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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, |
5a0de581 | 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 | ||
54c85bb0 SS |
214 | Mind that argv[argc] must be NULL, same as those passed to a main |
215 | function in C. | |
216 | ||
cb1a09d0 AD |
217 | Now compile this program (I'll call it I<interp.c>) into an executable: |
218 | ||
96dbc785 | 219 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
cb1a09d0 AD |
220 | |
221 | After a successful compilation, you'll be able to use I<interp> just | |
222 | like perl itself: | |
223 | ||
224 | % interp | |
225 | print "Pretty Good Perl \n"; | |
226 | print "10890 - 9801 is ", 10890 - 9801; | |
227 | <CTRL-D> | |
228 | Pretty Good Perl | |
229 | 10890 - 9801 is 1089 | |
230 | ||
231 | or | |
232 | ||
233 | % interp -e 'printf("%x", 3735928559)' | |
234 | deadbeef | |
235 | ||
236 | You can also read and execute Perl statements from a file while in the | |
237 | midst of your C program, by placing the filename in I<argv[1]> before | |
e010571f | 238 | calling I<perl_run>. |
cb1a09d0 AD |
239 | |
240 | =head2 Calling a Perl subroutine from your C program | |
241 | ||
4929bf7b | 242 | To call individual Perl subroutines, you can use any of the B<call_*> |
7b8d334a | 243 | functions documented in L<perlcall>. |
4929bf7b | 244 | In this example we'll use C<call_argv>. |
cb1a09d0 AD |
245 | |
246 | That's shown below, in a program I'll call I<showtime.c>. | |
247 | ||
cb1a09d0 | 248 | #include <EXTERN.h> |
96dbc785 | 249 | #include <perl.h> |
250 | ||
251 | static PerlInterpreter *my_perl; | |
252 | ||
c07a80fd | 253 | int main(int argc, char **argv, char **env) |
cb1a09d0 | 254 | { |
8ebc5c01 | 255 | char *args[] = { NULL }; |
1ccffcf5 | 256 | PERL_SYS_INIT3(&argc,&argv,&env); |
cb1a09d0 AD |
257 | my_perl = perl_alloc(); |
258 | perl_construct(my_perl); | |
96dbc785 | 259 | |
260 | perl_parse(my_perl, NULL, argc, argv, NULL); | |
d95b23b2 | 261 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
96dbc785 | 262 | |
8ebc5c01 | 263 | /*** skipping perl_run() ***/ |
264 | ||
4929bf7b | 265 | call_argv("showtime", G_DISCARD | G_NOARGS, args); |
8ebc5c01 | 266 | |
cb1a09d0 AD |
267 | perl_destruct(my_perl); |
268 | perl_free(my_perl); | |
1ccffcf5 | 269 | PERL_SYS_TERM(); |
cb1a09d0 AD |
270 | } |
271 | ||
272 | where I<showtime> is a Perl subroutine that takes no arguments (that's the | |
96dbc785 | 273 | I<G_NOARGS>) and for which I'll ignore the return value (that's the |
cb1a09d0 AD |
274 | I<G_DISCARD>). Those flags, and others, are discussed in L<perlcall>. |
275 | ||
276 | I'll define the I<showtime> subroutine in a file called I<showtime.pl>: | |
277 | ||
5e6bcc01 | 278 | print "I shan't be printed."; |
96dbc785 | 279 | |
5e6bcc01 GID |
280 | sub showtime { |
281 | print time; | |
282 | } | |
cb1a09d0 | 283 | |
5e6bcc01 | 284 | Simple enough. Now compile and run: |
96dbc785 | 285 | |
5e6bcc01 GID |
286 | % cc -o showtime showtime.c \ |
287 | `perl -MExtUtils::Embed -e ccopts -e ldopts` | |
288 | % showtime showtime.pl | |
289 | 818284590 | |
cb1a09d0 AD |
290 | |
291 | yielding the number of seconds that elapsed between January 1, 1970 | |
8a7dc658 | 292 | (the beginning of the Unix epoch), and the moment I began writing this |
cb1a09d0 AD |
293 | sentence. |
294 | ||
5e6bcc01 | 295 | In this particular case we don't have to call I<perl_run>, as we set |
d95b23b2 AB |
296 | the PL_exit_flag PERL_EXIT_DESTRUCT_END which executes END blocks in |
297 | perl_destruct. | |
8ebc5c01 | 298 | |
8a7dc658 JO |
299 | If you want to pass arguments to the Perl subroutine, you can add |
300 | strings to the C<NULL>-terminated C<args> list passed to | |
4929bf7b | 301 | I<call_argv>. For other data types, or to examine return values, |
13a2d996 | 302 | you'll need to manipulate the Perl stack. That's demonstrated in |
5a0de581 | 303 | L</Fiddling with the Perl stack from your C program>. |
cb1a09d0 AD |
304 | |
305 | =head2 Evaluating a Perl statement from your C program | |
306 | ||
137443ea | 307 | Perl provides two API functions to evaluate pieces of Perl code. |
4929bf7b | 308 | These are L<perlapi/eval_sv> and L<perlapi/eval_pv>. |
137443ea | 309 | |
310 | Arguably, these are the only routines you'll ever need to execute | |
e010571f GS |
311 | snippets of Perl code from within your C program. Your code can be as |
312 | long as you wish; it can contain multiple statements; it can employ | |
313 | L<perlfunc/use>, L<perlfunc/require>, and L<perlfunc/do> to | |
314 | include external Perl files. | |
cb1a09d0 | 315 | |
4929bf7b | 316 | I<eval_pv> lets us evaluate individual Perl strings, and then |
96dbc785 | 317 | extract variables for coercion into C types. The following program, |
cb1a09d0 AD |
318 | I<string.c>, executes three Perl strings, extracting an C<int> from |
319 | the first, a C<float> from the second, and a C<char *> from the third. | |
320 | ||
5e6bcc01 GID |
321 | #include <EXTERN.h> |
322 | #include <perl.h> | |
c47ff5f1 | 323 | |
5e6bcc01 | 324 | static PerlInterpreter *my_perl; |
c47ff5f1 | 325 | |
5e6bcc01 GID |
326 | main (int argc, char **argv, char **env) |
327 | { | |
328 | char *embedding[] = { "", "-e", "0" }; | |
c47ff5f1 | 329 | |
5e6bcc01 GID |
330 | PERL_SYS_INIT3(&argc,&argv,&env); |
331 | my_perl = perl_alloc(); | |
332 | perl_construct( my_perl ); | |
c47ff5f1 | 333 | |
5e6bcc01 GID |
334 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
335 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; | |
336 | perl_run(my_perl); | |
c47ff5f1 | 337 | |
5e6bcc01 GID |
338 | /** Treat $a as an integer **/ |
339 | eval_pv("$a = 3; $a **= 2", TRUE); | |
340 | printf("a = %d\n", SvIV(get_sv("a", 0))); | |
c47ff5f1 | 341 | |
5e6bcc01 GID |
342 | /** Treat $a as a float **/ |
343 | eval_pv("$a = 3.14; $a **= 2", TRUE); | |
344 | printf("a = %f\n", SvNV(get_sv("a", 0))); | |
c47ff5f1 | 345 | |
5e6bcc01 GID |
346 | /** Treat $a as a string **/ |
347 | eval_pv( | |
348 | "$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE); | |
349 | printf("a = %s\n", SvPV_nolen(get_sv("a", 0))); | |
c47ff5f1 | 350 | |
5e6bcc01 GID |
351 | perl_destruct(my_perl); |
352 | perl_free(my_perl); | |
353 | PERL_SYS_TERM(); | |
354 | } | |
cb1a09d0 | 355 | |
5e6bcc01 GID |
356 | All of those strange functions with I<sv> in their names help convert Perl |
357 | scalars to C types. They're described in L<perlguts> and L<perlapi>. | |
cb1a09d0 AD |
358 | |
359 | If you compile and run I<string.c>, you'll see the results of using | |
360 | I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and | |
361 | I<SvPV()> to create a string: | |
362 | ||
363 | a = 9 | |
364 | a = 9.859600 | |
365 | a = Just Another Perl Hacker | |
366 | ||
8f183262 | 367 | In the example above, we've created a global variable to temporarily |
353c6505 | 368 | store the computed value of our eval'ed expression. It is also |
8f183262 | 369 | possible and in most cases a better strategy to fetch the return value |
4929bf7b | 370 | from I<eval_pv()> instead. Example: |
8f183262 | 371 | |
8f183262 | 372 | ... |
4929bf7b | 373 | SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); |
1c5b513e | 374 | printf("%s\n", SvPV_nolen(val)); |
8f183262 DM |
375 | ... |
376 | ||
377 | This way, we avoid namespace pollution by not creating global | |
378 | variables and we've simplified our code as well. | |
cb1a09d0 AD |
379 | |
380 | =head2 Performing Perl pattern matches and substitutions from your C program | |
381 | ||
4929bf7b | 382 | The I<eval_sv()> function lets us evaluate strings of Perl code, so we can |
cb1a09d0 AD |
383 | define some functions that use it to "specialize" in matches and |
384 | substitutions: I<match()>, I<substitute()>, and I<matches()>. | |
385 | ||
e010571f | 386 | I32 match(SV *string, char *pattern); |
cb1a09d0 | 387 | |
8a7dc658 JO |
388 | Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which |
389 | in your C program might appear as "/\\b\\w*\\b/"), match() | |
cb1a09d0 AD |
390 | returns 1 if the string matches the pattern and 0 otherwise. |
391 | ||
1f05cdcd | 392 | int substitute(SV **string, char *pattern); |
cb1a09d0 | 393 | |
1f05cdcd | 394 | Given a pointer to an C<SV> and an C<=~> operation (e.g., |
8a7dc658 | 395 | C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string |
5e6bcc01 GID |
396 | within the C<SV> as according to the operation, returning the number of |
397 | substitutions made. | |
cb1a09d0 | 398 | |
c70927a6 | 399 | SSize_t matches(SV *string, char *pattern, AV **matches); |
cb1a09d0 | 400 | |
1f05cdcd | 401 | Given an C<SV>, a pattern, and a pointer to an empty C<AV>, |
90fdbbb7 | 402 | matches() evaluates C<$string =~ $pattern> in a list context, and |
5e6bcc01 GID |
403 | fills in I<matches> with the array elements, returning the number of matches |
404 | found. | |
cb1a09d0 | 405 | |
96dbc785 | 406 | Here's a sample program, I<match.c>, that uses all three (long lines have |
407 | been wrapped here): | |
cb1a09d0 | 408 | |
1f05cdcd DM |
409 | #include <EXTERN.h> |
410 | #include <perl.h> | |
c47ff5f1 | 411 | |
7fef744d BD |
412 | static PerlInterpreter *my_perl; |
413 | ||
4929bf7b | 414 | /** my_eval_sv(code, error_check) |
5e6bcc01 GID |
415 | ** kinda like eval_sv(), |
416 | ** but we pop the return value off the stack | |
1f05cdcd | 417 | **/ |
4929bf7b | 418 | SV* my_eval_sv(SV *sv, I32 croak_on_error) |
1f05cdcd DM |
419 | { |
420 | dSP; | |
421 | SV* retval; | |
1c5b513e | 422 | |
c47ff5f1 | 423 | |
924508f0 | 424 | PUSHMARK(SP); |
4929bf7b | 425 | eval_sv(sv, G_SCALAR); |
c47ff5f1 | 426 | |
1f05cdcd DM |
427 | SPAGAIN; |
428 | retval = POPs; | |
429 | PUTBACK; | |
c47ff5f1 | 430 | |
9cde0e7f | 431 | if (croak_on_error && SvTRUE(ERRSV)) |
1c5b513e | 432 | croak(SvPVx_nolen(ERRSV)); |
c47ff5f1 | 433 | |
1f05cdcd DM |
434 | return retval; |
435 | } | |
c47ff5f1 | 436 | |
1f05cdcd DM |
437 | /** match(string, pattern) |
438 | ** | |
439 | ** Used for matches in a scalar context. | |
440 | ** | |
441 | ** Returns 1 if the match was successful; 0 otherwise. | |
442 | **/ | |
c47ff5f1 | 443 | |
1f05cdcd DM |
444 | I32 match(SV *string, char *pattern) |
445 | { | |
561b68a9 | 446 | SV *command = newSV(0), *retval; |
c47ff5f1 | 447 | |
1f05cdcd | 448 | sv_setpvf(command, "my $string = '%s'; $string =~ %s", |
1c5b513e | 449 | SvPV_nolen(string), pattern); |
c47ff5f1 | 450 | |
4929bf7b | 451 | retval = my_eval_sv(command, TRUE); |
1f05cdcd | 452 | SvREFCNT_dec(command); |
c47ff5f1 | 453 | |
1f05cdcd DM |
454 | return SvIV(retval); |
455 | } | |
c47ff5f1 | 456 | |
1f05cdcd DM |
457 | /** substitute(string, pattern) |
458 | ** | |
5e6bcc01 GID |
459 | ** Used for =~ operations that |
460 | ** modify their left-hand side (s/// and tr///) | |
1f05cdcd DM |
461 | ** |
462 | ** Returns the number of successful matches, and | |
463 | ** modifies the input string if there were any. | |
464 | **/ | |
c47ff5f1 | 465 | |
1f05cdcd DM |
466 | I32 substitute(SV **string, char *pattern) |
467 | { | |
561b68a9 | 468 | SV *command = newSV(0), *retval; |
c47ff5f1 | 469 | |
1f05cdcd | 470 | sv_setpvf(command, "$string = '%s'; ($string =~ %s)", |
1c5b513e | 471 | SvPV_nolen(*string), pattern); |
c47ff5f1 | 472 | |
4929bf7b | 473 | retval = my_eval_sv(command, TRUE); |
1f05cdcd | 474 | SvREFCNT_dec(command); |
c47ff5f1 | 475 | |
64ace3f8 | 476 | *string = get_sv("string", 0); |
1f05cdcd DM |
477 | return SvIV(retval); |
478 | } | |
c47ff5f1 | 479 | |
1f05cdcd DM |
480 | /** matches(string, pattern, matches) |
481 | ** | |
90fdbbb7 | 482 | ** Used for matches in a list context. |
1f05cdcd DM |
483 | ** |
484 | ** Returns the number of matches, | |
485 | ** and fills in **matches with the matching substrings | |
486 | **/ | |
c47ff5f1 | 487 | |
c70927a6 | 488 | SSize_t matches(SV *string, char *pattern, AV **match_list) |
1f05cdcd | 489 | { |
561b68a9 | 490 | SV *command = newSV(0); |
c70927a6 | 491 | SSize_t num_matches; |
c47ff5f1 | 492 | |
1f05cdcd | 493 | sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)", |
1c5b513e | 494 | SvPV_nolen(string), pattern); |
c47ff5f1 | 495 | |
4929bf7b | 496 | my_eval_sv(command, TRUE); |
1f05cdcd | 497 | SvREFCNT_dec(command); |
c47ff5f1 | 498 | |
cbfd0a87 | 499 | *match_list = get_av("array", 0); |
23aa77bc | 500 | num_matches = av_top_index(*match_list) + 1; |
c47ff5f1 | 501 | |
cb1a09d0 | 502 | return num_matches; |
1f05cdcd | 503 | } |
c47ff5f1 | 504 | |
1f05cdcd DM |
505 | main (int argc, char **argv, char **env) |
506 | { | |
a6006777 | 507 | char *embedding[] = { "", "-e", "0" }; |
1f05cdcd DM |
508 | AV *match_list; |
509 | I32 num_matches, i; | |
7fef744d | 510 | SV *text; |
c47ff5f1 | 511 | |
1ccffcf5 | 512 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d | 513 | my_perl = perl_alloc(); |
1f05cdcd | 514 | perl_construct(my_perl); |
96dbc785 | 515 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
d95b23b2 | 516 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
c47ff5f1 | 517 | |
561b68a9 | 518 | text = newSV(0); |
d3f3bf9f RGS |
519 | sv_setpv(text, "When he is at a convenience store and the " |
520 | "bill comes to some amount like 76 cents, Maynard is " | |
521 | "aware that there is something he *should* do, something " | |
522 | "that will enable him to get back a quarter, but he has " | |
523 | "no idea *what*. He fumbles through his red squeezey " | |
524 | "changepurse and gives the boy three extra pennies with " | |
525 | "his dollar, hoping that he might luck into the correct " | |
526 | "amount. The boy gives him back two of his own pennies " | |
527 | "and then the big shiny quarter that is his prize. " | |
528 | "-RICHH"); | |
c47ff5f1 | 529 | |
96dbc785 | 530 | if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/ |
1f05cdcd | 531 | printf("match: Text contains the word 'quarter'.\n\n"); |
96dbc785 | 532 | else |
1f05cdcd | 533 | printf("match: Text doesn't contain the word 'quarter'.\n\n"); |
c47ff5f1 | 534 | |
96dbc785 | 535 | if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/ |
1f05cdcd | 536 | printf("match: Text contains the word 'eighth'.\n\n"); |
96dbc785 | 537 | else |
1f05cdcd | 538 | printf("match: Text doesn't contain the word 'eighth'.\n\n"); |
c47ff5f1 | 539 | |
96dbc785 | 540 | /** Match all occurrences of /wi../ **/ |
541 | num_matches = matches(text, "m/(wi..)/g", &match_list); | |
542 | printf("matches: m/(wi..)/g found %d matches...\n", num_matches); | |
c47ff5f1 | 543 | |
96dbc785 | 544 | for (i = 0; i < num_matches; i++) |
5e6bcc01 GID |
545 | printf("match: %s\n", |
546 | SvPV_nolen(*av_fetch(match_list, i, FALSE))); | |
cb1a09d0 | 547 | printf("\n"); |
c47ff5f1 | 548 | |
96dbc785 | 549 | /** Remove all vowels from text **/ |
550 | num_matches = substitute(&text, "s/[aeiou]//gi"); | |
cb1a09d0 | 551 | if (num_matches) { |
c70927a6 FC |
552 | printf("substitute: s/[aeiou]//gi...%lu substitutions made.\n", |
553 | (unsigned long)num_matches); | |
1c5b513e | 554 | printf("Now text is: %s\n\n", SvPV_nolen(text)); |
cb1a09d0 | 555 | } |
c47ff5f1 | 556 | |
96dbc785 | 557 | /** Attempt a substitution **/ |
558 | if (!substitute(&text, "s/Perl/C/")) { | |
1f05cdcd | 559 | printf("substitute: s/Perl/C...No substitution made.\n\n"); |
cb1a09d0 | 560 | } |
c47ff5f1 | 561 | |
1f05cdcd | 562 | SvREFCNT_dec(text); |
9cde0e7f | 563 | PL_perl_destruct_level = 1; |
cb1a09d0 AD |
564 | perl_destruct(my_perl); |
565 | perl_free(my_perl); | |
1ccffcf5 | 566 | PERL_SYS_TERM(); |
1f05cdcd | 567 | } |
cb1a09d0 | 568 | |
96dbc785 | 569 | which produces the output (again, long lines have been wrapped here) |
cb1a09d0 | 570 | |
5e6bcc01 | 571 | match: Text contains the word 'quarter'. |
96dbc785 | 572 | |
5e6bcc01 | 573 | match: Text doesn't contain the word 'eighth'. |
96dbc785 | 574 | |
5e6bcc01 GID |
575 | matches: m/(wi..)/g found 2 matches... |
576 | match: will | |
577 | match: with | |
96dbc785 | 578 | |
5e6bcc01 GID |
579 | substitute: s/[aeiou]//gi...139 substitutions made. |
580 | Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts, | |
581 | Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt | |
582 | bck qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd | |
583 | gvs th by thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct | |
584 | mnt. Th by gvs hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s | |
585 | hs prz. -RCHH | |
96dbc785 | 586 | |
5e6bcc01 | 587 | substitute: s/Perl/C...No substitution made. |
96dbc785 | 588 | |
cb1a09d0 AD |
589 | =head2 Fiddling with the Perl stack from your C program |
590 | ||
591 | When trying to explain stacks, most computer science textbooks mumble | |
592 | something about spring-loaded columns of cafeteria plates: the last | |
593 | thing you pushed on the stack is the first thing you pop off. That'll | |
594 | do for our purposes: your C program will push some arguments onto "the Perl | |
595 | stack", shut its eyes while some magic happens, and then pop the | |
596 | results--the return value of your Perl subroutine--off the stack. | |
96dbc785 | 597 | |
cb1a09d0 AD |
598 | First you'll need to know how to convert between C types and Perl |
599 | types, with newSViv() and sv_setnv() and newAV() and all their | |
4929bf7b | 600 | friends. They're described in L<perlguts> and L<perlapi>. |
cb1a09d0 AD |
601 | |
602 | Then you'll need to know how to manipulate the Perl stack. That's | |
603 | described in L<perlcall>. | |
604 | ||
96dbc785 | 605 | Once you've understood those, embedding Perl in C is easy. |
cb1a09d0 | 606 | |
54310121 | 607 | Because C has no builtin function for integer exponentiation, let's |
cb1a09d0 | 608 | make Perl's ** operator available to it (this is less useful than it |
5f05dabc | 609 | sounds, because Perl implements ** with C's I<pow()> function). First |
cb1a09d0 AD |
610 | I'll create a stub exponentiation function in I<power.pl>: |
611 | ||
612 | sub expo { | |
613 | my ($a, $b) = @_; | |
614 | return $a ** $b; | |
615 | } | |
616 | ||
617 | Now I'll create a C program, I<power.c>, with a function | |
618 | I<PerlPower()> that contains all the perlguts necessary to push the | |
619 | two arguments into I<expo()> and to pop the return value out. Take a | |
620 | deep breath... | |
621 | ||
5e6bcc01 GID |
622 | #include <EXTERN.h> |
623 | #include <perl.h> | |
96dbc785 | 624 | |
5e6bcc01 | 625 | static PerlInterpreter *my_perl; |
96dbc785 | 626 | |
5e6bcc01 GID |
627 | static void |
628 | PerlPower(int a, int b) | |
629 | { | |
630 | dSP; /* initialize stack pointer */ | |
631 | ENTER; /* everything created after here */ | |
632 | SAVETMPS; /* ...is a temporary variable. */ | |
633 | PUSHMARK(SP); /* remember the stack pointer */ | |
634 | XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */ | |
635 | XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */ | |
636 | PUTBACK; /* make local stack pointer global */ | |
637 | call_pv("expo", G_SCALAR); /* call the function */ | |
638 | SPAGAIN; /* refresh stack pointer */ | |
639 | /* pop the return value from stack */ | |
640 | printf ("%d to the %dth power is %d.\n", a, b, POPi); | |
641 | PUTBACK; | |
642 | FREETMPS; /* free that return value */ | |
643 | LEAVE; /* ...and the XPUSHed "mortal" args.*/ | |
644 | } | |
96dbc785 | 645 | |
5e6bcc01 GID |
646 | int main (int argc, char **argv, char **env) |
647 | { | |
648 | char *my_argv[] = { "", "power.pl" }; | |
96dbc785 | 649 | |
5e6bcc01 GID |
650 | PERL_SYS_INIT3(&argc,&argv,&env); |
651 | my_perl = perl_alloc(); | |
652 | perl_construct( my_perl ); | |
96dbc785 | 653 | |
5e6bcc01 GID |
654 | perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL); |
655 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; | |
656 | perl_run(my_perl); | |
96dbc785 | 657 | |
5e6bcc01 | 658 | PerlPower(3, 4); /*** Compute 3 ** 4 ***/ |
96dbc785 | 659 | |
5e6bcc01 GID |
660 | perl_destruct(my_perl); |
661 | perl_free(my_perl); | |
662 | PERL_SYS_TERM(); | |
663 | } | |
96dbc785 | 664 | |
cb1a09d0 AD |
665 | |
666 | ||
667 | Compile and run: | |
668 | ||
96dbc785 | 669 | % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
670 | ||
671 | % power | |
cb1a09d0 AD |
672 | 3 to the 4th power is 81. |
673 | ||
a6006777 | 674 | =head2 Maintaining a persistent interpreter |
675 | ||
8a7dc658 JO |
676 | When developing interactive and/or potentially long-running |
677 | applications, it's a good idea to maintain a persistent interpreter | |
678 | rather than allocating and constructing a new interpreter multiple | |
679 | times. The major reason is speed: since Perl will only be loaded into | |
54310121 | 680 | memory once. |
8a7dc658 JO |
681 | |
682 | However, you have to be more cautious with namespace and variable | |
683 | scoping when using a persistent interpreter. In previous examples | |
684 | we've been using global variables in the default package C<main>. We | |
685 | knew exactly what code would be run, and assumed we could avoid | |
686 | variable collisions and outrageous symbol table growth. | |
687 | ||
688 | Let's say your application is a server that will occasionally run Perl | |
689 | code from some arbitrary file. Your server has no way of knowing what | |
690 | code it's going to run. Very dangerous. | |
691 | ||
692 | If the file is pulled in by C<perl_parse()>, compiled into a newly | |
693 | constructed interpreter, and subsequently cleaned out with | |
694 | C<perl_destruct()> afterwards, you're shielded from most namespace | |
695 | troubles. | |
696 | ||
697 | One way to avoid namespace collisions in this scenario is to translate | |
698 | the filename into a guaranteed-unique package name, and then compile | |
e010571f | 699 | the code into that package using L<perlfunc/eval>. In the example |
8a7dc658 JO |
700 | below, each file will only be compiled once. Or, the application |
701 | might choose to clean out the symbol table associated with the file | |
4929bf7b | 702 | after it's no longer needed. Using L<perlapi/call_argv>, We'll |
8a7dc658 JO |
703 | call the subroutine C<Embed::Persistent::eval_file> which lives in the |
704 | file C<persistent.pl> and pass the filename and boolean cleanup/cache | |
a6006777 | 705 | flag as arguments. |
706 | ||
8a7dc658 JO |
707 | Note that the process will continue to grow for each file that it |
708 | uses. In addition, there might be C<AUTOLOAD>ed subroutines and other | |
709 | conditions that cause Perl's symbol table to grow. You might want to | |
710 | add some logic that keeps track of the process size, or restarts | |
711 | itself after a certain number of requests, to ensure that memory | |
712 | consumption is minimized. You'll also want to scope your variables | |
e010571f | 713 | with L<perlfunc/my> whenever possible. |
a6006777 | 714 | |
54310121 | 715 | |
a6006777 | 716 | package Embed::Persistent; |
717 | #persistent.pl | |
54310121 | 718 | |
a6006777 | 719 | use strict; |
77ca0c92 | 720 | our %Cache; |
1ee082b7 | 721 | use Symbol qw(delete_package); |
54310121 | 722 | |
a6006777 | 723 | sub valid_package_name { |
724 | my($string) = @_; | |
725 | $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg; | |
726 | # second pass only for words starting with a digit | |
727 | $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg; | |
54310121 | 728 | |
a6006777 | 729 | # Dress it up as a real package name |
730 | $string =~ s|/|::|g; | |
731 | return "Embed" . $string; | |
732 | } | |
54310121 | 733 | |
a6006777 | 734 | sub eval_file { |
735 | my($filename, $delete) = @_; | |
736 | my $package = valid_package_name($filename); | |
737 | my $mtime = -M $filename; | |
738 | if(defined $Cache{$package}{mtime} | |
739 | && | |
54310121 | 740 | $Cache{$package}{mtime} <= $mtime) |
a6006777 | 741 | { |
54310121 | 742 | # we have compiled this subroutine already, |
8ebc5c01 | 743 | # it has not been updated on disk, nothing left to do |
744 | print STDERR "already compiled $package->handler\n"; | |
a6006777 | 745 | } |
746 | else { | |
8ebc5c01 | 747 | local *FH; |
748 | open FH, $filename or die "open '$filename' $!"; | |
749 | local($/) = undef; | |
750 | my $sub = <FH>; | |
751 | close FH; | |
54310121 | 752 | |
8ebc5c01 | 753 | #wrap the code into a subroutine inside our unique package |
754 | my $eval = qq{package $package; sub handler { $sub; }}; | |
755 | { | |
756 | # hide our variables within this block | |
757 | my($filename,$mtime,$package,$sub); | |
758 | eval $eval; | |
759 | } | |
760 | die $@ if $@; | |
54310121 | 761 | |
8ebc5c01 | 762 | #cache it unless we're cleaning out each time |
763 | $Cache{$package}{mtime} = $mtime unless $delete; | |
a6006777 | 764 | } |
54310121 | 765 | |
a6006777 | 766 | eval {$package->handler;}; |
767 | die $@ if $@; | |
54310121 | 768 | |
a6006777 | 769 | delete_package($package) if $delete; |
54310121 | 770 | |
a6006777 | 771 | #take a look if you want |
772 | #print Devel::Symdump->rnew($package)->as_string, $/; | |
773 | } | |
54310121 | 774 | |
a6006777 | 775 | 1; |
54310121 | 776 | |
a6006777 | 777 | __END__ |
778 | ||
779 | /* persistent.c */ | |
54310121 | 780 | #include <EXTERN.h> |
781 | #include <perl.h> | |
782 | ||
5e6bcc01 GID |
783 | /* 1 = clean out filename's symbol table after each request, |
784 | 0 = don't | |
785 | */ | |
a6006777 | 786 | #ifndef DO_CLEAN |
787 | #define DO_CLEAN 0 | |
788 | #endif | |
54310121 | 789 | |
2307c6d0 SB |
790 | #define BUFFER_SIZE 1024 |
791 | ||
7fef744d | 792 | static PerlInterpreter *my_perl = NULL; |
54310121 | 793 | |
a6006777 | 794 | int |
795 | main(int argc, char **argv, char **env) | |
796 | { | |
797 | char *embedding[] = { "", "persistent.pl" }; | |
798 | char *args[] = { "", DO_CLEAN, NULL }; | |
2307c6d0 | 799 | char filename[BUFFER_SIZE]; |
a6006777 | 800 | int exitstatus = 0; |
54310121 | 801 | |
1ccffcf5 | 802 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d | 803 | if((my_perl = perl_alloc()) == NULL) { |
8ebc5c01 | 804 | fprintf(stderr, "no memory!"); |
805 | exit(1); | |
a6006777 | 806 | } |
7fef744d | 807 | perl_construct(my_perl); |
54310121 | 808 | |
5e6bcc01 GID |
809 | PL_origalen = 1; /* don't let $0 assignment update the |
810 | proctitle or embedding[0] */ | |
7fef744d | 811 | exitstatus = perl_parse(my_perl, NULL, 2, embedding, NULL); |
d95b23b2 | 812 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
54310121 | 813 | if(!exitstatus) { |
7fef744d | 814 | exitstatus = perl_run(my_perl); |
54310121 | 815 | |
2307c6d0 SB |
816 | while(printf("Enter file name: ") && |
817 | fgets(filename, BUFFER_SIZE, stdin)) { | |
54310121 | 818 | |
2307c6d0 | 819 | filename[strlen(filename)-1] = '\0'; /* strip \n */ |
5e6bcc01 GID |
820 | /* call the subroutine, |
821 | passing it the filename as an argument */ | |
8ebc5c01 | 822 | args[0] = filename; |
4929bf7b | 823 | call_argv("Embed::Persistent::eval_file", |
8ebc5c01 | 824 | G_DISCARD | G_EVAL, args); |
54310121 | 825 | |
8ebc5c01 | 826 | /* check $@ */ |
9cde0e7f | 827 | if(SvTRUE(ERRSV)) |
1c5b513e | 828 | fprintf(stderr, "eval error: %s\n", SvPV_nolen(ERRSV)); |
8ebc5c01 | 829 | } |
a6006777 | 830 | } |
54310121 | 831 | |
9cde0e7f | 832 | PL_perl_destruct_level = 0; |
7fef744d BD |
833 | perl_destruct(my_perl); |
834 | perl_free(my_perl); | |
1ccffcf5 | 835 | PERL_SYS_TERM(); |
a6006777 | 836 | exit(exitstatus); |
837 | } | |
838 | ||
a6006777 | 839 | Now compile: |
840 | ||
5e6bcc01 GID |
841 | % cc -o persistent persistent.c \ |
842 | `perl -MExtUtils::Embed -e ccopts -e ldopts` | |
a6006777 | 843 | |
d1be9408 | 844 | Here's an example script file: |
a6006777 | 845 | |
846 | #test.pl | |
847 | my $string = "hello"; | |
848 | foo($string); | |
849 | ||
850 | sub foo { | |
851 | print "foo says: @_\n"; | |
852 | } | |
853 | ||
854 | Now run: | |
855 | ||
856 | % persistent | |
857 | Enter file name: test.pl | |
858 | foo says: hello | |
859 | Enter file name: test.pl | |
860 | already compiled Embed::test_2epl->handler | |
861 | foo says: hello | |
862 | Enter file name: ^C | |
863 | ||
d95b23b2 AB |
864 | =head2 Execution of END blocks |
865 | ||
866 | Traditionally END blocks have been executed at the end of the perl_run. | |
867 | This causes problems for applications that never call perl_run. Since | |
868 | perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END> | |
869 | to get the new behaviour. This also enables the running of END blocks if | |
bf9cdc68 | 870 | the perl_parse fails and C<perl_destruct> will return the exit value. |
d95b23b2 | 871 | |
a2722ac9 GA |
872 | =head2 $0 assignments |
873 | ||
874 | When a perl script assigns a value to $0 then the perl runtime will | |
875 | try to make this value show up as the program name reported by "ps" by | |
876 | updating the memory pointed to by the argv passed to perl_parse() and | |
877 | also calling API functions like setproctitle() where available. This | |
878 | behaviour might not be appropriate when embedding perl and can be | |
879 | disabled by assigning the value C<1> to the variable C<PL_origalen> | |
880 | before perl_parse() is called. | |
881 | ||
882 | The F<persistent.c> example above is for instance likely to segfault | |
883 | when $0 is assigned to if the C<PL_origalen = 1;> assignment is | |
884 | removed. This because perl will try to write to the read only memory | |
885 | of the C<embedding[]> strings. | |
886 | ||
8ebc5c01 | 887 | =head2 Maintaining multiple interpreter instances |
888 | ||
8a7dc658 JO |
889 | Some rare applications will need to create more than one interpreter |
890 | during a session. Such an application might sporadically decide to | |
54310121 | 891 | release any resources associated with the interpreter. |
8a7dc658 JO |
892 | |
893 | The program must take care to ensure that this takes place I<before> | |
9bbedd82 JH |
894 | the next interpreter is constructed. By default, when perl is not |
895 | built with any special options, the global variable | |
9cde0e7f | 896 | C<PL_perl_destruct_level> is set to C<0>, since extra cleaning isn't |
9bbedd82 JH |
897 | usually needed when a program only ever creates a single interpreter |
898 | in its entire lifetime. | |
8a7dc658 | 899 | |
9cde0e7f | 900 | Setting C<PL_perl_destruct_level> to C<1> makes everything squeaky clean: |
8a7dc658 | 901 | |
8ebc5c01 | 902 | while(1) { |
903 | ... | |
9cde0e7f | 904 | /* reset global variables here with PL_perl_destruct_level = 1 */ |
bf9cdc68 | 905 | PL_perl_destruct_level = 1; |
54310121 | 906 | perl_construct(my_perl); |
8ebc5c01 | 907 | ... |
908 | /* clean and reset _everything_ during perl_destruct */ | |
bf9cdc68 | 909 | PL_perl_destruct_level = 1; |
54310121 | 910 | perl_destruct(my_perl); |
911 | perl_free(my_perl); | |
8ebc5c01 | 912 | ... |
913 | /* let's go do it again! */ | |
914 | } | |
915 | ||
54310121 | 916 | When I<perl_destruct()> is called, the interpreter's syntax parse tree |
bf9cdc68 RG |
917 | and symbol tables are cleaned up, and global variables are reset. The |
918 | second assignment to C<PL_perl_destruct_level> is needed because | |
919 | perl_construct resets it to C<0>. | |
8ebc5c01 | 920 | |
8a7dc658 | 921 | Now suppose we have more than one interpreter instance running at the |
9bbedd82 JH |
922 | same time. This is feasible, but only if you used the Configure option |
923 | C<-Dusemultiplicity> or the options C<-Dusethreads -Duseithreads> when | |
bf9cdc68 | 924 | building perl. By default, enabling one of these Configure options |
9bbedd82 | 925 | sets the per-interpreter global variable C<PL_perl_destruct_level> to |
bf9cdc68 RG |
926 | C<1>, so that thorough cleaning is automatic and interpreter variables |
927 | are initialized correctly. Even if you don't intend to run two or | |
928 | more interpreters at the same time, but to run them sequentially, like | |
929 | in the above example, it is recommended to build perl with the | |
930 | C<-Dusemultiplicity> option otherwise some interpreter variables may | |
931 | not be initialized correctly between consecutive runs and your | |
932 | application may crash. | |
9bbedd82 | 933 | |
832a833b JH |
934 | See also L<perlxs/Thread-aware system interfaces>. |
935 | ||
9bbedd82 JH |
936 | Using C<-Dusethreads -Duseithreads> rather than C<-Dusemultiplicity> |
937 | is more appropriate if you intend to run multiple interpreters | |
938 | concurrently in different threads, because it enables support for | |
939 | linking in the thread libraries of your system with the interpreter. | |
8ebc5c01 | 940 | |
941 | Let's give it a try: | |
942 | ||
943 | ||
944 | #include <EXTERN.h> | |
8a7dc658 | 945 | #include <perl.h> |
8ebc5c01 | 946 | |
947 | /* we're going to embed two interpreters */ | |
8ebc5c01 | 948 | |
8ebc5c01 | 949 | #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)" |
950 | ||
8ebc5c01 | 951 | int main(int argc, char **argv, char **env) |
952 | { | |
1ccffcf5 | 953 | PerlInterpreter *one_perl, *two_perl; |
8ebc5c01 | 954 | char *one_args[] = { "one_perl", SAY_HELLO }; |
955 | char *two_args[] = { "two_perl", SAY_HELLO }; | |
956 | ||
1ccffcf5 IZ |
957 | PERL_SYS_INIT3(&argc,&argv,&env); |
958 | one_perl = perl_alloc(); | |
959 | two_perl = perl_alloc(); | |
960 | ||
9bbedd82 | 961 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 962 | perl_construct(one_perl); |
9bbedd82 | 963 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 964 | perl_construct(two_perl); |
965 | ||
9bbedd82 | 966 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 967 | perl_parse(one_perl, NULL, 3, one_args, (char **)NULL); |
9bbedd82 | 968 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 969 | perl_parse(two_perl, NULL, 3, two_args, (char **)NULL); |
970 | ||
9bbedd82 | 971 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 972 | perl_run(one_perl); |
9bbedd82 | 973 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 974 | perl_run(two_perl); |
975 | ||
9bbedd82 | 976 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 977 | perl_destruct(one_perl); |
9bbedd82 | 978 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 979 | perl_destruct(two_perl); |
980 | ||
9bbedd82 | 981 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 | 982 | perl_free(one_perl); |
9bbedd82 | 983 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 | 984 | perl_free(two_perl); |
1ccffcf5 | 985 | PERL_SYS_TERM(); |
8ebc5c01 | 986 | } |
987 | ||
9bbedd82 JH |
988 | Note the calls to PERL_SET_CONTEXT(). These are necessary to initialize |
989 | the global state that tracks which interpreter is the "current" one on | |
990 | the particular process or thread that may be running it. It should | |
991 | always be used if you have more than one interpreter and are making | |
992 | perl API calls on both interpreters in an interleaved fashion. | |
993 | ||
994 | PERL_SET_CONTEXT(interp) should also be called whenever C<interp> is | |
995 | used by a thread that did not create it (using either perl_alloc(), or | |
996 | the more esoteric perl_clone()). | |
8ebc5c01 | 997 | |
998 | Compile as usual: | |
999 | ||
5e6bcc01 GID |
1000 | % cc -o multiplicity multiplicity.c \ |
1001 | `perl -MExtUtils::Embed -e ccopts -e ldopts` | |
8ebc5c01 | 1002 | |
1003 | Run it, Run it: | |
1004 | ||
1005 | % multiplicity | |
1006 | Hi, I'm one_perl | |
1007 | Hi, I'm two_perl | |
1008 | ||
5e6bcc01 GID |
1009 | =head2 Using Perl modules, which themselves use C libraries, from your C |
1010 | program | |
96dbc785 | 1011 | |
1012 | If you've played with the examples above and tried to embed a script | |
5e6bcc01 GID |
1013 | that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++ |
1014 | library, this probably happened: | |
96dbc785 | 1015 | |
1016 | ||
1017 | Can't load module Socket, dynamic loading not available in this perl. | |
1018 | (You may need to build a new perl executable which either supports | |
1019 | dynamic loading or has the Socket module statically linked into it.) | |
1020 | ||
1021 | ||
1022 | What's wrong? | |
1023 | ||
1024 | Your interpreter doesn't know how to communicate with these extensions | |
1025 | on its own. A little glue will help. Up until now you've been | |
1026 | calling I<perl_parse()>, handing it NULL for the second argument: | |
1027 | ||
1028 | perl_parse(my_perl, NULL, argc, my_argv, NULL); | |
1029 | ||
5e6bcc01 GID |
1030 | That's where the glue code can be inserted to create the initial contact |
1031 | between Perl and linked C/C++ routines. Let's take a look some pieces of | |
1032 | I<perlmain.c> to see how Perl does this: | |
96dbc785 | 1033 | |
cc7dda15 | 1034 | static void xs_init (pTHX); |
96dbc785 | 1035 | |
cc7dda15 GS |
1036 | EXTERN_C void boot_DynaLoader (pTHX_ CV* cv); |
1037 | EXTERN_C void boot_Socket (pTHX_ CV* cv); | |
96dbc785 | 1038 | |
1039 | ||
1040 | EXTERN_C void | |
cc7dda15 | 1041 | xs_init(pTHX) |
96dbc785 | 1042 | { |
1043 | char *file = __FILE__; | |
1044 | /* DynaLoader is a special case */ | |
1045 | newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file); | |
1046 | newXS("Socket::bootstrap", boot_Socket, file); | |
1047 | } | |
1048 | ||
1049 | Simply put: for each extension linked with your Perl executable | |
1050 | (determined during its initial configuration on your | |
1051 | computer or when adding a new extension), | |
1052 | a Perl subroutine is created to incorporate the extension's | |
1053 | routines. Normally, that subroutine is named | |
1054 | I<Module::bootstrap()> and is invoked when you say I<use Module>. In | |
1055 | turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl | |
1056 | counterpart for each of the extension's XSUBs. Don't worry about this | |
1057 | part; leave that to the I<xsubpp> and extension authors. If your | |
1058 | extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()> | |
1059 | for you on the fly. In fact, if you have a working DynaLoader then there | |
5f05dabc | 1060 | is rarely any need to link in any other extensions statically. |
96dbc785 | 1061 | |
1062 | ||
1063 | Once you have this code, slap it into the second argument of I<perl_parse()>: | |
1064 | ||
1065 | ||
1066 | perl_parse(my_perl, xs_init, argc, my_argv, NULL); | |
1067 | ||
1068 | ||
1069 | Then compile: | |
1070 | ||
8a7dc658 | 1071 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
96dbc785 | 1072 | |
1073 | % interp | |
1074 | use Socket; | |
1075 | use SomeDynamicallyLoadedModule; | |
1076 | ||
1077 | print "Now I can use extensions!\n"' | |
1078 | ||
1079 | B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code. | |
1080 | ||
8a7dc658 | 1081 | % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c |
96dbc785 | 1082 | % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts` |
1083 | % cc -c interp.c `perl -MExtUtils::Embed -e ccopts` | |
8a7dc658 | 1084 | % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts` |
96dbc785 | 1085 | |
4929bf7b | 1086 | Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details. |
96dbc785 | 1087 | |
ccd65d51 KW |
1088 | =head2 Using embedded Perl with POSIX locales |
1089 | ||
1090 | (See L<perllocale> for information about these.) | |
1091 | When a Perl interpreter normally starts up, it tells the system it wants | |
1092 | to use the system's default locale. This is often, but not necessarily, | |
1093 | the "C" or "POSIX" locale. Absent a S<C<"use locale">> within the perl | |
1094 | code, this mostly has no effect (but see L<perllocale/Not within the | |
d6ded950 | 1095 | scope of "use locale">). Also, there is not a problem if the |
ccd65d51 KW |
1096 | locale you want to use in your embedded Perl is the same as the system |
1097 | default. However, this doesn't work if you have set up and want to use | |
1098 | a locale that isn't the system default one. Starting in Perl v5.20, you | |
1099 | can tell the embedded Perl interpreter that the locale is already | |
1100 | properly set up, and to skip doing its own normal initialization. It | |
1101 | skips if the environment variable C<PERL_SKIP_LOCALE_INIT> is set (even | |
1102 | if set to 0 or C<"">). A Perl that has this capability will define the | |
1103 | C pre-processor symbol C<HAS_SKIP_LOCALE_INIT>. This allows code that | |
1104 | has to work with multiple Perl versions to do some sort of work-around | |
1105 | when confronted with an earlier Perl. | |
1106 | ||
35209cc8 JH |
1107 | =head1 Hiding Perl_ |
1108 | ||
e1020413 | 1109 | If you completely hide the short forms of the Perl public API, |
d51482e4 | 1110 | add -DPERL_NO_SHORT_NAMES to the compilation flags. This means that |
35209cc8 JH |
1111 | for example instead of writing |
1112 | ||
1113 | warn("%d bottles of beer on the wall", bottlecount); | |
1114 | ||
1115 | you will have to write the explicit full form | |
1116 | ||
1117 | Perl_warn(aTHX_ "%d bottles of beer on the wall", bottlecount); | |
1118 | ||
96090e4f LB |
1119 | (See L<perlguts/"Background and PERL_IMPLICIT_CONTEXT"> for the explanation |
1120 | of the C<aTHX_>. ) Hiding the short forms is very useful for avoiding | |
35209cc8 JH |
1121 | all sorts of nasty (C preprocessor or otherwise) conflicts with other |
1122 | software packages (Perl defines about 2400 APIs with these short names, | |
1123 | take or leave few hundred, so there certainly is room for conflict.) | |
1124 | ||
cb1a09d0 AD |
1125 | =head1 MORAL |
1126 | ||
1127 | You can sometimes I<write faster code> in C, but | |
5f05dabc | 1128 | you can always I<write code faster> in Perl. Because you can use |
cb1a09d0 AD |
1129 | each from the other, combine them as you wish. |
1130 | ||
1131 | ||
1132 | =head1 AUTHOR | |
1133 | ||
8eabb633 JH |
1134 | Jon Orwant <F<orwant@media.mit.edu>> and Doug MacEachern |
1135 | <F<dougm@covalent.net>>, with small contributions from Tim Bunce, Tom | |
e010571f GS |
1136 | Christiansen, Guy Decoux, Hallvard Furuseth, Dov Grobgeld, and Ilya |
1137 | Zakharevich. | |
cb1a09d0 | 1138 | |
e010571f | 1139 | Doug MacEachern has an article on embedding in Volume 1, Issue 4 of |
f224927c | 1140 | The Perl Journal ( http://www.tpj.com/ ). Doug is also the developer of the |
e010571f GS |
1141 | most widely-used Perl embedding: the mod_perl system |
1142 | (perl.apache.org), which embeds Perl in the Apache web server. | |
1143 | Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl | |
1144 | have used this model for Oracle, Netscape and Internet Information | |
1145 | Server Perl plugins. | |
cb1a09d0 | 1146 | |
8a7dc658 JO |
1147 | =head1 COPYRIGHT |
1148 | ||
e010571f | 1149 | Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant. All |
8a7dc658 JO |
1150 | Rights Reserved. |
1151 | ||
608704e1 | 1152 | This document may be distributed under the same terms as Perl itself. |