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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 | |
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15 | Read L<perlxstut>, L<perlxs>, L<h2xs>, L<perlguts>, and L<perlapi>. |
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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 | |
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38 | =over 5 |
39 | |
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40 | =item * |
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41 | |
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42 | Compiling your C program |
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43 | |
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44 | =item * |
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45 | |
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46 | Adding a Perl interpreter to your C program |
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47 | |
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48 | =item * |
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49 | |
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50 | Calling a Perl subroutine from your C program |
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51 | |
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52 | =item * |
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53 | |
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54 | Evaluating a Perl statement from your C program |
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55 | |
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56 | =item * |
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57 | |
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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 |
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79 | |
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80 | =back |
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81 | |
82 | =head2 Compiling your C program |
83 | |
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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.) |
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87 | |
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88 | Also, every C program that uses Perl must link in the I<perl library>. |
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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 | |
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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. |
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100 | |
101 | If your copy of Perl is recent enough to contain this documentation |
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102 | (version 5.002 or later), then the perl library (and I<EXTERN.h> and |
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103 | I<perl.h>, which you'll also need) will reside in a directory |
104 | that looks like this: |
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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 | |
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118 | perl -MConfig -e 'print $Config{archlib}' |
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119 | |
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120 | Here's how you'd compile the example in the next section, |
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121 | L<Adding a Perl interpreter to your C program>, on my Linux box: |
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122 | |
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123 | % gcc -O2 -Dbool=char -DHAS_BOOL -I/usr/local/include |
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124 | -I/usr/local/lib/perl5/i586-linux/5.003/CORE |
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125 | -L/usr/local/lib/perl5/i586-linux/5.003/CORE |
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126 | -o interp interp.c -lperl -lm |
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127 | |
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128 | (That's all one line.) On my DEC Alpha running old 5.003_05, the |
129 | incantation is a bit different: |
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130 | |
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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 |
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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 |
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138 | "ccflags" information. |
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139 | |
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140 | You'll have to choose the appropriate compiler (I<cc>, I<gcc>, et al.) for |
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141 | your machine: C<perl -MConfig -e 'print $Config{cc}'> will tell you what |
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142 | to use. |
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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>. |
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150 | |
151 | You may have to add extra libraries as well. Which ones? |
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152 | Perhaps those printed by |
153 | |
154 | perl -MConfig -e 'print $Config{libs}' |
155 | |
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156 | Provided your perl binary was properly configured and installed the |
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157 | B<ExtUtils::Embed> module will determine all of this information for |
158 | you: |
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159 | |
160 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
161 | |
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162 | If the B<ExtUtils::Embed> module isn't part of your Perl distribution, |
163 | you can retrieve it from |
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164 | http://www.perl.com/perl/CPAN/modules/by-module/ExtUtils/ |
165 | (If this documentation came from your Perl distribution, then you're |
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166 | running 5.004 or better and you already have it.) |
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167 | |
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168 | The B<ExtUtils::Embed> kit on CPAN also contains all source code for |
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169 | the examples in this document, tests, additional examples and other |
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170 | information you may find useful. |
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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>, |
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176 | included in the source distribution. Here's a bastardized, nonportable |
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177 | version of I<miniperlmain.c> containing the essentials of embedding: |
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178 | |
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179 | #include <EXTERN.h> /* from the Perl distribution */ |
180 | #include <perl.h> /* from the Perl distribution */ |
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181 | |
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182 | static PerlInterpreter *my_perl; /*** The Perl interpreter ***/ |
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183 | |
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184 | int main(int argc, char **argv, char **env) |
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185 | { |
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186 | PERL_SYS_INIT3(&argc,&argv,&env); |
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187 | my_perl = perl_alloc(); |
188 | perl_construct(my_perl); |
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189 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
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190 | perl_parse(my_perl, NULL, argc, argv, (char **)NULL); |
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191 | perl_run(my_perl); |
192 | perl_destruct(my_perl); |
193 | perl_free(my_perl); |
1ccffcf5 |
194 | PERL_SYS_TERM(); |
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195 | } |
196 | |
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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 |
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199 | C<NULL>, which means that the current environment will be used. The macros |
200 | PERL_SYS_INIT3() and PERL_SYS_TERM() provide system-specific tune up |
201 | of the C runtime environment necessary to run Perl interpreters; since |
202 | PERL_SYS_INIT3() may change C<env>, it may be more appropriate to provide |
203 | C<env> as an argument to perl_parse(). |
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204 | |
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205 | Now compile this program (I'll call it I<interp.c>) into an executable: |
206 | |
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207 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
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208 | |
209 | After a successful compilation, you'll be able to use I<interp> just |
210 | like perl itself: |
211 | |
212 | % interp |
213 | print "Pretty Good Perl \n"; |
214 | print "10890 - 9801 is ", 10890 - 9801; |
215 | <CTRL-D> |
216 | Pretty Good Perl |
217 | 10890 - 9801 is 1089 |
218 | |
219 | or |
220 | |
221 | % interp -e 'printf("%x", 3735928559)' |
222 | deadbeef |
223 | |
224 | You can also read and execute Perl statements from a file while in the |
225 | midst of your C program, by placing the filename in I<argv[1]> before |
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226 | calling I<perl_run>. |
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227 | |
228 | =head2 Calling a Perl subroutine from your C program |
229 | |
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230 | To call individual Perl subroutines, you can use any of the B<call_*> |
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231 | functions documented in L<perlcall>. |
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232 | In this example we'll use C<call_argv>. |
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233 | |
234 | That's shown below, in a program I'll call I<showtime.c>. |
235 | |
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236 | #include <EXTERN.h> |
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237 | #include <perl.h> |
238 | |
239 | static PerlInterpreter *my_perl; |
240 | |
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241 | int main(int argc, char **argv, char **env) |
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242 | { |
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243 | char *args[] = { NULL }; |
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244 | PERL_SYS_INIT3(&argc,&argv,&env); |
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245 | my_perl = perl_alloc(); |
246 | perl_construct(my_perl); |
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247 | |
248 | perl_parse(my_perl, NULL, argc, argv, NULL); |
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249 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
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250 | |
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251 | /*** skipping perl_run() ***/ |
252 | |
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253 | call_argv("showtime", G_DISCARD | G_NOARGS, args); |
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254 | |
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255 | perl_destruct(my_perl); |
256 | perl_free(my_perl); |
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257 | PERL_SYS_TERM(); |
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258 | } |
259 | |
260 | where I<showtime> is a Perl subroutine that takes no arguments (that's the |
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261 | I<G_NOARGS>) and for which I'll ignore the return value (that's the |
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262 | I<G_DISCARD>). Those flags, and others, are discussed in L<perlcall>. |
263 | |
264 | I'll define the I<showtime> subroutine in a file called I<showtime.pl>: |
265 | |
266 | print "I shan't be printed."; |
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267 | |
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268 | sub showtime { |
269 | print time; |
270 | } |
271 | |
272 | Simple enough. Now compile and run: |
273 | |
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274 | % cc -o showtime showtime.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
275 | |
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276 | % showtime showtime.pl |
277 | 818284590 |
278 | |
279 | yielding the number of seconds that elapsed between January 1, 1970 |
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280 | (the beginning of the Unix epoch), and the moment I began writing this |
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281 | sentence. |
282 | |
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283 | In this particular case we don't have to call I<perl_run>, as we set |
284 | the PL_exit_flag PERL_EXIT_DESTRUCT_END which executes END blocks in |
285 | perl_destruct. |
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286 | |
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287 | If you want to pass arguments to the Perl subroutine, you can add |
288 | strings to the C<NULL>-terminated C<args> list passed to |
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289 | I<call_argv>. For other data types, or to examine return values, |
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290 | you'll need to manipulate the Perl stack. That's demonstrated in |
291 | L<Fiddling with the Perl stack from your C program>. |
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292 | |
293 | =head2 Evaluating a Perl statement from your C program |
294 | |
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295 | Perl provides two API functions to evaluate pieces of Perl code. |
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296 | These are L<perlapi/eval_sv> and L<perlapi/eval_pv>. |
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297 | |
298 | Arguably, these are the only routines you'll ever need to execute |
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299 | snippets of Perl code from within your C program. Your code can be as |
300 | long as you wish; it can contain multiple statements; it can employ |
301 | L<perlfunc/use>, L<perlfunc/require>, and L<perlfunc/do> to |
302 | include external Perl files. |
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303 | |
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304 | I<eval_pv> lets us evaluate individual Perl strings, and then |
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305 | extract variables for coercion into C types. The following program, |
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306 | I<string.c>, executes three Perl strings, extracting an C<int> from |
307 | the first, a C<float> from the second, and a C<char *> from the third. |
308 | |
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309 | #include <EXTERN.h> |
310 | #include <perl.h> |
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311 | |
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312 | static PerlInterpreter *my_perl; |
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313 | |
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314 | main (int argc, char **argv, char **env) |
cb1a09d0 |
315 | { |
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316 | STRLEN n_a; |
137443ea |
317 | char *embedding[] = { "", "-e", "0" }; |
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318 | |
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319 | PERL_SYS_INIT3(&argc,&argv,&env); |
137443ea |
320 | my_perl = perl_alloc(); |
321 | perl_construct( my_perl ); |
c47ff5f1 |
322 | |
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323 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
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324 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
137443ea |
325 | perl_run(my_perl); |
c47ff5f1 |
326 | |
137443ea |
327 | /** Treat $a as an integer **/ |
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328 | eval_pv("$a = 3; $a **= 2", TRUE); |
329 | printf("a = %d\n", SvIV(get_sv("a", FALSE))); |
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330 | |
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331 | /** Treat $a as a float **/ |
4929bf7b |
332 | eval_pv("$a = 3.14; $a **= 2", TRUE); |
333 | printf("a = %f\n", SvNV(get_sv("a", FALSE))); |
c47ff5f1 |
334 | |
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335 | /** Treat $a as a string **/ |
4929bf7b |
336 | eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE); |
337 | printf("a = %s\n", SvPV(get_sv("a", FALSE), n_a)); |
c47ff5f1 |
338 | |
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339 | perl_destruct(my_perl); |
340 | perl_free(my_perl); |
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341 | PERL_SYS_TERM(); |
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342 | } |
343 | |
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344 | All of those strange functions with I<sv> in their names help convert Perl scalars to C types. They're described in L<perlguts> and L<perlapi>. |
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345 | |
346 | If you compile and run I<string.c>, you'll see the results of using |
347 | I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and |
348 | I<SvPV()> to create a string: |
349 | |
350 | a = 9 |
351 | a = 9.859600 |
352 | a = Just Another Perl Hacker |
353 | |
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354 | In the example above, we've created a global variable to temporarily |
355 | store the computed value of our eval'd expression. It is also |
356 | possible and in most cases a better strategy to fetch the return value |
4929bf7b |
357 | from I<eval_pv()> instead. Example: |
8f183262 |
358 | |
8f183262 |
359 | ... |
2d8e6c8d |
360 | STRLEN n_a; |
4929bf7b |
361 | SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); |
2d8e6c8d |
362 | printf("%s\n", SvPV(val,n_a)); |
8f183262 |
363 | ... |
364 | |
365 | This way, we avoid namespace pollution by not creating global |
366 | variables and we've simplified our code as well. |
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367 | |
368 | =head2 Performing Perl pattern matches and substitutions from your C program |
369 | |
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370 | The I<eval_sv()> function lets us evaluate strings of Perl code, so we can |
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371 | define some functions that use it to "specialize" in matches and |
372 | substitutions: I<match()>, I<substitute()>, and I<matches()>. |
373 | |
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374 | I32 match(SV *string, char *pattern); |
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375 | |
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376 | Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which |
377 | in your C program might appear as "/\\b\\w*\\b/"), match() |
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378 | returns 1 if the string matches the pattern and 0 otherwise. |
379 | |
1f05cdcd |
380 | int substitute(SV **string, char *pattern); |
cb1a09d0 |
381 | |
1f05cdcd |
382 | Given a pointer to an C<SV> and an C<=~> operation (e.g., |
8a7dc658 |
383 | C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string |
bf9cdc68 |
384 | within the C<SV> as according to the operation, returning the number of substitutions |
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385 | made. |
cb1a09d0 |
386 | |
1f05cdcd |
387 | int matches(SV *string, char *pattern, AV **matches); |
cb1a09d0 |
388 | |
1f05cdcd |
389 | Given an C<SV>, a pattern, and a pointer to an empty C<AV>, |
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390 | matches() evaluates C<$string =~ $pattern> in a list context, and |
1f05cdcd |
391 | fills in I<matches> with the array elements, returning the number of matches found. |
cb1a09d0 |
392 | |
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393 | Here's a sample program, I<match.c>, that uses all three (long lines have |
394 | been wrapped here): |
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395 | |
1f05cdcd |
396 | #include <EXTERN.h> |
397 | #include <perl.h> |
c47ff5f1 |
398 | |
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399 | static PerlInterpreter *my_perl; |
400 | |
4929bf7b |
401 | /** my_eval_sv(code, error_check) |
402 | ** kinda like eval_sv(), |
1f05cdcd |
403 | ** but we pop the return value off the stack |
404 | **/ |
4929bf7b |
405 | SV* my_eval_sv(SV *sv, I32 croak_on_error) |
1f05cdcd |
406 | { |
407 | dSP; |
408 | SV* retval; |
2d8e6c8d |
409 | STRLEN n_a; |
c47ff5f1 |
410 | |
924508f0 |
411 | PUSHMARK(SP); |
4929bf7b |
412 | eval_sv(sv, G_SCALAR); |
c47ff5f1 |
413 | |
1f05cdcd |
414 | SPAGAIN; |
415 | retval = POPs; |
416 | PUTBACK; |
c47ff5f1 |
417 | |
9cde0e7f |
418 | if (croak_on_error && SvTRUE(ERRSV)) |
2d8e6c8d |
419 | croak(SvPVx(ERRSV, n_a)); |
c47ff5f1 |
420 | |
1f05cdcd |
421 | return retval; |
422 | } |
c47ff5f1 |
423 | |
1f05cdcd |
424 | /** match(string, pattern) |
425 | ** |
426 | ** Used for matches in a scalar context. |
427 | ** |
428 | ** Returns 1 if the match was successful; 0 otherwise. |
429 | **/ |
c47ff5f1 |
430 | |
1f05cdcd |
431 | I32 match(SV *string, char *pattern) |
432 | { |
561b68a9 |
433 | SV *command = newSV(0), *retval; |
2d8e6c8d |
434 | STRLEN n_a; |
c47ff5f1 |
435 | |
1f05cdcd |
436 | sv_setpvf(command, "my $string = '%s'; $string =~ %s", |
2d8e6c8d |
437 | SvPV(string,n_a), pattern); |
c47ff5f1 |
438 | |
4929bf7b |
439 | retval = my_eval_sv(command, TRUE); |
1f05cdcd |
440 | SvREFCNT_dec(command); |
c47ff5f1 |
441 | |
1f05cdcd |
442 | return SvIV(retval); |
443 | } |
c47ff5f1 |
444 | |
1f05cdcd |
445 | /** substitute(string, pattern) |
446 | ** |
447 | ** Used for =~ operations that modify their left-hand side (s/// and tr///) |
448 | ** |
449 | ** Returns the number of successful matches, and |
450 | ** modifies the input string if there were any. |
451 | **/ |
c47ff5f1 |
452 | |
1f05cdcd |
453 | I32 substitute(SV **string, char *pattern) |
454 | { |
561b68a9 |
455 | SV *command = newSV(0), *retval; |
2d8e6c8d |
456 | STRLEN n_a; |
c47ff5f1 |
457 | |
1f05cdcd |
458 | sv_setpvf(command, "$string = '%s'; ($string =~ %s)", |
2d8e6c8d |
459 | SvPV(*string,n_a), pattern); |
c47ff5f1 |
460 | |
4929bf7b |
461 | retval = my_eval_sv(command, TRUE); |
1f05cdcd |
462 | SvREFCNT_dec(command); |
c47ff5f1 |
463 | |
4929bf7b |
464 | *string = get_sv("string", FALSE); |
1f05cdcd |
465 | return SvIV(retval); |
466 | } |
c47ff5f1 |
467 | |
1f05cdcd |
468 | /** matches(string, pattern, matches) |
469 | ** |
90fdbbb7 |
470 | ** Used for matches in a list context. |
1f05cdcd |
471 | ** |
472 | ** Returns the number of matches, |
473 | ** and fills in **matches with the matching substrings |
474 | **/ |
c47ff5f1 |
475 | |
1f05cdcd |
476 | I32 matches(SV *string, char *pattern, AV **match_list) |
477 | { |
561b68a9 |
478 | SV *command = newSV(0); |
cb1a09d0 |
479 | I32 num_matches; |
2d8e6c8d |
480 | STRLEN n_a; |
c47ff5f1 |
481 | |
1f05cdcd |
482 | sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)", |
2d8e6c8d |
483 | SvPV(string,n_a), pattern); |
c47ff5f1 |
484 | |
4929bf7b |
485 | my_eval_sv(command, TRUE); |
1f05cdcd |
486 | SvREFCNT_dec(command); |
c47ff5f1 |
487 | |
4929bf7b |
488 | *match_list = get_av("array", FALSE); |
1f05cdcd |
489 | num_matches = av_len(*match_list) + 1; /** assume $[ is 0 **/ |
c47ff5f1 |
490 | |
cb1a09d0 |
491 | return num_matches; |
1f05cdcd |
492 | } |
c47ff5f1 |
493 | |
1f05cdcd |
494 | main (int argc, char **argv, char **env) |
495 | { |
a6006777 |
496 | char *embedding[] = { "", "-e", "0" }; |
1f05cdcd |
497 | AV *match_list; |
498 | I32 num_matches, i; |
7fef744d |
499 | SV *text; |
2d8e6c8d |
500 | STRLEN n_a; |
c47ff5f1 |
501 | |
1ccffcf5 |
502 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d |
503 | my_perl = perl_alloc(); |
1f05cdcd |
504 | perl_construct(my_perl); |
96dbc785 |
505 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
d95b23b2 |
506 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
c47ff5f1 |
507 | |
561b68a9 |
508 | text = newSV(0); |
d3f3bf9f |
509 | sv_setpv(text, "When he is at a convenience store and the " |
510 | "bill comes to some amount like 76 cents, Maynard is " |
511 | "aware that there is something he *should* do, something " |
512 | "that will enable him to get back a quarter, but he has " |
513 | "no idea *what*. He fumbles through his red squeezey " |
514 | "changepurse and gives the boy three extra pennies with " |
515 | "his dollar, hoping that he might luck into the correct " |
516 | "amount. The boy gives him back two of his own pennies " |
517 | "and then the big shiny quarter that is his prize. " |
518 | "-RICHH"); |
c47ff5f1 |
519 | |
96dbc785 |
520 | if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/ |
1f05cdcd |
521 | printf("match: Text contains the word 'quarter'.\n\n"); |
96dbc785 |
522 | else |
1f05cdcd |
523 | printf("match: Text doesn't contain the word 'quarter'.\n\n"); |
c47ff5f1 |
524 | |
96dbc785 |
525 | if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/ |
1f05cdcd |
526 | printf("match: Text contains the word 'eighth'.\n\n"); |
96dbc785 |
527 | else |
1f05cdcd |
528 | printf("match: Text doesn't contain the word 'eighth'.\n\n"); |
c47ff5f1 |
529 | |
96dbc785 |
530 | /** Match all occurrences of /wi../ **/ |
531 | num_matches = matches(text, "m/(wi..)/g", &match_list); |
532 | printf("matches: m/(wi..)/g found %d matches...\n", num_matches); |
c47ff5f1 |
533 | |
96dbc785 |
534 | for (i = 0; i < num_matches; i++) |
2d8e6c8d |
535 | printf("match: %s\n", SvPV(*av_fetch(match_list, i, FALSE),n_a)); |
cb1a09d0 |
536 | printf("\n"); |
c47ff5f1 |
537 | |
96dbc785 |
538 | /** Remove all vowels from text **/ |
539 | num_matches = substitute(&text, "s/[aeiou]//gi"); |
cb1a09d0 |
540 | if (num_matches) { |
1f05cdcd |
541 | printf("substitute: s/[aeiou]//gi...%d substitutions made.\n", |
542 | num_matches); |
2d8e6c8d |
543 | printf("Now text is: %s\n\n", SvPV(text,n_a)); |
cb1a09d0 |
544 | } |
c47ff5f1 |
545 | |
96dbc785 |
546 | /** Attempt a substitution **/ |
547 | if (!substitute(&text, "s/Perl/C/")) { |
1f05cdcd |
548 | printf("substitute: s/Perl/C...No substitution made.\n\n"); |
cb1a09d0 |
549 | } |
c47ff5f1 |
550 | |
1f05cdcd |
551 | SvREFCNT_dec(text); |
9cde0e7f |
552 | PL_perl_destruct_level = 1; |
cb1a09d0 |
553 | perl_destruct(my_perl); |
554 | perl_free(my_perl); |
1ccffcf5 |
555 | PERL_SYS_TERM(); |
1f05cdcd |
556 | } |
cb1a09d0 |
557 | |
96dbc785 |
558 | which produces the output (again, long lines have been wrapped here) |
cb1a09d0 |
559 | |
8a7dc658 |
560 | match: Text contains the word 'quarter'. |
96dbc785 |
561 | |
8a7dc658 |
562 | match: Text doesn't contain the word 'eighth'. |
96dbc785 |
563 | |
8a7dc658 |
564 | matches: m/(wi..)/g found 2 matches... |
cb1a09d0 |
565 | match: will |
566 | match: with |
96dbc785 |
567 | |
8a7dc658 |
568 | substitute: s/[aeiou]//gi...139 substitutions made. |
54310121 |
569 | Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts, |
96dbc785 |
570 | Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt bck |
571 | qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd gvs th by |
572 | thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct mnt. Th by gvs |
573 | hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s hs prz. -RCHH |
574 | |
8a7dc658 |
575 | substitute: s/Perl/C...No substitution made. |
96dbc785 |
576 | |
cb1a09d0 |
577 | =head2 Fiddling with the Perl stack from your C program |
578 | |
579 | When trying to explain stacks, most computer science textbooks mumble |
580 | something about spring-loaded columns of cafeteria plates: the last |
581 | thing you pushed on the stack is the first thing you pop off. That'll |
582 | do for our purposes: your C program will push some arguments onto "the Perl |
583 | stack", shut its eyes while some magic happens, and then pop the |
584 | results--the return value of your Perl subroutine--off the stack. |
96dbc785 |
585 | |
cb1a09d0 |
586 | First you'll need to know how to convert between C types and Perl |
587 | types, with newSViv() and sv_setnv() and newAV() and all their |
4929bf7b |
588 | friends. They're described in L<perlguts> and L<perlapi>. |
cb1a09d0 |
589 | |
590 | Then you'll need to know how to manipulate the Perl stack. That's |
591 | described in L<perlcall>. |
592 | |
96dbc785 |
593 | Once you've understood those, embedding Perl in C is easy. |
cb1a09d0 |
594 | |
54310121 |
595 | Because C has no builtin function for integer exponentiation, let's |
cb1a09d0 |
596 | make Perl's ** operator available to it (this is less useful than it |
5f05dabc |
597 | sounds, because Perl implements ** with C's I<pow()> function). First |
cb1a09d0 |
598 | I'll create a stub exponentiation function in I<power.pl>: |
599 | |
600 | sub expo { |
601 | my ($a, $b) = @_; |
602 | return $a ** $b; |
603 | } |
604 | |
605 | Now I'll create a C program, I<power.c>, with a function |
606 | I<PerlPower()> that contains all the perlguts necessary to push the |
607 | two arguments into I<expo()> and to pop the return value out. Take a |
608 | deep breath... |
609 | |
cb1a09d0 |
610 | #include <EXTERN.h> |
611 | #include <perl.h> |
96dbc785 |
612 | |
cb1a09d0 |
613 | static PerlInterpreter *my_perl; |
96dbc785 |
614 | |
cb1a09d0 |
615 | static void |
616 | PerlPower(int a, int b) |
617 | { |
618 | dSP; /* initialize stack pointer */ |
619 | ENTER; /* everything created after here */ |
620 | SAVETMPS; /* ...is a temporary variable. */ |
924508f0 |
621 | PUSHMARK(SP); /* remember the stack pointer */ |
cb1a09d0 |
622 | XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */ |
623 | XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */ |
624 | PUTBACK; /* make local stack pointer global */ |
4929bf7b |
625 | call_pv("expo", G_SCALAR); /* call the function */ |
cb1a09d0 |
626 | SPAGAIN; /* refresh stack pointer */ |
627 | /* pop the return value from stack */ |
628 | printf ("%d to the %dth power is %d.\n", a, b, POPi); |
96dbc785 |
629 | PUTBACK; |
cb1a09d0 |
630 | FREETMPS; /* free that return value */ |
631 | LEAVE; /* ...and the XPUSHed "mortal" args.*/ |
632 | } |
96dbc785 |
633 | |
634 | int main (int argc, char **argv, char **env) |
cb1a09d0 |
635 | { |
95b76e31 |
636 | char *my_argv[] = { "", "power.pl" }; |
96dbc785 |
637 | |
1ccffcf5 |
638 | PERL_SYS_INIT3(&argc,&argv,&env); |
cb1a09d0 |
639 | my_perl = perl_alloc(); |
640 | perl_construct( my_perl ); |
96dbc785 |
641 | |
95b76e31 |
642 | perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL); |
d95b23b2 |
643 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
8ebc5c01 |
644 | perl_run(my_perl); |
96dbc785 |
645 | |
cb1a09d0 |
646 | PerlPower(3, 4); /*** Compute 3 ** 4 ***/ |
96dbc785 |
647 | |
cb1a09d0 |
648 | perl_destruct(my_perl); |
649 | perl_free(my_perl); |
1ccffcf5 |
650 | PERL_SYS_TERM(); |
cb1a09d0 |
651 | } |
96dbc785 |
652 | |
cb1a09d0 |
653 | |
654 | |
655 | Compile and run: |
656 | |
96dbc785 |
657 | % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
658 | |
659 | % power |
cb1a09d0 |
660 | 3 to the 4th power is 81. |
661 | |
a6006777 |
662 | =head2 Maintaining a persistent interpreter |
663 | |
8a7dc658 |
664 | When developing interactive and/or potentially long-running |
665 | applications, it's a good idea to maintain a persistent interpreter |
666 | rather than allocating and constructing a new interpreter multiple |
667 | times. The major reason is speed: since Perl will only be loaded into |
54310121 |
668 | memory once. |
8a7dc658 |
669 | |
670 | However, you have to be more cautious with namespace and variable |
671 | scoping when using a persistent interpreter. In previous examples |
672 | we've been using global variables in the default package C<main>. We |
673 | knew exactly what code would be run, and assumed we could avoid |
674 | variable collisions and outrageous symbol table growth. |
675 | |
676 | Let's say your application is a server that will occasionally run Perl |
677 | code from some arbitrary file. Your server has no way of knowing what |
678 | code it's going to run. Very dangerous. |
679 | |
680 | If the file is pulled in by C<perl_parse()>, compiled into a newly |
681 | constructed interpreter, and subsequently cleaned out with |
682 | C<perl_destruct()> afterwards, you're shielded from most namespace |
683 | troubles. |
684 | |
685 | One way to avoid namespace collisions in this scenario is to translate |
686 | the filename into a guaranteed-unique package name, and then compile |
e010571f |
687 | the code into that package using L<perlfunc/eval>. In the example |
8a7dc658 |
688 | below, each file will only be compiled once. Or, the application |
689 | might choose to clean out the symbol table associated with the file |
4929bf7b |
690 | after it's no longer needed. Using L<perlapi/call_argv>, We'll |
8a7dc658 |
691 | call the subroutine C<Embed::Persistent::eval_file> which lives in the |
692 | file C<persistent.pl> and pass the filename and boolean cleanup/cache |
a6006777 |
693 | flag as arguments. |
694 | |
8a7dc658 |
695 | Note that the process will continue to grow for each file that it |
696 | uses. In addition, there might be C<AUTOLOAD>ed subroutines and other |
697 | conditions that cause Perl's symbol table to grow. You might want to |
698 | add some logic that keeps track of the process size, or restarts |
699 | itself after a certain number of requests, to ensure that memory |
700 | consumption is minimized. You'll also want to scope your variables |
e010571f |
701 | with L<perlfunc/my> whenever possible. |
a6006777 |
702 | |
54310121 |
703 | |
a6006777 |
704 | package Embed::Persistent; |
705 | #persistent.pl |
54310121 |
706 | |
a6006777 |
707 | use strict; |
77ca0c92 |
708 | our %Cache; |
1ee082b7 |
709 | use Symbol qw(delete_package); |
54310121 |
710 | |
a6006777 |
711 | sub valid_package_name { |
712 | my($string) = @_; |
713 | $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg; |
714 | # second pass only for words starting with a digit |
715 | $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg; |
54310121 |
716 | |
a6006777 |
717 | # Dress it up as a real package name |
718 | $string =~ s|/|::|g; |
719 | return "Embed" . $string; |
720 | } |
54310121 |
721 | |
a6006777 |
722 | sub eval_file { |
723 | my($filename, $delete) = @_; |
724 | my $package = valid_package_name($filename); |
725 | my $mtime = -M $filename; |
726 | if(defined $Cache{$package}{mtime} |
727 | && |
54310121 |
728 | $Cache{$package}{mtime} <= $mtime) |
a6006777 |
729 | { |
54310121 |
730 | # we have compiled this subroutine already, |
8ebc5c01 |
731 | # it has not been updated on disk, nothing left to do |
732 | print STDERR "already compiled $package->handler\n"; |
a6006777 |
733 | } |
734 | else { |
8ebc5c01 |
735 | local *FH; |
736 | open FH, $filename or die "open '$filename' $!"; |
737 | local($/) = undef; |
738 | my $sub = <FH>; |
739 | close FH; |
54310121 |
740 | |
8ebc5c01 |
741 | #wrap the code into a subroutine inside our unique package |
742 | my $eval = qq{package $package; sub handler { $sub; }}; |
743 | { |
744 | # hide our variables within this block |
745 | my($filename,$mtime,$package,$sub); |
746 | eval $eval; |
747 | } |
748 | die $@ if $@; |
54310121 |
749 | |
8ebc5c01 |
750 | #cache it unless we're cleaning out each time |
751 | $Cache{$package}{mtime} = $mtime unless $delete; |
a6006777 |
752 | } |
54310121 |
753 | |
a6006777 |
754 | eval {$package->handler;}; |
755 | die $@ if $@; |
54310121 |
756 | |
a6006777 |
757 | delete_package($package) if $delete; |
54310121 |
758 | |
a6006777 |
759 | #take a look if you want |
760 | #print Devel::Symdump->rnew($package)->as_string, $/; |
761 | } |
54310121 |
762 | |
a6006777 |
763 | 1; |
54310121 |
764 | |
a6006777 |
765 | __END__ |
766 | |
767 | /* persistent.c */ |
54310121 |
768 | #include <EXTERN.h> |
769 | #include <perl.h> |
770 | |
a6006777 |
771 | /* 1 = clean out filename's symbol table after each request, 0 = don't */ |
772 | #ifndef DO_CLEAN |
773 | #define DO_CLEAN 0 |
774 | #endif |
54310121 |
775 | |
2307c6d0 |
776 | #define BUFFER_SIZE 1024 |
777 | |
7fef744d |
778 | static PerlInterpreter *my_perl = NULL; |
54310121 |
779 | |
a6006777 |
780 | int |
781 | main(int argc, char **argv, char **env) |
782 | { |
783 | char *embedding[] = { "", "persistent.pl" }; |
784 | char *args[] = { "", DO_CLEAN, NULL }; |
2307c6d0 |
785 | char filename[BUFFER_SIZE]; |
a6006777 |
786 | int exitstatus = 0; |
2d8e6c8d |
787 | STRLEN n_a; |
54310121 |
788 | |
1ccffcf5 |
789 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d |
790 | if((my_perl = perl_alloc()) == NULL) { |
8ebc5c01 |
791 | fprintf(stderr, "no memory!"); |
792 | exit(1); |
a6006777 |
793 | } |
7fef744d |
794 | perl_construct(my_perl); |
54310121 |
795 | |
a2722ac9 |
796 | PL_origalen = 1; /* don't let $0 assignment update the proctitle or embedding[0] */ |
7fef744d |
797 | exitstatus = perl_parse(my_perl, NULL, 2, embedding, NULL); |
d95b23b2 |
798 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
54310121 |
799 | if(!exitstatus) { |
7fef744d |
800 | exitstatus = perl_run(my_perl); |
54310121 |
801 | |
2307c6d0 |
802 | while(printf("Enter file name: ") && |
803 | fgets(filename, BUFFER_SIZE, stdin)) { |
54310121 |
804 | |
2307c6d0 |
805 | filename[strlen(filename)-1] = '\0'; /* strip \n */ |
8ebc5c01 |
806 | /* call the subroutine, passing it the filename as an argument */ |
807 | args[0] = filename; |
4929bf7b |
808 | call_argv("Embed::Persistent::eval_file", |
8ebc5c01 |
809 | G_DISCARD | G_EVAL, args); |
54310121 |
810 | |
8ebc5c01 |
811 | /* check $@ */ |
9cde0e7f |
812 | if(SvTRUE(ERRSV)) |
2d8e6c8d |
813 | fprintf(stderr, "eval error: %s\n", SvPV(ERRSV,n_a)); |
8ebc5c01 |
814 | } |
a6006777 |
815 | } |
54310121 |
816 | |
9cde0e7f |
817 | PL_perl_destruct_level = 0; |
7fef744d |
818 | perl_destruct(my_perl); |
819 | perl_free(my_perl); |
1ccffcf5 |
820 | PERL_SYS_TERM(); |
a6006777 |
821 | exit(exitstatus); |
822 | } |
823 | |
a6006777 |
824 | Now compile: |
825 | |
54310121 |
826 | % cc -o persistent persistent.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
a6006777 |
827 | |
d1be9408 |
828 | Here's an example script file: |
a6006777 |
829 | |
830 | #test.pl |
831 | my $string = "hello"; |
832 | foo($string); |
833 | |
834 | sub foo { |
835 | print "foo says: @_\n"; |
836 | } |
837 | |
838 | Now run: |
839 | |
840 | % persistent |
841 | Enter file name: test.pl |
842 | foo says: hello |
843 | Enter file name: test.pl |
844 | already compiled Embed::test_2epl->handler |
845 | foo says: hello |
846 | Enter file name: ^C |
847 | |
d95b23b2 |
848 | =head2 Execution of END blocks |
849 | |
850 | Traditionally END blocks have been executed at the end of the perl_run. |
851 | This causes problems for applications that never call perl_run. Since |
852 | perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END> |
853 | to get the new behaviour. This also enables the running of END blocks if |
bf9cdc68 |
854 | the perl_parse fails and C<perl_destruct> will return the exit value. |
d95b23b2 |
855 | |
a2722ac9 |
856 | =head2 $0 assignments |
857 | |
858 | When a perl script assigns a value to $0 then the perl runtime will |
859 | try to make this value show up as the program name reported by "ps" by |
860 | updating the memory pointed to by the argv passed to perl_parse() and |
861 | also calling API functions like setproctitle() where available. This |
862 | behaviour might not be appropriate when embedding perl and can be |
863 | disabled by assigning the value C<1> to the variable C<PL_origalen> |
864 | before perl_parse() is called. |
865 | |
866 | The F<persistent.c> example above is for instance likely to segfault |
867 | when $0 is assigned to if the C<PL_origalen = 1;> assignment is |
868 | removed. This because perl will try to write to the read only memory |
869 | of the C<embedding[]> strings. |
870 | |
8ebc5c01 |
871 | =head2 Maintaining multiple interpreter instances |
872 | |
8a7dc658 |
873 | Some rare applications will need to create more than one interpreter |
874 | during a session. Such an application might sporadically decide to |
54310121 |
875 | release any resources associated with the interpreter. |
8a7dc658 |
876 | |
877 | The program must take care to ensure that this takes place I<before> |
9bbedd82 |
878 | the next interpreter is constructed. By default, when perl is not |
879 | built with any special options, the global variable |
9cde0e7f |
880 | C<PL_perl_destruct_level> is set to C<0>, since extra cleaning isn't |
9bbedd82 |
881 | usually needed when a program only ever creates a single interpreter |
882 | in its entire lifetime. |
8a7dc658 |
883 | |
9cde0e7f |
884 | Setting C<PL_perl_destruct_level> to C<1> makes everything squeaky clean: |
8a7dc658 |
885 | |
8ebc5c01 |
886 | while(1) { |
887 | ... |
9cde0e7f |
888 | /* reset global variables here with PL_perl_destruct_level = 1 */ |
bf9cdc68 |
889 | PL_perl_destruct_level = 1; |
54310121 |
890 | perl_construct(my_perl); |
8ebc5c01 |
891 | ... |
892 | /* clean and reset _everything_ during perl_destruct */ |
bf9cdc68 |
893 | PL_perl_destruct_level = 1; |
54310121 |
894 | perl_destruct(my_perl); |
895 | perl_free(my_perl); |
8ebc5c01 |
896 | ... |
897 | /* let's go do it again! */ |
898 | } |
899 | |
54310121 |
900 | When I<perl_destruct()> is called, the interpreter's syntax parse tree |
bf9cdc68 |
901 | and symbol tables are cleaned up, and global variables are reset. The |
902 | second assignment to C<PL_perl_destruct_level> is needed because |
903 | perl_construct resets it to C<0>. |
8ebc5c01 |
904 | |
8a7dc658 |
905 | Now suppose we have more than one interpreter instance running at the |
9bbedd82 |
906 | same time. This is feasible, but only if you used the Configure option |
907 | C<-Dusemultiplicity> or the options C<-Dusethreads -Duseithreads> when |
bf9cdc68 |
908 | building perl. By default, enabling one of these Configure options |
9bbedd82 |
909 | sets the per-interpreter global variable C<PL_perl_destruct_level> to |
bf9cdc68 |
910 | C<1>, so that thorough cleaning is automatic and interpreter variables |
911 | are initialized correctly. Even if you don't intend to run two or |
912 | more interpreters at the same time, but to run them sequentially, like |
913 | in the above example, it is recommended to build perl with the |
914 | C<-Dusemultiplicity> option otherwise some interpreter variables may |
915 | not be initialized correctly between consecutive runs and your |
916 | application may crash. |
9bbedd82 |
917 | |
832a833b |
918 | See also L<perlxs/Thread-aware system interfaces>. |
919 | |
9bbedd82 |
920 | Using C<-Dusethreads -Duseithreads> rather than C<-Dusemultiplicity> |
921 | is more appropriate if you intend to run multiple interpreters |
922 | concurrently in different threads, because it enables support for |
923 | linking in the thread libraries of your system with the interpreter. |
8ebc5c01 |
924 | |
925 | Let's give it a try: |
926 | |
927 | |
928 | #include <EXTERN.h> |
8a7dc658 |
929 | #include <perl.h> |
8ebc5c01 |
930 | |
931 | /* we're going to embed two interpreters */ |
932 | /* we're going to embed two interpreters */ |
933 | |
8ebc5c01 |
934 | #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)" |
935 | |
8ebc5c01 |
936 | int main(int argc, char **argv, char **env) |
937 | { |
1ccffcf5 |
938 | PerlInterpreter *one_perl, *two_perl; |
8ebc5c01 |
939 | char *one_args[] = { "one_perl", SAY_HELLO }; |
940 | char *two_args[] = { "two_perl", SAY_HELLO }; |
941 | |
1ccffcf5 |
942 | PERL_SYS_INIT3(&argc,&argv,&env); |
943 | one_perl = perl_alloc(); |
944 | two_perl = perl_alloc(); |
945 | |
9bbedd82 |
946 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
947 | perl_construct(one_perl); |
9bbedd82 |
948 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
949 | perl_construct(two_perl); |
950 | |
9bbedd82 |
951 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
952 | perl_parse(one_perl, NULL, 3, one_args, (char **)NULL); |
9bbedd82 |
953 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
954 | perl_parse(two_perl, NULL, 3, two_args, (char **)NULL); |
955 | |
9bbedd82 |
956 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
957 | perl_run(one_perl); |
9bbedd82 |
958 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
959 | perl_run(two_perl); |
960 | |
9bbedd82 |
961 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
962 | perl_destruct(one_perl); |
9bbedd82 |
963 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
964 | perl_destruct(two_perl); |
965 | |
9bbedd82 |
966 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
967 | perl_free(one_perl); |
9bbedd82 |
968 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
969 | perl_free(two_perl); |
1ccffcf5 |
970 | PERL_SYS_TERM(); |
8ebc5c01 |
971 | } |
972 | |
9bbedd82 |
973 | Note the calls to PERL_SET_CONTEXT(). These are necessary to initialize |
974 | the global state that tracks which interpreter is the "current" one on |
975 | the particular process or thread that may be running it. It should |
976 | always be used if you have more than one interpreter and are making |
977 | perl API calls on both interpreters in an interleaved fashion. |
978 | |
979 | PERL_SET_CONTEXT(interp) should also be called whenever C<interp> is |
980 | used by a thread that did not create it (using either perl_alloc(), or |
981 | the more esoteric perl_clone()). |
8ebc5c01 |
982 | |
983 | Compile as usual: |
984 | |
985 | % cc -o multiplicity multiplicity.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
986 | |
987 | Run it, Run it: |
988 | |
989 | % multiplicity |
990 | Hi, I'm one_perl |
991 | Hi, I'm two_perl |
992 | |
96dbc785 |
993 | =head2 Using Perl modules, which themselves use C libraries, from your C program |
994 | |
995 | If you've played with the examples above and tried to embed a script |
996 | that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++ library, |
997 | this probably happened: |
998 | |
999 | |
1000 | Can't load module Socket, dynamic loading not available in this perl. |
1001 | (You may need to build a new perl executable which either supports |
1002 | dynamic loading or has the Socket module statically linked into it.) |
1003 | |
1004 | |
1005 | What's wrong? |
1006 | |
1007 | Your interpreter doesn't know how to communicate with these extensions |
1008 | on its own. A little glue will help. Up until now you've been |
1009 | calling I<perl_parse()>, handing it NULL for the second argument: |
1010 | |
1011 | perl_parse(my_perl, NULL, argc, my_argv, NULL); |
1012 | |
1013 | That's where the glue code can be inserted to create the initial contact between |
1014 | Perl and linked C/C++ routines. Let's take a look some pieces of I<perlmain.c> |
1015 | to see how Perl does this: |
1016 | |
cc7dda15 |
1017 | static void xs_init (pTHX); |
96dbc785 |
1018 | |
cc7dda15 |
1019 | EXTERN_C void boot_DynaLoader (pTHX_ CV* cv); |
1020 | EXTERN_C void boot_Socket (pTHX_ CV* cv); |
96dbc785 |
1021 | |
1022 | |
1023 | EXTERN_C void |
cc7dda15 |
1024 | xs_init(pTHX) |
96dbc785 |
1025 | { |
1026 | char *file = __FILE__; |
1027 | /* DynaLoader is a special case */ |
1028 | newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file); |
1029 | newXS("Socket::bootstrap", boot_Socket, file); |
1030 | } |
1031 | |
1032 | Simply put: for each extension linked with your Perl executable |
1033 | (determined during its initial configuration on your |
1034 | computer or when adding a new extension), |
1035 | a Perl subroutine is created to incorporate the extension's |
1036 | routines. Normally, that subroutine is named |
1037 | I<Module::bootstrap()> and is invoked when you say I<use Module>. In |
1038 | turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl |
1039 | counterpart for each of the extension's XSUBs. Don't worry about this |
1040 | part; leave that to the I<xsubpp> and extension authors. If your |
1041 | extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()> |
1042 | for you on the fly. In fact, if you have a working DynaLoader then there |
5f05dabc |
1043 | is rarely any need to link in any other extensions statically. |
96dbc785 |
1044 | |
1045 | |
1046 | Once you have this code, slap it into the second argument of I<perl_parse()>: |
1047 | |
1048 | |
1049 | perl_parse(my_perl, xs_init, argc, my_argv, NULL); |
1050 | |
1051 | |
1052 | Then compile: |
1053 | |
8a7dc658 |
1054 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
96dbc785 |
1055 | |
1056 | % interp |
1057 | use Socket; |
1058 | use SomeDynamicallyLoadedModule; |
1059 | |
1060 | print "Now I can use extensions!\n"' |
1061 | |
1062 | B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code. |
1063 | |
8a7dc658 |
1064 | % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c |
96dbc785 |
1065 | % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts` |
1066 | % cc -c interp.c `perl -MExtUtils::Embed -e ccopts` |
8a7dc658 |
1067 | % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts` |
96dbc785 |
1068 | |
4929bf7b |
1069 | Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details. |
96dbc785 |
1070 | |
13a2d996 |
1071 | =head1 Embedding Perl under Win32 |
53f52f58 |
1072 | |
cc7dda15 |
1073 | In general, all of the source code shown here should work unmodified under |
1074 | Windows. |
53f52f58 |
1075 | |
cc7dda15 |
1076 | However, there are some caveats about the command-line examples shown. |
1077 | For starters, backticks won't work under the Win32 native command shell. |
53f52f58 |
1078 | The ExtUtils::Embed kit on CPAN ships with a script called |
1079 | B<genmake>, which generates a simple makefile to build a program from |
e010571f |
1080 | a single C source file. It can be used like this: |
53f52f58 |
1081 | |
1082 | C:\ExtUtils-Embed\eg> perl genmake interp.c |
1083 | C:\ExtUtils-Embed\eg> nmake |
1084 | C:\ExtUtils-Embed\eg> interp -e "print qq{I'm embedded in Win32!\n}" |
1085 | |
e010571f |
1086 | You may wish to use a more robust environment such as the Microsoft |
1087 | Developer Studio. In this case, run this to generate perlxsi.c: |
53f52f58 |
1088 | |
1089 | perl -MExtUtils::Embed -e xsinit |
1090 | |
e010571f |
1091 | Create a new project and Insert -> Files into Project: perlxsi.c, |
1092 | perl.lib, and your own source files, e.g. interp.c. Typically you'll |
1093 | find perl.lib in B<C:\perl\lib\CORE>, if not, you should see the |
1094 | B<CORE> directory relative to C<perl -V:archlib>. The studio will |
1095 | also need this path so it knows where to find Perl include files. |
1096 | This path can be added via the Tools -> Options -> Directories menu. |
1097 | Finally, select Build -> Build interp.exe and you're ready to go. |
96dbc785 |
1098 | |
35209cc8 |
1099 | =head1 Hiding Perl_ |
1100 | |
1101 | If you completely hide the short forms forms of the Perl public API, |
d51482e4 |
1102 | add -DPERL_NO_SHORT_NAMES to the compilation flags. This means that |
35209cc8 |
1103 | for example instead of writing |
1104 | |
1105 | warn("%d bottles of beer on the wall", bottlecount); |
1106 | |
1107 | you will have to write the explicit full form |
1108 | |
1109 | Perl_warn(aTHX_ "%d bottles of beer on the wall", bottlecount); |
1110 | |
1111 | (See L<perlguts/Background and PERL_IMPLICIT_CONTEXT for the explanation |
1112 | of the C<aTHX_>.> ) Hiding the short forms is very useful for avoiding |
1113 | all sorts of nasty (C preprocessor or otherwise) conflicts with other |
1114 | software packages (Perl defines about 2400 APIs with these short names, |
1115 | take or leave few hundred, so there certainly is room for conflict.) |
1116 | |
cb1a09d0 |
1117 | =head1 MORAL |
1118 | |
1119 | You can sometimes I<write faster code> in C, but |
5f05dabc |
1120 | you can always I<write code faster> in Perl. Because you can use |
cb1a09d0 |
1121 | each from the other, combine them as you wish. |
1122 | |
1123 | |
1124 | =head1 AUTHOR |
1125 | |
8eabb633 |
1126 | Jon Orwant <F<orwant@media.mit.edu>> and Doug MacEachern |
1127 | <F<dougm@covalent.net>>, with small contributions from Tim Bunce, Tom |
e010571f |
1128 | Christiansen, Guy Decoux, Hallvard Furuseth, Dov Grobgeld, and Ilya |
1129 | Zakharevich. |
cb1a09d0 |
1130 | |
e010571f |
1131 | Doug MacEachern has an article on embedding in Volume 1, Issue 4 of |
f224927c |
1132 | The Perl Journal ( http://www.tpj.com/ ). Doug is also the developer of the |
e010571f |
1133 | most widely-used Perl embedding: the mod_perl system |
1134 | (perl.apache.org), which embeds Perl in the Apache web server. |
1135 | Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl |
1136 | have used this model for Oracle, Netscape and Internet Information |
1137 | Server Perl plugins. |
cb1a09d0 |
1138 | |
8a7dc658 |
1139 | =head1 COPYRIGHT |
1140 | |
e010571f |
1141 | Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant. All |
8a7dc658 |
1142 | Rights Reserved. |
1143 | |
e010571f |
1144 | Permission is granted to make and distribute verbatim copies of this |
1145 | documentation provided the copyright notice and this permission notice are |
1146 | preserved on all copies. |
1147 | |
1148 | Permission is granted to copy and distribute modified versions of this |
1149 | documentation under the conditions for verbatim copying, provided also |
1150 | that they are marked clearly as modified versions, that the authors' |
1151 | names and title are unchanged (though subtitles and additional |
1152 | authors' names may be added), and that the entire resulting derived |
1153 | work is distributed under the terms of a permission notice identical |
1154 | to this one. |
1155 | |
1156 | Permission is granted to copy and distribute translations of this |
1157 | documentation into another language, under the above conditions for |
1158 | modified versions. |