=item B<Use C from Perl?>
-Read L<perlcall> and L<perlxs>.
+Read L<perlxs>, L<perlxstut> and L<h2xs>.
=item B<Use a Unix program from Perl?>
=item B<Use Perl from Perl?>
-Read about L<perlfunc/do> and L<perlfunc/eval> and L<perlfunc/require>
-and L<perlfunc/use>.
+Read about do(), eval(), require(), and use() in L<perlfunc>.
=item B<Use C from C?>
=head2 ROADMAP
-L<Compiling your C program>
+Compiling your C program
There's one example in each of the nine sections:
-L<Adding a Perl interpreter to your C program>
+=over 4
-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 Compiling your C program
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:
+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
=head2 Calling a Perl subroutine from your C program
To call individual Perl subroutines, you can use any of the B<perl_call_*>
-functions documented in the L<perlcall> manpage.
-In this example we'll use I<perl_call_argv>.
+functions documented in L<perlcall>.
+In this example we'll use perl_call_argv().
That's shown below, in a program I'll call I<showtime.c>.
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>.
+last section of this document: 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 perl_eval_sv() and perl_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.
+use(), require(), and do() to include external Perl files.
-I<perl_eval_pv()> lets us evaluate individual Perl strings, and then
+perl_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.
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 L<perl_eval_pv> instead. Example:
+from perl_eval_pv() instead. Example:
...
SV *val = perl_eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE);
dSP;
SV* retval;
- PUSHMARK(sp);
+ PUSHMARK(SP);
perl_eval_sv(sv, G_SCALAR);
SPAGAIN;
I32 match(SV *string, char *pattern)
{
- SV *command = newSV(0), *retval;
+ SV *command = NEWSV(1099, 0), *retval;
sv_setpvf(command, "my $string = '%s'; $string =~ %s",
SvPV(string,na), pattern);
I32 substitute(SV **string, char *pattern)
{
- SV *command = newSV(0), *retval;
+ SV *command = NEWSV(1099, 0), *retval;
sv_setpvf(command, "$string = '%s'; ($string =~ %s)",
SvPV(*string,na), pattern);
I32 matches(SV *string, char *pattern, AV **match_list)
{
- SV *command = newSV(0);
+ SV *command = NEWSV(1099, 0);
I32 num_matches;
sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)",
char *embedding[] = { "", "-e", "0" };
AV *match_list;
I32 num_matches, i;
- SV *text = newSV(0);
+ SV *text = NEWSV(1099,0);
perl_construct(my_perl);
perl_parse(my_perl, NULL, 3, embedding, NULL);
dSP; /* initialize stack pointer */
ENTER; /* everything created after here */
SAVETMPS; /* ...is a temporary variable. */
- PUSHMARK(sp); /* remember the stack pointer */
+ 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 */
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
+the code into that package using 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 perl_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.
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.
+with my() whenever possible.
package Embed::Persistent;
use strict;
use vars '%Cache';
+ use Symbol qw(delete_package);
sub valid_package_name {
my($string) = @_;
return "Embed" . $string;
}
- #borrowed from Safe.pm
- sub delete_package {
- my $pkg = shift;
- my ($stem, $leaf);
-
- no strict 'refs';
- $pkg = "main::$pkg\::"; # expand to full symbol table name
- ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
-
- my $stem_symtab = *{$stem}{HASH};
-
- delete $stem_symtab->{$leaf};
- }
-
sub eval_file {
my($filename, $delete) = @_;
my $package = valid_package_name($filename);
Check out Doug's article on embedding in Volume 1, Issue 4 of The Perl
Journal. Info about TPJ is available from http://tpj.com.
-April 14, 1997
+July 17, 1997
Some of this material is excerpted from Jon Orwant's book: I<Perl 5
Interactive>, Waite Group Press, 1996 (ISBN 1-57169-064-6) and appears
projects / p5sagit/p5-mst-13.2.git / blobdiff