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1 | =head1 NAME |
2 | |
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3 | perlembed - how to embed perl in your C program |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
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7 | =head2 PREAMBLE |
8 | |
9 | Do you want to: |
10 | |
11 | =over 5 |
12 | |
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13 | =item B<Use C from Perl?> |
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14 | |
15 | Read L<perlcall> and L<perlxs>. |
16 | |
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17 | =item B<Use a Unix program from Perl?> |
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18 | |
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19 | Read about back-quotes and about C<system> and C<exec> in L<perlfunc>. |
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20 | |
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21 | =item B<Use Perl from Perl?> |
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22 | |
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23 | Read about L<perlfunc/do> and L<perlfunc/eval> and L<perlfunc/require> |
24 | and L<perlfunc/use>. |
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25 | |
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26 | =item B<Use C from C?> |
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27 | |
28 | Rethink your design. |
29 | |
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30 | =item B<Use Perl from C?> |
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31 | |
32 | Read on... |
33 | |
34 | =back |
35 | |
36 | =head2 ROADMAP |
37 | |
38 | L<Compiling your C program> |
39 | |
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40 | There's one example in each of the nine sections: |
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41 | |
42 | L<Adding a Perl interpreter to your C program> |
43 | |
44 | L<Calling a Perl subroutine from your C program> |
45 | |
46 | L<Evaluating a Perl statement from your C program> |
47 | |
48 | L<Performing Perl pattern matches and substitutions from your C program> |
49 | |
50 | L<Fiddling with the Perl stack from your C program> |
51 | |
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52 | L<Maintaining a persistent interpreter> |
53 | |
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54 | L<Maintaining multiple interpreter instances> |
55 | |
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56 | L<Using Perl modules, which themselves use C libraries, from your C program> |
57 | |
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58 | L<Embedding Perl under Win32> |
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59 | |
60 | =head2 Compiling your C program |
61 | |
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62 | If you have trouble compiling the scripts in this documentation, |
63 | you're not alone. The cardinal rule: COMPILE THE PROGRAMS IN EXACTLY |
64 | THE SAME WAY THAT YOUR PERL WAS COMPILED. (Sorry for yelling.) |
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65 | |
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66 | Also, every C program that uses Perl must link in the I<perl library>. |
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67 | What's that, you ask? Perl is itself written in C; the perl library |
68 | is the collection of compiled C programs that were used to create your |
69 | perl executable (I</usr/bin/perl> or equivalent). (Corollary: you |
70 | can't use Perl from your C program unless Perl has been compiled on |
71 | your machine, or installed properly--that's why you shouldn't blithely |
72 | copy Perl executables from machine to machine without also copying the |
73 | I<lib> directory.) |
74 | |
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75 | When you use Perl from C, your C program will--usually--allocate, |
76 | "run", and deallocate a I<PerlInterpreter> object, which is defined by |
77 | the perl library. |
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78 | |
79 | If your copy of Perl is recent enough to contain this documentation |
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80 | (version 5.002 or later), then the perl library (and I<EXTERN.h> and |
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81 | I<perl.h>, which you'll also need) will reside in a directory |
82 | that looks like this: |
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83 | |
84 | /usr/local/lib/perl5/your_architecture_here/CORE |
85 | |
86 | or perhaps just |
87 | |
88 | /usr/local/lib/perl5/CORE |
89 | |
90 | or maybe something like |
91 | |
92 | /usr/opt/perl5/CORE |
93 | |
94 | Execute this statement for a hint about where to find CORE: |
95 | |
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96 | perl -MConfig -e 'print $Config{archlib}' |
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97 | |
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98 | Here's how you'd compile the example in the next section, |
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99 | L<Adding a Perl interpreter to your C program>, on my Linux box: |
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100 | |
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101 | % gcc -O2 -Dbool=char -DHAS_BOOL -I/usr/local/include |
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102 | -I/usr/local/lib/perl5/i586-linux/5.003/CORE |
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103 | -L/usr/local/lib/perl5/i586-linux/5.003/CORE |
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104 | -o interp interp.c -lperl -lm |
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105 | |
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106 | (That's all one line.) On my DEC Alpha running 5.003_05, the incantation |
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107 | is a bit different: |
108 | |
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109 | % cc -O2 -Olimit 2900 -DSTANDARD_C -I/usr/local/include |
110 | -I/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE |
111 | -L/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE -L/usr/local/lib |
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112 | -D__LANGUAGE_C__ -D_NO_PROTO -o interp interp.c -lperl -lm |
113 | |
114 | How can you figure out what to add? Assuming your Perl is post-5.001, |
115 | execute a C<perl -V> command and pay special attention to the "cc" and |
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116 | "ccflags" information. |
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117 | |
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118 | You'll have to choose the appropriate compiler (I<cc>, I<gcc>, et al.) for |
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119 | your machine: C<perl -MConfig -e 'print $Config{cc}'> will tell you what |
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120 | to use. |
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121 | |
122 | You'll also have to choose the appropriate library directory |
123 | (I</usr/local/lib/...>) for your machine. If your compiler complains |
124 | that certain functions are undefined, or that it can't locate |
125 | I<-lperl>, then you need to change the path following the C<-L>. If it |
126 | complains that it can't find I<EXTERN.h> and I<perl.h>, you need to |
127 | change the path following the C<-I>. |
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128 | |
129 | You may have to add extra libraries as well. Which ones? |
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130 | Perhaps those printed by |
131 | |
132 | perl -MConfig -e 'print $Config{libs}' |
133 | |
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134 | Provided your perl binary was properly configured and installed the |
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135 | B<ExtUtils::Embed> module will determine all of this information for |
136 | you: |
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137 | |
138 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
139 | |
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140 | If the B<ExtUtils::Embed> module isn't part of your Perl distribution, |
141 | you can retrieve it from |
142 | http://www.perl.com/perl/CPAN/modules/by-module/ExtUtils::Embed. (If |
143 | this documentation came from your Perl distribution, then you're |
144 | running 5.004 or better and you already have it.) |
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145 | |
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146 | The B<ExtUtils::Embed> kit on CPAN also contains all source code for |
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147 | the examples in this document, tests, additional examples and other |
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148 | information you may find useful. |
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149 | |
150 | =head2 Adding a Perl interpreter to your C program |
151 | |
152 | In a sense, perl (the C program) is a good example of embedding Perl |
153 | (the language), so I'll demonstrate embedding with I<miniperlmain.c>, |
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154 | from the source distribution. Here's a bastardized, nonportable |
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155 | version of I<miniperlmain.c> containing the essentials of embedding: |
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156 | |
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157 | #include <EXTERN.h> /* from the Perl distribution */ |
158 | #include <perl.h> /* from the Perl distribution */ |
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159 | |
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160 | static PerlInterpreter *my_perl; /*** The Perl interpreter ***/ |
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161 | |
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162 | int main(int argc, char **argv, char **env) |
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163 | { |
164 | my_perl = perl_alloc(); |
165 | perl_construct(my_perl); |
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166 | perl_parse(my_perl, NULL, argc, argv, (char **)NULL); |
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167 | perl_run(my_perl); |
168 | perl_destruct(my_perl); |
169 | perl_free(my_perl); |
170 | } |
171 | |
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172 | Notice that we don't use the C<env> pointer. Normally handed to |
173 | C<perl_parse> as its final argument, C<env> here is replaced by |
174 | C<NULL>, which means that the current environment will be used. |
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175 | |
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176 | Now compile this program (I'll call it I<interp.c>) into an executable: |
177 | |
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178 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
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179 | |
180 | After a successful compilation, you'll be able to use I<interp> just |
181 | like perl itself: |
182 | |
183 | % interp |
184 | print "Pretty Good Perl \n"; |
185 | print "10890 - 9801 is ", 10890 - 9801; |
186 | <CTRL-D> |
187 | Pretty Good Perl |
188 | 10890 - 9801 is 1089 |
189 | |
190 | or |
191 | |
192 | % interp -e 'printf("%x", 3735928559)' |
193 | deadbeef |
194 | |
195 | You can also read and execute Perl statements from a file while in the |
196 | midst of your C program, by placing the filename in I<argv[1]> before |
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197 | calling I<perl_run()>. |
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198 | |
199 | =head2 Calling a Perl subroutine from your C program |
200 | |
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201 | To call individual Perl subroutines, you can use any of the B<perl_call_*> |
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202 | functions documented in the L<perlcall> manpage. |
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203 | In this example we'll use I<perl_call_argv>. |
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204 | |
205 | That's shown below, in a program I'll call I<showtime.c>. |
206 | |
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207 | #include <EXTERN.h> |
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208 | #include <perl.h> |
209 | |
210 | static PerlInterpreter *my_perl; |
211 | |
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212 | int main(int argc, char **argv, char **env) |
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213 | { |
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214 | char *args[] = { NULL }; |
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215 | my_perl = perl_alloc(); |
216 | perl_construct(my_perl); |
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217 | |
218 | perl_parse(my_perl, NULL, argc, argv, NULL); |
219 | |
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220 | /*** skipping perl_run() ***/ |
221 | |
222 | perl_call_argv("showtime", G_DISCARD | G_NOARGS, args); |
223 | |
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224 | perl_destruct(my_perl); |
225 | perl_free(my_perl); |
226 | } |
227 | |
228 | where I<showtime> is a Perl subroutine that takes no arguments (that's the |
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229 | I<G_NOARGS>) and for which I'll ignore the return value (that's the |
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230 | I<G_DISCARD>). Those flags, and others, are discussed in L<perlcall>. |
231 | |
232 | I'll define the I<showtime> subroutine in a file called I<showtime.pl>: |
233 | |
234 | print "I shan't be printed."; |
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235 | |
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236 | sub showtime { |
237 | print time; |
238 | } |
239 | |
240 | Simple enough. Now compile and run: |
241 | |
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242 | % cc -o showtime showtime.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
243 | |
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244 | % showtime showtime.pl |
245 | 818284590 |
246 | |
247 | yielding the number of seconds that elapsed between January 1, 1970 |
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248 | (the beginning of the Unix epoch), and the moment I began writing this |
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249 | sentence. |
250 | |
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251 | In this particular case we don't have to call I<perl_run>, but in |
252 | general it's considered good practice to ensure proper initialization |
253 | of library code, including execution of all object C<DESTROY> methods |
254 | and package C<END {}> blocks. |
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255 | |
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256 | If you want to pass arguments to the Perl subroutine, you can add |
257 | strings to the C<NULL>-terminated C<args> list passed to |
258 | I<perl_call_argv>. For other data types, or to examine return values, |
259 | you'll need to manipulate the Perl stack. That's demonstrated in the |
260 | last section of this document: L<Fiddling with the Perl stack from |
261 | your C program>. |
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262 | |
263 | =head2 Evaluating a Perl statement from your C program |
264 | |
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265 | Perl provides two API functions to evaluate pieces of Perl code. |
266 | These are L<perlguts/perl_eval_sv()> and L<perlguts/perl_eval_pv()>. |
267 | |
268 | Arguably, these are the only routines you'll ever need to execute |
269 | snippets of Perl code from within your C program. Your code can be |
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270 | as long as you wish; it can contain multiple statements; it can employ |
271 | L<perlfunc/use>, L<perlfunc/require> and L<perlfunc/do> to include |
272 | external Perl files. |
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273 | |
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274 | I<perl_eval_pv()> lets us evaluate individual Perl strings, and then |
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275 | extract variables for coercion into C types. The following program, |
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276 | I<string.c>, executes three Perl strings, extracting an C<int> from |
277 | the first, a C<float> from the second, and a C<char *> from the third. |
278 | |
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279 | #include <EXTERN.h> |
280 | #include <perl.h> |
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281 | |
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282 | static PerlInterpreter *my_perl; |
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283 | |
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284 | main (int argc, char **argv, char **env) |
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285 | { |
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286 | char *embedding[] = { "", "-e", "0" }; |
287 | |
288 | my_perl = perl_alloc(); |
289 | perl_construct( my_perl ); |
290 | |
291 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
292 | perl_run(my_perl); |
293 | |
294 | /** Treat $a as an integer **/ |
295 | perl_eval_pv("$a = 3; $a **= 2", TRUE); |
296 | printf("a = %d\n", SvIV(perl_get_sv("a", FALSE))); |
297 | |
298 | /** Treat $a as a float **/ |
299 | perl_eval_pv("$a = 3.14; $a **= 2", TRUE); |
300 | printf("a = %f\n", SvNV(perl_get_sv("a", FALSE))); |
301 | |
302 | /** Treat $a as a string **/ |
303 | perl_eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE); |
304 | printf("a = %s\n", SvPV(perl_get_sv("a", FALSE), na)); |
305 | |
306 | perl_destruct(my_perl); |
307 | perl_free(my_perl); |
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308 | } |
309 | |
310 | All of those strange functions with I<sv> in their names help convert Perl scalars to C types. They're described in L<perlguts>. |
311 | |
312 | If you compile and run I<string.c>, you'll see the results of using |
313 | I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and |
314 | I<SvPV()> to create a string: |
315 | |
316 | a = 9 |
317 | a = 9.859600 |
318 | a = Just Another Perl Hacker |
319 | |
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320 | In the example above, we've created a global variable to temporarily |
321 | store the computed value of our eval'd expression. It is also |
322 | possible and in most cases a better strategy to fetch the return value |
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323 | from L<perl_eval_pv> instead. Example: |
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324 | |
8f183262 |
325 | ... |
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326 | SV *val = perl_eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); |
8f183262 |
327 | printf("%s\n", SvPV(val,na)); |
328 | ... |
329 | |
330 | This way, we avoid namespace pollution by not creating global |
331 | variables and we've simplified our code as well. |
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332 | |
333 | =head2 Performing Perl pattern matches and substitutions from your C program |
334 | |
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335 | The I<perl_eval_pv()> function lets us evaluate strings of Perl code, so we can |
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336 | define some functions that use it to "specialize" in matches and |
337 | substitutions: I<match()>, I<substitute()>, and I<matches()>. |
338 | |
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339 | char match(char *string, char *pattern); |
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340 | |
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341 | Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which |
342 | in your C program might appear as "/\\b\\w*\\b/"), match() |
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343 | returns 1 if the string matches the pattern and 0 otherwise. |
344 | |
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345 | int substitute(char *string[], char *pattern); |
346 | |
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347 | Given a pointer to a string and an C<=~> operation (e.g., |
348 | C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string |
349 | according to the operation, returning the number of substitutions |
350 | made. |
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351 | |
352 | int matches(char *string, char *pattern, char **matches[]); |
353 | |
354 | Given a string, a pattern, and a pointer to an empty array of strings, |
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355 | matches() evaluates C<$string =~ $pattern> in an array context, and |
356 | fills in I<matches> with the array elements (allocating memory as it |
357 | does so), returning the number of matches found. |
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358 | |
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359 | Here's a sample program, I<match.c>, that uses all three (long lines have |
360 | been wrapped here): |
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361 | |
cb1a09d0 |
362 | #include <EXTERN.h> |
363 | #include <perl.h> |
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364 | |
cb1a09d0 |
365 | static PerlInterpreter *my_perl; |
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366 | |
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367 | /** match(string, pattern) |
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368 | ** |
369 | ** Used for matches in a scalar context. |
370 | ** |
371 | ** Returns 1 if the match was successful; 0 otherwise. |
372 | **/ |
373 | char match(char *string, char *pattern) |
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374 | { |
375 | char *command; |
376 | command = malloc(sizeof(char) * strlen(string) + strlen(pattern) + 37); |
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377 | sprintf(command, "$string = '%s'; $return = $string =~ %s", |
8ebc5c01 |
378 | string, pattern); |
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379 | perl_eval_pv(command, TRUE); |
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380 | free(command); |
381 | return SvIV(perl_get_sv("return", FALSE)); |
382 | } |
cb1a09d0 |
383 | /** substitute(string, pattern) |
96dbc785 |
384 | ** |
385 | ** Used for =~ operations that modify their left-hand side (s/// and tr///) |
386 | ** |
387 | ** Returns the number of successful matches, and |
388 | ** modifies the input string if there were any. |
389 | **/ |
390 | int substitute(char *string[], char *pattern) |
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391 | { |
392 | char *command; |
393 | STRLEN length; |
394 | command = malloc(sizeof(char) * strlen(*string) + strlen(pattern) + 35); |
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395 | sprintf(command, "$string = '%s'; $ret = ($string =~ %s)", |
8ebc5c01 |
396 | *string, pattern); |
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397 | perl_eval_pv(command, TRUE); |
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398 | free(command); |
399 | *string = SvPV(perl_get_sv("string", FALSE), length); |
400 | return SvIV(perl_get_sv("ret", FALSE)); |
cb1a09d0 |
401 | } |
cb1a09d0 |
402 | /** matches(string, pattern, matches) |
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403 | ** |
404 | ** Used for matches in an array context. |
405 | ** |
406 | ** Returns the number of matches, |
407 | ** and fills in **matches with the matching substrings (allocates memory!) |
408 | **/ |
409 | int matches(char *string, char *pattern, char **match_list[]) |
cb1a09d0 |
410 | { |
411 | char *command; |
412 | SV *current_match; |
413 | AV *array; |
414 | I32 num_matches; |
415 | STRLEN length; |
416 | int i; |
cb1a09d0 |
417 | command = malloc(sizeof(char) * strlen(string) + strlen(pattern) + 38); |
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418 | sprintf(command, "$string = '%s'; @array = ($string =~ %s)", |
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419 | string, pattern); |
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420 | perl_eval_pv(command, TRUE); |
cb1a09d0 |
421 | free(command); |
422 | array = perl_get_av("array", FALSE); |
423 | num_matches = av_len(array) + 1; /** assume $[ is 0 **/ |
96dbc785 |
424 | *match_list = (char **) malloc(sizeof(char *) * num_matches); |
425 | for (i = 0; i <= num_matches; i++) { |
cb1a09d0 |
426 | current_match = av_shift(array); |
96dbc785 |
427 | (*match_list)[i] = SvPV(current_match, length); |
cb1a09d0 |
428 | } |
429 | return num_matches; |
430 | } |
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431 | main (int argc, char **argv, char **env) |
cb1a09d0 |
432 | { |
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433 | char *embedding[] = { "", "-e", "0" }; |
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434 | char *text, **match_list; |
cb1a09d0 |
435 | int num_matches, i; |
436 | int j; |
cb1a09d0 |
437 | my_perl = perl_alloc(); |
438 | perl_construct( my_perl ); |
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439 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
8ebc5c01 |
440 | perl_run(my_perl); |
441 | |
cb1a09d0 |
442 | text = (char *) malloc(sizeof(char) * 486); /** A long string follows! **/ |
96dbc785 |
443 | sprintf(text, "%s", "When he is at a convenience store and the bill \ |
444 | comes to some amount like 76 cents, Maynard is aware that there is \ |
445 | something he *should* do, something that will enable him to get back \ |
446 | a quarter, but he has no idea *what*. He fumbles through his red \ |
447 | squeezey changepurse and gives the boy three extra pennies with his \ |
448 | dollar, hoping that he might luck into the correct amount. The boy \ |
449 | gives him back two of his own pennies and then the big shiny quarter \ |
450 | that is his prize. -RICHH"); |
451 | if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/ |
452 | printf("match: Text contains the word 'quarter'.\n\n"); |
453 | else |
454 | printf("match: Text doesn't contain the word 'quarter'.\n\n"); |
455 | if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/ |
456 | printf("match: Text contains the word 'eighth'.\n\n"); |
457 | else |
458 | printf("match: Text doesn't contain the word 'eighth'.\n\n"); |
459 | /** Match all occurrences of /wi../ **/ |
460 | num_matches = matches(text, "m/(wi..)/g", &match_list); |
461 | printf("matches: m/(wi..)/g found %d matches...\n", num_matches); |
462 | for (i = 0; i < num_matches; i++) |
463 | printf("match: %s\n", match_list[i]); |
cb1a09d0 |
464 | printf("\n"); |
465 | for (i = 0; i < num_matches; i++) { |
96dbc785 |
466 | free(match_list[i]); |
cb1a09d0 |
467 | } |
96dbc785 |
468 | free(match_list); |
469 | /** Remove all vowels from text **/ |
470 | num_matches = substitute(&text, "s/[aeiou]//gi"); |
cb1a09d0 |
471 | if (num_matches) { |
96dbc785 |
472 | printf("substitute: s/[aeiou]//gi...%d substitutions made.\n", |
8ebc5c01 |
473 | num_matches); |
cb1a09d0 |
474 | printf("Now text is: %s\n\n", text); |
475 | } |
96dbc785 |
476 | /** Attempt a substitution **/ |
477 | if (!substitute(&text, "s/Perl/C/")) { |
478 | printf("substitute: s/Perl/C...No substitution made.\n\n"); |
cb1a09d0 |
479 | } |
cb1a09d0 |
480 | free(text); |
cb1a09d0 |
481 | perl_destruct(my_perl); |
482 | perl_free(my_perl); |
483 | } |
484 | |
96dbc785 |
485 | which produces the output (again, long lines have been wrapped here) |
cb1a09d0 |
486 | |
8a7dc658 |
487 | match: Text contains the word 'quarter'. |
96dbc785 |
488 | |
8a7dc658 |
489 | match: Text doesn't contain the word 'eighth'. |
96dbc785 |
490 | |
8a7dc658 |
491 | matches: m/(wi..)/g found 2 matches... |
cb1a09d0 |
492 | match: will |
493 | match: with |
96dbc785 |
494 | |
8a7dc658 |
495 | substitute: s/[aeiou]//gi...139 substitutions made. |
54310121 |
496 | Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts, |
96dbc785 |
497 | Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt bck |
498 | qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd gvs th by |
499 | thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct mnt. Th by gvs |
500 | hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s hs prz. -RCHH |
501 | |
8a7dc658 |
502 | substitute: s/Perl/C...No substitution made. |
96dbc785 |
503 | |
cb1a09d0 |
504 | =head2 Fiddling with the Perl stack from your C program |
505 | |
506 | When trying to explain stacks, most computer science textbooks mumble |
507 | something about spring-loaded columns of cafeteria plates: the last |
508 | thing you pushed on the stack is the first thing you pop off. That'll |
509 | do for our purposes: your C program will push some arguments onto "the Perl |
510 | stack", shut its eyes while some magic happens, and then pop the |
511 | results--the return value of your Perl subroutine--off the stack. |
96dbc785 |
512 | |
cb1a09d0 |
513 | First you'll need to know how to convert between C types and Perl |
514 | types, with newSViv() and sv_setnv() and newAV() and all their |
515 | friends. They're described in L<perlguts>. |
516 | |
517 | Then you'll need to know how to manipulate the Perl stack. That's |
518 | described in L<perlcall>. |
519 | |
96dbc785 |
520 | Once you've understood those, embedding Perl in C is easy. |
cb1a09d0 |
521 | |
54310121 |
522 | Because C has no builtin function for integer exponentiation, let's |
cb1a09d0 |
523 | make Perl's ** operator available to it (this is less useful than it |
5f05dabc |
524 | sounds, because Perl implements ** with C's I<pow()> function). First |
cb1a09d0 |
525 | I'll create a stub exponentiation function in I<power.pl>: |
526 | |
527 | sub expo { |
528 | my ($a, $b) = @_; |
529 | return $a ** $b; |
530 | } |
531 | |
532 | Now I'll create a C program, I<power.c>, with a function |
533 | I<PerlPower()> that contains all the perlguts necessary to push the |
534 | two arguments into I<expo()> and to pop the return value out. Take a |
535 | deep breath... |
536 | |
cb1a09d0 |
537 | #include <EXTERN.h> |
538 | #include <perl.h> |
96dbc785 |
539 | |
cb1a09d0 |
540 | static PerlInterpreter *my_perl; |
96dbc785 |
541 | |
cb1a09d0 |
542 | static void |
543 | PerlPower(int a, int b) |
544 | { |
545 | dSP; /* initialize stack pointer */ |
546 | ENTER; /* everything created after here */ |
547 | SAVETMPS; /* ...is a temporary variable. */ |
548 | PUSHMARK(sp); /* remember the stack pointer */ |
549 | XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */ |
550 | XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */ |
551 | PUTBACK; /* make local stack pointer global */ |
552 | perl_call_pv("expo", G_SCALAR); /* call the function */ |
553 | SPAGAIN; /* refresh stack pointer */ |
554 | /* pop the return value from stack */ |
555 | printf ("%d to the %dth power is %d.\n", a, b, POPi); |
96dbc785 |
556 | PUTBACK; |
cb1a09d0 |
557 | FREETMPS; /* free that return value */ |
558 | LEAVE; /* ...and the XPUSHed "mortal" args.*/ |
559 | } |
96dbc785 |
560 | |
561 | int main (int argc, char **argv, char **env) |
cb1a09d0 |
562 | { |
563 | char *my_argv[2]; |
96dbc785 |
564 | |
cb1a09d0 |
565 | my_perl = perl_alloc(); |
566 | perl_construct( my_perl ); |
96dbc785 |
567 | |
cb1a09d0 |
568 | my_argv[1] = (char *) malloc(10); |
569 | sprintf(my_argv[1], "power.pl"); |
96dbc785 |
570 | |
571 | perl_parse(my_perl, NULL, argc, my_argv, NULL); |
8ebc5c01 |
572 | perl_run(my_perl); |
96dbc785 |
573 | |
cb1a09d0 |
574 | PerlPower(3, 4); /*** Compute 3 ** 4 ***/ |
96dbc785 |
575 | |
cb1a09d0 |
576 | perl_destruct(my_perl); |
577 | perl_free(my_perl); |
578 | } |
96dbc785 |
579 | |
cb1a09d0 |
580 | |
581 | |
582 | Compile and run: |
583 | |
96dbc785 |
584 | % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
585 | |
586 | % power |
cb1a09d0 |
587 | 3 to the 4th power is 81. |
588 | |
a6006777 |
589 | =head2 Maintaining a persistent interpreter |
590 | |
8a7dc658 |
591 | When developing interactive and/or potentially long-running |
592 | applications, it's a good idea to maintain a persistent interpreter |
593 | rather than allocating and constructing a new interpreter multiple |
594 | times. The major reason is speed: since Perl will only be loaded into |
54310121 |
595 | memory once. |
8a7dc658 |
596 | |
597 | However, you have to be more cautious with namespace and variable |
598 | scoping when using a persistent interpreter. In previous examples |
599 | we've been using global variables in the default package C<main>. We |
600 | knew exactly what code would be run, and assumed we could avoid |
601 | variable collisions and outrageous symbol table growth. |
602 | |
603 | Let's say your application is a server that will occasionally run Perl |
604 | code from some arbitrary file. Your server has no way of knowing what |
605 | code it's going to run. Very dangerous. |
606 | |
607 | If the file is pulled in by C<perl_parse()>, compiled into a newly |
608 | constructed interpreter, and subsequently cleaned out with |
609 | C<perl_destruct()> afterwards, you're shielded from most namespace |
610 | troubles. |
611 | |
612 | One way to avoid namespace collisions in this scenario is to translate |
613 | the filename into a guaranteed-unique package name, and then compile |
614 | the code into that package using L<perlfunc/eval>. In the example |
615 | below, each file will only be compiled once. Or, the application |
616 | might choose to clean out the symbol table associated with the file |
617 | after it's no longer needed. Using L<perlcall/perl_call_argv>, We'll |
618 | call the subroutine C<Embed::Persistent::eval_file> which lives in the |
619 | file C<persistent.pl> and pass the filename and boolean cleanup/cache |
a6006777 |
620 | flag as arguments. |
621 | |
8a7dc658 |
622 | Note that the process will continue to grow for each file that it |
623 | uses. In addition, there might be C<AUTOLOAD>ed subroutines and other |
624 | conditions that cause Perl's symbol table to grow. You might want to |
625 | add some logic that keeps track of the process size, or restarts |
626 | itself after a certain number of requests, to ensure that memory |
627 | consumption is minimized. You'll also want to scope your variables |
628 | with L<perlfunc/my> whenever possible. |
a6006777 |
629 | |
54310121 |
630 | |
a6006777 |
631 | package Embed::Persistent; |
632 | #persistent.pl |
54310121 |
633 | |
a6006777 |
634 | use strict; |
635 | use vars '%Cache'; |
54310121 |
636 | |
a6006777 |
637 | sub valid_package_name { |
638 | my($string) = @_; |
639 | $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg; |
640 | # second pass only for words starting with a digit |
641 | $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg; |
54310121 |
642 | |
a6006777 |
643 | # Dress it up as a real package name |
644 | $string =~ s|/|::|g; |
645 | return "Embed" . $string; |
646 | } |
54310121 |
647 | |
a6006777 |
648 | #borrowed from Safe.pm |
649 | sub delete_package { |
650 | my $pkg = shift; |
651 | my ($stem, $leaf); |
54310121 |
652 | |
a6006777 |
653 | no strict 'refs'; |
8ebc5c01 |
654 | $pkg = "main::$pkg\::"; # expand to full symbol table name |
a6006777 |
655 | ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; |
54310121 |
656 | |
a6006777 |
657 | my $stem_symtab = *{$stem}{HASH}; |
54310121 |
658 | |
a6006777 |
659 | delete $stem_symtab->{$leaf}; |
660 | } |
54310121 |
661 | |
a6006777 |
662 | sub eval_file { |
663 | my($filename, $delete) = @_; |
664 | my $package = valid_package_name($filename); |
665 | my $mtime = -M $filename; |
666 | if(defined $Cache{$package}{mtime} |
667 | && |
54310121 |
668 | $Cache{$package}{mtime} <= $mtime) |
a6006777 |
669 | { |
54310121 |
670 | # we have compiled this subroutine already, |
8ebc5c01 |
671 | # it has not been updated on disk, nothing left to do |
672 | print STDERR "already compiled $package->handler\n"; |
a6006777 |
673 | } |
674 | else { |
8ebc5c01 |
675 | local *FH; |
676 | open FH, $filename or die "open '$filename' $!"; |
677 | local($/) = undef; |
678 | my $sub = <FH>; |
679 | close FH; |
54310121 |
680 | |
8ebc5c01 |
681 | #wrap the code into a subroutine inside our unique package |
682 | my $eval = qq{package $package; sub handler { $sub; }}; |
683 | { |
684 | # hide our variables within this block |
685 | my($filename,$mtime,$package,$sub); |
686 | eval $eval; |
687 | } |
688 | die $@ if $@; |
54310121 |
689 | |
8ebc5c01 |
690 | #cache it unless we're cleaning out each time |
691 | $Cache{$package}{mtime} = $mtime unless $delete; |
a6006777 |
692 | } |
54310121 |
693 | |
a6006777 |
694 | eval {$package->handler;}; |
695 | die $@ if $@; |
54310121 |
696 | |
a6006777 |
697 | delete_package($package) if $delete; |
54310121 |
698 | |
a6006777 |
699 | #take a look if you want |
700 | #print Devel::Symdump->rnew($package)->as_string, $/; |
701 | } |
54310121 |
702 | |
a6006777 |
703 | 1; |
54310121 |
704 | |
a6006777 |
705 | __END__ |
706 | |
707 | /* persistent.c */ |
54310121 |
708 | #include <EXTERN.h> |
709 | #include <perl.h> |
710 | |
a6006777 |
711 | /* 1 = clean out filename's symbol table after each request, 0 = don't */ |
712 | #ifndef DO_CLEAN |
713 | #define DO_CLEAN 0 |
714 | #endif |
54310121 |
715 | |
a6006777 |
716 | static PerlInterpreter *perl = NULL; |
54310121 |
717 | |
a6006777 |
718 | int |
719 | main(int argc, char **argv, char **env) |
720 | { |
721 | char *embedding[] = { "", "persistent.pl" }; |
722 | char *args[] = { "", DO_CLEAN, NULL }; |
723 | char filename [1024]; |
724 | int exitstatus = 0; |
54310121 |
725 | |
a6006777 |
726 | if((perl = perl_alloc()) == NULL) { |
8ebc5c01 |
727 | fprintf(stderr, "no memory!"); |
728 | exit(1); |
a6006777 |
729 | } |
54310121 |
730 | perl_construct(perl); |
731 | |
a6006777 |
732 | exitstatus = perl_parse(perl, NULL, 2, embedding, NULL); |
54310121 |
733 | |
734 | if(!exitstatus) { |
8ebc5c01 |
735 | exitstatus = perl_run(perl); |
54310121 |
736 | |
8ebc5c01 |
737 | while(printf("Enter file name: ") && gets(filename)) { |
54310121 |
738 | |
8ebc5c01 |
739 | /* call the subroutine, passing it the filename as an argument */ |
740 | args[0] = filename; |
54310121 |
741 | perl_call_argv("Embed::Persistent::eval_file", |
8ebc5c01 |
742 | G_DISCARD | G_EVAL, args); |
54310121 |
743 | |
8ebc5c01 |
744 | /* check $@ */ |
54310121 |
745 | if(SvTRUE(GvSV(errgv))) |
8ebc5c01 |
746 | fprintf(stderr, "eval error: %s\n", SvPV(GvSV(errgv),na)); |
747 | } |
a6006777 |
748 | } |
54310121 |
749 | |
a6006777 |
750 | perl_destruct_level = 0; |
54310121 |
751 | perl_destruct(perl); |
752 | perl_free(perl); |
a6006777 |
753 | exit(exitstatus); |
754 | } |
755 | |
a6006777 |
756 | Now compile: |
757 | |
54310121 |
758 | % cc -o persistent persistent.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
a6006777 |
759 | |
760 | Here's a example script file: |
761 | |
762 | #test.pl |
763 | my $string = "hello"; |
764 | foo($string); |
765 | |
766 | sub foo { |
767 | print "foo says: @_\n"; |
768 | } |
769 | |
770 | Now run: |
771 | |
772 | % persistent |
773 | Enter file name: test.pl |
774 | foo says: hello |
775 | Enter file name: test.pl |
776 | already compiled Embed::test_2epl->handler |
777 | foo says: hello |
778 | Enter file name: ^C |
779 | |
8ebc5c01 |
780 | =head2 Maintaining multiple interpreter instances |
781 | |
8a7dc658 |
782 | Some rare applications will need to create more than one interpreter |
783 | during a session. Such an application might sporadically decide to |
54310121 |
784 | release any resources associated with the interpreter. |
8a7dc658 |
785 | |
786 | The program must take care to ensure that this takes place I<before> |
787 | the next interpreter is constructed. By default, the global variable |
788 | C<perl_destruct_level> is set to C<0>, since extra cleaning isn't |
789 | needed when a program has only one interpreter. |
790 | |
791 | Setting C<perl_destruct_level> to C<1> makes everything squeaky clean: |
792 | |
54310121 |
793 | perl_destruct_level = 1; |
8ebc5c01 |
794 | |
8ebc5c01 |
795 | while(1) { |
796 | ... |
797 | /* reset global variables here with perl_destruct_level = 1 */ |
54310121 |
798 | perl_construct(my_perl); |
8ebc5c01 |
799 | ... |
800 | /* clean and reset _everything_ during perl_destruct */ |
54310121 |
801 | perl_destruct(my_perl); |
802 | perl_free(my_perl); |
8ebc5c01 |
803 | ... |
804 | /* let's go do it again! */ |
805 | } |
806 | |
54310121 |
807 | When I<perl_destruct()> is called, the interpreter's syntax parse tree |
808 | and symbol tables are cleaned up, and global variables are reset. |
8ebc5c01 |
809 | |
8a7dc658 |
810 | Now suppose we have more than one interpreter instance running at the |
811 | same time. This is feasible, but only if you used the |
812 | C<-DMULTIPLICITY> flag when building Perl. By default, that sets |
813 | C<perl_destruct_level> to C<1>. |
8ebc5c01 |
814 | |
815 | Let's give it a try: |
816 | |
817 | |
818 | #include <EXTERN.h> |
8a7dc658 |
819 | #include <perl.h> |
8ebc5c01 |
820 | |
821 | /* we're going to embed two interpreters */ |
822 | /* we're going to embed two interpreters */ |
823 | |
8ebc5c01 |
824 | #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)" |
825 | |
8ebc5c01 |
826 | int main(int argc, char **argv, char **env) |
827 | { |
54310121 |
828 | PerlInterpreter |
8ebc5c01 |
829 | *one_perl = perl_alloc(), |
54310121 |
830 | *two_perl = perl_alloc(); |
8ebc5c01 |
831 | char *one_args[] = { "one_perl", SAY_HELLO }; |
832 | char *two_args[] = { "two_perl", SAY_HELLO }; |
833 | |
834 | perl_construct(one_perl); |
835 | perl_construct(two_perl); |
836 | |
837 | perl_parse(one_perl, NULL, 3, one_args, (char **)NULL); |
838 | perl_parse(two_perl, NULL, 3, two_args, (char **)NULL); |
839 | |
840 | perl_run(one_perl); |
841 | perl_run(two_perl); |
842 | |
843 | perl_destruct(one_perl); |
844 | perl_destruct(two_perl); |
845 | |
846 | perl_free(one_perl); |
847 | perl_free(two_perl); |
848 | } |
849 | |
850 | |
851 | Compile as usual: |
852 | |
853 | % cc -o multiplicity multiplicity.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
854 | |
855 | Run it, Run it: |
856 | |
857 | % multiplicity |
858 | Hi, I'm one_perl |
859 | Hi, I'm two_perl |
860 | |
96dbc785 |
861 | =head2 Using Perl modules, which themselves use C libraries, from your C program |
862 | |
863 | If you've played with the examples above and tried to embed a script |
864 | that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++ library, |
865 | this probably happened: |
866 | |
867 | |
868 | Can't load module Socket, dynamic loading not available in this perl. |
869 | (You may need to build a new perl executable which either supports |
870 | dynamic loading or has the Socket module statically linked into it.) |
871 | |
872 | |
873 | What's wrong? |
874 | |
875 | Your interpreter doesn't know how to communicate with these extensions |
876 | on its own. A little glue will help. Up until now you've been |
877 | calling I<perl_parse()>, handing it NULL for the second argument: |
878 | |
879 | perl_parse(my_perl, NULL, argc, my_argv, NULL); |
880 | |
881 | That's where the glue code can be inserted to create the initial contact between |
882 | Perl and linked C/C++ routines. Let's take a look some pieces of I<perlmain.c> |
883 | to see how Perl does this: |
884 | |
885 | |
886 | #ifdef __cplusplus |
887 | # define EXTERN_C extern "C" |
888 | #else |
889 | # define EXTERN_C extern |
890 | #endif |
891 | |
892 | static void xs_init _((void)); |
893 | |
894 | EXTERN_C void boot_DynaLoader _((CV* cv)); |
895 | EXTERN_C void boot_Socket _((CV* cv)); |
896 | |
897 | |
898 | EXTERN_C void |
899 | xs_init() |
900 | { |
901 | char *file = __FILE__; |
902 | /* DynaLoader is a special case */ |
903 | newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file); |
904 | newXS("Socket::bootstrap", boot_Socket, file); |
905 | } |
906 | |
907 | Simply put: for each extension linked with your Perl executable |
908 | (determined during its initial configuration on your |
909 | computer or when adding a new extension), |
910 | a Perl subroutine is created to incorporate the extension's |
911 | routines. Normally, that subroutine is named |
912 | I<Module::bootstrap()> and is invoked when you say I<use Module>. In |
913 | turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl |
914 | counterpart for each of the extension's XSUBs. Don't worry about this |
915 | part; leave that to the I<xsubpp> and extension authors. If your |
916 | extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()> |
917 | for you on the fly. In fact, if you have a working DynaLoader then there |
5f05dabc |
918 | is rarely any need to link in any other extensions statically. |
96dbc785 |
919 | |
920 | |
921 | Once you have this code, slap it into the second argument of I<perl_parse()>: |
922 | |
923 | |
924 | perl_parse(my_perl, xs_init, argc, my_argv, NULL); |
925 | |
926 | |
927 | Then compile: |
928 | |
8a7dc658 |
929 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
96dbc785 |
930 | |
931 | % interp |
932 | use Socket; |
933 | use SomeDynamicallyLoadedModule; |
934 | |
935 | print "Now I can use extensions!\n"' |
936 | |
937 | B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code. |
938 | |
8a7dc658 |
939 | % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c |
96dbc785 |
940 | % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts` |
941 | % cc -c interp.c `perl -MExtUtils::Embed -e ccopts` |
8a7dc658 |
942 | % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts` |
96dbc785 |
943 | |
944 | Consult L<perlxs> and L<perlguts> for more details. |
945 | |
53f52f58 |
946 | =head1 Embedding Perl under Win32 |
947 | |
948 | At the time of this writing, there are two versions of Perl which run |
949 | under Win32. Interfacing to Activeware's Perl library is quite |
950 | different from the examples in this documentation, as significant |
951 | changes were made to the internal Perl API. However, it is possible |
952 | to embed Activeware's Perl runtime, see the Perl for Win32 FAQ: |
953 | http://www.perl.com/perl/faq/win32/Perl_for_Win32_FAQ.html |
954 | |
955 | With the "official" Perl version 5.004 or higher, all the examples |
956 | within this documentation will compile and run untouched, although, |
957 | the build process is slightly different between Unix and Win32. |
958 | |
959 | For starters, backticks don't work under the Win32 native command shell! |
960 | The ExtUtils::Embed kit on CPAN ships with a script called |
961 | B<genmake>, which generates a simple makefile to build a program from |
962 | a single C source file. It can be used like so: |
963 | |
964 | C:\ExtUtils-Embed\eg> perl genmake interp.c |
965 | C:\ExtUtils-Embed\eg> nmake |
966 | C:\ExtUtils-Embed\eg> interp -e "print qq{I'm embedded in Win32!\n}" |
967 | |
968 | You may wish to use a more robust environment such as the MS Developer |
969 | stdio. In this case, to generate perlxsi.c run: |
970 | |
971 | perl -MExtUtils::Embed -e xsinit |
972 | |
973 | Create a new project, Insert -> Files into Project: perlxsi.c, perl.lib, |
974 | and your own source files, e.g. interp.c. Typically you'll find |
975 | perl.lib in B<C:\perl\lib\CORE>, if not, you should see the B<CORE> |
976 | directory relative to C<perl -V:archlib>. |
977 | The studio will also need this path so it knows where to find Perl |
978 | include files. This path can be added via the Tools -> Options -> |
979 | Directories menu. Finnally, select Build -> Build interp.exe and |
980 | you're ready to go! |
96dbc785 |
981 | |
cb1a09d0 |
982 | =head1 MORAL |
983 | |
984 | You can sometimes I<write faster code> in C, but |
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985 | you can always I<write code faster> in Perl. Because you can use |
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986 | each from the other, combine them as you wish. |
987 | |
988 | |
989 | =head1 AUTHOR |
990 | |
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991 | Jon Orwant and <F<orwant@tpj.com>> and Doug MacEachern <F<dougm@osf.org>>, |
992 | with small contributions from Tim Bunce, Tom Christiansen, Hallvard Furuseth, |
993 | Dov Grobgeld, and Ilya Zakharevich. |
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994 | |
995 | Check out Doug's article on embedding in Volume 1, Issue 4 of The Perl |
996 | Journal. Info about TPJ is available from http://tpj.com. |
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997 | |
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998 | April 14, 1997 |
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999 | |
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1000 | Some of this material is excerpted from Jon Orwant's book: I<Perl 5 |
1001 | Interactive>, Waite Group Press, 1996 (ISBN 1-57169-064-6) and appears |
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1002 | courtesy of Waite Group Press. |
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1003 | |
1004 | =head1 COPYRIGHT |
1005 | |
1006 | Copyright (C) 1995, 1996, 1997 Doug MacEachern and Jon Orwant. All |
1007 | Rights Reserved. |
1008 | |
1009 | Although destined for release with the standard Perl distribution, |
1010 | this document is not public domain, nor is any of Perl and its |
1011 | documentation. Permission is granted to freely distribute verbatim |
1012 | copies of this document provided that no modifications outside of |
1013 | formatting be made, and that this notice remain intact. You are |
1014 | permitted and encouraged to use its code and derivatives thereof in |
1015 | your own source code for fun or for profit as you see fit. |