=item B<Use C from Perl?>
-Read L<perlxstut>, L<perlxs>, L<h2xs>, and L<perlguts>.
+Read L<perlxstut>, L<perlxs>, L<h2xs>, L<perlguts>, and L<perlapi>.
=item B<Use a Unix program from Perl?>
=over 5
-L<Compiling your C program>
+=item *
-L<Adding a Perl interpreter to your C program>
+Compiling your C program
-L<Calling a Perl subroutine from your C program>
+=item *
-L<Evaluating a Perl statement from your C program>
+Adding a Perl interpreter to your C program
-L<Performing Perl pattern matches and substitutions from your C program>
+=item *
-L<Fiddling with the Perl stack from your C program>
+Calling a Perl subroutine from your C program
-L<Maintaining a persistent interpreter>
+=item *
-L<Maintaining multiple interpreter instances>
+Evaluating a Perl statement from your C program
-L<Using Perl modules, which themselves use C libraries, from your C program>
+=item *
-L<Embedding Perl under Win32>
+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 Calling a Perl subroutine from your C program
-To call individual Perl subroutines, you can use any of the B<perl_call_*>
+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<perl_call_argv>.
+In this example we'll use C<call_argv>.
That's shown below, in a program I'll call I<showtime.c>.
/*** skipping perl_run() ***/
- perl_call_argv("showtime", G_DISCARD | G_NOARGS, args);
+ call_argv("showtime", G_DISCARD | G_NOARGS, args);
perl_destruct(my_perl);
perl_free(my_perl);
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<perl_call_argv>. For other data types, or to examine return values,
-you'll need to manipulate the Perl stack. That's demonstrated in the
-last section of this document: L<Fiddling with the Perl stack from
-your C program>.
+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<perlguts/perl_eval_sv> and L<perlguts/perl_eval_pv>.
+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
L<perlfunc/use>, L<perlfunc/require>, and L<perlfunc/do> to
include external Perl files.
-I<perl_eval_pv> lets us evaluate individual Perl strings, and then
+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)
{
STRLEN n_a;
char *embedding[] = { "", "-e", "0" };
-
+
my_perl = perl_alloc();
perl_construct( my_perl );
-
+
perl_parse(my_perl, NULL, 3, embedding, NULL);
perl_run(my_perl);
-
+
/** Treat $a as an integer **/
- perl_eval_pv("$a = 3; $a **= 2", TRUE);
- printf("a = %d\n", SvIV(perl_get_sv("a", FALSE)));
-
+ eval_pv("$a = 3; $a **= 2", TRUE);
+ printf("a = %d\n", SvIV(get_sv("a", FALSE)));
+
/** Treat $a as a float **/
- perl_eval_pv("$a = 3.14; $a **= 2", TRUE);
- printf("a = %f\n", SvNV(perl_get_sv("a", FALSE)));
-
+ eval_pv("$a = 3.14; $a **= 2", TRUE);
+ printf("a = %f\n", SvNV(get_sv("a", FALSE)));
+
/** Treat $a as a string **/
- perl_eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE);
- printf("a = %s\n", SvPV(perl_get_sv("a", FALSE), n_a));
-
+ eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE);
+ printf("a = %s\n", SvPV(get_sv("a", FALSE), n_a));
+
perl_destruct(my_perl);
perl_free(my_perl);
}
-All of those strange functions with I<sv> in their names help convert Perl scalars to C types. They're described in L<perlguts>.
+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
In the example above, we've created a global variable to temporarily
store the computed value of our eval'd expression. It is also
possible and in most cases a better strategy to fetch the return value
-from I<perl_eval_pv()> instead. Example:
+from I<eval_pv()> instead. Example:
...
STRLEN n_a;
- SV *val = perl_eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE);
+ SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE);
printf("%s\n", SvPV(val,n_a));
...
=head2 Performing Perl pattern matches and substitutions from your C program
-The I<perl_eval_sv()> function lets us evaluate strings of Perl code, so we can
+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()>.
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 =~ $pattern> in an array context, and
+matches() evaluates C<$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
#include <EXTERN.h>
#include <perl.h>
-
- /** my_perl_eval_sv(code, error_check)
- ** kinda like perl_eval_sv(),
+
+ /** my_eval_sv(code, error_check)
+ ** kinda like eval_sv(),
** but we pop the return value off the stack
**/
- SV* my_perl_eval_sv(SV *sv, I32 croak_on_error)
+ SV* my_eval_sv(SV *sv, I32 croak_on_error)
{
dSP;
SV* retval;
STRLEN n_a;
-
+
PUSHMARK(SP);
- perl_eval_sv(sv, G_SCALAR);
-
+ eval_sv(sv, G_SCALAR);
+
SPAGAIN;
retval = POPs;
PUTBACK;
-
+
if (croak_on_error && SvTRUE(ERRSV))
croak(SvPVx(ERRSV, n_a));
-
+
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(1099, 0), *retval;
STRLEN n_a;
-
+
sv_setpvf(command, "my $string = '%s'; $string =~ %s",
SvPV(string,n_a), pattern);
-
- retval = my_perl_eval_sv(command, TRUE);
+
+ retval = my_eval_sv(command, TRUE);
SvREFCNT_dec(command);
-
+
return SvIV(retval);
}
-
+
/** substitute(string, pattern)
**
** Used for =~ operations that modify their left-hand side (s/// and tr///)
** Returns the number of successful matches, and
** modifies the input string if there were any.
**/
-
+
I32 substitute(SV **string, char *pattern)
{
SV *command = NEWSV(1099, 0), *retval;
STRLEN n_a;
-
+
sv_setpvf(command, "$string = '%s'; ($string =~ %s)",
SvPV(*string,n_a), pattern);
-
- retval = my_perl_eval_sv(command, TRUE);
+
+ retval = my_eval_sv(command, TRUE);
SvREFCNT_dec(command);
-
- *string = perl_get_sv("string", FALSE);
+
+ *string = get_sv("string", FALSE);
return SvIV(retval);
}
-
+
/** matches(string, pattern, matches)
**
- ** Used for matches in an array context.
+ ** 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(1099, 0);
I32 num_matches;
STRLEN n_a;
-
+
sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)",
SvPV(string,n_a), pattern);
-
- my_perl_eval_sv(command, TRUE);
+
+ my_eval_sv(command, TRUE);
SvREFCNT_dec(command);
-
- *match_list = perl_get_av("array", FALSE);
+
+ *match_list = get_av("array", FALSE);
num_matches = av_len(*match_list) + 1; /** assume $[ is 0 **/
-
+
return num_matches;
}
-
+
main (int argc, char **argv, char **env)
{
PerlInterpreter *my_perl = perl_alloc();
I32 num_matches, i;
SV *text = NEWSV(1099,0);
STRLEN n_a;
-
+
perl_construct(my_perl);
perl_parse(my_perl, NULL, 3, embedding, NULL);
-
+
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(*av_fetch(match_list, i, FALSE),n_a));
printf("\n");
-
+
/** Remove all vowels from text **/
num_matches = substitute(&text, "s/[aeiou]//gi");
if (num_matches) {
num_matches);
printf("Now text is: %s\n\n", SvPV(text,n_a));
}
-
+
/** 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);
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>.
+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>.
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 */
- perl_call_pv("expo", G_SCALAR); /* call the function */
+ 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);
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<perlcall/perl_call_argv>, We'll
+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.
/* call the subroutine, passing it the filename as an argument */
args[0] = filename;
- perl_call_argv("Embed::Persistent::eval_file",
+ call_argv("Embed::Persistent::eval_file",
G_DISCARD | G_EVAL, args);
/* check $@ */
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, the global variable
+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
-needed when a program has only one interpreter.
+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:
and symbol tables are cleaned up, and global variables are reset.
Now suppose we have more than one interpreter instance running at the
-same time. This is feasible, but only if you used the
-C<-DMULTIPLICITY> flag when building Perl. By default, that sets
-C<PL_perl_destruct_level> to C<1>.
+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.
+
+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:
char *one_args[] = { "one_perl", SAY_HELLO };
char *two_args[] = { "two_perl", SAY_HELLO };
+ 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);
}
+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:
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);
- #ifdef __cplusplus
- # define EXTERN_C extern "C"
- #else
- # define EXTERN_C extern
- #endif
-
- static void xs_init (void);
-
- EXTERN_C void boot_DynaLoader (CV* cv);
- EXTERN_C void boot_Socket (CV* cv);
+ EXTERN_C void boot_DynaLoader (pTHX_ CV* cv);
+ EXTERN_C void boot_Socket (pTHX_ CV* cv);
EXTERN_C void
- xs_init()
+ xs_init(pTHX)
{
char *file = __FILE__;
/* DynaLoader is a special case */
% cc -c interp.c `perl -MExtUtils::Embed -e ccopts`
% cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts`
-Consult L<perlxs> and L<perlguts> for more details.
+Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details.
=head1 Embedding Perl under Win32
-At the time of this writing (5.004), there are two versions of Perl
-which run under Win32. (The two versions are merging in 5.005.)
-Interfacing to ActiveState's Perl library is quite different from the
-examples in this documentation, as significant changes were made to
-the internal Perl API. However, it is possible to embed ActiveState's
-Perl runtime. For details, see the Perl for Win32 FAQ at
-http://www.perl.com/CPAN/doc/FAQs/win32/perlwin32faq.html.
-
-With the "official" Perl version 5.004 or higher, all the examples
-within this documentation will compile and run untouched, although
-the build process is slightly different between Unix and Win32.
+In general, all of the source code shown here should work unmodified under
+Windows.
-For starters, backticks don't work under the Win32 native command shell.
+However, there are some caveats about the command-line examples shown.
+For starters, backticks won't work under the Win32 native command shell.
The ExtUtils::Embed kit on CPAN ships with a script called
B<genmake>, which generates a simple makefile to build a program from
a single C source file. It can be used like this:
https://perl5.git.perl.org / perl5.git / blobdiff