Commit | Line | Data |
---|---|---|
8990e307 | 1 | package AutoLoader; |
21c92a1d | 2 | |
4d6b4052 | 3 | use 5.6.0; |
17f410f9 | 4 | our(@EXPORT, @EXPORT_OK, $VERSION); |
f06db76b | 5 | |
adaafad2 | 6 | my $is_dosish; |
ed79a026 | 7 | my $is_epoc; |
adaafad2 | 8 | my $is_vms; |
084592ab | 9 | my $is_macos; |
adaafad2 | 10 | |
1be0b951 CS |
11 | BEGIN { |
12 | require Exporter; | |
e3d0cac0 IZ |
13 | @EXPORT = @EXPORT = (); |
14 | @EXPORT_OK = @EXPORT_OK = qw(AUTOLOAD); | |
2986a63f | 15 | $is_dosish = $^O eq 'dos' || $^O eq 'os2' || $^O eq 'MSWin32' || $^O eq 'NetWare'; |
ed79a026 | 16 | $is_epoc = $^O eq 'epoc'; |
adaafad2 | 17 | $is_vms = $^O eq 'VMS'; |
084592ab | 18 | $is_macos = $^O eq 'MacOS'; |
88d01e8d | 19 | $VERSION = '5.59'; |
1be0b951 | 20 | } |
f06db76b | 21 | |
8990e307 | 22 | AUTOLOAD { |
7d4fbd98 GS |
23 | my $sub = $AUTOLOAD; |
24 | my $filename; | |
5a556d17 NIS |
25 | # Braces used to preserve $1 et al. |
26 | { | |
adaafad2 GS |
27 | # Try to find the autoloaded file from the package-qualified |
28 | # name of the sub. e.g., if the sub needed is | |
29 | # Getopt::Long::GetOptions(), then $INC{Getopt/Long.pm} is | |
30 | # something like '/usr/lib/perl5/Getopt/Long.pm', and the | |
31 | # autoload file is '/usr/lib/perl5/auto/Getopt/Long/GetOptions.al'. | |
32 | # | |
33 | # However, if @INC is a relative path, this might not work. If, | |
34 | # for example, @INC = ('lib'), then $INC{Getopt/Long.pm} is | |
35 | # 'lib/Getopt/Long.pm', and we want to require | |
36 | # 'auto/Getopt/Long/GetOptions.al' (without the leading 'lib'). | |
37 | # In this case, we simple prepend the 'auto/' and let the | |
38 | # C<require> take care of the searching for us. | |
39 | ||
7d4fbd98 | 40 | my ($pkg,$func) = ($sub =~ /(.*)::([^:]+)$/); |
adaafad2 | 41 | $pkg =~ s#::#/#g; |
7d4fbd98 | 42 | if (defined($filename = $INC{"$pkg.pm"})) { |
084592ab CN |
43 | if ($is_macos) { |
44 | $pkg =~ tr#/#:#; | |
45 | $filename =~ s#^(.*)$pkg\.pm\z#$1auto:$pkg:$func.al#s; | |
46 | } else { | |
47 | $filename =~ s#^(.*)$pkg\.pm\z#$1auto/$pkg/$func.al#s; | |
48 | } | |
adaafad2 GS |
49 | |
50 | # if the file exists, then make sure that it is a | |
51 | # a fully anchored path (i.e either '/usr/lib/auto/foo/bar.al', | |
52 | # or './lib/auto/foo/bar.al'. This avoids C<require> searching | |
53 | # (and failing) to find the 'lib/auto/foo/bar.al' because it | |
54 | # looked for 'lib/lib/auto/foo/bar.al', given @INC = ('lib'). | |
55 | ||
7d4fbd98 | 56 | if (-r $filename) { |
14a089c5 | 57 | unless ($filename =~ m|^/|s) { |
adaafad2 | 58 | if ($is_dosish) { |
14a089c5 | 59 | unless ($filename =~ m{^([a-z]:)?[\\/]}is) { |
2986a63f JH |
60 | if ($^O ne 'NetWare') { |
61 | $filename = "./$filename"; | |
62 | } else { | |
63 | $filename = "$filename"; | |
64 | } | |
adaafad2 GS |
65 | } |
66 | } | |
ed79a026 OF |
67 | elsif ($is_epoc) { |
68 | unless ($filename =~ m{^([a-z?]:)?[\\/]}is) { | |
69 | $filename = "./$filename"; | |
70 | } | |
4d6b4052 JH |
71 | } |
72 | elsif ($is_vms) { | |
7d4fbd98 GS |
73 | # XXX todo by VMSmiths |
74 | $filename = "./$filename"; | |
adaafad2 | 75 | } |
084592ab | 76 | elsif (!$is_macos) { |
7d4fbd98 | 77 | $filename = "./$filename"; |
adaafad2 GS |
78 | } |
79 | } | |
80 | } | |
81 | else { | |
7d4fbd98 | 82 | $filename = undef; |
adaafad2 GS |
83 | } |
84 | } | |
7d4fbd98 | 85 | unless (defined $filename) { |
adaafad2 | 86 | # let C<require> do the searching |
7d4fbd98 GS |
87 | $filename = "auto/$sub.al"; |
88 | $filename =~ s#::#/#g; | |
adaafad2 | 89 | } |
5a556d17 | 90 | } |
e14baed2 | 91 | my $save = $@; |
212caf55 | 92 | local $!; # Do not munge the value. |
7d4fbd98 | 93 | eval { local $SIG{__DIE__}; require $filename }; |
8990e307 | 94 | if ($@) { |
7d4fbd98 GS |
95 | if (substr($sub,-9) eq '::DESTROY') { |
96 | *$sub = sub {}; | |
e14baed2 | 97 | } else { |
98 | # The load might just have failed because the filename was too | |
99 | # long for some old SVR3 systems which treat long names as errors. | |
100 | # If we can succesfully truncate a long name then it's worth a go. | |
101 | # There is a slight risk that we could pick up the wrong file here | |
102 | # but autosplit should have warned about that when splitting. | |
7d4fbd98 GS |
103 | if ($filename =~ s/(\w{12,})\.al$/substr($1,0,11).".al"/e){ |
104 | eval { local $SIG{__DIE__}; require $filename }; | |
e14baed2 | 105 | } |
106 | if ($@){ | |
107 | $@ =~ s/ at .*\n//; | |
fb73857a | 108 | my $error = $@; |
109 | require Carp; | |
110 | Carp::croak($error); | |
e14baed2 | 111 | } |
a0d0e21e | 112 | } |
8990e307 | 113 | } |
e14baed2 | 114 | $@ = $save; |
7d4fbd98 | 115 | goto &$sub; |
8990e307 | 116 | } |
1be0b951 | 117 | |
c2960299 | 118 | sub import { |
1be0b951 CS |
119 | my $pkg = shift; |
120 | my $callpkg = caller; | |
121 | ||
122 | # | |
123 | # Export symbols, but not by accident of inheritance. | |
124 | # | |
125 | ||
e3d0cac0 IZ |
126 | if ($pkg eq 'AutoLoader') { |
127 | local $Exporter::ExportLevel = 1; | |
128 | Exporter::import $pkg, @_; | |
129 | } | |
1be0b951 CS |
130 | |
131 | # | |
c2960299 AD |
132 | # Try to find the autosplit index file. Eg., if the call package |
133 | # is POSIX, then $INC{POSIX.pm} is something like | |
134 | # '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in | |
135 | # '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that. | |
136 | # | |
137 | # However, if @INC is a relative path, this might not work. If, | |
138 | # for example, @INC = ('lib'), then | |
139 | # $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require | |
140 | # 'auto/POSIX/autosplit.ix' (without the leading 'lib'). | |
141 | # | |
1be0b951 | 142 | |
1c1c7f20 | 143 | (my $calldir = $callpkg) =~ s#::#/#g; |
1be0b951 CS |
144 | my $path = $INC{$calldir . '.pm'}; |
145 | if (defined($path)) { | |
c2960299 | 146 | # Try absolute path name. |
4d6b4052 JH |
147 | if ($is_macos) { |
148 | (my $malldir = $calldir) =~ tr#/#:#; | |
149 | $path =~ s#^(.*)$malldir\.pm\z#$1auto:$malldir:autosplit.ix#s; | |
150 | } else { | |
151 | $path =~ s#^(.*)$calldir\.pm\z#$1auto/$calldir/autosplit.ix#; | |
152 | } | |
153 | ||
c2960299 AD |
154 | eval { require $path; }; |
155 | # If that failed, try relative path with normal @INC searching. | |
156 | if ($@) { | |
1be0b951 | 157 | $path ="auto/$calldir/autosplit.ix"; |
c2960299 AD |
158 | eval { require $path; }; |
159 | } | |
fb73857a | 160 | if ($@) { |
161 | my $error = $@; | |
162 | require Carp; | |
163 | Carp::carp($error); | |
164 | } | |
f06db76b | 165 | } |
f06db76b | 166 | } |
8990e307 | 167 | |
cb0cff20 JH |
168 | sub unimport { |
169 | my $callpkg = caller; | |
170 | eval "package $callpkg; sub AUTOLOAD;"; | |
171 | } | |
172 | ||
8990e307 | 173 | 1; |
1be0b951 CS |
174 | |
175 | __END__ | |
176 | ||
177 | =head1 NAME | |
178 | ||
179 | AutoLoader - load subroutines only on demand | |
180 | ||
181 | =head1 SYNOPSIS | |
182 | ||
183 | package Foo; | |
184 | use AutoLoader 'AUTOLOAD'; # import the default AUTOLOAD subroutine | |
185 | ||
186 | package Bar; | |
187 | use AutoLoader; # don't import AUTOLOAD, define our own | |
188 | sub AUTOLOAD { | |
189 | ... | |
190 | $AutoLoader::AUTOLOAD = "..."; | |
191 | goto &AutoLoader::AUTOLOAD; | |
192 | } | |
193 | ||
194 | =head1 DESCRIPTION | |
195 | ||
196 | The B<AutoLoader> module works with the B<AutoSplit> module and the | |
197 | C<__END__> token to defer the loading of some subroutines until they are | |
198 | used rather than loading them all at once. | |
199 | ||
200 | To use B<AutoLoader>, the author of a module has to place the | |
201 | definitions of subroutines to be autoloaded after an C<__END__> token. | |
202 | (See L<perldata>.) The B<AutoSplit> module can then be run manually to | |
203 | extract the definitions into individual files F<auto/funcname.al>. | |
204 | ||
205 | B<AutoLoader> implements an AUTOLOAD subroutine. When an undefined | |
206 | subroutine in is called in a client module of B<AutoLoader>, | |
207 | B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a | |
208 | file with a name related to the location of the file from which the | |
209 | client module was read. As an example, if F<POSIX.pm> is located in | |
210 | F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl | |
211 | subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where | |
212 | the C<.al> file has the same name as the subroutine, sans package. If | |
213 | such a file exists, AUTOLOAD will read and evaluate it, | |
214 | thus (presumably) defining the needed subroutine. AUTOLOAD will then | |
215 | C<goto> the newly defined subroutine. | |
216 | ||
f610777f | 217 | Once this process completes for a given function, it is defined, so |
1be0b951 CS |
218 | future calls to the subroutine will bypass the AUTOLOAD mechanism. |
219 | ||
220 | =head2 Subroutine Stubs | |
221 | ||
222 | In order for object method lookup and/or prototype checking to operate | |
223 | correctly even when methods have not yet been defined it is necessary to | |
224 | "forward declare" each subroutine (as in C<sub NAME;>). See | |
225 | L<perlsub/"SYNOPSIS">. Such forward declaration creates "subroutine | |
226 | stubs", which are place holders with no code. | |
227 | ||
228 | The AutoSplit and B<AutoLoader> modules automate the creation of forward | |
229 | declarations. The AutoSplit module creates an 'index' file containing | |
230 | forward declarations of all the AutoSplit subroutines. When the | |
231 | AutoLoader module is 'use'd it loads these declarations into its callers | |
232 | package. | |
233 | ||
234 | Because of this mechanism it is important that B<AutoLoader> is always | |
235 | C<use>d and not C<require>d. | |
236 | ||
237 | =head2 Using B<AutoLoader>'s AUTOLOAD Subroutine | |
238 | ||
239 | In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must> | |
240 | explicitly import it: | |
241 | ||
242 | use AutoLoader 'AUTOLOAD'; | |
243 | ||
244 | =head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine | |
245 | ||
246 | Some modules, mainly extensions, provide their own AUTOLOAD subroutines. | |
247 | They typically need to check for some special cases (such as constants) | |
248 | and then fallback to B<AutoLoader>'s AUTOLOAD for the rest. | |
249 | ||
250 | Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine. | |
251 | Instead, they should define their own AUTOLOAD subroutines along these | |
252 | lines: | |
253 | ||
254 | use AutoLoader; | |
fb73857a | 255 | use Carp; |
1be0b951 CS |
256 | |
257 | sub AUTOLOAD { | |
7d4fbd98 GS |
258 | my $sub = $AUTOLOAD; |
259 | (my $constname = $sub) =~ s/.*:://; | |
1be0b951 CS |
260 | my $val = constant($constname, @_ ? $_[0] : 0); |
261 | if ($! != 0) { | |
265f5c4a | 262 | if ($! =~ /Invalid/ || $!{EINVAL}) { |
7d4fbd98 | 263 | $AutoLoader::AUTOLOAD = $sub; |
1be0b951 CS |
264 | goto &AutoLoader::AUTOLOAD; |
265 | } | |
266 | else { | |
267 | croak "Your vendor has not defined constant $constname"; | |
268 | } | |
269 | } | |
7d4fbd98 GS |
270 | *$sub = sub { $val }; # same as: eval "sub $sub { $val }"; |
271 | goto &$sub; | |
1be0b951 CS |
272 | } |
273 | ||
274 | If any module's own AUTOLOAD subroutine has no need to fallback to the | |
275 | AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit | |
276 | subroutines), then that module should not use B<AutoLoader> at all. | |
277 | ||
278 | =head2 Package Lexicals | |
279 | ||
280 | Package lexicals declared with C<my> in the main block of a package | |
281 | using B<AutoLoader> will not be visible to auto-loaded subroutines, due to | |
282 | the fact that the given scope ends at the C<__END__> marker. A module | |
283 | using such variables as package globals will not work properly under the | |
284 | B<AutoLoader>. | |
285 | ||
286 | The C<vars> pragma (see L<perlmod/"vars">) may be used in such | |
287 | situations as an alternative to explicitly qualifying all globals with | |
288 | the package namespace. Variables pre-declared with this pragma will be | |
289 | visible to any autoloaded routines (but will not be invisible outside | |
290 | the package, unfortunately). | |
291 | ||
cb0cff20 JH |
292 | =head2 Not Using AutoLoader |
293 | ||
294 | You can stop using AutoLoader by simply | |
295 | ||
296 | no AutoLoader; | |
297 | ||
1be0b951 CS |
298 | =head2 B<AutoLoader> vs. B<SelfLoader> |
299 | ||
300 | The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the | |
301 | loading of subroutines. | |
302 | ||
303 | B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>. | |
304 | While this avoids the use of a hierarchy of disk files and the | |
305 | associated open/close for each routine loaded, B<SelfLoader> suffers a | |
306 | startup speed disadvantage in the one-time parsing of the lines after | |
307 | C<__DATA__>, after which routines are cached. B<SelfLoader> can also | |
308 | handle multiple packages in a file. | |
309 | ||
310 | B<AutoLoader> only reads code as it is requested, and in many cases | |
f610777f | 311 | should be faster, but requires a mechanism like B<AutoSplit> be used to |
1be0b951 CS |
312 | create the individual files. L<ExtUtils::MakeMaker> will invoke |
313 | B<AutoSplit> automatically if B<AutoLoader> is used in a module source | |
314 | file. | |
315 | ||
316 | =head1 CAVEATS | |
317 | ||
318 | AutoLoaders prior to Perl 5.002 had a slightly different interface. Any | |
319 | old modules which use B<AutoLoader> should be changed to the new calling | |
320 | style. Typically this just means changing a require to a use, adding | |
321 | the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader> | |
322 | from C<@ISA>. | |
323 | ||
324 | On systems with restrictions on file name length, the file corresponding | |
325 | to a subroutine may have a shorter name that the routine itself. This | |
326 | can lead to conflicting file names. The I<AutoSplit> package warns of | |
327 | these potential conflicts when used to split a module. | |
328 | ||
adaafad2 GS |
329 | AutoLoader may fail to find the autosplit files (or even find the wrong |
330 | ones) in cases where C<@INC> contains relative paths, B<and> the program | |
331 | does C<chdir>. | |
332 | ||
1be0b951 CS |
333 | =head1 SEE ALSO |
334 | ||
335 | L<SelfLoader> - an autoloader that doesn't use external files. | |
336 | ||
337 | =cut |