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86530b38 AT |
1 | package SelfLoader; |
2 | # use Carp; | |
3 | require Exporter; | |
4 | @ISA = qw(Exporter); | |
5 | @EXPORT = qw(AUTOLOAD); | |
6 | $VERSION = "1.0903"; | |
7 | sub Version {$VERSION} | |
8 | $DEBUG = 0; | |
9 | ||
10 | my %Cache; # private cache for all SelfLoader's client packages | |
11 | ||
12 | # allow checking for valid ': attrlist' attachments | |
13 | my $nested; | |
14 | $nested = qr{ \( (?: (?> [^()]+ ) | (??{ $nested }) )* \) }x; | |
15 | my $one_attr = qr{ (?> (?! \d) \w+ (?:$nested)? ) (?:\s*\:\s*|\s+(?!\:)) }x; | |
16 | my $attr_list = qr{ \s* : \s* (?: $one_attr )* }x; | |
17 | ||
18 | sub croak { require Carp; goto &Carp::croak } | |
19 | ||
20 | AUTOLOAD { | |
21 | print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if $DEBUG; | |
22 | my $SL_code = $Cache{$AUTOLOAD}; | |
23 | my $save = $@; # evals in both AUTOLOAD and _load_stubs can corrupt $@ | |
24 | unless ($SL_code) { | |
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"}; | |
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; | |
33 | } | |
34 | print STDERR "SelfLoader::AUTOLOAD eval: $SL_code\n" if $DEBUG; | |
35 | ||
36 | eval $SL_code; | |
37 | if ($@) { | |
38 | $@ =~ s/ at .*\n//; | |
39 | croak $@; | |
40 | } | |
41 | $@ = $save; | |
42 | defined(&$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 { | |
50 | # $endlines is used by Devel::SelfStubber to capture lines after __END__ | |
51 | my($self, $callpack, $endlines) = @_; | |
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 | ||
61 | local($/) = "\n"; | |
62 | while(defined($line = <$fh>) and $line !~ m/^__END__/) { | |
63 | if ($line =~ m/^sub\s+([\w:]+)\s*((?:\([\\\$\@\%\&\*\;]*\))?(?:$attr_list)?)/) { | |
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,$line); | |
96 | } | |
97 | } | |
98 | if (defined($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 | } | |
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; | |
116 | (require Carp), Carp::carp("Redefining sub $fullname") | |
117 | if exists $Cache{$fullname}; | |
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__ | |
128 | ||
129 | =head1 NAME | |
130 | ||
131 | SelfLoader - load functions only on demand | |
132 | ||
133 | =head1 SYNOPSIS | |
134 | ||
135 | package FOOBAR; | |
136 | use SelfLoader; | |
137 | ||
138 | ... (initializing code) | |
139 | ||
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 | |
147 | autoloaded from after the C<__DATA__> token. See also | |
148 | L<perlsub/"Autoloading">. | |
149 | ||
150 | =head2 The __DATA__ token | |
151 | ||
152 | The C<__DATA__> token tells the perl compiler that the perl code | |
153 | for compilation is finished. Everything after the C<__DATA__> token | |
154 | is available for reading via the filehandle FOOBAR::DATA, | |
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 | |
158 | automatically retrievable, whereas data after C<__DATA__> is. | |
159 | The C<__DATA__> token is not recognized in versions of perl prior to | |
160 | 5.001m. | |
161 | ||
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 | |
164 | package that is encountered by the compiler is the one accessible | |
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' | |
170 | program, since the compiler encounters the 'require'd file later. | |
171 | ||
172 | =head2 SelfLoader autoloading | |
173 | ||
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 | |
177 | that can be loaded in later - usually because they may never | |
178 | be called. | |
179 | ||
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 | |
182 | when it is called. The costs are the one-time parsing of the | |
183 | data after C<__DATA__>, and a load delay for the _first_ | |
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 | ||
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 | |
192 | filehandle open on the line after that token. | |
193 | ||
194 | The B<SelfLoader> exports the C<AUTOLOAD> subroutine to the | |
195 | package using the B<SelfLoader>, and this loads the called | |
196 | subroutine when it is first called. | |
197 | ||
198 | There is no advantage to putting subroutines which will _always_ | |
199 | be called after the C<__DATA__> token. | |
200 | ||
201 | =head2 Autoloading and package lexicals | |
202 | ||
203 | A 'my $pack_lexical' statement makes the variable $pack_lexical | |
204 | local _only_ to the file up to the C<__DATA__> token. Subroutines | |
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 | |
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>. | |
214 | ||
215 | =head2 SelfLoader and AutoLoader | |
216 | ||
217 | The B<SelfLoader> can replace the AutoLoader - just change 'use AutoLoader' | |
218 | to 'use SelfLoader' (though note that the B<SelfLoader> exports | |
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), | |
221 | and the C<__END__> token to C<__DATA__>. You will need perl version 5.001m | |
222 | or later to use this (version 5.001 with all patches up to patch m). | |
223 | ||
224 | There is no need to inherit from the B<SelfLoader>. | |
225 | ||
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. | |
228 | There is a maintenance gain in not needing to run AutoSplit on the module | |
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 | |
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. | |
234 | ||
235 | =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle. | |
236 | ||
237 | This section is only relevant if you want to use | |
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 | |
252 | that filehandle (and ONLY if you want to), you should either | |
253 | ||
254 | 1. Put all your subroutine declarations immediately after | |
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> | |
258 | reads first by calling 'SelfLoader-E<gt>load_stubs();', or by using a | |
259 | function which is selfloaded; | |
260 | ||
261 | or | |
262 | ||
263 | 2. You should read the C<FOOBAR::DATA> filehandle first, leaving | |
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 | |
286 | adding the statement 'SelfLoader-E<gt>load_stubs();' to the module to do | |
287 | this. | |
288 | ||
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> | |
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 | |
299 | should note that this requires exporting the C<SelfLoader::AUTOLOAD> to | |
300 | every package which requires it. This is done automatically by the | |
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 | |
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 | ||
312 | will all be loaded correctly by the B<SelfLoader>, and the B<SelfLoader> | |
313 | will ensure that the packages 'foo' and 'baz' correctly have the | |
314 | B<SelfLoader> C<AUTOLOAD> method when the data after C<__DATA__> is first | |
315 | parsed. | |
316 | ||
317 | =cut |