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8990e307 |
1 | package AutoLoader; |
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2 | |
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3 | use 5.005_64; |
4 | our(@EXPORT, @EXPORT_OK, $VERSION); |
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5 | |
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6 | my $is_dosish; |
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7 | my $is_epoc; |
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8 | my $is_vms; |
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9 | my $is_macos; |
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10 | |
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11 | BEGIN { |
12 | require Exporter; |
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13 | @EXPORT = @EXPORT = (); |
14 | @EXPORT_OK = @EXPORT_OK = qw(AUTOLOAD); |
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15 | $is_dosish = $^O eq 'dos' || $^O eq 'os2' || $^O eq 'MSWin32' || $^O eq 'NetWare'; |
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16 | $is_epoc = $^O eq 'epoc'; |
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17 | $is_vms = $^O eq 'VMS'; |
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18 | $is_macos = $^O eq 'MacOS'; |
19 | $VERSION = '5.58'; |
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20 | } |
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21 | |
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22 | AUTOLOAD { |
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23 | my $sub = $AUTOLOAD; |
24 | my $filename; |
5a556d17 |
25 | # Braces used to preserve $1 et al. |
26 | { |
adaafad2 |
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 $INC{Getopt/Long.pm} is |
35 | # 'lib/Getopt/Long.pm', and we want to require |
36 | # 'auto/Getopt/Long/GetOptions.al' (without the leading 'lib'). |
37 | # In this case, we simple prepend the 'auto/' and let the |
38 | # C<require> take care of the searching for us. |
39 | |
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40 | my ($pkg,$func) = ($sub =~ /(.*)::([^:]+)$/); |
adaafad2 |
41 | $pkg =~ s#::#/#g; |
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42 | if (defined($filename = $INC{"$pkg.pm"})) { |
084592ab |
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 |
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 | |
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56 | if (-r $filename) { |
14a089c5 |
57 | unless ($filename =~ m|^/|s) { |
adaafad2 |
58 | if ($is_dosish) { |
14a089c5 |
59 | unless ($filename =~ m{^([a-z]:)?[\\/]}is) { |
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60 | if ($^O ne 'NetWare') { |
61 | $filename = "./$filename"; |
62 | } else { |
63 | $filename = "$filename"; |
64 | } |
adaafad2 |
65 | } |
66 | } |
ed79a026 |
67 | elsif ($is_epoc) { |
68 | unless ($filename =~ m{^([a-z?]:)?[\\/]}is) { |
69 | $filename = "./$filename"; |
70 | } |
71 | }elsif ($is_vms) { |
7d4fbd98 |
72 | # XXX todo by VMSmiths |
73 | $filename = "./$filename"; |
adaafad2 |
74 | } |
084592ab |
75 | elsif (!$is_macos) { |
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76 | $filename = "./$filename"; |
adaafad2 |
77 | } |
78 | } |
79 | } |
80 | else { |
7d4fbd98 |
81 | $filename = undef; |
adaafad2 |
82 | } |
83 | } |
7d4fbd98 |
84 | unless (defined $filename) { |
adaafad2 |
85 | # let C<require> do the searching |
7d4fbd98 |
86 | $filename = "auto/$sub.al"; |
87 | $filename =~ s#::#/#g; |
adaafad2 |
88 | } |
5a556d17 |
89 | } |
e14baed2 |
90 | my $save = $@; |
212caf55 |
91 | local $!; # Do not munge the value. |
7d4fbd98 |
92 | eval { local $SIG{__DIE__}; require $filename }; |
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93 | if ($@) { |
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94 | if (substr($sub,-9) eq '::DESTROY') { |
95 | *$sub = sub {}; |
e14baed2 |
96 | } else { |
97 | # The load might just have failed because the filename was too |
98 | # long for some old SVR3 systems which treat long names as errors. |
99 | # If we can succesfully truncate a long name then it's worth a go. |
100 | # There is a slight risk that we could pick up the wrong file here |
101 | # but autosplit should have warned about that when splitting. |
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102 | if ($filename =~ s/(\w{12,})\.al$/substr($1,0,11).".al"/e){ |
103 | eval { local $SIG{__DIE__}; require $filename }; |
e14baed2 |
104 | } |
105 | if ($@){ |
106 | $@ =~ s/ at .*\n//; |
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107 | my $error = $@; |
108 | require Carp; |
109 | Carp::croak($error); |
e14baed2 |
110 | } |
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111 | } |
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112 | } |
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113 | $@ = $save; |
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114 | goto &$sub; |
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115 | } |
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116 | |
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117 | sub import { |
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118 | my $pkg = shift; |
119 | my $callpkg = caller; |
120 | |
121 | # |
122 | # Export symbols, but not by accident of inheritance. |
123 | # |
124 | |
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125 | if ($pkg eq 'AutoLoader') { |
126 | local $Exporter::ExportLevel = 1; |
127 | Exporter::import $pkg, @_; |
128 | } |
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129 | |
130 | # |
c2960299 |
131 | # Try to find the autosplit index file. Eg., if the call package |
132 | # is POSIX, then $INC{POSIX.pm} is something like |
133 | # '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in |
134 | # '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that. |
135 | # |
136 | # However, if @INC is a relative path, this might not work. If, |
137 | # for example, @INC = ('lib'), then |
138 | # $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require |
139 | # 'auto/POSIX/autosplit.ix' (without the leading 'lib'). |
140 | # |
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141 | |
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142 | (my $calldir = $callpkg) =~ s#::#/#g; |
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143 | my $path = $INC{$calldir . '.pm'}; |
144 | if (defined($path)) { |
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145 | # Try absolute path name. |
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146 | $path =~ s#^(.*)$calldir\.pm$#$1auto/$calldir/autosplit.ix#; |
c2960299 |
147 | eval { require $path; }; |
148 | # If that failed, try relative path with normal @INC searching. |
149 | if ($@) { |
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150 | $path ="auto/$calldir/autosplit.ix"; |
c2960299 |
151 | eval { require $path; }; |
152 | } |
fb73857a |
153 | if ($@) { |
154 | my $error = $@; |
155 | require Carp; |
156 | Carp::carp($error); |
157 | } |
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158 | } |
f06db76b |
159 | } |
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160 | |
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161 | sub unimport { |
162 | my $callpkg = caller; |
163 | eval "package $callpkg; sub AUTOLOAD;"; |
164 | } |
165 | |
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166 | 1; |
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167 | |
168 | __END__ |
169 | |
170 | =head1 NAME |
171 | |
172 | AutoLoader - load subroutines only on demand |
173 | |
174 | =head1 SYNOPSIS |
175 | |
176 | package Foo; |
177 | use AutoLoader 'AUTOLOAD'; # import the default AUTOLOAD subroutine |
178 | |
179 | package Bar; |
180 | use AutoLoader; # don't import AUTOLOAD, define our own |
181 | sub AUTOLOAD { |
182 | ... |
183 | $AutoLoader::AUTOLOAD = "..."; |
184 | goto &AutoLoader::AUTOLOAD; |
185 | } |
186 | |
187 | =head1 DESCRIPTION |
188 | |
189 | The B<AutoLoader> module works with the B<AutoSplit> module and the |
190 | C<__END__> token to defer the loading of some subroutines until they are |
191 | used rather than loading them all at once. |
192 | |
193 | To use B<AutoLoader>, the author of a module has to place the |
194 | definitions of subroutines to be autoloaded after an C<__END__> token. |
195 | (See L<perldata>.) The B<AutoSplit> module can then be run manually to |
196 | extract the definitions into individual files F<auto/funcname.al>. |
197 | |
198 | B<AutoLoader> implements an AUTOLOAD subroutine. When an undefined |
199 | subroutine in is called in a client module of B<AutoLoader>, |
200 | B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a |
201 | file with a name related to the location of the file from which the |
202 | client module was read. As an example, if F<POSIX.pm> is located in |
203 | F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl |
204 | subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where |
205 | the C<.al> file has the same name as the subroutine, sans package. If |
206 | such a file exists, AUTOLOAD will read and evaluate it, |
207 | thus (presumably) defining the needed subroutine. AUTOLOAD will then |
208 | C<goto> the newly defined subroutine. |
209 | |
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210 | Once this process completes for a given function, it is defined, so |
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211 | future calls to the subroutine will bypass the AUTOLOAD mechanism. |
212 | |
213 | =head2 Subroutine Stubs |
214 | |
215 | In order for object method lookup and/or prototype checking to operate |
216 | correctly even when methods have not yet been defined it is necessary to |
217 | "forward declare" each subroutine (as in C<sub NAME;>). See |
218 | L<perlsub/"SYNOPSIS">. Such forward declaration creates "subroutine |
219 | stubs", which are place holders with no code. |
220 | |
221 | The AutoSplit and B<AutoLoader> modules automate the creation of forward |
222 | declarations. The AutoSplit module creates an 'index' file containing |
223 | forward declarations of all the AutoSplit subroutines. When the |
224 | AutoLoader module is 'use'd it loads these declarations into its callers |
225 | package. |
226 | |
227 | Because of this mechanism it is important that B<AutoLoader> is always |
228 | C<use>d and not C<require>d. |
229 | |
230 | =head2 Using B<AutoLoader>'s AUTOLOAD Subroutine |
231 | |
232 | In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must> |
233 | explicitly import it: |
234 | |
235 | use AutoLoader 'AUTOLOAD'; |
236 | |
237 | =head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine |
238 | |
239 | Some modules, mainly extensions, provide their own AUTOLOAD subroutines. |
240 | They typically need to check for some special cases (such as constants) |
241 | and then fallback to B<AutoLoader>'s AUTOLOAD for the rest. |
242 | |
243 | Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine. |
244 | Instead, they should define their own AUTOLOAD subroutines along these |
245 | lines: |
246 | |
247 | use AutoLoader; |
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248 | use Carp; |
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249 | |
250 | sub AUTOLOAD { |
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251 | my $sub = $AUTOLOAD; |
252 | (my $constname = $sub) =~ s/.*:://; |
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253 | my $val = constant($constname, @_ ? $_[0] : 0); |
254 | if ($! != 0) { |
265f5c4a |
255 | if ($! =~ /Invalid/ || $!{EINVAL}) { |
7d4fbd98 |
256 | $AutoLoader::AUTOLOAD = $sub; |
1be0b951 |
257 | goto &AutoLoader::AUTOLOAD; |
258 | } |
259 | else { |
260 | croak "Your vendor has not defined constant $constname"; |
261 | } |
262 | } |
7d4fbd98 |
263 | *$sub = sub { $val }; # same as: eval "sub $sub { $val }"; |
264 | goto &$sub; |
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265 | } |
266 | |
267 | If any module's own AUTOLOAD subroutine has no need to fallback to the |
268 | AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit |
269 | subroutines), then that module should not use B<AutoLoader> at all. |
270 | |
271 | =head2 Package Lexicals |
272 | |
273 | Package lexicals declared with C<my> in the main block of a package |
274 | using B<AutoLoader> will not be visible to auto-loaded subroutines, due to |
275 | the fact that the given scope ends at the C<__END__> marker. A module |
276 | using such variables as package globals will not work properly under the |
277 | B<AutoLoader>. |
278 | |
279 | The C<vars> pragma (see L<perlmod/"vars">) may be used in such |
280 | situations as an alternative to explicitly qualifying all globals with |
281 | the package namespace. Variables pre-declared with this pragma will be |
282 | visible to any autoloaded routines (but will not be invisible outside |
283 | the package, unfortunately). |
284 | |
cb0cff20 |
285 | =head2 Not Using AutoLoader |
286 | |
287 | You can stop using AutoLoader by simply |
288 | |
289 | no AutoLoader; |
290 | |
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291 | =head2 B<AutoLoader> vs. B<SelfLoader> |
292 | |
293 | The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the |
294 | loading of subroutines. |
295 | |
296 | B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>. |
297 | While this avoids the use of a hierarchy of disk files and the |
298 | associated open/close for each routine loaded, B<SelfLoader> suffers a |
299 | startup speed disadvantage in the one-time parsing of the lines after |
300 | C<__DATA__>, after which routines are cached. B<SelfLoader> can also |
301 | handle multiple packages in a file. |
302 | |
303 | B<AutoLoader> only reads code as it is requested, and in many cases |
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304 | should be faster, but requires a mechanism like B<AutoSplit> be used to |
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305 | create the individual files. L<ExtUtils::MakeMaker> will invoke |
306 | B<AutoSplit> automatically if B<AutoLoader> is used in a module source |
307 | file. |
308 | |
309 | =head1 CAVEATS |
310 | |
311 | AutoLoaders prior to Perl 5.002 had a slightly different interface. Any |
312 | old modules which use B<AutoLoader> should be changed to the new calling |
313 | style. Typically this just means changing a require to a use, adding |
314 | the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader> |
315 | from C<@ISA>. |
316 | |
317 | On systems with restrictions on file name length, the file corresponding |
318 | to a subroutine may have a shorter name that the routine itself. This |
319 | can lead to conflicting file names. The I<AutoSplit> package warns of |
320 | these potential conflicts when used to split a module. |
321 | |
adaafad2 |
322 | AutoLoader may fail to find the autosplit files (or even find the wrong |
323 | ones) in cases where C<@INC> contains relative paths, B<and> the program |
324 | does C<chdir>. |
325 | |
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326 | =head1 SEE ALSO |
327 | |
328 | L<SelfLoader> - an autoloader that doesn't use external files. |
329 | |
330 | =cut |