Commit | Line | Data |
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f8881bd9 | 1 | package SelfLoader; |
e3d0cac0 | 2 | # use Carp; |
f8881bd9 AD |
3 | require Exporter; |
4 | @ISA = qw(Exporter); | |
5 | @EXPORT = qw(AUTOLOAD); | |
0120eecf | 6 | $VERSION = "1.0901"; |
52128c7b | 7 | sub Version {$VERSION} |
f8881bd9 AD |
8 | $DEBUG = 0; |
9 | ||
10 | my %Cache; # private cache for all SelfLoader's client packages | |
11 | ||
09bef843 SB |
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 SB |
16 | my $attr_list = qr{ \s* : \s* (?: $one_attr )* }x; |
17 | ||
e3d0cac0 IZ |
18 | sub croak { require Carp; goto &Carp::croak } |
19 | ||
f8881bd9 AD |
20 | AUTOLOAD { |
21 | print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if $DEBUG; | |
c7675058 JG |
22 | my $SL_code = $Cache{$AUTOLOAD}; |
23 | unless ($SL_code) { | |
f8881bd9 AD |
24 | # Maybe this pack had stubs before __DATA__, and never initialized. |
25 | # Or, this maybe an automatic DESTROY method call when none exists. | |
26 | $AUTOLOAD =~ m/^(.*)::/; | |
27 | SelfLoader->_load_stubs($1) unless exists $Cache{"${1}::<DATA"}; | |
c7675058 JG |
28 | $SL_code = $Cache{$AUTOLOAD}; |
29 | $SL_code = "sub $AUTOLOAD { }" | |
30 | if (!$SL_code and $AUTOLOAD =~ m/::DESTROY$/); | |
31 | croak "Undefined subroutine $AUTOLOAD" unless $SL_code; | |
f8881bd9 | 32 | } |
c7675058 JG |
33 | print STDERR "SelfLoader::AUTOLOAD eval: $SL_code\n" if $DEBUG; |
34 | eval $SL_code; | |
f8881bd9 AD |
35 | if ($@) { |
36 | $@ =~ s/ at .*\n//; | |
37 | croak $@; | |
38 | } | |
39 | defined(&$AUTOLOAD) || die "SelfLoader inconsistency error"; | |
40 | delete $Cache{$AUTOLOAD}; | |
41 | goto &$AUTOLOAD | |
42 | } | |
43 | ||
44 | sub load_stubs { shift->_load_stubs((caller)[0]) } | |
45 | ||
46 | sub _load_stubs { | |
47 | my($self, $callpack) = @_; | |
48 | my $fh = \*{"${callpack}::DATA"}; | |
49 | my $currpack = $callpack; | |
50 | my($line,$name,@lines, @stubs, $protoype); | |
51 | ||
52 | print STDERR "SelfLoader::load_stubs($callpack)\n" if $DEBUG; | |
53 | croak("$callpack doesn't contain an __DATA__ token") | |
54 | unless fileno($fh); | |
55 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached | |
56 | ||
52128c7b | 57 | local($/) = "\n"; |
40da2db3 | 58 | while(defined($line = <$fh>) and $line !~ m/^__END__/) { |
09bef843 | 59 | if ($line =~ m/^sub\s+([\w:]+)\s*((?:\([\\\$\@\%\&\*\;]*\))?(?:$attr_list)?)/) { |
f8881bd9 AD |
60 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
61 | $protoype = $2; | |
62 | @lines = ($line); | |
63 | if (index($1,'::') == -1) { # simple sub name | |
64 | $name = "${currpack}::$1"; | |
65 | } else { # sub name with package | |
66 | $name = $1; | |
67 | $name =~ m/^(.*)::/; | |
68 | if (defined(&{"${1}::AUTOLOAD"})) { | |
69 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || | |
70 | die 'SelfLoader Error: attempt to specify Selfloading', | |
71 | " sub $name in non-selfloading module $1"; | |
72 | } else { | |
73 | $self->export($1,'AUTOLOAD'); | |
74 | } | |
75 | } | |
76 | } elsif ($line =~ m/^package\s+([\w:]+)/) { # A package declared | |
77 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); | |
78 | $self->_package_defined($line); | |
79 | $name = ''; | |
80 | @lines = (); | |
81 | $currpack = $1; | |
82 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached | |
83 | if (defined(&{"${1}::AUTOLOAD"})) { | |
84 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || | |
85 | die 'SelfLoader Error: attempt to specify Selfloading', | |
86 | " package $currpack which already has AUTOLOAD"; | |
87 | } else { | |
88 | $self->export($currpack,'AUTOLOAD'); | |
89 | } | |
90 | } else { | |
91 | push(@lines,$line); | |
92 | } | |
93 | } | |
94 | close($fh) unless defined($line) && $line =~ /^__END__\s*DATA/; # __END__ | |
95 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); | |
96 | eval join('', @stubs) if @stubs; | |
97 | } | |
98 | ||
99 | ||
100 | sub _add_to_cache { | |
101 | my($self,$fullname,$pack,$lines, $protoype) = @_; | |
102 | return () unless $fullname; | |
e3d0cac0 IZ |
103 | (require Carp), Carp::carp("Redefining sub $fullname") |
104 | if exists $Cache{$fullname}; | |
f8881bd9 AD |
105 | $Cache{$fullname} = join('', "package $pack; ",@$lines); |
106 | print STDERR "SelfLoader cached $fullname: $Cache{$fullname}" if $DEBUG; | |
107 | # return stub to be eval'd | |
108 | defined($protoype) ? "sub $fullname $protoype;" : "sub $fullname;" | |
109 | } | |
110 | ||
111 | sub _package_defined {} | |
112 | ||
113 | 1; | |
114 | __END__ | |
cb1a09d0 | 115 | |
f8881bd9 AD |
116 | =head1 NAME |
117 | ||
118 | SelfLoader - load functions only on demand | |
119 | ||
120 | =head1 SYNOPSIS | |
121 | ||
122 | package FOOBAR; | |
123 | use SelfLoader; | |
3cb6de81 | 124 | |
f8881bd9 | 125 | ... (initializing code) |
3cb6de81 | 126 | |
f8881bd9 AD |
127 | __DATA__ |
128 | sub {.... | |
129 | ||
130 | ||
131 | =head1 DESCRIPTION | |
132 | ||
133 | This module tells its users that functions in the FOOBAR package are to be | |
463e8aa9 | 134 | autoloaded from after the C<__DATA__> token. See also |
135 | L<perlsub/"Autoloading">. | |
f8881bd9 AD |
136 | |
137 | =head2 The __DATA__ token | |
138 | ||
463e8aa9 | 139 | The C<__DATA__> token tells the perl compiler that the perl code |
140 | for compilation is finished. Everything after the C<__DATA__> token | |
f8881bd9 | 141 | is available for reading via the filehandle FOOBAR::DATA, |
463e8aa9 | 142 | where FOOBAR is the name of the current package when the C<__DATA__> |
143 | token is reached. This works just the same as C<__END__> does in | |
144 | package 'main', but for other modules data after C<__END__> is not | |
f610777f | 145 | automatically retrievable, whereas data after C<__DATA__> is. |
463e8aa9 | 146 | The C<__DATA__> token is not recognized in versions of perl prior to |
f8881bd9 AD |
147 | 5.001m. |
148 | ||
463e8aa9 | 149 | Note that it is possible to have C<__DATA__> tokens in the same package |
150 | in multiple files, and that the last C<__DATA__> token in a given | |
f8881bd9 | 151 | package that is encountered by the compiler is the one accessible |
463e8aa9 | 152 | by the filehandle. This also applies to C<__END__> and main, i.e. if |
153 | the 'main' program has an C<__END__>, but a module 'require'd (_not_ 'use'd) | |
154 | by that program has a 'package main;' declaration followed by an 'C<__DATA__>', | |
155 | then the C<DATA> filehandle is set to access the data after the C<__DATA__> | |
156 | in the module, _not_ the data after the C<__END__> token in the 'main' | |
f8881bd9 AD |
157 | program, since the compiler encounters the 'require'd file later. |
158 | ||
159 | =head2 SelfLoader autoloading | |
160 | ||
463e8aa9 | 161 | The B<SelfLoader> works by the user placing the C<__DATA__> |
162 | token I<after> perl code which needs to be compiled and | |
163 | run at 'require' time, but I<before> subroutine declarations | |
f8881bd9 AD |
164 | that can be loaded in later - usually because they may never |
165 | be called. | |
166 | ||
463e8aa9 | 167 | The B<SelfLoader> will read from the FOOBAR::DATA filehandle to |
168 | load in the data after C<__DATA__>, and load in any subroutine | |
f8881bd9 | 169 | when it is called. The costs are the one-time parsing of the |
463e8aa9 | 170 | data after C<__DATA__>, and a load delay for the _first_ |
f8881bd9 AD |
171 | call of any autoloaded function. The benefits (hopefully) |
172 | are a speeded up compilation phase, with no need to load | |
173 | functions which are never used. | |
174 | ||
463e8aa9 | 175 | The B<SelfLoader> will stop reading from C<__DATA__> if |
176 | it encounters the C<__END__> token - just as you would expect. | |
177 | If the C<__END__> token is present, and is followed by the | |
178 | token DATA, then the B<SelfLoader> leaves the FOOBAR::DATA | |
f8881bd9 AD |
179 | filehandle open on the line after that token. |
180 | ||
463e8aa9 | 181 | The B<SelfLoader> exports the C<AUTOLOAD> subroutine to the |
182 | package using the B<SelfLoader>, and this loads the called | |
f8881bd9 AD |
183 | subroutine when it is first called. |
184 | ||
185 | There is no advantage to putting subroutines which will _always_ | |
463e8aa9 | 186 | be called after the C<__DATA__> token. |
f8881bd9 AD |
187 | |
188 | =head2 Autoloading and package lexicals | |
189 | ||
190 | A 'my $pack_lexical' statement makes the variable $pack_lexical | |
463e8aa9 | 191 | local _only_ to the file up to the C<__DATA__> token. Subroutines |
f8881bd9 AD |
192 | declared elsewhere _cannot_ see these types of variables, |
193 | just as if you declared subroutines in the package but in another | |
194 | file, they cannot see these variables. | |
195 | ||
196 | So specifically, autoloaded functions cannot see package | |
463e8aa9 | 197 | lexicals (this applies to both the B<SelfLoader> and the Autoloader). |
198 | The C<vars> pragma provides an alternative to defining package-level | |
199 | globals that will be visible to autoloaded routines. See the documentation | |
200 | on B<vars> in the pragma section of L<perlmod>. | |
f8881bd9 AD |
201 | |
202 | =head2 SelfLoader and AutoLoader | |
203 | ||
463e8aa9 | 204 | The B<SelfLoader> can replace the AutoLoader - just change 'use AutoLoader' |
205 | to 'use SelfLoader' (though note that the B<SelfLoader> exports | |
f8881bd9 AD |
206 | the AUTOLOAD function - but if you have your own AUTOLOAD and |
207 | are using the AutoLoader too, you probably know what you're doing), | |
463e8aa9 | 208 | and the C<__END__> token to C<__DATA__>. You will need perl version 5.001m |
f8881bd9 AD |
209 | or later to use this (version 5.001 with all patches up to patch m). |
210 | ||
463e8aa9 | 211 | There is no need to inherit from the B<SelfLoader>. |
f8881bd9 | 212 | |
463e8aa9 | 213 | The B<SelfLoader> works similarly to the AutoLoader, but picks up the |
214 | subs from after the C<__DATA__> instead of in the 'lib/auto' directory. | |
f610777f | 215 | There is a maintenance gain in not needing to run AutoSplit on the module |
f8881bd9 AD |
216 | at installation, and a runtime gain in not needing to keep opening and |
217 | closing files to load subs. There is a runtime loss in needing | |
463e8aa9 | 218 | to parse the code after the C<__DATA__>. Details of the B<AutoLoader> and |
219 | another view of these distinctions can be found in that module's | |
220 | documentation. | |
f8881bd9 AD |
221 | |
222 | =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle. | |
223 | ||
224 | This section is only relevant if you want to use | |
463e8aa9 | 225 | the C<FOOBAR::DATA> together with the B<SelfLoader>. |
226 | ||
227 | Data after the C<__DATA__> token in a module is read using the | |
228 | FOOBAR::DATA filehandle. C<__END__> can still be used to denote the end | |
229 | of the C<__DATA__> section if followed by the token DATA - this is supported | |
230 | by the B<SelfLoader>. The C<FOOBAR::DATA> filehandle is left open if an | |
231 | C<__END__> followed by a DATA is found, with the filehandle positioned at | |
232 | the start of the line after the C<__END__> token. If no C<__END__> token is | |
233 | present, or an C<__END__> token with no DATA token on the same line, then | |
234 | the filehandle is closed. | |
235 | ||
236 | The B<SelfLoader> reads from wherever the current | |
237 | position of the C<FOOBAR::DATA> filehandle is, until the | |
238 | EOF or C<__END__>. This means that if you want to use | |
f8881bd9 AD |
239 | that filehandle (and ONLY if you want to), you should either |
240 | ||
241 | 1. Put all your subroutine declarations immediately after | |
463e8aa9 | 242 | the C<__DATA__> token and put your own data after those |
243 | declarations, using the C<__END__> token to mark the end | |
244 | of subroutine declarations. You must also ensure that the B<SelfLoader> | |
1fef88e7 | 245 | reads first by calling 'SelfLoader-E<gt>load_stubs();', or by using a |
f8881bd9 AD |
246 | function which is selfloaded; |
247 | ||
248 | or | |
249 | ||
463e8aa9 | 250 | 2. You should read the C<FOOBAR::DATA> filehandle first, leaving |
f8881bd9 AD |
251 | the handle open and positioned at the first line of subroutine |
252 | declarations. | |
253 | ||
254 | You could conceivably do both. | |
255 | ||
256 | =head2 Classes and inherited methods. | |
257 | ||
258 | For modules which are not classes, this section is not relevant. | |
259 | This section is only relevant if you have methods which could | |
260 | be inherited. | |
261 | ||
262 | A subroutine stub (or forward declaration) looks like | |
263 | ||
264 | sub stub; | |
265 | ||
266 | i.e. it is a subroutine declaration without the body of the | |
267 | subroutine. For modules which are not classes, there is no real | |
268 | need for stubs as far as autoloading is concerned. | |
269 | ||
270 | For modules which ARE classes, and need to handle inherited methods, | |
271 | stubs are needed to ensure that the method inheritance mechanism works | |
272 | properly. You can load the stubs into the module at 'require' time, by | |
1fef88e7 | 273 | adding the statement 'SelfLoader-E<gt>load_stubs();' to the module to do |
f8881bd9 AD |
274 | this. |
275 | ||
463e8aa9 | 276 | The alternative is to put the stubs in before the C<__DATA__> token BEFORE |
277 | releasing the module, and for this purpose the C<Devel::SelfStubber> | |
f8881bd9 AD |
278 | module is available. However this does require the extra step of ensuring |
279 | that the stubs are in the module. If this is done I strongly recommend | |
280 | that this is done BEFORE releasing the module - it should NOT be done | |
281 | at install time in general. | |
282 | ||
283 | =head1 Multiple packages and fully qualified subroutine names | |
284 | ||
285 | Subroutines in multiple packages within the same file are supported - but you | |
463e8aa9 | 286 | should note that this requires exporting the C<SelfLoader::AUTOLOAD> to |
f8881bd9 | 287 | every package which requires it. This is done automatically by the |
463e8aa9 | 288 | B<SelfLoader> when it first loads the subs into the cache, but you should |
289 | really specify it in the initialization before the C<__DATA__> by putting | |
f8881bd9 AD |
290 | a 'use SelfLoader' statement in each package. |
291 | ||
292 | Fully qualified subroutine names are also supported. For example, | |
293 | ||
294 | __DATA__ | |
295 | sub foo::bar {23} | |
296 | package baz; | |
297 | sub dob {32} | |
298 | ||
463e8aa9 | 299 | will all be loaded correctly by the B<SelfLoader>, and the B<SelfLoader> |
f8881bd9 | 300 | will ensure that the packages 'foo' and 'baz' correctly have the |
463e8aa9 | 301 | B<SelfLoader> C<AUTOLOAD> method when the data after C<__DATA__> is first |
302 | parsed. | |
f8881bd9 AD |
303 | |
304 | =cut |