Commit | Line | Data |
f8881bd9 |
1 | package SelfLoader; |
e3d0cac0 |
2 | # use Carp; |
f8881bd9 |
3 | require Exporter; |
4 | @ISA = qw(Exporter); |
5 | @EXPORT = qw(AUTOLOAD); |
bfdd1499 |
6 | $VERSION = "1.0902"; |
52128c7b |
7 | sub Version {$VERSION} |
f8881bd9 |
8 | $DEBUG = 0; |
9 | |
10 | my %Cache; # private cache for all SelfLoader's client packages |
11 | |
09bef843 |
12 | # allow checking for valid ': attrlist' attachments |
13 | my $nested; |
14455d6c |
14 | $nested = qr{ \( (?: (?> [^()]+ ) | (??{ $nested }) )* \) }x; |
0120eecf |
15 | my $one_attr = qr{ (?> (?! \d) \w+ (?:$nested)? ) (?:\s*\:\s*|\s+(?!\:)) }x; |
09bef843 |
16 | my $attr_list = qr{ \s* : \s* (?: $one_attr )* }x; |
17 | |
e3d0cac0 |
18 | sub croak { require Carp; goto &Carp::croak } |
19 | |
f8881bd9 |
20 | AUTOLOAD { |
21 | print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if $DEBUG; |
c7675058 |
22 | my $SL_code = $Cache{$AUTOLOAD}; |
bfdd1499 |
23 | my $save = $@; # evals in both AUTOLOAD and _load_stubs can corrupt $@ |
c7675058 |
24 | unless ($SL_code) { |
f8881bd9 |
25 | # Maybe this pack had stubs before __DATA__, and never initialized. |
26 | # Or, this maybe an automatic DESTROY method call when none exists. |
27 | $AUTOLOAD =~ m/^(.*)::/; |
28 | SelfLoader->_load_stubs($1) unless exists $Cache{"${1}::<DATA"}; |
c7675058 |
29 | $SL_code = $Cache{$AUTOLOAD}; |
30 | $SL_code = "sub $AUTOLOAD { }" |
31 | if (!$SL_code and $AUTOLOAD =~ m/::DESTROY$/); |
32 | croak "Undefined subroutine $AUTOLOAD" unless $SL_code; |
f8881bd9 |
33 | } |
c7675058 |
34 | print STDERR "SelfLoader::AUTOLOAD eval: $SL_code\n" if $DEBUG; |
bfdd1499 |
35 | |
c7675058 |
36 | eval $SL_code; |
f8881bd9 |
37 | if ($@) { |
38 | $@ =~ s/ at .*\n//; |
39 | croak $@; |
40 | } |
bfdd1499 |
41 | $@ = $save; |
f8881bd9 |
42 | defined(&$AUTOLOAD) || die "SelfLoader inconsistency error"; |
43 | delete $Cache{$AUTOLOAD}; |
44 | goto &$AUTOLOAD |
45 | } |
46 | |
47 | sub load_stubs { shift->_load_stubs((caller)[0]) } |
48 | |
49 | sub _load_stubs { |
33235a50 |
50 | # $endlines is used by Devel::SelfStubber to capture lines after __END__ |
51 | my($self, $callpack, $endlines) = @_; |
f8881bd9 |
52 | my $fh = \*{"${callpack}::DATA"}; |
53 | my $currpack = $callpack; |
54 | my($line,$name,@lines, @stubs, $protoype); |
55 | |
56 | print STDERR "SelfLoader::load_stubs($callpack)\n" if $DEBUG; |
57 | croak("$callpack doesn't contain an __DATA__ token") |
58 | unless fileno($fh); |
59 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached |
60 | |
52128c7b |
61 | local($/) = "\n"; |
40da2db3 |
62 | while(defined($line = <$fh>) and $line !~ m/^__END__/) { |
09bef843 |
63 | if ($line =~ m/^sub\s+([\w:]+)\s*((?:\([\\\$\@\%\&\*\;]*\))?(?:$attr_list)?)/) { |
f8881bd9 |
64 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
65 | $protoype = $2; |
66 | @lines = ($line); |
67 | if (index($1,'::') == -1) { # simple sub name |
68 | $name = "${currpack}::$1"; |
69 | } else { # sub name with package |
70 | $name = $1; |
71 | $name =~ m/^(.*)::/; |
72 | if (defined(&{"${1}::AUTOLOAD"})) { |
73 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || |
74 | die 'SelfLoader Error: attempt to specify Selfloading', |
75 | " sub $name in non-selfloading module $1"; |
76 | } else { |
77 | $self->export($1,'AUTOLOAD'); |
78 | } |
79 | } |
80 | } elsif ($line =~ m/^package\s+([\w:]+)/) { # A package declared |
81 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
82 | $self->_package_defined($line); |
83 | $name = ''; |
84 | @lines = (); |
85 | $currpack = $1; |
86 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached |
87 | if (defined(&{"${1}::AUTOLOAD"})) { |
88 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || |
89 | die 'SelfLoader Error: attempt to specify Selfloading', |
90 | " package $currpack which already has AUTOLOAD"; |
91 | } else { |
92 | $self->export($currpack,'AUTOLOAD'); |
93 | } |
94 | } else { |
95 | push(@lines,$line); |
96 | } |
97 | } |
33235a50 |
98 | if (defined($line) && $line =~ /^__END__/) { # __END__ |
99 | unless ($line =~ /^__END__\s*DATA/) { |
100 | if ($endlines) { |
101 | # Devel::SelfStubber would like us to capture the lines after |
102 | # __END__ so it can write out the entire file |
103 | @$endlines = <$fh>; |
104 | } |
105 | close($fh); |
106 | } |
107 | } |
f8881bd9 |
108 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
109 | eval join('', @stubs) if @stubs; |
110 | } |
111 | |
112 | |
113 | sub _add_to_cache { |
114 | my($self,$fullname,$pack,$lines, $protoype) = @_; |
115 | return () unless $fullname; |
e3d0cac0 |
116 | (require Carp), Carp::carp("Redefining sub $fullname") |
117 | if exists $Cache{$fullname}; |
f8881bd9 |
118 | $Cache{$fullname} = join('', "package $pack; ",@$lines); |
119 | print STDERR "SelfLoader cached $fullname: $Cache{$fullname}" if $DEBUG; |
120 | # return stub to be eval'd |
121 | defined($protoype) ? "sub $fullname $protoype;" : "sub $fullname;" |
122 | } |
123 | |
124 | sub _package_defined {} |
125 | |
126 | 1; |
127 | __END__ |
cb1a09d0 |
128 | |
f8881bd9 |
129 | =head1 NAME |
130 | |
131 | SelfLoader - load functions only on demand |
132 | |
133 | =head1 SYNOPSIS |
134 | |
135 | package FOOBAR; |
136 | use SelfLoader; |
3cb6de81 |
137 | |
f8881bd9 |
138 | ... (initializing code) |
3cb6de81 |
139 | |
f8881bd9 |
140 | __DATA__ |
141 | sub {.... |
142 | |
143 | |
144 | =head1 DESCRIPTION |
145 | |
146 | This module tells its users that functions in the FOOBAR package are to be |
463e8aa9 |
147 | autoloaded from after the C<__DATA__> token. See also |
148 | L<perlsub/"Autoloading">. |
f8881bd9 |
149 | |
150 | =head2 The __DATA__ token |
151 | |
463e8aa9 |
152 | The C<__DATA__> token tells the perl compiler that the perl code |
153 | for compilation is finished. Everything after the C<__DATA__> token |
f8881bd9 |
154 | is available for reading via the filehandle FOOBAR::DATA, |
463e8aa9 |
155 | where FOOBAR is the name of the current package when the C<__DATA__> |
156 | token is reached. This works just the same as C<__END__> does in |
157 | package 'main', but for other modules data after C<__END__> is not |
f610777f |
158 | automatically retrievable, whereas data after C<__DATA__> is. |
463e8aa9 |
159 | The C<__DATA__> token is not recognized in versions of perl prior to |
f8881bd9 |
160 | 5.001m. |
161 | |
463e8aa9 |
162 | Note that it is possible to have C<__DATA__> tokens in the same package |
163 | in multiple files, and that the last C<__DATA__> token in a given |
f8881bd9 |
164 | package that is encountered by the compiler is the one accessible |
463e8aa9 |
165 | by the filehandle. This also applies to C<__END__> and main, i.e. if |
166 | the 'main' program has an C<__END__>, but a module 'require'd (_not_ 'use'd) |
167 | by that program has a 'package main;' declaration followed by an 'C<__DATA__>', |
168 | then the C<DATA> filehandle is set to access the data after the C<__DATA__> |
169 | in the module, _not_ the data after the C<__END__> token in the 'main' |
f8881bd9 |
170 | program, since the compiler encounters the 'require'd file later. |
171 | |
172 | =head2 SelfLoader autoloading |
173 | |
463e8aa9 |
174 | The B<SelfLoader> works by the user placing the C<__DATA__> |
175 | token I<after> perl code which needs to be compiled and |
176 | run at 'require' time, but I<before> subroutine declarations |
f8881bd9 |
177 | that can be loaded in later - usually because they may never |
178 | be called. |
179 | |
463e8aa9 |
180 | The B<SelfLoader> will read from the FOOBAR::DATA filehandle to |
181 | load in the data after C<__DATA__>, and load in any subroutine |
f8881bd9 |
182 | when it is called. The costs are the one-time parsing of the |
463e8aa9 |
183 | data after C<__DATA__>, and a load delay for the _first_ |
f8881bd9 |
184 | call of any autoloaded function. The benefits (hopefully) |
185 | are a speeded up compilation phase, with no need to load |
186 | functions which are never used. |
187 | |
463e8aa9 |
188 | The B<SelfLoader> will stop reading from C<__DATA__> if |
189 | it encounters the C<__END__> token - just as you would expect. |
190 | If the C<__END__> token is present, and is followed by the |
191 | token DATA, then the B<SelfLoader> leaves the FOOBAR::DATA |
f8881bd9 |
192 | filehandle open on the line after that token. |
193 | |
463e8aa9 |
194 | The B<SelfLoader> exports the C<AUTOLOAD> subroutine to the |
195 | package using the B<SelfLoader>, and this loads the called |
f8881bd9 |
196 | subroutine when it is first called. |
197 | |
198 | There is no advantage to putting subroutines which will _always_ |
463e8aa9 |
199 | be called after the C<__DATA__> token. |
f8881bd9 |
200 | |
201 | =head2 Autoloading and package lexicals |
202 | |
203 | A 'my $pack_lexical' statement makes the variable $pack_lexical |
463e8aa9 |
204 | local _only_ to the file up to the C<__DATA__> token. Subroutines |
f8881bd9 |
205 | declared elsewhere _cannot_ see these types of variables, |
206 | just as if you declared subroutines in the package but in another |
207 | file, they cannot see these variables. |
208 | |
209 | So specifically, autoloaded functions cannot see package |
463e8aa9 |
210 | lexicals (this applies to both the B<SelfLoader> and the Autoloader). |
211 | The C<vars> pragma provides an alternative to defining package-level |
212 | globals that will be visible to autoloaded routines. See the documentation |
213 | on B<vars> in the pragma section of L<perlmod>. |
f8881bd9 |
214 | |
215 | =head2 SelfLoader and AutoLoader |
216 | |
463e8aa9 |
217 | The B<SelfLoader> can replace the AutoLoader - just change 'use AutoLoader' |
218 | to 'use SelfLoader' (though note that the B<SelfLoader> exports |
f8881bd9 |
219 | the AUTOLOAD function - but if you have your own AUTOLOAD and |
220 | are using the AutoLoader too, you probably know what you're doing), |
463e8aa9 |
221 | and the C<__END__> token to C<__DATA__>. You will need perl version 5.001m |
f8881bd9 |
222 | or later to use this (version 5.001 with all patches up to patch m). |
223 | |
463e8aa9 |
224 | There is no need to inherit from the B<SelfLoader>. |
f8881bd9 |
225 | |
463e8aa9 |
226 | The B<SelfLoader> works similarly to the AutoLoader, but picks up the |
227 | subs from after the C<__DATA__> instead of in the 'lib/auto' directory. |
f610777f |
228 | There is a maintenance gain in not needing to run AutoSplit on the module |
f8881bd9 |
229 | at installation, and a runtime gain in not needing to keep opening and |
230 | closing files to load subs. There is a runtime loss in needing |
463e8aa9 |
231 | to parse the code after the C<__DATA__>. Details of the B<AutoLoader> and |
232 | another view of these distinctions can be found in that module's |
233 | documentation. |
f8881bd9 |
234 | |
235 | =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle. |
236 | |
237 | This section is only relevant if you want to use |
463e8aa9 |
238 | the C<FOOBAR::DATA> together with the B<SelfLoader>. |
239 | |
240 | Data after the C<__DATA__> token in a module is read using the |
241 | FOOBAR::DATA filehandle. C<__END__> can still be used to denote the end |
242 | of the C<__DATA__> section if followed by the token DATA - this is supported |
243 | by the B<SelfLoader>. The C<FOOBAR::DATA> filehandle is left open if an |
244 | C<__END__> followed by a DATA is found, with the filehandle positioned at |
245 | the start of the line after the C<__END__> token. If no C<__END__> token is |
246 | present, or an C<__END__> token with no DATA token on the same line, then |
247 | the filehandle is closed. |
248 | |
249 | The B<SelfLoader> reads from wherever the current |
250 | position of the C<FOOBAR::DATA> filehandle is, until the |
251 | EOF or C<__END__>. This means that if you want to use |
f8881bd9 |
252 | that filehandle (and ONLY if you want to), you should either |
253 | |
254 | 1. Put all your subroutine declarations immediately after |
463e8aa9 |
255 | the C<__DATA__> token and put your own data after those |
256 | declarations, using the C<__END__> token to mark the end |
257 | of subroutine declarations. You must also ensure that the B<SelfLoader> |
1fef88e7 |
258 | reads first by calling 'SelfLoader-E<gt>load_stubs();', or by using a |
f8881bd9 |
259 | function which is selfloaded; |
260 | |
261 | or |
262 | |
463e8aa9 |
263 | 2. You should read the C<FOOBAR::DATA> filehandle first, leaving |
f8881bd9 |
264 | the handle open and positioned at the first line of subroutine |
265 | declarations. |
266 | |
267 | You could conceivably do both. |
268 | |
269 | =head2 Classes and inherited methods. |
270 | |
271 | For modules which are not classes, this section is not relevant. |
272 | This section is only relevant if you have methods which could |
273 | be inherited. |
274 | |
275 | A subroutine stub (or forward declaration) looks like |
276 | |
277 | sub stub; |
278 | |
279 | i.e. it is a subroutine declaration without the body of the |
280 | subroutine. For modules which are not classes, there is no real |
281 | need for stubs as far as autoloading is concerned. |
282 | |
283 | For modules which ARE classes, and need to handle inherited methods, |
284 | stubs are needed to ensure that the method inheritance mechanism works |
285 | properly. You can load the stubs into the module at 'require' time, by |
1fef88e7 |
286 | adding the statement 'SelfLoader-E<gt>load_stubs();' to the module to do |
f8881bd9 |
287 | this. |
288 | |
463e8aa9 |
289 | The alternative is to put the stubs in before the C<__DATA__> token BEFORE |
290 | releasing the module, and for this purpose the C<Devel::SelfStubber> |
f8881bd9 |
291 | module is available. However this does require the extra step of ensuring |
292 | that the stubs are in the module. If this is done I strongly recommend |
293 | that this is done BEFORE releasing the module - it should NOT be done |
294 | at install time in general. |
295 | |
296 | =head1 Multiple packages and fully qualified subroutine names |
297 | |
298 | Subroutines in multiple packages within the same file are supported - but you |
463e8aa9 |
299 | should note that this requires exporting the C<SelfLoader::AUTOLOAD> to |
f8881bd9 |
300 | every package which requires it. This is done automatically by the |
463e8aa9 |
301 | B<SelfLoader> when it first loads the subs into the cache, but you should |
302 | really specify it in the initialization before the C<__DATA__> by putting |
f8881bd9 |
303 | a 'use SelfLoader' statement in each package. |
304 | |
305 | Fully qualified subroutine names are also supported. For example, |
306 | |
307 | __DATA__ |
308 | sub foo::bar {23} |
309 | package baz; |
310 | sub dob {32} |
311 | |
463e8aa9 |
312 | will all be loaded correctly by the B<SelfLoader>, and the B<SelfLoader> |
f8881bd9 |
313 | will ensure that the packages 'foo' and 'baz' correctly have the |
463e8aa9 |
314 | B<SelfLoader> C<AUTOLOAD> method when the data after C<__DATA__> is first |
315 | parsed. |
f8881bd9 |
316 | |
317 | =cut |