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