5 @EXPORT = qw(AUTOLOAD);
6 $VERSION = 1.06; sub Version {$VERSION}
9 my %Cache; # private cache for all SelfLoader's client packages
12 print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if $DEBUG;
13 my $code = $Cache{$AUTOLOAD};
15 # Maybe this pack had stubs before __DATA__, and never initialized.
16 # Or, this maybe an automatic DESTROY method call when none exists.
17 $AUTOLOAD =~ m/^(.*)::/;
18 SelfLoader->_load_stubs($1) unless exists $Cache{"${1}::<DATA"};
19 $code = $Cache{$AUTOLOAD};
20 $code = "sub $AUTOLOAD { }" if (!$code and $AUTOLOAD =~ m/::DESTROY$/);
21 croak "Undefined subroutine $AUTOLOAD" unless $code;
23 print STDERR "SelfLoader::AUTOLOAD eval: $code\n" if $DEBUG;
29 defined(&$AUTOLOAD) || die "SelfLoader inconsistency error";
30 delete $Cache{$AUTOLOAD};
34 sub load_stubs { shift->_load_stubs((caller)[0]) }
37 my($self, $callpack) = @_;
38 my $fh = \*{"${callpack}::DATA"};
39 my $currpack = $callpack;
40 my($line,$name,@lines, @stubs, $protoype);
42 print STDERR "SelfLoader::load_stubs($callpack)\n" if $DEBUG;
43 croak("$callpack doesn't contain an __DATA__ token")
45 $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached
47 while($line = <$fh> and $line !~ m/^__END__/) {
48 if ($line =~ m/^sub\s+([\w:]+)\s*(\([\$\@\;\%\\]*\))?/) { # A sub declared
49 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
52 if (index($1,'::') == -1) { # simple sub name
53 $name = "${currpack}::$1";
54 } else { # sub name with package
57 if (defined(&{"${1}::AUTOLOAD"})) {
58 \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD ||
59 die 'SelfLoader Error: attempt to specify Selfloading',
60 " sub $name in non-selfloading module $1";
62 $self->export($1,'AUTOLOAD');
65 } elsif ($line =~ m/^package\s+([\w:]+)/) { # A package declared
66 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
67 $self->_package_defined($line);
71 $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached
72 if (defined(&{"${1}::AUTOLOAD"})) {
73 \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD ||
74 die 'SelfLoader Error: attempt to specify Selfloading',
75 " package $currpack which already has AUTOLOAD";
77 $self->export($currpack,'AUTOLOAD');
83 close($fh) unless defined($line) && $line =~ /^__END__\s*DATA/; # __END__
84 push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype));
85 eval join('', @stubs) if @stubs;
90 my($self,$fullname,$pack,$lines, $protoype) = @_;
91 return () unless $fullname;
92 carp("Redefining sub $fullname") if exists $Cache{$fullname};
93 $Cache{$fullname} = join('', "package $pack; ",@$lines);
94 print STDERR "SelfLoader cached $fullname: $Cache{$fullname}" if $DEBUG;
95 # return stub to be eval'd
96 defined($protoype) ? "sub $fullname $protoype;" : "sub $fullname;"
99 sub _package_defined {}
106 SelfLoader - load functions only on demand
113 ... (initializing code)
121 This module tells its users that functions in the FOOBAR package are to be
122 autoloaded from after the __DATA__ token. See also L<perlsub/"Autoloading">.
124 =head2 The __DATA__ token
126 The __DATA__ token tells the perl compiler that the perl code
127 for compilation is finished. Everything after the __DATA__ token
128 is available for reading via the filehandle FOOBAR::DATA,
129 where FOOBAR is the name of the current package when the __DATA__
130 token is reached. This works just the same as __END__ does in
131 package 'main', but for other modules data after __END__ is not
132 automatically retreivable , whereas data after __DATA__ is.
133 The __DATA__ token is not recognized in versions of perl prior to
136 Note that it is possible to have __DATA__ tokens in the same package
137 in multiple files, and that the last __DATA__ token in a given
138 package that is encountered by the compiler is the one accessible
139 by the filehandle. This also applies to __END__ and main, i.e. if
140 the 'main' program has an __END__, but a module 'require'd (_not_ 'use'd)
141 by that program has a 'package main;' declaration followed by an '__DATA__',
142 then the DATA filehandle is set to access the data after the __DATA__
143 in the module, _not_ the data after the __END__ token in the 'main'
144 program, since the compiler encounters the 'require'd file later.
146 =head2 SelfLoader autoloading
148 The SelfLoader works by the user placing the __DATA__
149 token _after_ perl code which needs to be compiled and
150 run at 'require' time, but _before_ subroutine declarations
151 that can be loaded in later - usually because they may never
154 The SelfLoader will read from the FOOBAR::DATA filehandle to
155 load in the data after __DATA__, and load in any subroutine
156 when it is called. The costs are the one-time parsing of the
157 data after __DATA__, and a load delay for the _first_
158 call of any autoloaded function. The benefits (hopefully)
159 are a speeded up compilation phase, with no need to load
160 functions which are never used.
162 The SelfLoader will stop reading from __DATA__ if
163 it encounters the __END__ token - just as you would expect.
164 If the __END__ token is present, and is followed by the
165 token DATA, then the SelfLoader leaves the FOOBAR::DATA
166 filehandle open on the line after that token.
168 The SelfLoader exports the AUTOLOAD subroutine to the
169 package using the SelfLoader, and this loads the called
170 subroutine when it is first called.
172 There is no advantage to putting subroutines which will _always_
173 be called after the __DATA__ token.
175 =head2 Autoloading and package lexicals
177 A 'my $pack_lexical' statement makes the variable $pack_lexical
178 local _only_ to the file up to the __DATA__ token. Subroutines
179 declared elsewhere _cannot_ see these types of variables,
180 just as if you declared subroutines in the package but in another
181 file, they cannot see these variables.
183 So specifically, autoloaded functions cannot see package
184 lexicals (this applies to both the SelfLoader and the Autoloader).
186 =head2 SelfLoader and AutoLoader
188 The SelfLoader can replace the AutoLoader - just change 'use AutoLoader'
189 to 'use SelfLoader' (though note that the SelfLoader exports
190 the AUTOLOAD function - but if you have your own AUTOLOAD and
191 are using the AutoLoader too, you probably know what you're doing),
192 and the __END__ token to __DATA__. You will need perl version 5.001m
193 or later to use this (version 5.001 with all patches up to patch m).
195 There is no need to inherit from the SelfLoader.
197 The SelfLoader works similarly to the AutoLoader, but picks up the
198 subs from after the __DATA__ instead of in the 'lib/auto' directory.
199 There is a maintainance gain in not needing to run AutoSplit on the module
200 at installation, and a runtime gain in not needing to keep opening and
201 closing files to load subs. There is a runtime loss in needing
202 to parse the code after the __DATA__.
204 =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle.
206 This section is only relevant if you want to use
207 the FOOBAR::DATA together with the SelfLoader.
209 Data after the __DATA__ token in a module is read using the
210 FOOBAR::DATA filehandle. __END__ can still be used to denote the end
211 of the __DATA__ section if followed by the token DATA - this is supported
212 by the SelfLoader. The FOOBAR::DATA filehandle is left open if an __END__
213 followed by a DATA is found, with the filehandle positioned at the start
214 of the line after the __END__ token. If no __END__ token is present,
215 or an __END__ token with no DATA token on the same line, then the filehandle
218 The SelfLoader reads from wherever the current
219 position of the FOOBAR::DATA filehandle is, until the
220 EOF or __END__. This means that if you want to use
221 that filehandle (and ONLY if you want to), you should either
223 1. Put all your subroutine declarations immediately after
224 the __DATA__ token and put your own data after those
225 declarations, using the __END__ token to mark the end
226 of subroutine declarations. You must also ensure that the SelfLoader
227 reads first by calling 'SelfLoader->load_stubs();', or by using a
228 function which is selfloaded;
232 2. You should read the FOOBAR::DATA filehandle first, leaving
233 the handle open and positioned at the first line of subroutine
236 You could conceivably do both.
238 =head2 Classes and inherited methods.
240 For modules which are not classes, this section is not relevant.
241 This section is only relevant if you have methods which could
244 A subroutine stub (or forward declaration) looks like
248 i.e. it is a subroutine declaration without the body of the
249 subroutine. For modules which are not classes, there is no real
250 need for stubs as far as autoloading is concerned.
252 For modules which ARE classes, and need to handle inherited methods,
253 stubs are needed to ensure that the method inheritance mechanism works
254 properly. You can load the stubs into the module at 'require' time, by
255 adding the statement 'SelfLoader->load_stubs();' to the module to do
258 The alternative is to put the stubs in before the __DATA__ token BEFORE
259 releasing the module, and for this purpose the Devel::SelfStubber
260 module is available. However this does require the extra step of ensuring
261 that the stubs are in the module. If this is done I strongly recommend
262 that this is done BEFORE releasing the module - it should NOT be done
263 at install time in general.
265 =head1 Multiple packages and fully qualified subroutine names
267 Subroutines in multiple packages within the same file are supported - but you
268 should note that this requires exporting the SelfLoader::AUTOLOAD to
269 every package which requires it. This is done automatically by the
270 SelfLoader when it first loads the subs into the cache, but you should
271 really specify it in the initialization before the __DATA__ by putting
272 a 'use SelfLoader' statement in each package.
274 Fully qualified subroutine names are also supported. For example,
281 will all be loaded correctly by the SelfLoader, and the SelfLoader
282 will ensure that the packages 'foo' and 'baz' correctly have the
283 SelfLoader AUTOLOAD method when the data after __DATA__ is first parsed.