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1 | package SelfLoader; |
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2 | require Exporter; |
3 | @ISA = qw(Exporter); |
4 | @EXPORT = qw(AUTOLOAD); |
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5 | $VERSION = "1.10"; |
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6 | sub Version {$VERSION} |
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7 | $DEBUG = 0; |
8 | |
9 | my %Cache; # private cache for all SelfLoader's client packages |
10 | |
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11 | # allow checking for valid ': attrlist' attachments |
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12 | # (we use 'our' rather than 'my' here, due to the rather complex and buggy |
13 | # behaviour of lexicals with qr// and (??{$lex}) ) |
14 | our $nested; |
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15 | $nested = qr{ \( (?: (?> [^()]+ ) | (??{ $nested }) )* \) }x; |
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16 | our $one_attr = qr{ (?> (?! \d) \w+ (?:$nested)? ) (?:\s*\:\s*|\s+(?!\:)) }x; |
17 | our $attr_list = qr{ \s* : \s* (?: $one_attr )* }x; |
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18 | |
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19 | # in croak and carp, protect $@ from "require Carp;" RT #40216 |
20 | |
21 | sub croak { { local $@; require Carp; } goto &Carp::croak } |
22 | sub carp { { local $@; require Carp; } goto &Carp::carp } |
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23 | |
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24 | AUTOLOAD { |
25 | print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if $DEBUG; |
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26 | my $SL_code = $Cache{$AUTOLOAD}; |
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27 | my $save = $@; # evals in both AUTOLOAD and _load_stubs can corrupt $@ |
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28 | unless ($SL_code) { |
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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"}; |
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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; |
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37 | } |
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38 | print STDERR "SelfLoader::AUTOLOAD eval: $SL_code\n" if $DEBUG; |
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39 | |
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40 | eval $SL_code; |
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41 | if ($@) { |
42 | $@ =~ s/ at .*\n//; |
43 | croak $@; |
44 | } |
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45 | $@ = $save; |
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46 | defined(&$AUTOLOAD) || die "SelfLoader inconsistency error"; |
47 | delete $Cache{$AUTOLOAD}; |
48 | goto &$AUTOLOAD |
49 | } |
50 | |
51 | sub load_stubs { shift->_load_stubs((caller)[0]) } |
52 | |
53 | sub _load_stubs { |
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54 | # $endlines is used by Devel::SelfStubber to capture lines after __END__ |
55 | my($self, $callpack, $endlines) = @_; |
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56 | my $fh = \*{"${callpack}::DATA"}; |
57 | my $currpack = $callpack; |
58 | my($line,$name,@lines, @stubs, $protoype); |
59 | |
60 | print STDERR "SelfLoader::load_stubs($callpack)\n" if $DEBUG; |
61 | croak("$callpack doesn't contain an __DATA__ token") |
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62 | unless defined fileno($fh); |
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63 | # Protect: fork() shares the file pointer between the parent and the kid |
64 | open my $nfh, '<&', $fh or croak "reopen: $!";# dup() the fd |
65 | close $fh or die "close: $1"; # autocloses, but be paranoid |
66 | open $fh, '<&', $nfh or croak "reopen2: $!"; # dup() the fd "back" |
67 | close $nfh or die "close after reopen: $1"; # autocloses, but be paranoid |
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68 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached |
69 | |
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70 | local($/) = "\n"; |
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71 | while(defined($line = <$fh>) and $line !~ m/^__END__/) { |
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72 | if ($line =~ m/^sub\s+([\w:]+)\s*((?:\([\\\$\@\%\&\*\;]*\))?(?:$attr_list)?)/) { |
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73 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
74 | $protoype = $2; |
75 | @lines = ($line); |
76 | if (index($1,'::') == -1) { # simple sub name |
77 | $name = "${currpack}::$1"; |
78 | } else { # sub name with package |
79 | $name = $1; |
80 | $name =~ m/^(.*)::/; |
81 | if (defined(&{"${1}::AUTOLOAD"})) { |
82 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || |
83 | die 'SelfLoader Error: attempt to specify Selfloading', |
84 | " sub $name in non-selfloading module $1"; |
85 | } else { |
86 | $self->export($1,'AUTOLOAD'); |
87 | } |
88 | } |
89 | } elsif ($line =~ m/^package\s+([\w:]+)/) { # A package declared |
90 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
91 | $self->_package_defined($line); |
92 | $name = ''; |
93 | @lines = (); |
94 | $currpack = $1; |
95 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached |
96 | if (defined(&{"${1}::AUTOLOAD"})) { |
97 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || |
98 | die 'SelfLoader Error: attempt to specify Selfloading', |
99 | " package $currpack which already has AUTOLOAD"; |
100 | } else { |
101 | $self->export($currpack,'AUTOLOAD'); |
102 | } |
103 | } else { |
104 | push(@lines,$line); |
105 | } |
106 | } |
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107 | if (defined($line) && $line =~ /^__END__/) { # __END__ |
108 | unless ($line =~ /^__END__\s*DATA/) { |
109 | if ($endlines) { |
110 | # Devel::SelfStubber would like us to capture the lines after |
111 | # __END__ so it can write out the entire file |
112 | @$endlines = <$fh>; |
113 | } |
114 | close($fh); |
115 | } |
116 | } |
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117 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
118 | eval join('', @stubs) if @stubs; |
119 | } |
120 | |
121 | |
122 | sub _add_to_cache { |
123 | my($self,$fullname,$pack,$lines, $protoype) = @_; |
124 | return () unless $fullname; |
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125 | carp("Redefining sub $fullname") |
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126 | if exists $Cache{$fullname}; |
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127 | $Cache{$fullname} = join('', "package $pack; ",@$lines); |
128 | print STDERR "SelfLoader cached $fullname: $Cache{$fullname}" if $DEBUG; |
129 | # return stub to be eval'd |
130 | defined($protoype) ? "sub $fullname $protoype;" : "sub $fullname;" |
131 | } |
132 | |
133 | sub _package_defined {} |
134 | |
135 | 1; |
136 | __END__ |
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137 | |
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138 | =head1 NAME |
139 | |
140 | SelfLoader - load functions only on demand |
141 | |
142 | =head1 SYNOPSIS |
143 | |
144 | package FOOBAR; |
145 | use SelfLoader; |
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146 | |
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147 | ... (initializing code) |
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148 | |
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149 | __DATA__ |
150 | sub {.... |
151 | |
152 | |
153 | =head1 DESCRIPTION |
154 | |
155 | This module tells its users that functions in the FOOBAR package are to be |
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156 | autoloaded from after the C<__DATA__> token. See also |
157 | L<perlsub/"Autoloading">. |
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158 | |
159 | =head2 The __DATA__ token |
160 | |
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161 | The C<__DATA__> token tells the perl compiler that the perl code |
162 | for compilation is finished. Everything after the C<__DATA__> token |
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163 | is available for reading via the filehandle FOOBAR::DATA, |
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164 | where FOOBAR is the name of the current package when the C<__DATA__> |
165 | token is reached. This works just the same as C<__END__> does in |
166 | package 'main', but for other modules data after C<__END__> is not |
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167 | automatically retrievable, whereas data after C<__DATA__> is. |
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168 | The C<__DATA__> token is not recognized in versions of perl prior to |
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169 | 5.001m. |
170 | |
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171 | Note that it is possible to have C<__DATA__> tokens in the same package |
172 | in multiple files, and that the last C<__DATA__> token in a given |
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173 | package that is encountered by the compiler is the one accessible |
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174 | by the filehandle. This also applies to C<__END__> and main, i.e. if |
175 | the 'main' program has an C<__END__>, but a module 'require'd (_not_ 'use'd) |
176 | by that program has a 'package main;' declaration followed by an 'C<__DATA__>', |
177 | then the C<DATA> filehandle is set to access the data after the C<__DATA__> |
178 | in the module, _not_ the data after the C<__END__> token in the 'main' |
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179 | program, since the compiler encounters the 'require'd file later. |
180 | |
181 | =head2 SelfLoader autoloading |
182 | |
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183 | The B<SelfLoader> works by the user placing the C<__DATA__> |
184 | token I<after> perl code which needs to be compiled and |
185 | run at 'require' time, but I<before> subroutine declarations |
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186 | that can be loaded in later - usually because they may never |
187 | be called. |
188 | |
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189 | The B<SelfLoader> will read from the FOOBAR::DATA filehandle to |
190 | load in the data after C<__DATA__>, and load in any subroutine |
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191 | when it is called. The costs are the one-time parsing of the |
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192 | data after C<__DATA__>, and a load delay for the _first_ |
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193 | call of any autoloaded function. The benefits (hopefully) |
194 | are a speeded up compilation phase, with no need to load |
195 | functions which are never used. |
196 | |
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197 | The B<SelfLoader> will stop reading from C<__DATA__> if |
198 | it encounters the C<__END__> token - just as you would expect. |
199 | If the C<__END__> token is present, and is followed by the |
200 | token DATA, then the B<SelfLoader> leaves the FOOBAR::DATA |
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201 | filehandle open on the line after that token. |
202 | |
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203 | The B<SelfLoader> exports the C<AUTOLOAD> subroutine to the |
204 | package using the B<SelfLoader>, and this loads the called |
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205 | subroutine when it is first called. |
206 | |
207 | There is no advantage to putting subroutines which will _always_ |
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208 | be called after the C<__DATA__> token. |
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209 | |
210 | =head2 Autoloading and package lexicals |
211 | |
212 | A 'my $pack_lexical' statement makes the variable $pack_lexical |
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213 | local _only_ to the file up to the C<__DATA__> token. Subroutines |
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214 | declared elsewhere _cannot_ see these types of variables, |
215 | just as if you declared subroutines in the package but in another |
216 | file, they cannot see these variables. |
217 | |
218 | So specifically, autoloaded functions cannot see package |
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219 | lexicals (this applies to both the B<SelfLoader> and the Autoloader). |
220 | The C<vars> pragma provides an alternative to defining package-level |
221 | globals that will be visible to autoloaded routines. See the documentation |
222 | on B<vars> in the pragma section of L<perlmod>. |
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223 | |
224 | =head2 SelfLoader and AutoLoader |
225 | |
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226 | The B<SelfLoader> can replace the AutoLoader - just change 'use AutoLoader' |
227 | to 'use SelfLoader' (though note that the B<SelfLoader> exports |
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228 | the AUTOLOAD function - but if you have your own AUTOLOAD and |
229 | are using the AutoLoader too, you probably know what you're doing), |
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230 | and the C<__END__> token to C<__DATA__>. You will need perl version 5.001m |
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231 | or later to use this (version 5.001 with all patches up to patch m). |
232 | |
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233 | There is no need to inherit from the B<SelfLoader>. |
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234 | |
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235 | The B<SelfLoader> works similarly to the AutoLoader, but picks up the |
236 | subs from after the C<__DATA__> instead of in the 'lib/auto' directory. |
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237 | There is a maintenance gain in not needing to run AutoSplit on the module |
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238 | at installation, and a runtime gain in not needing to keep opening and |
239 | closing files to load subs. There is a runtime loss in needing |
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240 | to parse the code after the C<__DATA__>. Details of the B<AutoLoader> and |
241 | another view of these distinctions can be found in that module's |
242 | documentation. |
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243 | |
244 | =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle. |
245 | |
246 | This section is only relevant if you want to use |
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247 | the C<FOOBAR::DATA> together with the B<SelfLoader>. |
248 | |
249 | Data after the C<__DATA__> token in a module is read using the |
250 | FOOBAR::DATA filehandle. C<__END__> can still be used to denote the end |
251 | of the C<__DATA__> section if followed by the token DATA - this is supported |
252 | by the B<SelfLoader>. The C<FOOBAR::DATA> filehandle is left open if an |
253 | C<__END__> followed by a DATA is found, with the filehandle positioned at |
254 | the start of the line after the C<__END__> token. If no C<__END__> token is |
255 | present, or an C<__END__> token with no DATA token on the same line, then |
256 | the filehandle is closed. |
257 | |
258 | The B<SelfLoader> reads from wherever the current |
259 | position of the C<FOOBAR::DATA> filehandle is, until the |
260 | EOF or C<__END__>. This means that if you want to use |
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261 | that filehandle (and ONLY if you want to), you should either |
262 | |
263 | 1. Put all your subroutine declarations immediately after |
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264 | the C<__DATA__> token and put your own data after those |
265 | declarations, using the C<__END__> token to mark the end |
266 | of subroutine declarations. You must also ensure that the B<SelfLoader> |
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267 | reads first by calling 'SelfLoader-E<gt>load_stubs();', or by using a |
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268 | function which is selfloaded; |
269 | |
270 | or |
271 | |
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272 | 2. You should read the C<FOOBAR::DATA> filehandle first, leaving |
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273 | the handle open and positioned at the first line of subroutine |
274 | declarations. |
275 | |
276 | You could conceivably do both. |
277 | |
278 | =head2 Classes and inherited methods. |
279 | |
280 | For modules which are not classes, this section is not relevant. |
281 | This section is only relevant if you have methods which could |
282 | be inherited. |
283 | |
284 | A subroutine stub (or forward declaration) looks like |
285 | |
286 | sub stub; |
287 | |
288 | i.e. it is a subroutine declaration without the body of the |
289 | subroutine. For modules which are not classes, there is no real |
290 | need for stubs as far as autoloading is concerned. |
291 | |
292 | For modules which ARE classes, and need to handle inherited methods, |
293 | stubs are needed to ensure that the method inheritance mechanism works |
294 | properly. You can load the stubs into the module at 'require' time, by |
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295 | adding the statement 'SelfLoader-E<gt>load_stubs();' to the module to do |
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296 | this. |
297 | |
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298 | The alternative is to put the stubs in before the C<__DATA__> token BEFORE |
299 | releasing the module, and for this purpose the C<Devel::SelfStubber> |
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300 | module is available. However this does require the extra step of ensuring |
301 | that the stubs are in the module. If this is done I strongly recommend |
302 | that this is done BEFORE releasing the module - it should NOT be done |
303 | at install time in general. |
304 | |
305 | =head1 Multiple packages and fully qualified subroutine names |
306 | |
307 | Subroutines in multiple packages within the same file are supported - but you |
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308 | should note that this requires exporting the C<SelfLoader::AUTOLOAD> to |
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309 | every package which requires it. This is done automatically by the |
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310 | B<SelfLoader> when it first loads the subs into the cache, but you should |
311 | really specify it in the initialization before the C<__DATA__> by putting |
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312 | a 'use SelfLoader' statement in each package. |
313 | |
314 | Fully qualified subroutine names are also supported. For example, |
315 | |
316 | __DATA__ |
317 | sub foo::bar {23} |
318 | package baz; |
319 | sub dob {32} |
320 | |
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321 | will all be loaded correctly by the B<SelfLoader>, and the B<SelfLoader> |
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322 | will ensure that the packages 'foo' and 'baz' correctly have the |
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323 | B<SelfLoader> C<AUTOLOAD> method when the data after C<__DATA__> is first |
324 | parsed. |
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325 | |
326 | =cut |