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-=head1 NAME
-
-perlembed - how to embed perl in your C program
-
-=head1 DESCRIPTION
-
-=head2 PREAMBLE
-
-Do you want to:
-
-=over 5
-
-=item B<Use C from Perl?>
-
-Read L<perlxstut>, L<perlxs>, L<h2xs>, L<perlguts>, and L<perlapi>.
-
-=item B<Use a Unix program from Perl?>
-
-Read about back-quotes and about C<system> and C<exec> in L<perlfunc>.
-
-=item B<Use Perl from Perl?>
-
-Read about L<perlfunc/do> and L<perlfunc/eval> and L<perlfunc/require>
-and L<perlfunc/use>.
-
-=item B<Use C from C?>
-
-Rethink your design.
-
-=item B<Use Perl from C?>
-
-Read on...
-
-=back
-
-=head2 ROADMAP
-
-=over 5
-
-=item *
-
-Compiling your C program
-
-=item *
-
-Adding a Perl interpreter to your C program
-
-=item *
-
-Calling a Perl subroutine from your C program
-
-=item *
-
-Evaluating a Perl statement from your C program
-
-=item *
-
-Performing Perl pattern matches and substitutions from your C program
-
-=item *
-
-Fiddling with the Perl stack from your C program
-
-=item *
-
-Maintaining a persistent interpreter
-
-=item *
-
-Maintaining multiple interpreter instances
-
-=item *
-
-Using Perl modules, which themselves use C libraries, from your C program
-
-=item *
-
-Embedding Perl under Win32
-
-=back
-
-=head2 Compiling your C program
-
-If you have trouble compiling the scripts in this documentation,
-you're not alone. The cardinal rule: COMPILE THE PROGRAMS IN EXACTLY
-THE SAME WAY THAT YOUR PERL WAS COMPILED. (Sorry for yelling.)
-
-Also, every C program that uses Perl must link in the I<perl library>.
-What's that, you ask? Perl is itself written in C; the perl library
-is the collection of compiled C programs that were used to create your
-perl executable (I</usr/bin/perl> or equivalent). (Corollary: you
-can't use Perl from your C program unless Perl has been compiled on
-your machine, or installed properly--that's why you shouldn't blithely
-copy Perl executables from machine to machine without also copying the
-I<lib> directory.)
-
-When you use Perl from C, your C program will--usually--allocate,
-"run", and deallocate a I<PerlInterpreter> object, which is defined by
-the perl library.
-
-If your copy of Perl is recent enough to contain this documentation
-(version 5.002 or later), then the perl library (and I<EXTERN.h> and
-I<perl.h>, which you'll also need) will reside in a directory
-that looks like this:
-
- /usr/local/lib/perl5/your_architecture_here/CORE
-
-or perhaps just
-
- /usr/local/lib/perl5/CORE
-
-or maybe something like
-
- /usr/opt/perl5/CORE
-
-Execute this statement for a hint about where to find CORE:
-
- perl -MConfig -e 'print $Config{archlib}'
-
-Here's how you'd compile the example in the next section,
-L<Adding a Perl interpreter to your C program>, on my Linux box:
-
- % gcc -O2 -Dbool=char -DHAS_BOOL -I/usr/local/include
- -I/usr/local/lib/perl5/i586-linux/5.003/CORE
- -L/usr/local/lib/perl5/i586-linux/5.003/CORE
- -o interp interp.c -lperl -lm
-
-(That's all one line.) On my DEC Alpha running old 5.003_05, the
-incantation is a bit different:
-
- % cc -O2 -Olimit 2900 -DSTANDARD_C -I/usr/local/include
- -I/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE
- -L/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE -L/usr/local/lib
- -D__LANGUAGE_C__ -D_NO_PROTO -o interp interp.c -lperl -lm
-
-How can you figure out what to add? Assuming your Perl is post-5.001,
-execute a C<perl -V> command and pay special attention to the "cc" and
-"ccflags" information.
-
-You'll have to choose the appropriate compiler (I<cc>, I<gcc>, et al.) for
-your machine: C<perl -MConfig -e 'print $Config{cc}'> will tell you what
-to use.
-
-You'll also have to choose the appropriate library directory
-(I</usr/local/lib/...>) for your machine. If your compiler complains
-that certain functions are undefined, or that it can't locate
-I<-lperl>, then you need to change the path following the C<-L>. If it
-complains that it can't find I<EXTERN.h> and I<perl.h>, you need to
-change the path following the C<-I>.
-
-You may have to add extra libraries as well. Which ones?
-Perhaps those printed by
-
- perl -MConfig -e 'print $Config{libs}'
-
-Provided your perl binary was properly configured and installed the
-B<ExtUtils::Embed> module will determine all of this information for
-you:
-
- % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
-
-If the B<ExtUtils::Embed> module isn't part of your Perl distribution,
-you can retrieve it from
-http://www.perl.com/perl/CPAN/modules/by-module/ExtUtils/
-(If this documentation came from your Perl distribution, then you're
-running 5.004 or better and you already have it.)
-
-The B<ExtUtils::Embed> kit on CPAN also contains all source code for
-the examples in this document, tests, additional examples and other
-information you may find useful.
-
-=head2 Adding a Perl interpreter to your C program
-
-In a sense, perl (the C program) is a good example of embedding Perl
-(the language), so I'll demonstrate embedding with I<miniperlmain.c>,
-included in the source distribution. Here's a bastardized, non-portable
-version of I<miniperlmain.c> containing the essentials of embedding:
-
- #include <EXTERN.h> /* from the Perl distribution */
- #include <perl.h> /* from the Perl distribution */
-
- static PerlInterpreter *my_perl; /*** The Perl interpreter ***/
-
- int main(int argc, char **argv, char **env)
- {
- PERL_SYS_INIT3(&argc,&argv,&env);
- my_perl = perl_alloc();
- perl_construct(my_perl);
- PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
- perl_parse(my_perl, NULL, argc, argv, (char **)NULL);
- perl_run(my_perl);
- perl_destruct(my_perl);
- perl_free(my_perl);
- PERL_SYS_TERM();
- }
-
-Notice that we don't use the C<env> pointer. Normally handed to
-C<perl_parse> as its final argument, C<env> here is replaced by
-C<NULL>, which means that the current environment will be used.
-
-The macros PERL_SYS_INIT3() and PERL_SYS_TERM() provide system-specific
-tune up of the C runtime environment necessary to run Perl interpreters;
-they should only be called once regardless of how many interpreters you
-create or destroy. Call PERL_SYS_INIT3() before you create your first
-interpreter, and PERL_SYS_TERM() after you free your last interpreter.
-
-Since PERL_SYS_INIT3() may change C<env>, it may be more appropriate to
-provide C<env> as an argument to perl_parse().
-
-Also notice that no matter what arguments you pass to perl_parse(),
-PERL_SYS_INIT3() must be invoked on the C main() argc, argv and env and
-only once.
-
-Now compile this program (I'll call it I<interp.c>) into an executable:
-
- % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
-
-After a successful compilation, you'll be able to use I<interp> just
-like perl itself:
-
- % interp
- print "Pretty Good Perl \n";
- print "10890 - 9801 is ", 10890 - 9801;
- <CTRL-D>
- Pretty Good Perl
- 10890 - 9801 is 1089
-
-or
-
- % interp -e 'printf("%x", 3735928559)'
- deadbeef
-
-You can also read and execute Perl statements from a file while in the
-midst of your C program, by placing the filename in I<argv[1]> before
-calling I<perl_run>.
-
-=head2 Calling a Perl subroutine from your C program
-
-To call individual Perl subroutines, you can use any of the B<call_*>
-functions documented in L<perlcall>.
-In this example we'll use C<call_argv>.
-
-That's shown below, in a program I'll call I<showtime.c>.
-
- #include <EXTERN.h>
- #include <perl.h>
-
- static PerlInterpreter *my_perl;
-
- int main(int argc, char **argv, char **env)
- {
- char *args[] = { NULL };
- PERL_SYS_INIT3(&argc,&argv,&env);
- my_perl = perl_alloc();
- perl_construct(my_perl);
-
- perl_parse(my_perl, NULL, argc, argv, NULL);
- PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
-
- /*** skipping perl_run() ***/
-
- call_argv("showtime", G_DISCARD | G_NOARGS, args);
-
- perl_destruct(my_perl);
- perl_free(my_perl);
- PERL_SYS_TERM();
- }
-
-where I<showtime> is a Perl subroutine that takes no arguments (that's the
-I<G_NOARGS>) and for which I'll ignore the return value (that's the
-I<G_DISCARD>). Those flags, and others, are discussed in L<perlcall>.
-
-I'll define the I<showtime> subroutine in a file called I<showtime.pl>:
-
- print "I shan't be printed.";
-
- sub showtime {
- print time;
- }
-
-Simple enough. Now compile and run:
-
- % cc -o showtime showtime.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
-
- % showtime showtime.pl
- 818284590
-
-yielding the number of seconds that elapsed between January 1, 1970
-(the beginning of the Unix epoch), and the moment I began writing this
-sentence.
-
-In this particular case we don't have to call I<perl_run>, as we set
-the PL_exit_flag PERL_EXIT_DESTRUCT_END which executes END blocks in
-perl_destruct.
-
-If you want to pass arguments to the Perl subroutine, you can add
-strings to the C<NULL>-terminated C<args> list passed to
-I<call_argv>. For other data types, or to examine return values,
-you'll need to manipulate the Perl stack. That's demonstrated in
-L<Fiddling with the Perl stack from your C program>.
-
-=head2 Evaluating a Perl statement from your C program
-
-Perl provides two API functions to evaluate pieces of Perl code.
-These are L<perlapi/eval_sv> and L<perlapi/eval_pv>.
-
-Arguably, these are the only routines you'll ever need to execute
-snippets of Perl code from within your C program. Your code can be as
-long as you wish; it can contain multiple statements; it can employ
-L<perlfunc/use>, L<perlfunc/require>, and L<perlfunc/do> to
-include external Perl files.
-
-I<eval_pv> lets us evaluate individual Perl strings, and then
-extract variables for coercion into C types. The following program,
-I<string.c>, executes three Perl strings, extracting an C<int> from
-the first, a C<float> from the second, and a C<char *> from the third.
-
- #include <EXTERN.h>
- #include <perl.h>
-
- static PerlInterpreter *my_perl;
-
- main (int argc, char **argv, char **env)
- {
- char *embedding[] = { "", "-e", "0" };
-
- PERL_SYS_INIT3(&argc,&argv,&env);
- my_perl = perl_alloc();
- perl_construct( my_perl );
-
- perl_parse(my_perl, NULL, 3, embedding, NULL);
- PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
- perl_run(my_perl);
-
- /** Treat $a as an integer **/
- eval_pv("$a = 3; $a **= 2", TRUE);
- printf("a = %d\n", SvIV(get_sv("a", 0)));
-
- /** Treat $a as a float **/
- eval_pv("$a = 3.14; $a **= 2", TRUE);
- printf("a = %f\n", SvNV(get_sv("a", 0)));
-
- /** Treat $a as a string **/
- eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE);
- printf("a = %s\n", SvPV_nolen(get_sv("a", 0)));
-
- perl_destruct(my_perl);
- perl_free(my_perl);
- PERL_SYS_TERM();
- }
-
-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>.
-
-If you compile and run I<string.c>, you'll see the results of using
-I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and
-I<SvPV()> to create a string:
-
- a = 9
- a = 9.859600
- a = Just Another Perl Hacker
-
-In the example above, we've created a global variable to temporarily
-store the computed value of our eval'ed expression. It is also
-possible and in most cases a better strategy to fetch the return value
-from I<eval_pv()> instead. Example:
-
- ...
- SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE);
- printf("%s\n", SvPV_nolen(val));
- ...
-
-This way, we avoid namespace pollution by not creating global
-variables and we've simplified our code as well.
-
-=head2 Performing Perl pattern matches and substitutions from your C program
-
-The I<eval_sv()> function lets us evaluate strings of Perl code, so we can
-define some functions that use it to "specialize" in matches and
-substitutions: I<match()>, I<substitute()>, and I<matches()>.
-
- I32 match(SV *string, char *pattern);
-
-Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which
-in your C program might appear as "/\\b\\w*\\b/"), match()
-returns 1 if the string matches the pattern and 0 otherwise.
-
- int substitute(SV **string, char *pattern);
-
-Given a pointer to an C<SV> and an C<=~> operation (e.g.,
-C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string
-within the C<SV> as according to the operation, returning the number of substitutions
-made.
-
- int matches(SV *string, char *pattern, AV **matches);
-
-Given an C<SV>, a pattern, and a pointer to an empty C<AV>,
-matches() evaluates C<$string =~ $pattern> in a list context, and
-fills in I<matches> with the array elements, returning the number of matches found.
-
-Here's a sample program, I<match.c>, that uses all three (long lines have
-been wrapped here):
-
- #include <EXTERN.h>
- #include <perl.h>
-
- static PerlInterpreter *my_perl;
-
- /** my_eval_sv(code, error_check)
- ** kinda like eval_sv(),
- ** but we pop the return value off the stack
- **/
- SV* my_eval_sv(SV *sv, I32 croak_on_error)
- {
- dSP;
- SV* retval;
-
-
- PUSHMARK(SP);
- eval_sv(sv, G_SCALAR);
-
- SPAGAIN;
- retval = POPs;
- PUTBACK;
-
- if (croak_on_error && SvTRUE(ERRSV))
- croak(SvPVx_nolen(ERRSV));
-
- return retval;
- }
-
- /** match(string, pattern)
- **
- ** Used for matches in a scalar context.
- **
- ** Returns 1 if the match was successful; 0 otherwise.
- **/
-
- I32 match(SV *string, char *pattern)
- {
- SV *command = newSV(0), *retval;
-
- sv_setpvf(command, "my $string = '%s'; $string =~ %s",
- SvPV_nolen(string), pattern);
-
- retval = my_eval_sv(command, TRUE);
- SvREFCNT_dec(command);
-
- return SvIV(retval);
- }
-
- /** substitute(string, pattern)
- **
- ** Used for =~ operations that modify their left-hand side (s/// and tr///)
- **
- ** Returns the number of successful matches, and
- ** modifies the input string if there were any.
- **/
-
- I32 substitute(SV **string, char *pattern)
- {
- SV *command = newSV(0), *retval;
-
- sv_setpvf(command, "$string = '%s'; ($string =~ %s)",
- SvPV_nolen(*string), pattern);
-
- retval = my_eval_sv(command, TRUE);
- SvREFCNT_dec(command);
-
- *string = get_sv("string", 0);
- return SvIV(retval);
- }
-
- /** matches(string, pattern, matches)
- **
- ** Used for matches in a list context.
- **
- ** Returns the number of matches,
- ** and fills in **matches with the matching substrings
- **/
-
- I32 matches(SV *string, char *pattern, AV **match_list)
- {
- SV *command = newSV(0);
- I32 num_matches;
-
- sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)",
- SvPV_nolen(string), pattern);
-
- my_eval_sv(command, TRUE);
- SvREFCNT_dec(command);
-
- *match_list = get_av("array", 0);
- num_matches = av_len(*match_list) + 1;
-
- return num_matches;
- }
-
- main (int argc, char **argv, char **env)
- {
- char *embedding[] = { "", "-e", "0" };
- AV *match_list;
- I32 num_matches, i;
- SV *text;
-
- PERL_SYS_INIT3(&argc,&argv,&env);
- my_perl = perl_alloc();
- perl_construct(my_perl);
- perl_parse(my_perl, NULL, 3, embedding, NULL);
- PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
-
- text = newSV(0);
- sv_setpv(text, "When he is at a convenience store and the "
- "bill comes to some amount like 76 cents, Maynard is "
- "aware that there is something he *should* do, something "
- "that will enable him to get back a quarter, but he has "
- "no idea *what*. He fumbles through his red squeezey "
- "changepurse and gives the boy three extra pennies with "
- "his dollar, hoping that he might luck into the correct "
- "amount. The boy gives him back two of his own pennies "
- "and then the big shiny quarter that is his prize. "
- "-RICHH");
-
- if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/
- printf("match: Text contains the word 'quarter'.\n\n");
- else
- printf("match: Text doesn't contain the word 'quarter'.\n\n");
-
- if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/
- printf("match: Text contains the word 'eighth'.\n\n");
- else
- printf("match: Text doesn't contain the word 'eighth'.\n\n");
-
- /** Match all occurrences of /wi../ **/
- num_matches = matches(text, "m/(wi..)/g", &match_list);
- printf("matches: m/(wi..)/g found %d matches...\n", num_matches);
-
- for (i = 0; i < num_matches; i++)
- printf("match: %s\n", SvPV_nolen(*av_fetch(match_list, i, FALSE)));
- printf("\n");
-
- /** Remove all vowels from text **/
- num_matches = substitute(&text, "s/[aeiou]//gi");
- if (num_matches) {
- printf("substitute: s/[aeiou]//gi...%d substitutions made.\n",
- num_matches);
- printf("Now text is: %s\n\n", SvPV_nolen(text));
- }
-
- /** Attempt a substitution **/
- if (!substitute(&text, "s/Perl/C/")) {
- printf("substitute: s/Perl/C...No substitution made.\n\n");
- }
-
- SvREFCNT_dec(text);
- PL_perl_destruct_level = 1;
- perl_destruct(my_perl);
- perl_free(my_perl);
- PERL_SYS_TERM();
- }
-
-which produces the output (again, long lines have been wrapped here)
-
- match: Text contains the word 'quarter'.
-
- match: Text doesn't contain the word 'eighth'.
-
- matches: m/(wi..)/g found 2 matches...
- match: will
- match: with
-
- substitute: s/[aeiou]//gi...139 substitutions made.
- Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts,
- Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt bck
- qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd gvs th by
- thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct mnt. Th by gvs
- hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s hs prz. -RCHH
-
- substitute: s/Perl/C...No substitution made.
-
-=head2 Fiddling with the Perl stack from your C program
-
-When trying to explain stacks, most computer science textbooks mumble
-something about spring-loaded columns of cafeteria plates: the last
-thing you pushed on the stack is the first thing you pop off. That'll
-do for our purposes: your C program will push some arguments onto "the Perl
-stack", shut its eyes while some magic happens, and then pop the
-results--the return value of your Perl subroutine--off the stack.
-
-First you'll need to know how to convert between C types and Perl
-types, with newSViv() and sv_setnv() and newAV() and all their
-friends. They're described in L<perlguts> and L<perlapi>.
-
-Then you'll need to know how to manipulate the Perl stack. That's
-described in L<perlcall>.
-
-Once you've understood those, embedding Perl in C is easy.
-
-Because C has no builtin function for integer exponentiation, let's
-make Perl's ** operator available to it (this is less useful than it
-sounds, because Perl implements ** with C's I<pow()> function). First
-I'll create a stub exponentiation function in I<power.pl>:
-
- sub expo {
- my ($a, $b) = @_;
- return $a ** $b;
- }
-
-Now I'll create a C program, I<power.c>, with a function
-I<PerlPower()> that contains all the perlguts necessary to push the
-two arguments into I<expo()> and to pop the return value out. Take a
-deep breath...
-
- #include <EXTERN.h>
- #include <perl.h>
-
- static PerlInterpreter *my_perl;
-
- static void
- PerlPower(int a, int b)
- {
- dSP; /* initialize stack pointer */
- ENTER; /* everything created after here */
- SAVETMPS; /* ...is a temporary variable. */
- PUSHMARK(SP); /* remember the stack pointer */
- XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */
- XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */
- PUTBACK; /* make local stack pointer global */
- call_pv("expo", G_SCALAR); /* call the function */
- SPAGAIN; /* refresh stack pointer */
- /* pop the return value from stack */
- printf ("%d to the %dth power is %d.\n", a, b, POPi);
- PUTBACK;
- FREETMPS; /* free that return value */
- LEAVE; /* ...and the XPUSHed "mortal" args.*/
- }
-
- int main (int argc, char **argv, char **env)
- {
- char *my_argv[] = { "", "power.pl" };
-
- PERL_SYS_INIT3(&argc,&argv,&env);
- my_perl = perl_alloc();
- perl_construct( my_perl );
-
- perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL);
- PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
- perl_run(my_perl);
-
- PerlPower(3, 4); /*** Compute 3 ** 4 ***/
-
- perl_destruct(my_perl);
- perl_free(my_perl);
- PERL_SYS_TERM();
- }
-
-
-
-Compile and run:
-
- % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
-
- % power
- 3 to the 4th power is 81.
-
-=head2 Maintaining a persistent interpreter
-
-When developing interactive and/or potentially long-running
-applications, it's a good idea to maintain a persistent interpreter
-rather than allocating and constructing a new interpreter multiple
-times. The major reason is speed: since Perl will only be loaded into
-memory once.
-
-However, you have to be more cautious with namespace and variable
-scoping when using a persistent interpreter. In previous examples
-we've been using global variables in the default package C<main>. We
-knew exactly what code would be run, and assumed we could avoid
-variable collisions and outrageous symbol table growth.
-
-Let's say your application is a server that will occasionally run Perl
-code from some arbitrary file. Your server has no way of knowing what
-code it's going to run. Very dangerous.
-
-If the file is pulled in by C<perl_parse()>, compiled into a newly
-constructed interpreter, and subsequently cleaned out with
-C<perl_destruct()> afterwards, you're shielded from most namespace
-troubles.
-
-One way to avoid namespace collisions in this scenario is to translate
-the filename into a guaranteed-unique package name, and then compile
-the code into that package using L<perlfunc/eval>. In the example
-below, each file will only be compiled once. Or, the application
-might choose to clean out the symbol table associated with the file
-after it's no longer needed. Using L<perlapi/call_argv>, We'll
-call the subroutine C<Embed::Persistent::eval_file> which lives in the
-file C<persistent.pl> and pass the filename and boolean cleanup/cache
-flag as arguments.
-
-Note that the process will continue to grow for each file that it
-uses. In addition, there might be C<AUTOLOAD>ed subroutines and other
-conditions that cause Perl's symbol table to grow. You might want to
-add some logic that keeps track of the process size, or restarts
-itself after a certain number of requests, to ensure that memory
-consumption is minimized. You'll also want to scope your variables
-with L<perlfunc/my> whenever possible.
-
-
- package Embed::Persistent;
- #persistent.pl
-
- use strict;
- our %Cache;
- use Symbol qw(delete_package);
-
- sub valid_package_name {
- my($string) = @_;
- $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg;
- # second pass only for words starting with a digit
- $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg;
-
- # Dress it up as a real package name
- $string =~ s|/|::|g;
- return "Embed" . $string;
- }
-
- sub eval_file {
- my($filename, $delete) = @_;
- my $package = valid_package_name($filename);
- my $mtime = -M $filename;
- if(defined $Cache{$package}{mtime}
- &&
- $Cache{$package}{mtime} <= $mtime)
- {
- # we have compiled this subroutine already,
- # it has not been updated on disk, nothing left to do
- print STDERR "already compiled $package->handler\n";
- }
- else {
- local *FH;
- open FH, $filename or die "open '$filename' $!";
- local($/) = undef;
- my $sub = <FH>;
- close FH;
-
- #wrap the code into a subroutine inside our unique package
- my $eval = qq{package $package; sub handler { $sub; }};
- {
- # hide our variables within this block
- my($filename,$mtime,$package,$sub);
- eval $eval;
- }
- die $@ if $@;
-
- #cache it unless we're cleaning out each time
- $Cache{$package}{mtime} = $mtime unless $delete;
- }
-
- eval {$package->handler;};
- die $@ if $@;
-
- delete_package($package) if $delete;
-
- #take a look if you want
- #print Devel::Symdump->rnew($package)->as_string, $/;
- }
-
- 1;
-
- __END__
-
- /* persistent.c */
- #include <EXTERN.h>
- #include <perl.h>
-
- /* 1 = clean out filename's symbol table after each request, 0 = don't */
- #ifndef DO_CLEAN
- #define DO_CLEAN 0
- #endif
-
- #define BUFFER_SIZE 1024
-
- static PerlInterpreter *my_perl = NULL;
-
- int
- main(int argc, char **argv, char **env)
- {
- char *embedding[] = { "", "persistent.pl" };
- char *args[] = { "", DO_CLEAN, NULL };
- char filename[BUFFER_SIZE];
- int exitstatus = 0;
-
- PERL_SYS_INIT3(&argc,&argv,&env);
- if((my_perl = perl_alloc()) == NULL) {
- fprintf(stderr, "no memory!");
- exit(1);
- }
- perl_construct(my_perl);
-
- PL_origalen = 1; /* don't let $0 assignment update the proctitle or embedding[0] */
- exitstatus = perl_parse(my_perl, NULL, 2, embedding, NULL);
- PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
- if(!exitstatus) {
- exitstatus = perl_run(my_perl);
-
- while(printf("Enter file name: ") &&
- fgets(filename, BUFFER_SIZE, stdin)) {
-
- filename[strlen(filename)-1] = '\0'; /* strip \n */
- /* call the subroutine, passing it the filename as an argument */
- args[0] = filename;
- call_argv("Embed::Persistent::eval_file",
- G_DISCARD | G_EVAL, args);
-
- /* check $@ */
- if(SvTRUE(ERRSV))
- fprintf(stderr, "eval error: %s\n", SvPV_nolen(ERRSV));
- }
- }
-
- PL_perl_destruct_level = 0;
- perl_destruct(my_perl);
- perl_free(my_perl);
- PERL_SYS_TERM();
- exit(exitstatus);
- }
-
-Now compile:
-
- % cc -o persistent persistent.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
-
-Here's an example script file:
-
- #test.pl
- my $string = "hello";
- foo($string);
-
- sub foo {
- print "foo says: @_\n";
- }
-
-Now run:
-
- % persistent
- Enter file name: test.pl
- foo says: hello
- Enter file name: test.pl
- already compiled Embed::test_2epl->handler
- foo says: hello
- Enter file name: ^C
-
-=head2 Execution of END blocks
-
-Traditionally END blocks have been executed at the end of the perl_run.
-This causes problems for applications that never call perl_run. Since
-perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END>
-to get the new behaviour. This also enables the running of END blocks if
-the perl_parse fails and C<perl_destruct> will return the exit value.
-
-=head2 $0 assignments
-
-When a perl script assigns a value to $0 then the perl runtime will
-try to make this value show up as the program name reported by "ps" by
-updating the memory pointed to by the argv passed to perl_parse() and
-also calling API functions like setproctitle() where available. This
-behaviour might not be appropriate when embedding perl and can be
-disabled by assigning the value C<1> to the variable C<PL_origalen>
-before perl_parse() is called.
-
-The F<persistent.c> example above is for instance likely to segfault
-when $0 is assigned to if the C<PL_origalen = 1;> assignment is
-removed. This because perl will try to write to the read only memory
-of the C<embedding[]> strings.
-
-=head2 Maintaining multiple interpreter instances
-
-Some rare applications will need to create more than one interpreter
-during a session. Such an application might sporadically decide to
-release any resources associated with the interpreter.
-
-The program must take care to ensure that this takes place I<before>
-the next interpreter is constructed. By default, when perl is not
-built with any special options, the global variable
-C<PL_perl_destruct_level> is set to C<0>, since extra cleaning isn't
-usually needed when a program only ever creates a single interpreter
-in its entire lifetime.
-
-Setting C<PL_perl_destruct_level> to C<1> makes everything squeaky clean:
-
- while(1) {
- ...
- /* reset global variables here with PL_perl_destruct_level = 1 */
- PL_perl_destruct_level = 1;
- perl_construct(my_perl);
- ...
- /* clean and reset _everything_ during perl_destruct */
- PL_perl_destruct_level = 1;
- perl_destruct(my_perl);
- perl_free(my_perl);
- ...
- /* let's go do it again! */
- }
-
-When I<perl_destruct()> is called, the interpreter's syntax parse tree
-and symbol tables are cleaned up, and global variables are reset. The
-second assignment to C<PL_perl_destruct_level> is needed because
-perl_construct resets it to C<0>.
-
-Now suppose we have more than one interpreter instance running at the
-same time. This is feasible, but only if you used the Configure option
-C<-Dusemultiplicity> or the options C<-Dusethreads -Duseithreads> when
-building perl. By default, enabling one of these Configure options
-sets the per-interpreter global variable C<PL_perl_destruct_level> to
-C<1>, so that thorough cleaning is automatic and interpreter variables
-are initialized correctly. Even if you don't intend to run two or
-more interpreters at the same time, but to run them sequentially, like
-in the above example, it is recommended to build perl with the
-C<-Dusemultiplicity> option otherwise some interpreter variables may
-not be initialized correctly between consecutive runs and your
-application may crash.
-
-See also L<perlxs/Thread-aware system interfaces>.
-
-Using C<-Dusethreads -Duseithreads> rather than C<-Dusemultiplicity>
-is more appropriate if you intend to run multiple interpreters
-concurrently in different threads, because it enables support for
-linking in the thread libraries of your system with the interpreter.
-
-Let's give it a try:
-
-
- #include <EXTERN.h>
- #include <perl.h>
-
- /* we're going to embed two interpreters */
-
- #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)"
-
- int main(int argc, char **argv, char **env)
- {
- PerlInterpreter *one_perl, *two_perl;
- char *one_args[] = { "one_perl", SAY_HELLO };
- char *two_args[] = { "two_perl", SAY_HELLO };
-
- PERL_SYS_INIT3(&argc,&argv,&env);
- one_perl = perl_alloc();
- two_perl = perl_alloc();
-
- PERL_SET_CONTEXT(one_perl);
- perl_construct(one_perl);
- PERL_SET_CONTEXT(two_perl);
- perl_construct(two_perl);
-
- PERL_SET_CONTEXT(one_perl);
- perl_parse(one_perl, NULL, 3, one_args, (char **)NULL);
- PERL_SET_CONTEXT(two_perl);
- perl_parse(two_perl, NULL, 3, two_args, (char **)NULL);
-
- PERL_SET_CONTEXT(one_perl);
- perl_run(one_perl);
- PERL_SET_CONTEXT(two_perl);
- perl_run(two_perl);
-
- PERL_SET_CONTEXT(one_perl);
- perl_destruct(one_perl);
- PERL_SET_CONTEXT(two_perl);
- perl_destruct(two_perl);
-
- PERL_SET_CONTEXT(one_perl);
- perl_free(one_perl);
- PERL_SET_CONTEXT(two_perl);
- perl_free(two_perl);
- PERL_SYS_TERM();
- }
-
-Note the calls to PERL_SET_CONTEXT(). These are necessary to initialize
-the global state that tracks which interpreter is the "current" one on
-the particular process or thread that may be running it. It should
-always be used if you have more than one interpreter and are making
-perl API calls on both interpreters in an interleaved fashion.
-
-PERL_SET_CONTEXT(interp) should also be called whenever C<interp> is
-used by a thread that did not create it (using either perl_alloc(), or
-the more esoteric perl_clone()).
-
-Compile as usual:
-
- % cc -o multiplicity multiplicity.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
-
-Run it, Run it:
-
- % multiplicity
- Hi, I'm one_perl
- Hi, I'm two_perl
-
-=head2 Using Perl modules, which themselves use C libraries, from your C program
-
-If you've played with the examples above and tried to embed a script
-that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++ library,
-this probably happened:
-
-
- Can't load module Socket, dynamic loading not available in this perl.
- (You may need to build a new perl executable which either supports
- dynamic loading or has the Socket module statically linked into it.)
-
-
-What's wrong?
-
-Your interpreter doesn't know how to communicate with these extensions
-on its own. A little glue will help. Up until now you've been
-calling I<perl_parse()>, handing it NULL for the second argument:
-
- perl_parse(my_perl, NULL, argc, my_argv, NULL);
-
-That's where the glue code can be inserted to create the initial contact between
-Perl and linked C/C++ routines. Let's take a look some pieces of I<perlmain.c>
-to see how Perl does this:
-
- static void xs_init (pTHX);
-
- EXTERN_C void boot_DynaLoader (pTHX_ CV* cv);
- EXTERN_C void boot_Socket (pTHX_ CV* cv);
-
-
- EXTERN_C void
- xs_init(pTHX)
- {
- char *file = __FILE__;
- /* DynaLoader is a special case */
- newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file);
- newXS("Socket::bootstrap", boot_Socket, file);
- }
-
-Simply put: for each extension linked with your Perl executable
-(determined during its initial configuration on your
-computer or when adding a new extension),
-a Perl subroutine is created to incorporate the extension's
-routines. Normally, that subroutine is named
-I<Module::bootstrap()> and is invoked when you say I<use Module>. In
-turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl
-counterpart for each of the extension's XSUBs. Don't worry about this
-part; leave that to the I<xsubpp> and extension authors. If your
-extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()>
-for you on the fly. In fact, if you have a working DynaLoader then there
-is rarely any need to link in any other extensions statically.
-
-
-Once you have this code, slap it into the second argument of I<perl_parse()>:
-
-
- perl_parse(my_perl, xs_init, argc, my_argv, NULL);
-
-
-Then compile:
-
- % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
-
- % interp
- use Socket;
- use SomeDynamicallyLoadedModule;
-
- print "Now I can use extensions!\n"'
-
-B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code.
-
- % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c
- % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts`
- % cc -c interp.c `perl -MExtUtils::Embed -e ccopts`
- % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts`
-
-Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details.
-
-=head1 Hiding Perl_
-
-If you completely hide the short forms of the Perl public API,
-add -DPERL_NO_SHORT_NAMES to the compilation flags. This means that
-for example instead of writing
-
- warn("%d bottles of beer on the wall", bottlecount);
-
-you will have to write the explicit full form
-
- Perl_warn(aTHX_ "%d bottles of beer on the wall", bottlecount);
-
-(See L<perlguts/"Background and PERL_IMPLICIT_CONTEXT"> for the explanation
-of the C<aTHX_>. ) Hiding the short forms is very useful for avoiding
-all sorts of nasty (C preprocessor or otherwise) conflicts with other
-software packages (Perl defines about 2400 APIs with these short names,
-take or leave few hundred, so there certainly is room for conflict.)
-
-=head1 MORAL
-
-You can sometimes I<write faster code> in C, but
-you can always I<write code faster> in Perl. Because you can use
-each from the other, combine them as you wish.
-
-
-=head1 AUTHOR
-
-Jon Orwant <F<orwant@media.mit.edu>> and Doug MacEachern
-<F<dougm@covalent.net>>, with small contributions from Tim Bunce, Tom
-Christiansen, Guy Decoux, Hallvard Furuseth, Dov Grobgeld, and Ilya
-Zakharevich.
-
-Doug MacEachern has an article on embedding in Volume 1, Issue 4 of
-The Perl Journal ( http://www.tpj.com/ ). Doug is also the developer of the
-most widely-used Perl embedding: the mod_perl system
-(perl.apache.org), which embeds Perl in the Apache web server.
-Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl
-have used this model for Oracle, Netscape and Internet Information
-Server Perl plugins.
-
-=head1 COPYRIGHT
-
-Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant. All
-Rights Reserved.
-
-This document may be distributed under the same terms as Perl itself.