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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, non-portable |
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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 | |
cb1a09d0 |
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 | char *embedding[] = { "", "-e", "0" }; |
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317 | |
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318 | PERL_SYS_INIT3(&argc,&argv,&env); |
137443ea |
319 | my_perl = perl_alloc(); |
320 | perl_construct( my_perl ); |
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321 | |
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322 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
d95b23b2 |
323 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
137443ea |
324 | perl_run(my_perl); |
c47ff5f1 |
325 | |
137443ea |
326 | /** Treat $a as an integer **/ |
4929bf7b |
327 | eval_pv("$a = 3; $a **= 2", TRUE); |
328 | printf("a = %d\n", SvIV(get_sv("a", FALSE))); |
c47ff5f1 |
329 | |
137443ea |
330 | /** Treat $a as a float **/ |
4929bf7b |
331 | eval_pv("$a = 3.14; $a **= 2", TRUE); |
332 | printf("a = %f\n", SvNV(get_sv("a", FALSE))); |
c47ff5f1 |
333 | |
137443ea |
334 | /** Treat $a as a string **/ |
4929bf7b |
335 | eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE); |
1c5b513e |
336 | printf("a = %s\n", SvPV_nolen(get_sv("a", FALSE))); |
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337 | |
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338 | perl_destruct(my_perl); |
339 | perl_free(my_perl); |
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340 | PERL_SYS_TERM(); |
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341 | } |
342 | |
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343 | 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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344 | |
345 | If you compile and run I<string.c>, you'll see the results of using |
346 | I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and |
347 | I<SvPV()> to create a string: |
348 | |
349 | a = 9 |
350 | a = 9.859600 |
351 | a = Just Another Perl Hacker |
352 | |
8f183262 |
353 | In the example above, we've created a global variable to temporarily |
353c6505 |
354 | store the computed value of our eval'ed expression. It is also |
8f183262 |
355 | possible and in most cases a better strategy to fetch the return value |
4929bf7b |
356 | from I<eval_pv()> instead. Example: |
8f183262 |
357 | |
8f183262 |
358 | ... |
4929bf7b |
359 | SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); |
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360 | printf("%s\n", SvPV_nolen(val)); |
8f183262 |
361 | ... |
362 | |
363 | This way, we avoid namespace pollution by not creating global |
364 | variables and we've simplified our code as well. |
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365 | |
366 | =head2 Performing Perl pattern matches and substitutions from your C program |
367 | |
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368 | The I<eval_sv()> function lets us evaluate strings of Perl code, so we can |
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369 | define some functions that use it to "specialize" in matches and |
370 | substitutions: I<match()>, I<substitute()>, and I<matches()>. |
371 | |
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372 | I32 match(SV *string, char *pattern); |
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373 | |
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374 | Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which |
375 | in your C program might appear as "/\\b\\w*\\b/"), match() |
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376 | returns 1 if the string matches the pattern and 0 otherwise. |
377 | |
1f05cdcd |
378 | int substitute(SV **string, char *pattern); |
cb1a09d0 |
379 | |
1f05cdcd |
380 | Given a pointer to an C<SV> and an C<=~> operation (e.g., |
8a7dc658 |
381 | C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string |
bf9cdc68 |
382 | within the C<SV> as according to the operation, returning the number of substitutions |
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383 | made. |
cb1a09d0 |
384 | |
1f05cdcd |
385 | int matches(SV *string, char *pattern, AV **matches); |
cb1a09d0 |
386 | |
1f05cdcd |
387 | Given an C<SV>, a pattern, and a pointer to an empty C<AV>, |
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388 | matches() evaluates C<$string =~ $pattern> in a list context, and |
1f05cdcd |
389 | fills in I<matches> with the array elements, returning the number of matches found. |
cb1a09d0 |
390 | |
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391 | Here's a sample program, I<match.c>, that uses all three (long lines have |
392 | been wrapped here): |
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393 | |
1f05cdcd |
394 | #include <EXTERN.h> |
395 | #include <perl.h> |
c47ff5f1 |
396 | |
7fef744d |
397 | static PerlInterpreter *my_perl; |
398 | |
4929bf7b |
399 | /** my_eval_sv(code, error_check) |
400 | ** kinda like eval_sv(), |
1f05cdcd |
401 | ** but we pop the return value off the stack |
402 | **/ |
4929bf7b |
403 | SV* my_eval_sv(SV *sv, I32 croak_on_error) |
1f05cdcd |
404 | { |
405 | dSP; |
406 | SV* retval; |
1c5b513e |
407 | |
c47ff5f1 |
408 | |
924508f0 |
409 | PUSHMARK(SP); |
4929bf7b |
410 | eval_sv(sv, G_SCALAR); |
c47ff5f1 |
411 | |
1f05cdcd |
412 | SPAGAIN; |
413 | retval = POPs; |
414 | PUTBACK; |
c47ff5f1 |
415 | |
9cde0e7f |
416 | if (croak_on_error && SvTRUE(ERRSV)) |
1c5b513e |
417 | croak(SvPVx_nolen(ERRSV)); |
c47ff5f1 |
418 | |
1f05cdcd |
419 | return retval; |
420 | } |
c47ff5f1 |
421 | |
1f05cdcd |
422 | /** match(string, pattern) |
423 | ** |
424 | ** Used for matches in a scalar context. |
425 | ** |
426 | ** Returns 1 if the match was successful; 0 otherwise. |
427 | **/ |
c47ff5f1 |
428 | |
1f05cdcd |
429 | I32 match(SV *string, char *pattern) |
430 | { |
561b68a9 |
431 | SV *command = newSV(0), *retval; |
c47ff5f1 |
432 | |
1f05cdcd |
433 | sv_setpvf(command, "my $string = '%s'; $string =~ %s", |
1c5b513e |
434 | SvPV_nolen(string), pattern); |
c47ff5f1 |
435 | |
4929bf7b |
436 | retval = my_eval_sv(command, TRUE); |
1f05cdcd |
437 | SvREFCNT_dec(command); |
c47ff5f1 |
438 | |
1f05cdcd |
439 | return SvIV(retval); |
440 | } |
c47ff5f1 |
441 | |
1f05cdcd |
442 | /** substitute(string, pattern) |
443 | ** |
444 | ** Used for =~ operations that modify their left-hand side (s/// and tr///) |
445 | ** |
446 | ** Returns the number of successful matches, and |
447 | ** modifies the input string if there were any. |
448 | **/ |
c47ff5f1 |
449 | |
1f05cdcd |
450 | I32 substitute(SV **string, char *pattern) |
451 | { |
561b68a9 |
452 | SV *command = newSV(0), *retval; |
c47ff5f1 |
453 | |
1f05cdcd |
454 | sv_setpvf(command, "$string = '%s'; ($string =~ %s)", |
1c5b513e |
455 | SvPV_nolen(*string), pattern); |
c47ff5f1 |
456 | |
4929bf7b |
457 | retval = my_eval_sv(command, TRUE); |
1f05cdcd |
458 | SvREFCNT_dec(command); |
c47ff5f1 |
459 | |
4929bf7b |
460 | *string = get_sv("string", FALSE); |
1f05cdcd |
461 | return SvIV(retval); |
462 | } |
c47ff5f1 |
463 | |
1f05cdcd |
464 | /** matches(string, pattern, matches) |
465 | ** |
90fdbbb7 |
466 | ** Used for matches in a list context. |
1f05cdcd |
467 | ** |
468 | ** Returns the number of matches, |
469 | ** and fills in **matches with the matching substrings |
470 | **/ |
c47ff5f1 |
471 | |
1f05cdcd |
472 | I32 matches(SV *string, char *pattern, AV **match_list) |
473 | { |
561b68a9 |
474 | SV *command = newSV(0); |
cb1a09d0 |
475 | I32 num_matches; |
c47ff5f1 |
476 | |
1f05cdcd |
477 | sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)", |
1c5b513e |
478 | SvPV_nolen(string), pattern); |
c47ff5f1 |
479 | |
4929bf7b |
480 | my_eval_sv(command, TRUE); |
1f05cdcd |
481 | SvREFCNT_dec(command); |
c47ff5f1 |
482 | |
4929bf7b |
483 | *match_list = get_av("array", FALSE); |
1f05cdcd |
484 | num_matches = av_len(*match_list) + 1; /** assume $[ is 0 **/ |
c47ff5f1 |
485 | |
cb1a09d0 |
486 | return num_matches; |
1f05cdcd |
487 | } |
c47ff5f1 |
488 | |
1f05cdcd |
489 | main (int argc, char **argv, char **env) |
490 | { |
a6006777 |
491 | char *embedding[] = { "", "-e", "0" }; |
1f05cdcd |
492 | AV *match_list; |
493 | I32 num_matches, i; |
7fef744d |
494 | SV *text; |
c47ff5f1 |
495 | |
1ccffcf5 |
496 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d |
497 | my_perl = perl_alloc(); |
1f05cdcd |
498 | perl_construct(my_perl); |
96dbc785 |
499 | perl_parse(my_perl, NULL, 3, embedding, NULL); |
d95b23b2 |
500 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
c47ff5f1 |
501 | |
561b68a9 |
502 | text = newSV(0); |
d3f3bf9f |
503 | sv_setpv(text, "When he is at a convenience store and the " |
504 | "bill comes to some amount like 76 cents, Maynard is " |
505 | "aware that there is something he *should* do, something " |
506 | "that will enable him to get back a quarter, but he has " |
507 | "no idea *what*. He fumbles through his red squeezey " |
508 | "changepurse and gives the boy three extra pennies with " |
509 | "his dollar, hoping that he might luck into the correct " |
510 | "amount. The boy gives him back two of his own pennies " |
511 | "and then the big shiny quarter that is his prize. " |
512 | "-RICHH"); |
c47ff5f1 |
513 | |
96dbc785 |
514 | if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/ |
1f05cdcd |
515 | printf("match: Text contains the word 'quarter'.\n\n"); |
96dbc785 |
516 | else |
1f05cdcd |
517 | printf("match: Text doesn't contain the word 'quarter'.\n\n"); |
c47ff5f1 |
518 | |
96dbc785 |
519 | if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/ |
1f05cdcd |
520 | printf("match: Text contains the word 'eighth'.\n\n"); |
96dbc785 |
521 | else |
1f05cdcd |
522 | printf("match: Text doesn't contain the word 'eighth'.\n\n"); |
c47ff5f1 |
523 | |
96dbc785 |
524 | /** Match all occurrences of /wi../ **/ |
525 | num_matches = matches(text, "m/(wi..)/g", &match_list); |
526 | printf("matches: m/(wi..)/g found %d matches...\n", num_matches); |
c47ff5f1 |
527 | |
96dbc785 |
528 | for (i = 0; i < num_matches; i++) |
1c5b513e |
529 | printf("match: %s\n", SvPV_nolen(*av_fetch(match_list, i, FALSE))); |
cb1a09d0 |
530 | printf("\n"); |
c47ff5f1 |
531 | |
96dbc785 |
532 | /** Remove all vowels from text **/ |
533 | num_matches = substitute(&text, "s/[aeiou]//gi"); |
cb1a09d0 |
534 | if (num_matches) { |
1f05cdcd |
535 | printf("substitute: s/[aeiou]//gi...%d substitutions made.\n", |
536 | num_matches); |
1c5b513e |
537 | printf("Now text is: %s\n\n", SvPV_nolen(text)); |
cb1a09d0 |
538 | } |
c47ff5f1 |
539 | |
96dbc785 |
540 | /** Attempt a substitution **/ |
541 | if (!substitute(&text, "s/Perl/C/")) { |
1f05cdcd |
542 | printf("substitute: s/Perl/C...No substitution made.\n\n"); |
cb1a09d0 |
543 | } |
c47ff5f1 |
544 | |
1f05cdcd |
545 | SvREFCNT_dec(text); |
9cde0e7f |
546 | PL_perl_destruct_level = 1; |
cb1a09d0 |
547 | perl_destruct(my_perl); |
548 | perl_free(my_perl); |
1ccffcf5 |
549 | PERL_SYS_TERM(); |
1f05cdcd |
550 | } |
cb1a09d0 |
551 | |
96dbc785 |
552 | which produces the output (again, long lines have been wrapped here) |
cb1a09d0 |
553 | |
8a7dc658 |
554 | match: Text contains the word 'quarter'. |
96dbc785 |
555 | |
8a7dc658 |
556 | match: Text doesn't contain the word 'eighth'. |
96dbc785 |
557 | |
8a7dc658 |
558 | matches: m/(wi..)/g found 2 matches... |
cb1a09d0 |
559 | match: will |
560 | match: with |
96dbc785 |
561 | |
8a7dc658 |
562 | substitute: s/[aeiou]//gi...139 substitutions made. |
54310121 |
563 | Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts, |
96dbc785 |
564 | Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt bck |
565 | qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd gvs th by |
566 | thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct mnt. Th by gvs |
567 | hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s hs prz. -RCHH |
568 | |
8a7dc658 |
569 | substitute: s/Perl/C...No substitution made. |
96dbc785 |
570 | |
cb1a09d0 |
571 | =head2 Fiddling with the Perl stack from your C program |
572 | |
573 | When trying to explain stacks, most computer science textbooks mumble |
574 | something about spring-loaded columns of cafeteria plates: the last |
575 | thing you pushed on the stack is the first thing you pop off. That'll |
576 | do for our purposes: your C program will push some arguments onto "the Perl |
577 | stack", shut its eyes while some magic happens, and then pop the |
578 | results--the return value of your Perl subroutine--off the stack. |
96dbc785 |
579 | |
cb1a09d0 |
580 | First you'll need to know how to convert between C types and Perl |
581 | types, with newSViv() and sv_setnv() and newAV() and all their |
4929bf7b |
582 | friends. They're described in L<perlguts> and L<perlapi>. |
cb1a09d0 |
583 | |
584 | Then you'll need to know how to manipulate the Perl stack. That's |
585 | described in L<perlcall>. |
586 | |
96dbc785 |
587 | Once you've understood those, embedding Perl in C is easy. |
cb1a09d0 |
588 | |
54310121 |
589 | Because C has no builtin function for integer exponentiation, let's |
cb1a09d0 |
590 | make Perl's ** operator available to it (this is less useful than it |
5f05dabc |
591 | sounds, because Perl implements ** with C's I<pow()> function). First |
cb1a09d0 |
592 | I'll create a stub exponentiation function in I<power.pl>: |
593 | |
594 | sub expo { |
595 | my ($a, $b) = @_; |
596 | return $a ** $b; |
597 | } |
598 | |
599 | Now I'll create a C program, I<power.c>, with a function |
600 | I<PerlPower()> that contains all the perlguts necessary to push the |
601 | two arguments into I<expo()> and to pop the return value out. Take a |
602 | deep breath... |
603 | |
cb1a09d0 |
604 | #include <EXTERN.h> |
605 | #include <perl.h> |
96dbc785 |
606 | |
cb1a09d0 |
607 | static PerlInterpreter *my_perl; |
96dbc785 |
608 | |
cb1a09d0 |
609 | static void |
610 | PerlPower(int a, int b) |
611 | { |
612 | dSP; /* initialize stack pointer */ |
613 | ENTER; /* everything created after here */ |
614 | SAVETMPS; /* ...is a temporary variable. */ |
924508f0 |
615 | PUSHMARK(SP); /* remember the stack pointer */ |
cb1a09d0 |
616 | XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */ |
617 | XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */ |
618 | PUTBACK; /* make local stack pointer global */ |
4929bf7b |
619 | call_pv("expo", G_SCALAR); /* call the function */ |
cb1a09d0 |
620 | SPAGAIN; /* refresh stack pointer */ |
621 | /* pop the return value from stack */ |
622 | printf ("%d to the %dth power is %d.\n", a, b, POPi); |
96dbc785 |
623 | PUTBACK; |
cb1a09d0 |
624 | FREETMPS; /* free that return value */ |
625 | LEAVE; /* ...and the XPUSHed "mortal" args.*/ |
626 | } |
96dbc785 |
627 | |
628 | int main (int argc, char **argv, char **env) |
cb1a09d0 |
629 | { |
95b76e31 |
630 | char *my_argv[] = { "", "power.pl" }; |
96dbc785 |
631 | |
1ccffcf5 |
632 | PERL_SYS_INIT3(&argc,&argv,&env); |
cb1a09d0 |
633 | my_perl = perl_alloc(); |
634 | perl_construct( my_perl ); |
96dbc785 |
635 | |
95b76e31 |
636 | perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL); |
d95b23b2 |
637 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
8ebc5c01 |
638 | perl_run(my_perl); |
96dbc785 |
639 | |
cb1a09d0 |
640 | PerlPower(3, 4); /*** Compute 3 ** 4 ***/ |
96dbc785 |
641 | |
cb1a09d0 |
642 | perl_destruct(my_perl); |
643 | perl_free(my_perl); |
1ccffcf5 |
644 | PERL_SYS_TERM(); |
cb1a09d0 |
645 | } |
96dbc785 |
646 | |
cb1a09d0 |
647 | |
648 | |
649 | Compile and run: |
650 | |
96dbc785 |
651 | % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
652 | |
653 | % power |
cb1a09d0 |
654 | 3 to the 4th power is 81. |
655 | |
a6006777 |
656 | =head2 Maintaining a persistent interpreter |
657 | |
8a7dc658 |
658 | When developing interactive and/or potentially long-running |
659 | applications, it's a good idea to maintain a persistent interpreter |
660 | rather than allocating and constructing a new interpreter multiple |
661 | times. The major reason is speed: since Perl will only be loaded into |
54310121 |
662 | memory once. |
8a7dc658 |
663 | |
664 | However, you have to be more cautious with namespace and variable |
665 | scoping when using a persistent interpreter. In previous examples |
666 | we've been using global variables in the default package C<main>. We |
667 | knew exactly what code would be run, and assumed we could avoid |
668 | variable collisions and outrageous symbol table growth. |
669 | |
670 | Let's say your application is a server that will occasionally run Perl |
671 | code from some arbitrary file. Your server has no way of knowing what |
672 | code it's going to run. Very dangerous. |
673 | |
674 | If the file is pulled in by C<perl_parse()>, compiled into a newly |
675 | constructed interpreter, and subsequently cleaned out with |
676 | C<perl_destruct()> afterwards, you're shielded from most namespace |
677 | troubles. |
678 | |
679 | One way to avoid namespace collisions in this scenario is to translate |
680 | the filename into a guaranteed-unique package name, and then compile |
e010571f |
681 | the code into that package using L<perlfunc/eval>. In the example |
8a7dc658 |
682 | below, each file will only be compiled once. Or, the application |
683 | might choose to clean out the symbol table associated with the file |
4929bf7b |
684 | after it's no longer needed. Using L<perlapi/call_argv>, We'll |
8a7dc658 |
685 | call the subroutine C<Embed::Persistent::eval_file> which lives in the |
686 | file C<persistent.pl> and pass the filename and boolean cleanup/cache |
a6006777 |
687 | flag as arguments. |
688 | |
8a7dc658 |
689 | Note that the process will continue to grow for each file that it |
690 | uses. In addition, there might be C<AUTOLOAD>ed subroutines and other |
691 | conditions that cause Perl's symbol table to grow. You might want to |
692 | add some logic that keeps track of the process size, or restarts |
693 | itself after a certain number of requests, to ensure that memory |
694 | consumption is minimized. You'll also want to scope your variables |
e010571f |
695 | with L<perlfunc/my> whenever possible. |
a6006777 |
696 | |
54310121 |
697 | |
a6006777 |
698 | package Embed::Persistent; |
699 | #persistent.pl |
54310121 |
700 | |
a6006777 |
701 | use strict; |
77ca0c92 |
702 | our %Cache; |
1ee082b7 |
703 | use Symbol qw(delete_package); |
54310121 |
704 | |
a6006777 |
705 | sub valid_package_name { |
706 | my($string) = @_; |
707 | $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg; |
708 | # second pass only for words starting with a digit |
709 | $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg; |
54310121 |
710 | |
a6006777 |
711 | # Dress it up as a real package name |
712 | $string =~ s|/|::|g; |
713 | return "Embed" . $string; |
714 | } |
54310121 |
715 | |
a6006777 |
716 | sub eval_file { |
717 | my($filename, $delete) = @_; |
718 | my $package = valid_package_name($filename); |
719 | my $mtime = -M $filename; |
720 | if(defined $Cache{$package}{mtime} |
721 | && |
54310121 |
722 | $Cache{$package}{mtime} <= $mtime) |
a6006777 |
723 | { |
54310121 |
724 | # we have compiled this subroutine already, |
8ebc5c01 |
725 | # it has not been updated on disk, nothing left to do |
726 | print STDERR "already compiled $package->handler\n"; |
a6006777 |
727 | } |
728 | else { |
8ebc5c01 |
729 | local *FH; |
730 | open FH, $filename or die "open '$filename' $!"; |
731 | local($/) = undef; |
732 | my $sub = <FH>; |
733 | close FH; |
54310121 |
734 | |
8ebc5c01 |
735 | #wrap the code into a subroutine inside our unique package |
736 | my $eval = qq{package $package; sub handler { $sub; }}; |
737 | { |
738 | # hide our variables within this block |
739 | my($filename,$mtime,$package,$sub); |
740 | eval $eval; |
741 | } |
742 | die $@ if $@; |
54310121 |
743 | |
8ebc5c01 |
744 | #cache it unless we're cleaning out each time |
745 | $Cache{$package}{mtime} = $mtime unless $delete; |
a6006777 |
746 | } |
54310121 |
747 | |
a6006777 |
748 | eval {$package->handler;}; |
749 | die $@ if $@; |
54310121 |
750 | |
a6006777 |
751 | delete_package($package) if $delete; |
54310121 |
752 | |
a6006777 |
753 | #take a look if you want |
754 | #print Devel::Symdump->rnew($package)->as_string, $/; |
755 | } |
54310121 |
756 | |
a6006777 |
757 | 1; |
54310121 |
758 | |
a6006777 |
759 | __END__ |
760 | |
761 | /* persistent.c */ |
54310121 |
762 | #include <EXTERN.h> |
763 | #include <perl.h> |
764 | |
a6006777 |
765 | /* 1 = clean out filename's symbol table after each request, 0 = don't */ |
766 | #ifndef DO_CLEAN |
767 | #define DO_CLEAN 0 |
768 | #endif |
54310121 |
769 | |
2307c6d0 |
770 | #define BUFFER_SIZE 1024 |
771 | |
7fef744d |
772 | static PerlInterpreter *my_perl = NULL; |
54310121 |
773 | |
a6006777 |
774 | int |
775 | main(int argc, char **argv, char **env) |
776 | { |
777 | char *embedding[] = { "", "persistent.pl" }; |
778 | char *args[] = { "", DO_CLEAN, NULL }; |
2307c6d0 |
779 | char filename[BUFFER_SIZE]; |
a6006777 |
780 | int exitstatus = 0; |
54310121 |
781 | |
1ccffcf5 |
782 | PERL_SYS_INIT3(&argc,&argv,&env); |
7fef744d |
783 | if((my_perl = perl_alloc()) == NULL) { |
8ebc5c01 |
784 | fprintf(stderr, "no memory!"); |
785 | exit(1); |
a6006777 |
786 | } |
7fef744d |
787 | perl_construct(my_perl); |
54310121 |
788 | |
a2722ac9 |
789 | PL_origalen = 1; /* don't let $0 assignment update the proctitle or embedding[0] */ |
7fef744d |
790 | exitstatus = perl_parse(my_perl, NULL, 2, embedding, NULL); |
d95b23b2 |
791 | PL_exit_flags |= PERL_EXIT_DESTRUCT_END; |
54310121 |
792 | if(!exitstatus) { |
7fef744d |
793 | exitstatus = perl_run(my_perl); |
54310121 |
794 | |
2307c6d0 |
795 | while(printf("Enter file name: ") && |
796 | fgets(filename, BUFFER_SIZE, stdin)) { |
54310121 |
797 | |
2307c6d0 |
798 | filename[strlen(filename)-1] = '\0'; /* strip \n */ |
8ebc5c01 |
799 | /* call the subroutine, passing it the filename as an argument */ |
800 | args[0] = filename; |
4929bf7b |
801 | call_argv("Embed::Persistent::eval_file", |
8ebc5c01 |
802 | G_DISCARD | G_EVAL, args); |
54310121 |
803 | |
8ebc5c01 |
804 | /* check $@ */ |
9cde0e7f |
805 | if(SvTRUE(ERRSV)) |
1c5b513e |
806 | fprintf(stderr, "eval error: %s\n", SvPV_nolen(ERRSV)); |
8ebc5c01 |
807 | } |
a6006777 |
808 | } |
54310121 |
809 | |
9cde0e7f |
810 | PL_perl_destruct_level = 0; |
7fef744d |
811 | perl_destruct(my_perl); |
812 | perl_free(my_perl); |
1ccffcf5 |
813 | PERL_SYS_TERM(); |
a6006777 |
814 | exit(exitstatus); |
815 | } |
816 | |
a6006777 |
817 | Now compile: |
818 | |
54310121 |
819 | % cc -o persistent persistent.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
a6006777 |
820 | |
d1be9408 |
821 | Here's an example script file: |
a6006777 |
822 | |
823 | #test.pl |
824 | my $string = "hello"; |
825 | foo($string); |
826 | |
827 | sub foo { |
828 | print "foo says: @_\n"; |
829 | } |
830 | |
831 | Now run: |
832 | |
833 | % persistent |
834 | Enter file name: test.pl |
835 | foo says: hello |
836 | Enter file name: test.pl |
837 | already compiled Embed::test_2epl->handler |
838 | foo says: hello |
839 | Enter file name: ^C |
840 | |
d95b23b2 |
841 | =head2 Execution of END blocks |
842 | |
843 | Traditionally END blocks have been executed at the end of the perl_run. |
844 | This causes problems for applications that never call perl_run. Since |
845 | perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END> |
846 | to get the new behaviour. This also enables the running of END blocks if |
bf9cdc68 |
847 | the perl_parse fails and C<perl_destruct> will return the exit value. |
d95b23b2 |
848 | |
a2722ac9 |
849 | =head2 $0 assignments |
850 | |
851 | When a perl script assigns a value to $0 then the perl runtime will |
852 | try to make this value show up as the program name reported by "ps" by |
853 | updating the memory pointed to by the argv passed to perl_parse() and |
854 | also calling API functions like setproctitle() where available. This |
855 | behaviour might not be appropriate when embedding perl and can be |
856 | disabled by assigning the value C<1> to the variable C<PL_origalen> |
857 | before perl_parse() is called. |
858 | |
859 | The F<persistent.c> example above is for instance likely to segfault |
860 | when $0 is assigned to if the C<PL_origalen = 1;> assignment is |
861 | removed. This because perl will try to write to the read only memory |
862 | of the C<embedding[]> strings. |
863 | |
8ebc5c01 |
864 | =head2 Maintaining multiple interpreter instances |
865 | |
8a7dc658 |
866 | Some rare applications will need to create more than one interpreter |
867 | during a session. Such an application might sporadically decide to |
54310121 |
868 | release any resources associated with the interpreter. |
8a7dc658 |
869 | |
870 | The program must take care to ensure that this takes place I<before> |
9bbedd82 |
871 | the next interpreter is constructed. By default, when perl is not |
872 | built with any special options, the global variable |
9cde0e7f |
873 | C<PL_perl_destruct_level> is set to C<0>, since extra cleaning isn't |
9bbedd82 |
874 | usually needed when a program only ever creates a single interpreter |
875 | in its entire lifetime. |
8a7dc658 |
876 | |
9cde0e7f |
877 | Setting C<PL_perl_destruct_level> to C<1> makes everything squeaky clean: |
8a7dc658 |
878 | |
8ebc5c01 |
879 | while(1) { |
880 | ... |
9cde0e7f |
881 | /* reset global variables here with PL_perl_destruct_level = 1 */ |
bf9cdc68 |
882 | PL_perl_destruct_level = 1; |
54310121 |
883 | perl_construct(my_perl); |
8ebc5c01 |
884 | ... |
885 | /* clean and reset _everything_ during perl_destruct */ |
bf9cdc68 |
886 | PL_perl_destruct_level = 1; |
54310121 |
887 | perl_destruct(my_perl); |
888 | perl_free(my_perl); |
8ebc5c01 |
889 | ... |
890 | /* let's go do it again! */ |
891 | } |
892 | |
54310121 |
893 | When I<perl_destruct()> is called, the interpreter's syntax parse tree |
bf9cdc68 |
894 | and symbol tables are cleaned up, and global variables are reset. The |
895 | second assignment to C<PL_perl_destruct_level> is needed because |
896 | perl_construct resets it to C<0>. |
8ebc5c01 |
897 | |
8a7dc658 |
898 | Now suppose we have more than one interpreter instance running at the |
9bbedd82 |
899 | same time. This is feasible, but only if you used the Configure option |
900 | C<-Dusemultiplicity> or the options C<-Dusethreads -Duseithreads> when |
bf9cdc68 |
901 | building perl. By default, enabling one of these Configure options |
9bbedd82 |
902 | sets the per-interpreter global variable C<PL_perl_destruct_level> to |
bf9cdc68 |
903 | C<1>, so that thorough cleaning is automatic and interpreter variables |
904 | are initialized correctly. Even if you don't intend to run two or |
905 | more interpreters at the same time, but to run them sequentially, like |
906 | in the above example, it is recommended to build perl with the |
907 | C<-Dusemultiplicity> option otherwise some interpreter variables may |
908 | not be initialized correctly between consecutive runs and your |
909 | application may crash. |
9bbedd82 |
910 | |
832a833b |
911 | See also L<perlxs/Thread-aware system interfaces>. |
912 | |
9bbedd82 |
913 | Using C<-Dusethreads -Duseithreads> rather than C<-Dusemultiplicity> |
914 | is more appropriate if you intend to run multiple interpreters |
915 | concurrently in different threads, because it enables support for |
916 | linking in the thread libraries of your system with the interpreter. |
8ebc5c01 |
917 | |
918 | Let's give it a try: |
919 | |
920 | |
921 | #include <EXTERN.h> |
8a7dc658 |
922 | #include <perl.h> |
8ebc5c01 |
923 | |
924 | /* we're going to embed two interpreters */ |
925 | /* we're going to embed two interpreters */ |
926 | |
8ebc5c01 |
927 | #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)" |
928 | |
8ebc5c01 |
929 | int main(int argc, char **argv, char **env) |
930 | { |
1ccffcf5 |
931 | PerlInterpreter *one_perl, *two_perl; |
8ebc5c01 |
932 | char *one_args[] = { "one_perl", SAY_HELLO }; |
933 | char *two_args[] = { "two_perl", SAY_HELLO }; |
934 | |
1ccffcf5 |
935 | PERL_SYS_INIT3(&argc,&argv,&env); |
936 | one_perl = perl_alloc(); |
937 | two_perl = perl_alloc(); |
938 | |
9bbedd82 |
939 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
940 | perl_construct(one_perl); |
9bbedd82 |
941 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
942 | perl_construct(two_perl); |
943 | |
9bbedd82 |
944 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
945 | perl_parse(one_perl, NULL, 3, one_args, (char **)NULL); |
9bbedd82 |
946 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
947 | perl_parse(two_perl, NULL, 3, two_args, (char **)NULL); |
948 | |
9bbedd82 |
949 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
950 | perl_run(one_perl); |
9bbedd82 |
951 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
952 | perl_run(two_perl); |
953 | |
9bbedd82 |
954 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
955 | perl_destruct(one_perl); |
9bbedd82 |
956 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
957 | perl_destruct(two_perl); |
958 | |
9bbedd82 |
959 | PERL_SET_CONTEXT(one_perl); |
8ebc5c01 |
960 | perl_free(one_perl); |
9bbedd82 |
961 | PERL_SET_CONTEXT(two_perl); |
8ebc5c01 |
962 | perl_free(two_perl); |
1ccffcf5 |
963 | PERL_SYS_TERM(); |
8ebc5c01 |
964 | } |
965 | |
9bbedd82 |
966 | Note the calls to PERL_SET_CONTEXT(). These are necessary to initialize |
967 | the global state that tracks which interpreter is the "current" one on |
968 | the particular process or thread that may be running it. It should |
969 | always be used if you have more than one interpreter and are making |
970 | perl API calls on both interpreters in an interleaved fashion. |
971 | |
972 | PERL_SET_CONTEXT(interp) should also be called whenever C<interp> is |
973 | used by a thread that did not create it (using either perl_alloc(), or |
974 | the more esoteric perl_clone()). |
8ebc5c01 |
975 | |
976 | Compile as usual: |
977 | |
978 | % cc -o multiplicity multiplicity.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
979 | |
980 | Run it, Run it: |
981 | |
982 | % multiplicity |
983 | Hi, I'm one_perl |
984 | Hi, I'm two_perl |
985 | |
96dbc785 |
986 | =head2 Using Perl modules, which themselves use C libraries, from your C program |
987 | |
988 | If you've played with the examples above and tried to embed a script |
989 | that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++ library, |
990 | this probably happened: |
991 | |
992 | |
993 | Can't load module Socket, dynamic loading not available in this perl. |
994 | (You may need to build a new perl executable which either supports |
995 | dynamic loading or has the Socket module statically linked into it.) |
996 | |
997 | |
998 | What's wrong? |
999 | |
1000 | Your interpreter doesn't know how to communicate with these extensions |
1001 | on its own. A little glue will help. Up until now you've been |
1002 | calling I<perl_parse()>, handing it NULL for the second argument: |
1003 | |
1004 | perl_parse(my_perl, NULL, argc, my_argv, NULL); |
1005 | |
1006 | That's where the glue code can be inserted to create the initial contact between |
1007 | Perl and linked C/C++ routines. Let's take a look some pieces of I<perlmain.c> |
1008 | to see how Perl does this: |
1009 | |
cc7dda15 |
1010 | static void xs_init (pTHX); |
96dbc785 |
1011 | |
cc7dda15 |
1012 | EXTERN_C void boot_DynaLoader (pTHX_ CV* cv); |
1013 | EXTERN_C void boot_Socket (pTHX_ CV* cv); |
96dbc785 |
1014 | |
1015 | |
1016 | EXTERN_C void |
cc7dda15 |
1017 | xs_init(pTHX) |
96dbc785 |
1018 | { |
1019 | char *file = __FILE__; |
1020 | /* DynaLoader is a special case */ |
1021 | newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file); |
1022 | newXS("Socket::bootstrap", boot_Socket, file); |
1023 | } |
1024 | |
1025 | Simply put: for each extension linked with your Perl executable |
1026 | (determined during its initial configuration on your |
1027 | computer or when adding a new extension), |
1028 | a Perl subroutine is created to incorporate the extension's |
1029 | routines. Normally, that subroutine is named |
1030 | I<Module::bootstrap()> and is invoked when you say I<use Module>. In |
1031 | turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl |
1032 | counterpart for each of the extension's XSUBs. Don't worry about this |
1033 | part; leave that to the I<xsubpp> and extension authors. If your |
1034 | extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()> |
1035 | for you on the fly. In fact, if you have a working DynaLoader then there |
5f05dabc |
1036 | is rarely any need to link in any other extensions statically. |
96dbc785 |
1037 | |
1038 | |
1039 | Once you have this code, slap it into the second argument of I<perl_parse()>: |
1040 | |
1041 | |
1042 | perl_parse(my_perl, xs_init, argc, my_argv, NULL); |
1043 | |
1044 | |
1045 | Then compile: |
1046 | |
8a7dc658 |
1047 | % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` |
96dbc785 |
1048 | |
1049 | % interp |
1050 | use Socket; |
1051 | use SomeDynamicallyLoadedModule; |
1052 | |
1053 | print "Now I can use extensions!\n"' |
1054 | |
1055 | B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code. |
1056 | |
8a7dc658 |
1057 | % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c |
96dbc785 |
1058 | % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts` |
1059 | % cc -c interp.c `perl -MExtUtils::Embed -e ccopts` |
8a7dc658 |
1060 | % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts` |
96dbc785 |
1061 | |
4929bf7b |
1062 | Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details. |
96dbc785 |
1063 | |
13a2d996 |
1064 | =head1 Embedding Perl under Win32 |
53f52f58 |
1065 | |
cc7dda15 |
1066 | In general, all of the source code shown here should work unmodified under |
1067 | Windows. |
53f52f58 |
1068 | |
cc7dda15 |
1069 | However, there are some caveats about the command-line examples shown. |
1070 | For starters, backticks won't work under the Win32 native command shell. |
53f52f58 |
1071 | The ExtUtils::Embed kit on CPAN ships with a script called |
1072 | B<genmake>, which generates a simple makefile to build a program from |
e010571f |
1073 | a single C source file. It can be used like this: |
53f52f58 |
1074 | |
1075 | C:\ExtUtils-Embed\eg> perl genmake interp.c |
1076 | C:\ExtUtils-Embed\eg> nmake |
1077 | C:\ExtUtils-Embed\eg> interp -e "print qq{I'm embedded in Win32!\n}" |
1078 | |
e010571f |
1079 | You may wish to use a more robust environment such as the Microsoft |
1080 | Developer Studio. In this case, run this to generate perlxsi.c: |
53f52f58 |
1081 | |
1082 | perl -MExtUtils::Embed -e xsinit |
1083 | |
e010571f |
1084 | Create a new project and Insert -> Files into Project: perlxsi.c, |
1085 | perl.lib, and your own source files, e.g. interp.c. Typically you'll |
1086 | find perl.lib in B<C:\perl\lib\CORE>, if not, you should see the |
1087 | B<CORE> directory relative to C<perl -V:archlib>. The studio will |
1088 | also need this path so it knows where to find Perl include files. |
1089 | This path can be added via the Tools -> Options -> Directories menu. |
1090 | Finally, select Build -> Build interp.exe and you're ready to go. |
96dbc785 |
1091 | |
35209cc8 |
1092 | =head1 Hiding Perl_ |
1093 | |
1094 | If you completely hide the short forms forms of the Perl public API, |
d51482e4 |
1095 | add -DPERL_NO_SHORT_NAMES to the compilation flags. This means that |
35209cc8 |
1096 | for example instead of writing |
1097 | |
1098 | warn("%d bottles of beer on the wall", bottlecount); |
1099 | |
1100 | you will have to write the explicit full form |
1101 | |
1102 | Perl_warn(aTHX_ "%d bottles of beer on the wall", bottlecount); |
1103 | |
1104 | (See L<perlguts/Background and PERL_IMPLICIT_CONTEXT for the explanation |
1105 | of the C<aTHX_>.> ) Hiding the short forms is very useful for avoiding |
1106 | all sorts of nasty (C preprocessor or otherwise) conflicts with other |
1107 | software packages (Perl defines about 2400 APIs with these short names, |
1108 | take or leave few hundred, so there certainly is room for conflict.) |
1109 | |
cb1a09d0 |
1110 | =head1 MORAL |
1111 | |
1112 | You can sometimes I<write faster code> in C, but |
5f05dabc |
1113 | you can always I<write code faster> in Perl. Because you can use |
cb1a09d0 |
1114 | each from the other, combine them as you wish. |
1115 | |
1116 | |
1117 | =head1 AUTHOR |
1118 | |
8eabb633 |
1119 | Jon Orwant <F<orwant@media.mit.edu>> and Doug MacEachern |
1120 | <F<dougm@covalent.net>>, with small contributions from Tim Bunce, Tom |
e010571f |
1121 | Christiansen, Guy Decoux, Hallvard Furuseth, Dov Grobgeld, and Ilya |
1122 | Zakharevich. |
cb1a09d0 |
1123 | |
e010571f |
1124 | Doug MacEachern has an article on embedding in Volume 1, Issue 4 of |
f224927c |
1125 | The Perl Journal ( http://www.tpj.com/ ). Doug is also the developer of the |
e010571f |
1126 | most widely-used Perl embedding: the mod_perl system |
1127 | (perl.apache.org), which embeds Perl in the Apache web server. |
1128 | Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl |
1129 | have used this model for Oracle, Netscape and Internet Information |
1130 | Server Perl plugins. |
cb1a09d0 |
1131 | |
8a7dc658 |
1132 | =head1 COPYRIGHT |
1133 | |
e010571f |
1134 | Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant. All |
8a7dc658 |
1135 | Rights Reserved. |
1136 | |
e010571f |
1137 | Permission is granted to make and distribute verbatim copies of this |
1138 | documentation provided the copyright notice and this permission notice are |
1139 | preserved on all copies. |
1140 | |
1141 | Permission is granted to copy and distribute modified versions of this |
1142 | documentation under the conditions for verbatim copying, provided also |
1143 | that they are marked clearly as modified versions, that the authors' |
1144 | names and title are unchanged (though subtitles and additional |
1145 | authors' names may be added), and that the entire resulting derived |
1146 | work is distributed under the terms of a permission notice identical |
1147 | to this one. |
1148 | |
1149 | Permission is granted to copy and distribute translations of this |
1150 | documentation into another language, under the above conditions for |
1151 | modified versions. |