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a0d0e21e LW |
1 | =head1 NAME |
2 | ||
cb1a09d0 | 3 | perlembed - how to embed perl in your C program |
a0d0e21e LW |
4 | |
5 | =head1 DESCRIPTION | |
6 | ||
cb1a09d0 AD |
7 | =head2 PREAMBLE |
8 | ||
9 | Do you want to: | |
10 | ||
11 | =over 5 | |
12 | ||
96dbc785 | 13 | =item B<Use C from Perl?> |
cb1a09d0 | 14 | |
4929bf7b | 15 | Read L<perlxstut>, L<perlxs>, L<h2xs>, L<perlguts>, and L<perlapi>. |
cb1a09d0 | 16 | |
54310121 | 17 | =item B<Use a Unix program from Perl?> |
cb1a09d0 | 18 | |
5f05dabc | 19 | Read about back-quotes and about C<system> and C<exec> in L<perlfunc>. |
cb1a09d0 | 20 | |
96dbc785 | 21 | =item B<Use Perl from Perl?> |
cb1a09d0 | 22 | |
5e6bcc01 | 23 | Read about L<perlfunc/do> and L<perlfunc/eval> and L<perlfunc/require> |
e010571f | 24 | and L<perlfunc/use>. |
cb1a09d0 | 25 | |
96dbc785 | 26 | =item B<Use C from C?> |
cb1a09d0 AD |
27 | |
28 | Rethink your design. | |
29 | ||
96dbc785 | 30 | =item B<Use Perl from C?> |
cb1a09d0 AD |
31 | |
32 | Read on... | |
33 | ||
34 | =back | |
35 | ||
36 | =head2 ROADMAP | |
37 | ||
707102d0 GS |
38 | =over 5 |
39 | ||
551e1d92 | 40 | =item * |
cb1a09d0 | 41 | |
551e1d92 | 42 | Compiling your C program |
cb1a09d0 | 43 | |
551e1d92 | 44 | =item * |
cb1a09d0 | 45 | |
551e1d92 | 46 | Adding a Perl interpreter to your C program |
cb1a09d0 | 47 | |
551e1d92 | 48 | =item * |
cb1a09d0 | 49 | |
551e1d92 | 50 | Calling a Perl subroutine from your C program |
cb1a09d0 | 51 | |
551e1d92 | 52 | =item * |
cb1a09d0 | 53 | |
551e1d92 | 54 | Evaluating a Perl statement from your C program |
a6006777 | 55 | |
551e1d92 | 56 | =item * |
8ebc5c01 | 57 | |
551e1d92 RB |
58 | Performing Perl pattern matches and substitutions from your C program |
59 | ||
60 | =item * | |
61 | ||
62 | Fiddling with the Perl stack from your C program | |
63 | ||
64 | =item * | |
65 | ||
66 | Maintaining a persistent interpreter | |
67 | ||
68 | =item * | |
69 | ||
70 | Maintaining multiple interpreter instances | |
71 | ||
72 | =item * | |
73 | ||
74 | Using Perl modules, which themselves use C libraries, from your C program | |
75 | ||
76 | =item * | |
77 | ||
78 | Embedding Perl under Win32 | |
96dbc785 | 79 | |
5e6bcc01 | 80 | =back |
cb1a09d0 AD |
81 | |
82 | =head2 Compiling your C program | |
83 | ||
8a7dc658 JO |
84 | If you have trouble compiling the scripts in this documentation, |
85 | you're not alone. The cardinal rule: COMPILE THE PROGRAMS IN EXACTLY | |
86 | THE SAME WAY THAT YOUR PERL WAS COMPILED. (Sorry for yelling.) | |
cb1a09d0 | 87 | |
8a7dc658 | 88 | Also, every C program that uses Perl must link in the I<perl library>. |
cb1a09d0 AD |
89 | What's that, you ask? Perl is itself written in C; the perl library |
90 | is the collection of compiled C programs that were used to create your | |
91 | perl executable (I</usr/bin/perl> or equivalent). (Corollary: you | |
92 | can't use Perl from your C program unless Perl has been compiled on | |
93 | your machine, or installed properly--that's why you shouldn't blithely | |
94 | copy Perl executables from machine to machine without also copying the | |
95 | I<lib> directory.) | |
96 | ||
8a7dc658 JO |
97 | When you use Perl from C, your C program will--usually--allocate, |
98 | "run", and deallocate a I<PerlInterpreter> object, which is defined by | |
99 | the perl library. | |
cb1a09d0 AD |
100 | |
101 | If your copy of Perl is recent enough to contain this documentation | |
a6006777 | 102 | (version 5.002 or later), then the perl library (and I<EXTERN.h> and |
8a7dc658 JO |
103 | I<perl.h>, which you'll also need) will reside in a directory |
104 | that looks like this: | |
cb1a09d0 AD |
105 | |
106 | /usr/local/lib/perl5/your_architecture_here/CORE | |
107 | ||
108 | or perhaps just | |
109 | ||
110 | /usr/local/lib/perl5/CORE | |
111 | ||
112 | or maybe something like | |
113 | ||
114 | /usr/opt/perl5/CORE | |
115 | ||
116 | Execute this statement for a hint about where to find CORE: | |
117 | ||
96dbc785 | 118 | perl -MConfig -e 'print $Config{archlib}' |
cb1a09d0 | 119 | |
54310121 | 120 | Here's how you'd compile the example in the next section, |
e010571f | 121 | L<Adding a Perl interpreter to your C program>, on my Linux box: |
cb1a09d0 | 122 | |
54310121 | 123 | % gcc -O2 -Dbool=char -DHAS_BOOL -I/usr/local/include |
8a7dc658 | 124 | -I/usr/local/lib/perl5/i586-linux/5.003/CORE |
54310121 | 125 | -L/usr/local/lib/perl5/i586-linux/5.003/CORE |
8a7dc658 | 126 | -o interp interp.c -lperl -lm |
cb1a09d0 | 127 | |
5e6bcc01 | 128 | (That's all one line.) On my DEC Alpha running old 5.003_05, the |
e010571f | 129 | incantation is a bit different: |
8a7dc658 | 130 | |
54310121 | 131 | % cc -O2 -Olimit 2900 -DSTANDARD_C -I/usr/local/include |
132 | -I/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE | |
133 | -L/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE -L/usr/local/lib | |
8a7dc658 JO |
134 | -D__LANGUAGE_C__ -D_NO_PROTO -o interp interp.c -lperl -lm |
135 | ||
136 | How can you figure out what to add? Assuming your Perl is post-5.001, | |
137 | execute a C<perl -V> command and pay special attention to the "cc" and | |
54310121 | 138 | "ccflags" information. |
8a7dc658 | 139 | |
54310121 | 140 | You'll have to choose the appropriate compiler (I<cc>, I<gcc>, et al.) for |
8a7dc658 | 141 | your machine: C<perl -MConfig -e 'print $Config{cc}'> will tell you what |
54310121 | 142 | to use. |
8a7dc658 JO |
143 | |
144 | You'll also have to choose the appropriate library directory | |
145 | (I</usr/local/lib/...>) for your machine. If your compiler complains | |
146 | that certain functions are undefined, or that it can't locate | |
147 | I<-lperl>, then you need to change the path following the C<-L>. If it | |
148 | complains that it can't find I<EXTERN.h> and I<perl.h>, you need to | |
149 | change the path following the C<-I>. | |
cb1a09d0 AD |
150 | |
151 | You may have to add extra libraries as well. Which ones? | |
96dbc785 | 152 | Perhaps those printed by |
153 | ||
154 | perl -MConfig -e 'print $Config{libs}' | |
155 | ||
54310121 | 156 | Provided your perl binary was properly configured and installed the |
8a7dc658 JO |
157 | B<ExtUtils::Embed> module will determine all of this information for |
158 | you: | |
96dbc785 | 159 | |
160 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` | |
161 | ||
8a7dc658 JO |
162 | If the B<ExtUtils::Embed> module isn't part of your Perl distribution, |
163 | you can retrieve it from | |
f224927c JH |
164 | http://www.perl.com/perl/CPAN/modules/by-module/ExtUtils/ |
165 | (If this documentation came from your Perl distribution, then you're | |
8a7dc658 | 166 | running 5.004 or better and you already have it.) |
96dbc785 | 167 | |
8a7dc658 | 168 | The B<ExtUtils::Embed> kit on CPAN also contains all source code for |
54310121 | 169 | the examples in this document, tests, additional examples and other |
8a7dc658 | 170 | information you may find useful. |
cb1a09d0 AD |
171 | |
172 | =head2 Adding a Perl interpreter to your C program | |
173 | ||
174 | In a sense, perl (the C program) is a good example of embedding Perl | |
175 | (the language), so I'll demonstrate embedding with I<miniperlmain.c>, | |
353c6505 | 176 | included in the source distribution. Here's a bastardized, non-portable |
8a7dc658 | 177 | version of I<miniperlmain.c> containing the essentials of embedding: |
cb1a09d0 | 178 | |
5e6bcc01 GID |
179 | #include <EXTERN.h> /* from the Perl distribution */ |
180 | #include <perl.h> /* from the Perl distribution */ | |
96dbc785 | 181 | |
5e6bcc01 | 182 | static PerlInterpreter *my_perl; /*** The Perl interpreter ***/ |
96dbc785 | 183 | |
5e6bcc01 GID |
184 | int main(int argc, char **argv, char **env) |
185 | { | |
1ccffcf5 | 186 | PERL_SYS_INIT3(&argc,&argv,&env); |
cb1a09d0 AD |
187 | my_perl = perl_alloc(); |
188 | perl_construct(my_perl); | |
d95b23b2 | 189 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
96dbc785 | 190 | perl_parse(my_perl, NULL, argc, argv, (char **)NULL); |
cb1a09d0 AD |
191 | perl_run(my_perl); |
192 | perl_destruct(my_perl); | |
193 | perl_free(my_perl); | |
1ccffcf5 | 194 | PERL_SYS_TERM(); |
5e6bcc01 | 195 | } |
cb1a09d0 | 196 | |
8a7dc658 JO |
197 | Notice that we don't use the C<env> pointer. Normally handed to |
198 | C<perl_parse> as its final argument, C<env> here is replaced by | |
eb533572 DM |
199 | C<NULL>, which means that the current environment will be used. |
200 | ||
201 | The macros PERL_SYS_INIT3() and PERL_SYS_TERM() provide system-specific | |
202 | tune up of the C runtime environment necessary to run Perl interpreters; | |
203 | they should only be called once regardless of how many interpreters you | |
204 | create or destroy. Call PERL_SYS_INIT3() before you create your first | |
205 | interpreter, and PERL_SYS_TERM() after you free your last interpreter. | |
206 | ||
207 | Since PERL_SYS_INIT3() may change C<env>, it may be more appropriate to | |
208 | provide C<env> as an argument to perl_parse(). | |
96dbc785 | 209 | |
31f6f5aa NT |
210 | Also notice that no matter what arguments you pass to perl_parse(), |
211 | PERL_SYS_INIT3() must be invoked on the C main() argc, argv and env and | |
212 | only once. | |
213 | ||
cb1a09d0 AD |
214 | Now compile this program (I'll call it I<interp.c>) into an executable: |
215 | ||
96dbc785 | 216 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
cb1a09d0 AD |
217 | |
218 | After a successful compilation, you'll be able to use I<interp> just | |
219 | like perl itself: | |
220 | ||
221 | % interp | |
222 | print "Pretty Good Perl \n"; | |
223 | print "10890 - 9801 is ", 10890 - 9801; | |
224 | <CTRL-D> | |
225 | Pretty Good Perl | |
226 | 10890 - 9801 is 1089 | |
227 | ||
228 | or | |
229 | ||
230 | % interp -e 'printf("%x", 3735928559)' | |
231 | deadbeef | |
232 | ||
233 | You can also read and execute Perl statements from a file while in the | |
234 | midst of your C program, by placing the filename in I<argv[1]> before | |
e010571f | 235 | calling I<perl_run>. |
cb1a09d0 AD |
236 | |
237 | =head2 Calling a Perl subroutine from your C program | |
238 | ||
4929bf7b | 239 | To call individual Perl subroutines, you can use any of the B<call_*> |
7b8d334a | 240 | functions documented in L<perlcall>. |
4929bf7b | 241 | In this example we'll use C<call_argv>. |
cb1a09d0 AD |
242 | |
243 | That's shown below, in a program I'll call I<showtime.c>. | |
244 | ||
cb1a09d0 | 245 | #include <EXTERN.h> |
96dbc785 | 246 | #include <perl.h> |
247 | ||
248 | static PerlInterpreter *my_perl; | |
249 | ||
c07a80fd | 250 | int main(int argc, char **argv, char **env) |
cb1a09d0 | 251 | { |
8ebc5c01 | 252 | char *args[] = { NULL }; |
1ccffcf5 | 253 | PERL_SYS_INIT3(&argc,&argv,&env); |
cb1a09d0 AD |
254 | my_perl = perl_alloc(); |
255 | perl_construct(my_perl); | |
96dbc785 | 256 | |
257 | perl_parse(my_perl, NULL, argc, argv, NULL); | |
d95b23b2 | 258 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
96dbc785 | 259 | |
8ebc5c01 | 260 | /*** skipping perl_run() ***/ |
261 | ||
4929bf7b | 262 | call_argv("showtime", G_DISCARD | G_NOARGS, args); |
8ebc5c01 | 263 | |
cb1a09d0 AD |
264 | perl_destruct(my_perl); |
265 | perl_free(my_perl); | |
1ccffcf5 | 266 | PERL_SYS_TERM(); |
cb1a09d0 AD |
267 | } |
268 | ||
269 | where I<showtime> is a Perl subroutine that takes no arguments (that's the | |
96dbc785 | 270 | I<G_NOARGS>) and for which I'll ignore the return value (that's the |
cb1a09d0 AD |
271 | I<G_DISCARD>). Those flags, and others, are discussed in L<perlcall>. |
272 | ||
273 | I'll define the I<showtime> subroutine in a file called I<showtime.pl>: | |
274 | ||
5e6bcc01 | 275 | print "I shan't be printed."; |
96dbc785 | 276 | |
5e6bcc01 GID |
277 | sub showtime { |
278 | print time; | |
279 | } | |
cb1a09d0 | 280 | |
5e6bcc01 | 281 | Simple enough. Now compile and run: |
96dbc785 | 282 | |
5e6bcc01 GID |
283 | % cc -o showtime showtime.c \ |
284 | `perl -MExtUtils::Embed -e ccopts -e ldopts` | |
285 | % showtime showtime.pl | |
286 | 818284590 | |
cb1a09d0 AD |
287 | |
288 | yielding the number of seconds that elapsed between January 1, 1970 | |
8a7dc658 | 289 | (the beginning of the Unix epoch), and the moment I began writing this |
cb1a09d0 AD |
290 | sentence. |
291 | ||
5e6bcc01 | 292 | In this particular case we don't have to call I<perl_run>, as we set |
d95b23b2 AB |
293 | the PL_exit_flag PERL_EXIT_DESTRUCT_END which executes END blocks in |
294 | perl_destruct. | |
8ebc5c01 | 295 | |
8a7dc658 JO |
296 | If you want to pass arguments to the Perl subroutine, you can add |
297 | strings to the C<NULL>-terminated C<args> list passed to | |
4929bf7b | 298 | I<call_argv>. For other data types, or to examine return values, |
13a2d996 SP |
299 | you'll need to manipulate the Perl stack. That's demonstrated in |
300 | L<Fiddling with the Perl stack from your C program>. | |
cb1a09d0 AD |
301 | |
302 | =head2 Evaluating a Perl statement from your C program | |
303 | ||
137443ea | 304 | Perl provides two API functions to evaluate pieces of Perl code. |
4929bf7b | 305 | These are L<perlapi/eval_sv> and L<perlapi/eval_pv>. |
137443ea | 306 | |
307 | Arguably, these are the only routines you'll ever need to execute | |
e010571f GS |
308 | snippets of Perl code from within your C program. Your code can be as |
309 | long as you wish; it can contain multiple statements; it can employ | |
310 | L<perlfunc/use>, L<perlfunc/require>, and L<perlfunc/do> to | |
311 | include external Perl files. | |
cb1a09d0 | 312 | |
4929bf7b | 313 | I<eval_pv> lets us evaluate individual Perl strings, and then |
96dbc785 | 314 | extract variables for coercion into C types. The following program, |
cb1a09d0 AD |
315 | I<string.c>, executes three Perl strings, extracting an C<int> from |
316 | the first, a C<float> from the second, and a C<char *> from the third. | |
317 | ||
5e6bcc01 GID |
318 | #include <EXTERN.h> |
319 | #include <perl.h> | |
c47ff5f1 | 320 | |
5e6bcc01 | 321 | static PerlInterpreter *my_perl; |
c47ff5f1 | 322 | |
5e6bcc01 GID |
323 | main (int argc, char **argv, char **env) |
324 | { | |
325 | char *embedding[] = { "", "-e", "0" }; | |
c47ff5f1 | 326 | |
5e6bcc01 GID |
327 | PERL_SYS_INIT3(&argc,&argv,&env); |
328 | my_perl = perl_alloc(); | |
329 | perl_construct( my_perl ); | |
c47ff5f1 | 330 | |
5e6bcc01 GID |
331 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
332 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; | |
333 | perl_run(my_perl); | |
c47ff5f1 | 334 | |
5e6bcc01 GID |
335 | /** Treat $a as an integer **/ |
336 | eval_pv("$a = 3; $a **= 2", TRUE); | |
337 | printf("a = %d\n", SvIV(get_sv("a", 0))); | |
c47ff5f1 | 338 | |
5e6bcc01 GID |
339 | /** Treat $a as a float **/ |
340 | eval_pv("$a = 3.14; $a **= 2", TRUE); | |
341 | printf("a = %f\n", SvNV(get_sv("a", 0))); | |
c47ff5f1 | 342 | |
5e6bcc01 GID |
343 | /** Treat $a as a string **/ |
344 | eval_pv( | |
345 | "$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE); | |
346 | printf("a = %s\n", SvPV_nolen(get_sv("a", 0))); | |
c47ff5f1 | 347 | |
5e6bcc01 GID |
348 | perl_destruct(my_perl); |
349 | perl_free(my_perl); | |
350 | PERL_SYS_TERM(); | |
351 | } | |
cb1a09d0 | 352 | |
5e6bcc01 GID |
353 | All of those strange functions with I<sv> in their names help convert Perl |
354 | scalars to C types. They're described in L<perlguts> and L<perlapi>. | |
cb1a09d0 AD |
355 | |
356 | If you compile and run I<string.c>, you'll see the results of using | |
357 | I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and | |
358 | I<SvPV()> to create a string: | |
359 | ||
360 | a = 9 | |
361 | a = 9.859600 | |
362 | a = Just Another Perl Hacker | |
363 | ||
8f183262 | 364 | In the example above, we've created a global variable to temporarily |
353c6505 | 365 | store the computed value of our eval'ed expression. It is also |
8f183262 | 366 | possible and in most cases a better strategy to fetch the return value |
4929bf7b | 367 | from I<eval_pv()> instead. Example: |
8f183262 | 368 | |
8f183262 | 369 | ... |
4929bf7b | 370 | SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); |
1c5b513e | 371 | printf("%s\n", SvPV_nolen(val)); |
8f183262 DM |
372 | ... |
373 | ||
374 | This way, we avoid namespace pollution by not creating global | |
375 | variables and we've simplified our code as well. | |
cb1a09d0 AD |
376 | |
377 | =head2 Performing Perl pattern matches and substitutions from your C program | |
378 | ||
4929bf7b | 379 | The I<eval_sv()> function lets us evaluate strings of Perl code, so we can |
cb1a09d0 AD |
380 | define some functions that use it to "specialize" in matches and |
381 | substitutions: I<match()>, I<substitute()>, and I<matches()>. | |
382 | ||
e010571f | 383 | I32 match(SV *string, char *pattern); |
cb1a09d0 | 384 | |
8a7dc658 JO |
385 | Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which |
386 | in your C program might appear as "/\\b\\w*\\b/"), match() | |
cb1a09d0 AD |
387 | returns 1 if the string matches the pattern and 0 otherwise. |
388 | ||
1f05cdcd | 389 | int substitute(SV **string, char *pattern); |
cb1a09d0 | 390 | |
1f05cdcd | 391 | Given a pointer to an C<SV> and an C<=~> operation (e.g., |
8a7dc658 | 392 | C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string |
5e6bcc01 GID |
393 | within the C<SV> as according to the operation, returning the number of |
394 | substitutions made. | |
cb1a09d0 | 395 | |
c70927a6 | 396 | SSize_t matches(SV *string, char *pattern, AV **matches); |
cb1a09d0 | 397 | |
1f05cdcd | 398 | Given an C<SV>, a pattern, and a pointer to an empty C<AV>, |
90fdbbb7 | 399 | matches() evaluates C<$string =~ $pattern> in a list context, and |
5e6bcc01 GID |
400 | fills in I<matches> with the array elements, returning the number of matches |
401 | found. | |
cb1a09d0 | 402 | |
96dbc785 | 403 | Here's a sample program, I<match.c>, that uses all three (long lines have |
404 | been wrapped here): | |
cb1a09d0 | 405 | |
1f05cdcd DM |
406 | #include <EXTERN.h> |
407 | #include <perl.h> | |
c47ff5f1 | 408 | |
7fef744d BD |
409 | static PerlInterpreter *my_perl; |
410 | ||
4929bf7b | 411 | /** my_eval_sv(code, error_check) |
5e6bcc01 GID |
412 | ** kinda like eval_sv(), |
413 | ** but we pop the return value off the stack | |
1f05cdcd | 414 | **/ |
4929bf7b | 415 | SV* my_eval_sv(SV *sv, I32 croak_on_error) |
1f05cdcd DM |
416 | { |
417 | dSP; | |
418 | SV* retval; | |
1c5b513e | 419 | |
c47ff5f1 | 420 | |
924508f0 | 421 | PUSHMARK(SP); |
4929bf7b | 422 | eval_sv(sv, G_SCALAR); |
c47ff5f1 | 423 | |
1f05cdcd DM |
424 | SPAGAIN; |
425 | retval = POPs; | |
426 | PUTBACK; | |
c47ff5f1 | 427 | |
9cde0e7f | 428 | if (croak_on_error && SvTRUE(ERRSV)) |
1c5b513e | 429 | croak(SvPVx_nolen(ERRSV)); |
c47ff5f1 | 430 | |
1f05cdcd DM |
431 | return retval; |
432 | } | |
c47ff5f1 | 433 | |
1f05cdcd DM |
434 | /** match(string, pattern) |
435 | ** | |
436 | ** Used for matches in a scalar context. | |
437 | ** | |
438 | ** Returns 1 if the match was successful; 0 otherwise. | |
439 | **/ | |
c47ff5f1 | 440 | |
1f05cdcd DM |
441 | I32 match(SV *string, char *pattern) |
442 | { | |
561b68a9 | 443 | SV *command = newSV(0), *retval; |
c47ff5f1 | 444 | |
1f05cdcd | 445 | sv_setpvf(command, "my $string = '%s'; $string =~ %s", |
1c5b513e | 446 | SvPV_nolen(string), pattern); |
c47ff5f1 | 447 | |
4929bf7b | 448 | retval = my_eval_sv(command, TRUE); |
1f05cdcd | 449 | SvREFCNT_dec(command); |
c47ff5f1 | 450 | |
1f05cdcd DM |
451 | return SvIV(retval); |
452 | } | |
c47ff5f1 | 453 | |
1f05cdcd DM |
454 | /** substitute(string, pattern) |
455 | ** | |
5e6bcc01 GID |
456 | ** Used for =~ operations that |
457 | ** modify their left-hand side (s/// and tr///) | |
1f05cdcd DM |
458 | ** |
459 | ** Returns the number of successful matches, and | |
460 | ** modifies the input string if there were any. | |
461 | **/ | |
c47ff5f1 | 462 | |
1f05cdcd DM |
463 | I32 substitute(SV **string, char *pattern) |
464 | { | |
561b68a9 | 465 | SV *command = newSV(0), *retval; |
c47ff5f1 | 466 | |
1f05cdcd | 467 | sv_setpvf(command, "$string = '%s'; ($string =~ %s)", |
1c5b513e | 468 | SvPV_nolen(*string), pattern); |
c47ff5f1 | 469 | |
4929bf7b | 470 | retval = my_eval_sv(command, TRUE); |
1f05cdcd | 471 | SvREFCNT_dec(command); |
c47ff5f1 | 472 | |
64ace3f8 | 473 | *string = get_sv("string", 0); |
1f05cdcd DM |
474 | return SvIV(retval); |
475 | } | |
c47ff5f1 | 476 | |
1f05cdcd DM |
477 | /** matches(string, pattern, matches) |
478 | ** | |
90fdbbb7 | 479 | ** Used for matches in a list context. |
1f05cdcd DM |
480 | ** |
481 | ** Returns the number of matches, | |
482 | ** and fills in **matches with the matching substrings | |
483 | **/ | |
c47ff5f1 | 484 | |
c70927a6 | 485 | SSize_t matches(SV *string, char *pattern, AV **match_list) |
1f05cdcd | 486 | { |
561b68a9 | 487 | SV *command = newSV(0); |
c70927a6 | 488 | SSize_t num_matches; |
c47ff5f1 | 489 | |
1f05cdcd | 490 | sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)", |
1c5b513e | 491 | SvPV_nolen(string), pattern); |
c47ff5f1 | 492 | |
4929bf7b | 493 | my_eval_sv(command, TRUE); |
1f05cdcd | 494 | SvREFCNT_dec(command); |
c47ff5f1 | 495 | |
cbfd0a87 | 496 | *match_list = get_av("array", 0); |
23aa77bc | 497 | num_matches = av_top_index(*match_list) + 1; |
c47ff5f1 | 498 | |
cb1a09d0 | 499 | return num_matches; |
1f05cdcd | 500 | } |
c47ff5f1 | 501 | |
1f05cdcd DM |
502 | main (int argc, char **argv, char **env) |
503 | { | |
a6006777 | 504 | char *embedding[] = { "", "-e", "0" }; |
1f05cdcd DM |
505 | AV *match_list; |
506 | I32 num_matches, i; | |
7fef744d | 507 | SV *text; |
c47ff5f1 | 508 | |
1ccffcf5 | 509 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d | 510 | my_perl = perl_alloc(); |
1f05cdcd | 511 | perl_construct(my_perl); |
96dbc785 | 512 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
d95b23b2 | 513 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
c47ff5f1 | 514 | |
561b68a9 | 515 | text = newSV(0); |
d3f3bf9f RGS |
516 | sv_setpv(text, "When he is at a convenience store and the " |
517 | "bill comes to some amount like 76 cents, Maynard is " | |
518 | "aware that there is something he *should* do, something " | |
519 | "that will enable him to get back a quarter, but he has " | |
520 | "no idea *what*. He fumbles through his red squeezey " | |
521 | "changepurse and gives the boy three extra pennies with " | |
522 | "his dollar, hoping that he might luck into the correct " | |
523 | "amount. The boy gives him back two of his own pennies " | |
524 | "and then the big shiny quarter that is his prize. " | |
525 | "-RICHH"); | |
c47ff5f1 | 526 | |
96dbc785 | 527 | if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/ |
1f05cdcd | 528 | printf("match: Text contains the word 'quarter'.\n\n"); |
96dbc785 | 529 | else |
1f05cdcd | 530 | printf("match: Text doesn't contain the word 'quarter'.\n\n"); |
c47ff5f1 | 531 | |
96dbc785 | 532 | if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/ |
1f05cdcd | 533 | printf("match: Text contains the word 'eighth'.\n\n"); |
96dbc785 | 534 | else |
1f05cdcd | 535 | printf("match: Text doesn't contain the word 'eighth'.\n\n"); |
c47ff5f1 | 536 | |
96dbc785 | 537 | /** Match all occurrences of /wi../ **/ |
538 | num_matches = matches(text, "m/(wi..)/g", &match_list); | |
539 | printf("matches: m/(wi..)/g found %d matches...\n", num_matches); | |
c47ff5f1 | 540 | |
96dbc785 | 541 | for (i = 0; i < num_matches; i++) |
5e6bcc01 GID |
542 | printf("match: %s\n", |
543 | SvPV_nolen(*av_fetch(match_list, i, FALSE))); | |
cb1a09d0 | 544 | printf("\n"); |
c47ff5f1 | 545 | |
96dbc785 | 546 | /** Remove all vowels from text **/ |
547 | num_matches = substitute(&text, "s/[aeiou]//gi"); | |
cb1a09d0 | 548 | if (num_matches) { |
c70927a6 FC |
549 | printf("substitute: s/[aeiou]//gi...%lu substitutions made.\n", |
550 | (unsigned long)num_matches); | |
1c5b513e | 551 | printf("Now text is: %s\n\n", SvPV_nolen(text)); |
cb1a09d0 | 552 | } |
c47ff5f1 | 553 | |
96dbc785 | 554 | /** Attempt a substitution **/ |
555 | if (!substitute(&text, "s/Perl/C/")) { | |
1f05cdcd | 556 | printf("substitute: s/Perl/C...No substitution made.\n\n"); |
cb1a09d0 | 557 | } |
c47ff5f1 | 558 | |
1f05cdcd | 559 | SvREFCNT_dec(text); |
9cde0e7f | 560 | PL_perl_destruct_level = 1; |
cb1a09d0 AD |
561 | perl_destruct(my_perl); |
562 | perl_free(my_perl); | |
1ccffcf5 | 563 | PERL_SYS_TERM(); |
1f05cdcd | 564 | } |
cb1a09d0 | 565 | |
96dbc785 | 566 | which produces the output (again, long lines have been wrapped here) |
cb1a09d0 | 567 | |
5e6bcc01 | 568 | match: Text contains the word 'quarter'. |
96dbc785 | 569 | |
5e6bcc01 | 570 | match: Text doesn't contain the word 'eighth'. |
96dbc785 | 571 | |
5e6bcc01 GID |
572 | matches: m/(wi..)/g found 2 matches... |
573 | match: will | |
574 | match: with | |
96dbc785 | 575 | |
5e6bcc01 GID |
576 | substitute: s/[aeiou]//gi...139 substitutions made. |
577 | Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts, | |
578 | Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt | |
579 | bck qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd | |
580 | gvs th by thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct | |
581 | mnt. Th by gvs hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s | |
582 | hs prz. -RCHH | |
96dbc785 | 583 | |
5e6bcc01 | 584 | substitute: s/Perl/C...No substitution made. |
96dbc785 | 585 | |
cb1a09d0 AD |
586 | =head2 Fiddling with the Perl stack from your C program |
587 | ||
588 | When trying to explain stacks, most computer science textbooks mumble | |
589 | something about spring-loaded columns of cafeteria plates: the last | |
590 | thing you pushed on the stack is the first thing you pop off. That'll | |
591 | do for our purposes: your C program will push some arguments onto "the Perl | |
592 | stack", shut its eyes while some magic happens, and then pop the | |
593 | results--the return value of your Perl subroutine--off the stack. | |
96dbc785 | 594 | |
cb1a09d0 AD |
595 | First you'll need to know how to convert between C types and Perl |
596 | types, with newSViv() and sv_setnv() and newAV() and all their | |
4929bf7b | 597 | friends. They're described in L<perlguts> and L<perlapi>. |
cb1a09d0 AD |
598 | |
599 | Then you'll need to know how to manipulate the Perl stack. That's | |
600 | described in L<perlcall>. | |
601 | ||
96dbc785 | 602 | Once you've understood those, embedding Perl in C is easy. |
cb1a09d0 | 603 | |
54310121 | 604 | Because C has no builtin function for integer exponentiation, let's |
cb1a09d0 | 605 | make Perl's ** operator available to it (this is less useful than it |
5f05dabc | 606 | sounds, because Perl implements ** with C's I<pow()> function). First |
cb1a09d0 AD |
607 | I'll create a stub exponentiation function in I<power.pl>: |
608 | ||
609 | sub expo { | |
610 | my ($a, $b) = @_; | |
611 | return $a ** $b; | |
612 | } | |
613 | ||
614 | Now I'll create a C program, I<power.c>, with a function | |
615 | I<PerlPower()> that contains all the perlguts necessary to push the | |
616 | two arguments into I<expo()> and to pop the return value out. Take a | |
617 | deep breath... | |
618 | ||
5e6bcc01 GID |
619 | #include <EXTERN.h> |
620 | #include <perl.h> | |
96dbc785 | 621 | |
5e6bcc01 | 622 | static PerlInterpreter *my_perl; |
96dbc785 | 623 | |
5e6bcc01 GID |
624 | static void |
625 | PerlPower(int a, int b) | |
626 | { | |
627 | dSP; /* initialize stack pointer */ | |
628 | ENTER; /* everything created after here */ | |
629 | SAVETMPS; /* ...is a temporary variable. */ | |
630 | PUSHMARK(SP); /* remember the stack pointer */ | |
631 | XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */ | |
632 | XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */ | |
633 | PUTBACK; /* make local stack pointer global */ | |
634 | call_pv("expo", G_SCALAR); /* call the function */ | |
635 | SPAGAIN; /* refresh stack pointer */ | |
636 | /* pop the return value from stack */ | |
637 | printf ("%d to the %dth power is %d.\n", a, b, POPi); | |
638 | PUTBACK; | |
639 | FREETMPS; /* free that return value */ | |
640 | LEAVE; /* ...and the XPUSHed "mortal" args.*/ | |
641 | } | |
96dbc785 | 642 | |
5e6bcc01 GID |
643 | int main (int argc, char **argv, char **env) |
644 | { | |
645 | char *my_argv[] = { "", "power.pl" }; | |
96dbc785 | 646 | |
5e6bcc01 GID |
647 | PERL_SYS_INIT3(&argc,&argv,&env); |
648 | my_perl = perl_alloc(); | |
649 | perl_construct( my_perl ); | |
96dbc785 | 650 | |
5e6bcc01 GID |
651 | perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL); |
652 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; | |
653 | perl_run(my_perl); | |
96dbc785 | 654 | |
5e6bcc01 | 655 | PerlPower(3, 4); /*** Compute 3 ** 4 ***/ |
96dbc785 | 656 | |
5e6bcc01 GID |
657 | perl_destruct(my_perl); |
658 | perl_free(my_perl); | |
659 | PERL_SYS_TERM(); | |
660 | } | |
96dbc785 | 661 | |
cb1a09d0 AD |
662 | |
663 | ||
664 | Compile and run: | |
665 | ||
96dbc785 | 666 | % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
667 | ||
668 | % power | |
cb1a09d0 AD |
669 | 3 to the 4th power is 81. |
670 | ||
a6006777 | 671 | =head2 Maintaining a persistent interpreter |
672 | ||
8a7dc658 JO |
673 | When developing interactive and/or potentially long-running |
674 | applications, it's a good idea to maintain a persistent interpreter | |
675 | rather than allocating and constructing a new interpreter multiple | |
676 | times. The major reason is speed: since Perl will only be loaded into | |
54310121 | 677 | memory once. |
8a7dc658 JO |
678 | |
679 | However, you have to be more cautious with namespace and variable | |
680 | scoping when using a persistent interpreter. In previous examples | |
681 | we've been using global variables in the default package C<main>. We | |
682 | knew exactly what code would be run, and assumed we could avoid | |
683 | variable collisions and outrageous symbol table growth. | |
684 | ||
685 | Let's say your application is a server that will occasionally run Perl | |
686 | code from some arbitrary file. Your server has no way of knowing what | |
687 | code it's going to run. Very dangerous. | |
688 | ||
689 | If the file is pulled in by C<perl_parse()>, compiled into a newly | |
690 | constructed interpreter, and subsequently cleaned out with | |
691 | C<perl_destruct()> afterwards, you're shielded from most namespace | |
692 | troubles. | |
693 | ||
694 | One way to avoid namespace collisions in this scenario is to translate | |
695 | the filename into a guaranteed-unique package name, and then compile | |
e010571f | 696 | the code into that package using L<perlfunc/eval>. In the example |
8a7dc658 JO |
697 | below, each file will only be compiled once. Or, the application |
698 | might choose to clean out the symbol table associated with the file | |
4929bf7b | 699 | after it's no longer needed. Using L<perlapi/call_argv>, We'll |
8a7dc658 JO |
700 | call the subroutine C<Embed::Persistent::eval_file> which lives in the |
701 | file C<persistent.pl> and pass the filename and boolean cleanup/cache | |
a6006777 | 702 | flag as arguments. |
703 | ||
8a7dc658 JO |
704 | Note that the process will continue to grow for each file that it |
705 | uses. In addition, there might be C<AUTOLOAD>ed subroutines and other | |
706 | conditions that cause Perl's symbol table to grow. You might want to | |
707 | add some logic that keeps track of the process size, or restarts | |
708 | itself after a certain number of requests, to ensure that memory | |
709 | consumption is minimized. You'll also want to scope your variables | |
e010571f | 710 | with L<perlfunc/my> whenever possible. |
a6006777 | 711 | |
54310121 | 712 | |
a6006777 | 713 | package Embed::Persistent; |
714 | #persistent.pl | |
54310121 | 715 | |
a6006777 | 716 | use strict; |
77ca0c92 | 717 | our %Cache; |
1ee082b7 | 718 | use Symbol qw(delete_package); |
54310121 | 719 | |
a6006777 | 720 | sub valid_package_name { |
721 | my($string) = @_; | |
722 | $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg; | |
723 | # second pass only for words starting with a digit | |
724 | $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg; | |
54310121 | 725 | |
a6006777 | 726 | # Dress it up as a real package name |
727 | $string =~ s|/|::|g; | |
728 | return "Embed" . $string; | |
729 | } | |
54310121 | 730 | |
a6006777 | 731 | sub eval_file { |
732 | my($filename, $delete) = @_; | |
733 | my $package = valid_package_name($filename); | |
734 | my $mtime = -M $filename; | |
735 | if(defined $Cache{$package}{mtime} | |
736 | && | |
54310121 | 737 | $Cache{$package}{mtime} <= $mtime) |
a6006777 | 738 | { |
54310121 | 739 | # we have compiled this subroutine already, |
8ebc5c01 | 740 | # it has not been updated on disk, nothing left to do |
741 | print STDERR "already compiled $package->handler\n"; | |
a6006777 | 742 | } |
743 | else { | |
8ebc5c01 | 744 | local *FH; |
745 | open FH, $filename or die "open '$filename' $!"; | |
746 | local($/) = undef; | |
747 | my $sub = <FH>; | |
748 | close FH; | |
54310121 | 749 | |
8ebc5c01 | 750 | #wrap the code into a subroutine inside our unique package |
751 | my $eval = qq{package $package; sub handler { $sub; }}; | |
752 | { | |
753 | # hide our variables within this block | |
754 | my($filename,$mtime,$package,$sub); | |
755 | eval $eval; | |
756 | } | |
757 | die $@ if $@; | |
54310121 | 758 | |
8ebc5c01 | 759 | #cache it unless we're cleaning out each time |
760 | $Cache{$package}{mtime} = $mtime unless $delete; | |
a6006777 | 761 | } |
54310121 | 762 | |
a6006777 | 763 | eval {$package->handler;}; |
764 | die $@ if $@; | |
54310121 | 765 | |
a6006777 | 766 | delete_package($package) if $delete; |
54310121 | 767 | |
a6006777 | 768 | #take a look if you want |
769 | #print Devel::Symdump->rnew($package)->as_string, $/; | |
770 | } | |
54310121 | 771 | |
a6006777 | 772 | 1; |
54310121 | 773 | |
a6006777 | 774 | __END__ |
775 | ||
776 | /* persistent.c */ | |
54310121 | 777 | #include <EXTERN.h> |
778 | #include <perl.h> | |
779 | ||
5e6bcc01 GID |
780 | /* 1 = clean out filename's symbol table after each request, |
781 | 0 = don't | |
782 | */ | |
a6006777 | 783 | #ifndef DO_CLEAN |
784 | #define DO_CLEAN 0 | |
785 | #endif | |
54310121 | 786 | |
2307c6d0 SB |
787 | #define BUFFER_SIZE 1024 |
788 | ||
7fef744d | 789 | static PerlInterpreter *my_perl = NULL; |
54310121 | 790 | |
a6006777 | 791 | int |
792 | main(int argc, char **argv, char **env) | |
793 | { | |
794 | char *embedding[] = { "", "persistent.pl" }; | |
795 | char *args[] = { "", DO_CLEAN, NULL }; | |
2307c6d0 | 796 | char filename[BUFFER_SIZE]; |
a6006777 | 797 | int exitstatus = 0; |
54310121 | 798 | |
1ccffcf5 | 799 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d | 800 | if((my_perl = perl_alloc()) == NULL) { |
8ebc5c01 | 801 | fprintf(stderr, "no memory!"); |
802 | exit(1); | |
a6006777 | 803 | } |
7fef744d | 804 | perl_construct(my_perl); |
54310121 | 805 | |
5e6bcc01 GID |
806 | PL_origalen = 1; /* don't let $0 assignment update the |
807 | proctitle or embedding[0] */ | |
7fef744d | 808 | exitstatus = perl_parse(my_perl, NULL, 2, embedding, NULL); |
d95b23b2 | 809 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
54310121 | 810 | if(!exitstatus) { |
7fef744d | 811 | exitstatus = perl_run(my_perl); |
54310121 | 812 | |
2307c6d0 SB |
813 | while(printf("Enter file name: ") && |
814 | fgets(filename, BUFFER_SIZE, stdin)) { | |
54310121 | 815 | |
2307c6d0 | 816 | filename[strlen(filename)-1] = '\0'; /* strip \n */ |
5e6bcc01 GID |
817 | /* call the subroutine, |
818 | passing it the filename as an argument */ | |
8ebc5c01 | 819 | args[0] = filename; |
4929bf7b | 820 | call_argv("Embed::Persistent::eval_file", |
8ebc5c01 | 821 | G_DISCARD | G_EVAL, args); |
54310121 | 822 | |
8ebc5c01 | 823 | /* check $@ */ |
9cde0e7f | 824 | if(SvTRUE(ERRSV)) |
1c5b513e | 825 | fprintf(stderr, "eval error: %s\n", SvPV_nolen(ERRSV)); |
8ebc5c01 | 826 | } |
a6006777 | 827 | } |
54310121 | 828 | |
9cde0e7f | 829 | PL_perl_destruct_level = 0; |
7fef744d BD |
830 | perl_destruct(my_perl); |
831 | perl_free(my_perl); | |
1ccffcf5 | 832 | PERL_SYS_TERM(); |
a6006777 | 833 | exit(exitstatus); |
834 | } | |
835 | ||
a6006777 | 836 | Now compile: |
837 | ||
5e6bcc01 GID |
838 | % cc -o persistent persistent.c \ |
839 | `perl -MExtUtils::Embed -e ccopts -e ldopts` | |
a6006777 | 840 | |
d1be9408 | 841 | Here's an example script file: |
a6006777 | 842 | |
843 | #test.pl | |
844 | my $string = "hello"; | |
845 | foo($string); | |
846 | ||
847 | sub foo { | |
848 | print "foo says: @_\n"; | |
849 | } | |
850 | ||
851 | Now run: | |
852 | ||
853 | % persistent | |
854 | Enter file name: test.pl | |
855 | foo says: hello | |
856 | Enter file name: test.pl | |
857 | already compiled Embed::test_2epl->handler | |
858 | foo says: hello | |
859 | Enter file name: ^C | |
860 | ||
d95b23b2 AB |
861 | =head2 Execution of END blocks |
862 | ||
863 | Traditionally END blocks have been executed at the end of the perl_run. | |
864 | This causes problems for applications that never call perl_run. Since | |
865 | perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END> | |
866 | to get the new behaviour. This also enables the running of END blocks if | |
bf9cdc68 | 867 | the perl_parse fails and C<perl_destruct> will return the exit value. |
d95b23b2 | 868 | |
a2722ac9 GA |
869 | =head2 $0 assignments |
870 | ||
871 | When a perl script assigns a value to $0 then the perl runtime will | |
872 | try to make this value show up as the program name reported by "ps" by | |
873 | updating the memory pointed to by the argv passed to perl_parse() and | |
874 | also calling API functions like setproctitle() where available. This | |
875 | behaviour might not be appropriate when embedding perl and can be | |
876 | disabled by assigning the value C<1> to the variable C<PL_origalen> | |
877 | before perl_parse() is called. | |
878 | ||
879 | The F<persistent.c> example above is for instance likely to segfault | |
880 | when $0 is assigned to if the C<PL_origalen = 1;> assignment is | |
881 | removed. This because perl will try to write to the read only memory | |
882 | of the C<embedding[]> strings. | |
883 | ||
8ebc5c01 | 884 | =head2 Maintaining multiple interpreter instances |
885 | ||
8a7dc658 JO |
886 | Some rare applications will need to create more than one interpreter |
887 | during a session. Such an application might sporadically decide to | |
54310121 | 888 | release any resources associated with the interpreter. |
8a7dc658 JO |
889 | |
890 | The program must take care to ensure that this takes place I<before> | |
9bbedd82 JH |
891 | the next interpreter is constructed. By default, when perl is not |
892 | built with any special options, the global variable | |
9cde0e7f | 893 | C<PL_perl_destruct_level> is set to C<0>, since extra cleaning isn't |
9bbedd82 JH |
894 | usually needed when a program only ever creates a single interpreter |
895 | in its entire lifetime. | |
8a7dc658 | 896 | |
9cde0e7f | 897 | Setting C<PL_perl_destruct_level> to C<1> makes everything squeaky clean: |
8a7dc658 | 898 | |
8ebc5c01 | 899 | while(1) { |
900 | ... | |
9cde0e7f | 901 | /* reset global variables here with PL_perl_destruct_level = 1 */ |
bf9cdc68 | 902 | PL_perl_destruct_level = 1; |
54310121 | 903 | perl_construct(my_perl); |
8ebc5c01 | 904 | ... |
905 | /* clean and reset _everything_ during perl_destruct */ | |
bf9cdc68 | 906 | PL_perl_destruct_level = 1; |
54310121 | 907 | perl_destruct(my_perl); |
908 | perl_free(my_perl); | |
8ebc5c01 | 909 | ... |
910 | /* let's go do it again! */ | |
911 | } | |
912 | ||
54310121 | 913 | When I<perl_destruct()> is called, the interpreter's syntax parse tree |
bf9cdc68 RG |
914 | and symbol tables are cleaned up, and global variables are reset. The |
915 | second assignment to C<PL_perl_destruct_level> is needed because | |
916 | perl_construct resets it to C<0>. | |
8ebc5c01 | 917 | |
8a7dc658 | 918 | Now suppose we have more than one interpreter instance running at the |
9bbedd82 JH |
919 | same time. This is feasible, but only if you used the Configure option |
920 | C<-Dusemultiplicity> or the options C<-Dusethreads -Duseithreads> when | |
bf9cdc68 | 921 | building perl. By default, enabling one of these Configure options |
9bbedd82 | 922 | sets the per-interpreter global variable C<PL_perl_destruct_level> to |
bf9cdc68 RG |
923 | C<1>, so that thorough cleaning is automatic and interpreter variables |
924 | are initialized correctly. Even if you don't intend to run two or | |
925 | more interpreters at the same time, but to run them sequentially, like | |
926 | in the above example, it is recommended to build perl with the | |
927 | C<-Dusemultiplicity> option otherwise some interpreter variables may | |
928 | not be initialized correctly between consecutive runs and your | |
929 | application may crash. | |
9bbedd82 | 930 | |
832a833b JH |
931 | See also L<perlxs/Thread-aware system interfaces>. |
932 | ||
9bbedd82 JH |
933 | Using C<-Dusethreads -Duseithreads> rather than C<-Dusemultiplicity> |
934 | is more appropriate if you intend to run multiple interpreters | |
935 | concurrently in different threads, because it enables support for | |
936 | linking in the thread libraries of your system with the interpreter. | |
8ebc5c01 | 937 | |
938 | Let's give it a try: | |
939 | ||
940 | ||
941 | #include <EXTERN.h> | |
8a7dc658 | 942 | #include <perl.h> |
8ebc5c01 | 943 | |
944 | /* we're going to embed two interpreters */ | |
8ebc5c01 | 945 | |
8ebc5c01 | 946 | #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)" |
947 | ||
8ebc5c01 | 948 | int main(int argc, char **argv, char **env) |
949 | { | |
1ccffcf5 | 950 | PerlInterpreter *one_perl, *two_perl; |
8ebc5c01 | 951 | char *one_args[] = { "one_perl", SAY_HELLO }; |
952 | char *two_args[] = { "two_perl", SAY_HELLO }; | |
953 | ||
1ccffcf5 IZ |
954 | PERL_SYS_INIT3(&argc,&argv,&env); |
955 | one_perl = perl_alloc(); | |
956 | two_perl = perl_alloc(); | |
957 | ||
9bbedd82 | 958 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 959 | perl_construct(one_perl); |
9bbedd82 | 960 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 961 | perl_construct(two_perl); |
962 | ||
9bbedd82 | 963 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 964 | perl_parse(one_perl, NULL, 3, one_args, (char **)NULL); |
9bbedd82 | 965 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 966 | perl_parse(two_perl, NULL, 3, two_args, (char **)NULL); |
967 | ||
9bbedd82 | 968 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 969 | perl_run(one_perl); |
9bbedd82 | 970 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 971 | perl_run(two_perl); |
972 | ||
9bbedd82 | 973 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 974 | perl_destruct(one_perl); |
9bbedd82 | 975 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 976 | perl_destruct(two_perl); |
977 | ||
9bbedd82 | 978 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 979 | perl_free(one_perl); |
9bbedd82 | 980 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 981 | perl_free(two_perl); |
1ccffcf5 | 982 | PERL_SYS_TERM(); |
8ebc5c01 | 983 | } |
984 | ||
9bbedd82 JH |
985 | Note the calls to PERL_SET_CONTEXT(). These are necessary to initialize |
986 | the global state that tracks which interpreter is the "current" one on | |
987 | the particular process or thread that may be running it. It should | |
988 | always be used if you have more than one interpreter and are making | |
989 | perl API calls on both interpreters in an interleaved fashion. | |
990 | ||
991 | PERL_SET_CONTEXT(interp) should also be called whenever C<interp> is | |
992 | used by a thread that did not create it (using either perl_alloc(), or | |
993 | the more esoteric perl_clone()). | |
8ebc5c01 | 994 | |
995 | Compile as usual: | |
996 | ||
5e6bcc01 GID |
997 | % cc -o multiplicity multiplicity.c \ |
998 | `perl -MExtUtils::Embed -e ccopts -e ldopts` | |
8ebc5c01 | 999 | |
1000 | Run it, Run it: | |
1001 | ||
1002 | % multiplicity | |
1003 | Hi, I'm one_perl | |
1004 | Hi, I'm two_perl | |
1005 | ||
5e6bcc01 GID |
1006 | =head2 Using Perl modules, which themselves use C libraries, from your C |
1007 | program | |
96dbc785 | 1008 | |
1009 | If you've played with the examples above and tried to embed a script | |
5e6bcc01 GID |
1010 | that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++ |
1011 | library, this probably happened: | |
96dbc785 | 1012 | |
1013 | ||
1014 | Can't load module Socket, dynamic loading not available in this perl. | |
1015 | (You may need to build a new perl executable which either supports | |
1016 | dynamic loading or has the Socket module statically linked into it.) | |
1017 | ||
1018 | ||
1019 | What's wrong? | |
1020 | ||
1021 | Your interpreter doesn't know how to communicate with these extensions | |
1022 | on its own. A little glue will help. Up until now you've been | |
1023 | calling I<perl_parse()>, handing it NULL for the second argument: | |
1024 | ||
1025 | perl_parse(my_perl, NULL, argc, my_argv, NULL); | |
1026 | ||
5e6bcc01 GID |
1027 | That's where the glue code can be inserted to create the initial contact |
1028 | between Perl and linked C/C++ routines. Let's take a look some pieces of | |
1029 | I<perlmain.c> to see how Perl does this: | |
96dbc785 | 1030 | |
cc7dda15 | 1031 | static void xs_init (pTHX); |
96dbc785 | 1032 | |
cc7dda15 GS |
1033 | EXTERN_C void boot_DynaLoader (pTHX_ CV* cv); |
1034 | EXTERN_C void boot_Socket (pTHX_ CV* cv); | |
96dbc785 | 1035 | |
1036 | ||
1037 | EXTERN_C void | |
cc7dda15 | 1038 | xs_init(pTHX) |
96dbc785 | 1039 | { |
1040 | char *file = __FILE__; | |
1041 | /* DynaLoader is a special case */ | |
1042 | newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file); | |
1043 | newXS("Socket::bootstrap", boot_Socket, file); | |
1044 | } | |
1045 | ||
1046 | Simply put: for each extension linked with your Perl executable | |
1047 | (determined during its initial configuration on your | |
1048 | computer or when adding a new extension), | |
1049 | a Perl subroutine is created to incorporate the extension's | |
1050 | routines. Normally, that subroutine is named | |
1051 | I<Module::bootstrap()> and is invoked when you say I<use Module>. In | |
1052 | turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl | |
1053 | counterpart for each of the extension's XSUBs. Don't worry about this | |
1054 | part; leave that to the I<xsubpp> and extension authors. If your | |
1055 | extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()> | |
1056 | for you on the fly. In fact, if you have a working DynaLoader then there | |
5f05dabc | 1057 | is rarely any need to link in any other extensions statically. |
96dbc785 | 1058 | |
1059 | ||
1060 | Once you have this code, slap it into the second argument of I<perl_parse()>: | |
1061 | ||
1062 | ||
1063 | perl_parse(my_perl, xs_init, argc, my_argv, NULL); | |
1064 | ||
1065 | ||
1066 | Then compile: | |
1067 | ||
8a7dc658 | 1068 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
96dbc785 | 1069 | |
1070 | % interp | |
1071 | use Socket; | |
1072 | use SomeDynamicallyLoadedModule; | |
1073 | ||
1074 | print "Now I can use extensions!\n"' | |
1075 | ||
1076 | B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code. | |
1077 | ||
8a7dc658 | 1078 | % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c |
96dbc785 | 1079 | % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts` |
1080 | % cc -c interp.c `perl -MExtUtils::Embed -e ccopts` | |
8a7dc658 | 1081 | % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts` |
96dbc785 | 1082 | |
4929bf7b | 1083 | Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details. |
96dbc785 | 1084 | |
ccd65d51 KW |
1085 | =head2 Using embedded Perl with POSIX locales |
1086 | ||
1087 | (See L<perllocale> for information about these.) | |
1088 | When a Perl interpreter normally starts up, it tells the system it wants | |
1089 | to use the system's default locale. This is often, but not necessarily, | |
1090 | the "C" or "POSIX" locale. Absent a S<C<"use locale">> within the perl | |
1091 | code, this mostly has no effect (but see L<perllocale/Not within the | |
d6ded950 | 1092 | scope of "use locale">). Also, there is not a problem if the |
ccd65d51 KW |
1093 | locale you want to use in your embedded Perl is the same as the system |
1094 | default. However, this doesn't work if you have set up and want to use | |
1095 | a locale that isn't the system default one. Starting in Perl v5.20, you | |
1096 | can tell the embedded Perl interpreter that the locale is already | |
1097 | properly set up, and to skip doing its own normal initialization. It | |
1098 | skips if the environment variable C<PERL_SKIP_LOCALE_INIT> is set (even | |
1099 | if set to 0 or C<"">). A Perl that has this capability will define the | |
1100 | C pre-processor symbol C<HAS_SKIP_LOCALE_INIT>. This allows code that | |
1101 | has to work with multiple Perl versions to do some sort of work-around | |
1102 | when confronted with an earlier Perl. | |
1103 | ||
35209cc8 JH |
1104 | =head1 Hiding Perl_ |
1105 | ||
e1020413 | 1106 | If you completely hide the short forms of the Perl public API, |
d51482e4 | 1107 | add -DPERL_NO_SHORT_NAMES to the compilation flags. This means that |
35209cc8 JH |
1108 | for example instead of writing |
1109 | ||
1110 | warn("%d bottles of beer on the wall", bottlecount); | |
1111 | ||
1112 | you will have to write the explicit full form | |
1113 | ||
1114 | Perl_warn(aTHX_ "%d bottles of beer on the wall", bottlecount); | |
1115 | ||
96090e4f LB |
1116 | (See L<perlguts/"Background and PERL_IMPLICIT_CONTEXT"> for the explanation |
1117 | of the C<aTHX_>. ) Hiding the short forms is very useful for avoiding | |
35209cc8 JH |
1118 | all sorts of nasty (C preprocessor or otherwise) conflicts with other |
1119 | software packages (Perl defines about 2400 APIs with these short names, | |
1120 | take or leave few hundred, so there certainly is room for conflict.) | |
1121 | ||
cb1a09d0 AD |
1122 | =head1 MORAL |
1123 | ||
1124 | You can sometimes I<write faster code> in C, but | |
5f05dabc | 1125 | you can always I<write code faster> in Perl. Because you can use |
cb1a09d0 AD |
1126 | each from the other, combine them as you wish. |
1127 | ||
1128 | ||
1129 | =head1 AUTHOR | |
1130 | ||
8eabb633 JH |
1131 | Jon Orwant <F<orwant@media.mit.edu>> and Doug MacEachern |
1132 | <F<dougm@covalent.net>>, with small contributions from Tim Bunce, Tom | |
e010571f GS |
1133 | Christiansen, Guy Decoux, Hallvard Furuseth, Dov Grobgeld, and Ilya |
1134 | Zakharevich. | |
cb1a09d0 | 1135 | |
e010571f | 1136 | Doug MacEachern has an article on embedding in Volume 1, Issue 4 of |
f224927c | 1137 | The Perl Journal ( http://www.tpj.com/ ). Doug is also the developer of the |
e010571f GS |
1138 | most widely-used Perl embedding: the mod_perl system |
1139 | (perl.apache.org), which embeds Perl in the Apache web server. | |
1140 | Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl | |
1141 | have used this model for Oracle, Netscape and Internet Information | |
1142 | Server Perl plugins. | |
cb1a09d0 | 1143 | |
8a7dc658 JO |
1144 | =head1 COPYRIGHT |
1145 | ||
e010571f | 1146 | Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant. All |
8a7dc658 JO |
1147 | Rights Reserved. |
1148 | ||
608704e1 | 1149 | This document may be distributed under the same terms as Perl itself. |