 our $one_attr = qr{ (?> (?! \d) \w+ (?:$nested)? ) (?:\s*\:\s*|\s+(?!\:)) }x;
17 our $attr_list = qr{ \s* : \s* (?: $one_attr )* }x;
19 # in croak and carp, protect $@ from "require Carp;" RT #40216
21 sub croak { { local $@; require Carp; } goto &Carp::croak }
22 sub carp { { local $@; require Carp; } goto &Carp::carp }
25 print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if $DEBUG;
26 my $SL_code = $Cache{$AUTOLOAD};
27 my $save = $@; # evals in both AUTOLOAD and _load_stubs can corrupt $@
29 # Maybe this pack had stubs before __DATA__, and never initialized.
30 # Or, this maybe an automatic DESTROY method call when none exists.
31 $AUTOLOAD =~ m/^(.*)::/;
32 SelfLoader->_load_stubs($1) unless exists $Cache{"${1}::<DATA"};
33 $SL_code = $Cache{$AUTOLOAD};
34 $SL_code = "sub $AUTOLOAD { }"
35 if (!$SL_code and $AUTOLOAD =~ m/::DESTROY$/);
36 croak "Undefined subroutine $AUTOLOAD" unless $SL_code;
38 print STDERR "SelfLoader::AUTOLOAD eval: $SL_code\n" if $DEBUG;
46 defined(&$AUTOLOAD) || die "SelfLoader inconsistency error";
47 delete $Cache{$AUTOLOAD};
51 sub load_stubs { shift->_load_stubs((caller)[0]) }
54 # $endlines is used by Devel::SelfStubber to capture lines after __END__
55 my($self, $callpack, $endlines) = @_;
56 my $fh = \*{"${callpack}::DATA"};
57 my $currpack = $callpack;
58 my($line,$name,@lines, @stubs, $protoype);
60 print STDERR "SelfLoader::load_stubs($callpack)\n" if $DEBUG;
61 croak("$callpack doesn't contain an __DATA__ token")
62 unless defined fileno($fh);
63 # Protect: fork() shares the file pointer between the parent and the kid
64 if(sysseek($fh, tell($fh), 0)) {
65 open my $nfh, '<&', $fh or croak "reopen: $!";# dup() the fd
66 close $fh or die "close: $1"; # autocloses, but be paranoid
67 open $fh, '<&', $nfh or croak "reopen2: $!"; # dup() the fd "back"
68 close $nfh or die "close after reopen: $1"; # autocloses, but be paranoid
70 $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached
73 while(defined($line = <$fh>) and $line !~ m/^__END__/) {
74 if ($line =~ m/^sub\s+([\w:]+)\s*((?:\([\\\$\@\%\&\*\;]*\))?(?:$attr_list)?)/) {
75 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
78 if (index($1,'::') == -1) { # simple sub name
79 $name = "${currpack}::$1";
80 } else { # sub name with package
83 if (defined(&{"${1}::AUTOLOAD"})) {
84 \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD ||
85 die 'SelfLoader Error: attempt to specify Selfloading',
86 " sub $name in non-selfloading module $1";
88 $self->export($1,'AUTOLOAD');
91 } elsif ($line =~ m/^package\s+([\w:]+)/) { # A package declared
92 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
93 $self->_package_defined($line);
97 $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached
98 if (defined(&{"${1}::AUTOLOAD"})) {
99 \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD ||
100 die 'SelfLoader Error: attempt to specify Selfloading',
101 " package $currpack which already has AUTOLOAD";
103 $self->export($currpack,'AUTOLOAD');
109 if (defined($line) && $line =~ /^__END__/) { # __END__
110 unless ($line =~ /^__END__\s*DATA/) {
112 # Devel::SelfStubber would like us to capture the lines after
113 # __END__ so it can write out the entire file
119 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
120 eval join('', @stubs) if @stubs;
125 my($self,$fullname,$pack,$lines, $protoype) = @_;
126 return () unless $fullname;
127 carp("Redefining sub $fullname")
128 if exists $Cache{$fullname};
129 $Cache{$fullname} = join('', "package $pack; ",@$lines);
130 print STDERR "SelfLoader cached $fullname: $Cache{$fullname}" if $DEBUG;
131 # return stub to be eval'd
132 defined($protoype) ? "sub $fullname $protoype;" : "sub $fullname;"
135 sub _package_defined {}
142 SelfLoader - load functions only on demand
149 ... (initializing code)
157 This module tells its users that functions in the FOOBAR package are to be
158 autoloaded from after the C<__DATA__> token. See also
159 L<perlsub/"Autoloading">.
161 =head2 The __DATA__ token
163 The C<__DATA__> token tells the perl compiler that the perl code
164 for compilation is finished. Everything after the C<__DATA__> token
165 is available for reading via the filehandle FOOBAR::DATA,
166 where FOOBAR is the name of the current package when the C<__DATA__>
167 token is reached. This works just the same as C<__END__> does in
168 package 'main', but for other modules data after C<__END__> is not
169 automatically retrievable, whereas data after C<__DATA__> is.
170 The C<__DATA__> token is not recognized in versions of perl prior to
173 Note that it is possible to have C<__DATA__> tokens in the same package
174 in multiple files, and that the last C<__DATA__> token in a given
175 package that is encountered by the compiler is the one accessible
176 by the filehandle. This also applies to C<__END__> and main, i.e. if
177 the 'main' program has an C<__END__>, but a module 'require'd (_not_ 'use'd)
178 by that program has a 'package main;' declaration followed by an 'C<__DATA__>',
179 then the C<DATA> filehandle is set to access the data after the C<__DATA__>
180 in the module, _not_ the data after the C<__END__> token in the 'main'
181 program, since the compiler encounters the 'require'd file later.
183 =head2 SelfLoader autoloading
185 The B<SelfLoader> works by the user placing the C<__DATA__>
186 token I<after> perl code which needs to be compiled and
187 run at 'require' time, but I<before> subroutine declarations
188 that can be loaded in later - usually because they may never
191 The B<SelfLoader> will read from the FOOBAR::DATA filehandle to
192 load in the data after C<__DATA__>, and load in any subroutine
193 when it is called. The costs are the one-time parsing of the
194 data after C<__DATA__>, and a load delay for the _first_
195 call of any autoloaded function. The benefits (hopefully)
196 are a speeded up compilation phase, with no need to load
197 functions which are never used.
199 The B<SelfLoader> will stop reading from C<__DATA__> if
200 it encounters the C<__END__> token - just as you would expect.
201 If the C<__END__> token is present, and is followed by the
202 token DATA, then the B<SelfLoader> leaves the FOOBAR::DATA
203 filehandle open on the line after that token.
205 The B<SelfLoader> exports the C<AUTOLOAD> subroutine to the
206 package using the B<SelfLoader>, and this loads the called
207 subroutine when it is first called.
209 There is no advantage to putting subroutines which will _always_
210 be called after the C<__DATA__> token.
212 =head2 Autoloading and package lexicals
214 A 'my $pack_lexical' statement makes the variable $pack_lexical
215 local _only_ to the file up to the C<__DATA__> token. Subroutines
216 declared elsewhere _cannot_ see these types of variables,
217 just as if you declared subroutines in the package but in another
218 file, they cannot see these variables.
220 So specifically, autoloaded functions cannot see package
221 lexicals (this applies to both the B<SelfLoader> and the Autoloader).
222 The C<vars> pragma provides an alternative to defining package-level
223 globals that will be visible to autoloaded routines. See the documentation
224 on B<vars> in the pragma section of L<perlmod>.
226 =head2 SelfLoader and AutoLoader
228 The B<SelfLoader> can replace the AutoLoader - just change 'use AutoLoader'
229 to 'use SelfLoader' (though note that the B<SelfLoader> exports
230 the AUTOLOAD function - but if you have your own AUTOLOAD and
231 are using the AutoLoader too, you probably know what you're doing),
232 and the C<__END__> token to C<__DATA__>. You will need perl version 5.001m
233 or later to use this (version 5.001 with all patches up to patch m).
235 There is no need to inherit from the B<SelfLoader>.
237 The B<SelfLoader> works similarly to the AutoLoader, but picks up the
238 subs from after the C<__DATA__> instead of in the 'lib/auto' directory.
239 There is a maintenance gain in not needing to run AutoSplit on the module
240 at installation, and a runtime gain in not needing to keep opening and
241 closing files to load subs. There is a runtime loss in needing
242 to parse the code after the C<__DATA__>. Details of the B<AutoLoader> and
243 another view of these distinctions can be found in that module's
246 =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle.
248 This section is only relevant if you want to use
249 the C<FOOBAR::DATA> together with the B<SelfLoader>.
251 Data after the C<__DATA__> token in a module is read using the
252 FOOBAR::DATA filehandle. C<__END__> can still be used to denote the end
253 of the C<__DATA__> section if followed by the token DATA - this is supported
254 by the B<SelfLoader>. The C<FOOBAR::DATA> filehandle is left open if an
255 C<__END__> followed by a DATA is found, with the filehandle positioned at
256 the start of the line after the C<__END__> token. If no C<__END__> token is
257 present, or an C<__END__> token with no DATA token on the same line, then
258 the filehandle is closed.
260 The B<SelfLoader> reads from wherever the current
261 position of the C<FOOBAR::DATA> filehandle is, until the
262 EOF or C<__END__>. This means that if you want to use
263 that filehandle (and ONLY if you want to), you should either
265 1. Put all your subroutine declarations immediately after
266 the C<__DATA__> token and put your own data after those
267 declarations, using the C<__END__> token to mark the end
268 of subroutine declarations. You must also ensure that the B<SelfLoader>
269 reads first by calling 'SelfLoader-E<gt>load_stubs();', or by using a
270 function which is selfloaded;
274 2. You should read the C<FOOBAR::DATA> filehandle first, leaving
275 the handle open and positioned at the first line of subroutine
278 You could conceivably do both.
280 =head2 Classes and inherited methods.
282 For modules which are not classes, this section is not relevant.
283 This section is only relevant if you have methods which could
286 A subroutine stub (or forward declaration) looks like
290 i.e. it is a subroutine declaration without the body of the
291 subroutine. For modules which are not classes, there is no real
292 need for stubs as far as autoloading is concerned.
294 For modules which ARE classes, and need to handle inherited methods,
295 stubs are needed to ensure that the method inheritance mechanism works
296 properly. You can load the stubs into the module at 'require' time, by
297 adding the statement 'SelfLoader-E<gt>load_stubs();' to the module to do
300 The alternative is to put the stubs in before the C<__DATA__> token BEFORE
301 releasing the module, and for this purpose the C<Devel::SelfStubber>
302 module is available. However this does require the extra step of ensuring
303 that the stubs are in the module. If this is done I strongly recommend
304 that this is done BEFORE releasing the module - it should NOT be done
305 at install time in general.
307 =head1 Multiple packages and fully qualified subroutine names
309 Subroutines in multiple packages within the same file are supported - but you
310 should note that this requires exporting the C<SelfLoader::AUTOLOAD> to
311 every package which requires it. This is done automatically by the
312 B<SelfLoader> when it first loads the subs into the cache, but you should
313 really specify it in the initialization before the C<__DATA__> by putting
314 a 'use SelfLoader' statement in each package.
316 Fully qualified subroutine names are also supported. For example,
323 will all be loaded correctly by the B<SelfLoader>, and the B<SelfLoader>
324 will ensure that the packages 'foo' and 'baz' correctly have the
325 B<SelfLoader> C<AUTOLOAD> method when the data after C<__DATA__> is first