From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/MAN/perlembed.htm | 885 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 885 insertions(+) create mode 100644 reference/C/MAN/perlembed.htm (limited to 'reference/C/MAN/perlembed.htm') diff --git a/reference/C/MAN/perlembed.htm b/reference/C/MAN/perlembed.htm new file mode 100644 index 0000000..2609362 --- /dev/null +++ b/reference/C/MAN/perlembed.htm @@ -0,0 +1,885 @@ +perlembed + +
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+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+
NAME
+
       perlembed - how to embed perl in your C program
+
+
DESCRIPTION
+
       PREAMBLE
+
+       Do you want to:
+
+       Use C from Perl?
+            Read the perlcall manpage and the perlxs manpage.
+
+       Use a UNIX program from Perl?
+            Read about backquotes and the system entry in the
+            perlfunc manpage and the exec entry in the perlfunc
+            manpage.
+
+       Use Perl from Perl?
+            Read about the do entry in the perlfunc manpage and
+            the eval entry in the perlfunc manpage and the use
+            entry in the perlmod manpage and the require entry in
+            the perlmod manpage.
+
+       Use C from C?
+            Rethink your design.
+
+       Use Perl from C?
+            Read on...
+
+       ROADMAP
+
+       the section on Compiling your C program
+
+       There's one example in each of the five sections:
+
+       the section on Adding a Perl interpreter to your C program
+
+       the section on Calling a Perl subroutine from your C
+       program
+
+       the section on Evaluating a Perl statement from your C
+       program
+
+       the section on Performing Perl pattern matches and
+       substitutions from your C program
+
+       the section on Fiddling with the Perl stack from your C
+       program
+
+       This documentation is UNIX specific.
+
+       Compiling your C program
+
+       Every C program that uses Perl must link in the perl
+       library.
+
+
+
+
30/Jan/96                perl 5.003 with                        1
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+       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 (/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 lib directory.)
+
+       Your C program will--usually--allocate, "run", and
+       deallocate a PerlInterpreter object, which is defined in
+       the perl library.
+
+       If your copy of Perl is recent enough to contain this
+       documentation (5.002 or later), then the perl library (and
+       EXTERN.h and perl.h, which you'll also need) will reside
+       in a directory resembling 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 -e 'use Config; print $Config{archlib}'
+
+       Here's how you might compile the example in the next
+       section, the section on Adding a Perl interpreter to your
+       C program, on a DEC Alpha running the OSF operating
+       system:
+
+           % cc -o interp interp.c -L/usr/local/lib/perl5/alpha-dec_osf/CORE
+           -I/usr/local/lib/perl5/alpha-dec_osf/CORE -lperl -lm
+
+       You'll have to choose the appropriate compiler (cc, gcc,
+       et al.)  and library directory (/usr/local/lib/...)  for
+       your machine.  If your compiler complains that certain
+       functions are undefined, or that it can't locate -lperl,
+       then you need to change the path following the -L.  If it
+       complains that it can't find EXTERN.h or perl.h, you need
+       to change the path following the -I.
+
+       You may have to add extra libraries as well.  Which ones?
+       Perhaps those printed by
+
+          perl -e 'use Config; print $Config{libs}'
+
+
+
+
+
30/Jan/96                perl 5.003 with                        2
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+       Adding a Perl interpreter to youur C program
+
+       In a sense, perl (the C program) is a good example of
+       embedding Perl (the language), so I'll demonstrate
+       embedding with miniperlmain.c, from the source
+       distribution.  Here's a bastardized, non-portable version
+       of miniperlmain.c containing the essentials of embedding:
+
+           #include <stdio.h>
+           #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)
+           {
+               my_perl = perl_alloc();
+               perl_construct(my_perl);
+               perl_parse(my_perl, NULL, argc, argv, env);
+               perl_run(my_perl);
+               perl_destruct(my_perl);
+               perl_free(my_perl);
+           }
+
+       Now compile this program (I'll call it interp.c) into an
+       executable:
+
+           % cc -o interp interp.c -L/usr/local/lib/perl5/alpha-dec_osf/CORE
+           -I/usr/local/lib/perl5/alpha-dec_osf/CORE -lperl -lm
+
+       After a successful compilation, you'll be able to use
+       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 argv[1] before calling perl_run().
+
+       Calling a Perl subroutine from yyour C program
+
+       To call individual Perl subroutines, you'll need to remove
+       the call to perl_run() and replace it with a call to
+       perl_call_argv().
+
+
+
+
30/Jan/96                perl 5.003 with                        3
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+       That's shown below, in a program I'll call showtime.c.
+
+           #include <stdio.h>
+           #include <EXTERN.h>
+           #include <perl.h>
+
+           static PerlInterpreter *my_perl;
+
+           int main(int argc, char **argv, char **env)
+           {
+               my_perl = perl_alloc();
+               perl_construct(my_perl);
+
+               perl_parse(my_perl, NULL, argc, argv, env);
+
+                                            /*** This replaces perl_run() ***/
+               perl_call_argv("showtime", G_DISCARD | G_NOARGS, argv);
+               perl_destruct(my_perl);
+               perl_free(my_perl);
+           }
+
+       where showtime is a Perl subroutine that takes no
+       arguments (that's the G_NOARGS) and for which I'll ignore
+       the return value (that's the G_DISCARD).  Those flags, and
+       others, are discussed in the perlcall manpage.
+
+       I'll define the showtime subroutine in a file called
+       showtime.pl:
+
+           print "I shan't be printed.";
+
+           sub showtime {
+               print time;
+           }
+
+       Simple enough.  Now compile and run:
+
+           % cc -o showtime showtime.c -L/usr/local/lib/perl5/alpha-dec_osf/CORE
+           -I/usr/local/lib/perl5/alpha-dec_osf/CORE -lperl -lm
+
+           % 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.
+
+       If you want to pass some arguments to the Perl subroutine,
+       or you want to access the return value, you'll need to
+       manipulate the Perl stack, demonstrated in the last
+       section of this document: the section on Fiddling with the
+       Perl stack from your C program
+
+
+
+
+
+
30/Jan/96                perl 5.003 with                        4
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+       Evaluating a Perl statement fr
om your C program
+

+       NOTE: This section, and the next, employ some very brittle
+       techniques for evaluting strings of Perl code.  Perl 5.002
+       contains some nifty features that enable A Better Way
+       (such as with the perl_eval_sv entry in the perlguts
+       manpage).  Look for updates to this document soon.
+
+       One way to evaluate a Perl string is to define a function
+       (we'll call ours perl_eval()) that wraps around Perl's the
+       eval entry in the perlfunc manpage.
+
+       Arguably, this is the only routine you'll ever need to
+       execute snippets of Perl code from within your C program.
+       Your string can be as long as you wish; it can contain
+       multiple statements; it can use the require entry in the
+       perlmod manpage or the do entry in the perlfunc manpage to
+       include external Perl files.
+
+       Our perl_eval() lets us evaluate individual Perl strings,
+       and then extract variables for coercion into C types.  The
+       following program, string.c, executes three Perl strings,
+       extracting an int from the first, a float from the second,
+       and a char * from the third.
+
+
+
+
+
+
+
+
+
+
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+
30/Jan/96                perl 5.003 with                        5
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+          #include <stdio.h>
+          #include <EXTERN.h>
+          #include <perl.h>
+
+          static PerlInterpreter *my_perl;
+
+          int perl_eval(char *string)
+          {
+            char *argv[2];
+            argv[0] = string;
+            argv[1] = NULL;
+            perl_call_argv("_eval_", 0, argv);
+          }
+
+          main (int argc, char **argv, char **env)
+          {
+            char *embedding[] = { "", "-e", "sub _eval_ { eval $_[0] }" };
+            STRLEN length;
+
+            my_perl = perl_alloc();
+            perl_construct( my_perl );
+
+            perl_parse(my_perl, NULL, 3, embedding, env);
+
+                                              /** Treat $a as an integer **/
+            perl_eval("$a = 3; $a **= 2");
+            printf("a = %d\n", SvIV(perl_get_sv("a", FALSE)));
+
+                                              /** Treat $a as a float **/
+            perl_eval("$a = 3.14; $a **= 2");
+            printf("a = %f\n", SvNV(perl_get_sv("a", FALSE)));
+
+                                              /** Treat $a as a string **/
+            perl_eval("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a); ");
+            printf("a = %s\n", SvPV(perl_get_sv("a", FALSE), length));
+
+            perl_destruct(my_perl);
+            perl_free(my_perl);
+          }
+
+       All of those strange functions with sv in their names help
+       convert Perl scalars to C types.  They're described in the
+       perlguts manpage.
+
+       If you compile and run string.c, you'll see the results of
+       using SvIV() to create an int, SvNV() to create a float,
+       and SvPV() to create a string:
+
+          a = 9
+          a = 9.859600
+          a = Just Another Perl Hacker
+
+
+
+
+
+
+
30/Jan/96                perl 5.003 with                        6
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+       Performing Perl pattern matche
s and substitutions from
+
       your C program
+
+       Our perl_eval() lets us evaluate strings of Perl code, so
+       we can define some functions that use it to "specialize"
+       in matches and substitutions: match(), substitute(), and
+       matches().
+
+          char match(char *string, char *pattern);
+
+       Given a string and a pattern (e.g. "m/clasp/" or
+       "/\b\w*\b/", which in your program might be represented as
+       "/\\b\\w*\\b/"), returns 1 if the string matches the
+       pattern and 0 otherwise.
+
+          int substitute(char *string[], char *pattern);
+
+       Given a pointer to a string and an "=~" operation (e.g.
+       "s/bob/robert/g" or "tr[A-Z][a-z]"), modifies the string
+       according to the operation, returning the number of
+       substitutions made.
+
+          int matches(char *string, char *pattern, char **matches[]);
+
+       Given a string, a pattern, and a pointer to an empty array
+       of strings, evaluates $string =~ $pattern in an array
+       context, and fills in matches with the array elements
+       (allocating memory as it does so), returning the number of
+       matches found.
+
+       Here's a sample program, match.c, that uses all three:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
30/Jan/96                perl 5.003 with                        7
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+          #include <stdio.h>
+          #include <EXTERN.h>
+          #include <perl.h>
+
+          static PerlInterpreter *my_perl;
+
+          int eval(char *string)
+          {
+            char *argv[2];
+            argv[0] = string;
+            argv[1] = NULL;
+            perl_call_argv("_eval_", 0, argv);
+          }
+
+          /** match(string, pattern)
+           **
+           ** Used for matches in a scalar context.
+           **
+           ** Returns 1 if the match was successful; 0 otherwise.
+           **/
+          char match(char *string, char *pattern)
+          {
+            char *command;
+            command = malloc(sizeof(char) * strlen(string) + strlen(pattern) + 37);
+            sprintf(command, "$string = '%s'; $return = $string =~ %s",
+               string, pattern);
+            perl_eval(command);
+            free(command);
+            return SvIV(perl_get_sv("return", FALSE));
+          }
+
+          /** substitute(string, pattern)
+           **
+           ** Used for =~ operations that modify their left-hand side (s/// and tr///)
+           **
+           ** Returns the number of successful matches, and
+           ** modifies the input string if there were any.
+           **/
+          int substitute(char *string[], char *pattern)
+          {
+            char *command;
+            STRLEN length;
+            command = malloc(sizeof(char) * strlen(*string) + strlen(pattern) + 35);
+            sprintf(command, "$string = '%s'; $ret = ($string =~ %s)",
+               *string, pattern);
+            perl_eval(command);
+            free(command);
+            *string = SvPV(perl_get_sv("string", FALSE), length);
+            return SvIV(perl_get_sv("ret", FALSE));
+          }
+
+          /** matches(string, pattern, matches)
+           **
+           ** Used for matches in an array context.
+
+
+
+
30/Jan/96                perl 5.003 with                        8
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+           **
+           ** Returns the number of matches,
+           ** and fills in **matches with the matching substrings (allocates memory!)
+           **/
+          int matches(char *string, char *pattern, char **matches[])
+          {
+            char *command;
+            SV *current_match;
+            AV *array;
+            I32 num_matches;
+            STRLEN length;
+            int i;
+
+            command = malloc(sizeof(char) * strlen(string) + strlen(pattern) + 38);
+            sprintf(command, "$string = '%s'; @array = ($string =~ %s)",
+               string, pattern);
+            perl_eval(command);
+            free(command);
+            array = perl_get_av("array", FALSE);
+            num_matches = av_len(array) + 1; /** assume $[ is 0 **/
+            *matches = (char **) malloc(sizeof(char *) * num_matches);
+            for (i = 0; i <= num_matches; i++) {
+              current_match = av_shift(array);
+              (*matches)[i] = SvPV(current_match, length);
+            }
+            return num_matches;
+          }
+
+          main (int argc, char **argv, char **env)
+          {
+            char *embedding[] = { "", "-e", "sub _eval_ { eval $_[0] }" };
+            char *text, **matches;
+            int num_matches, i;
+            int j;
+
+            my_perl = perl_alloc();
+            perl_construct( my_perl );
+
+            perl_parse(my_perl, NULL, 3, embedding, env);
+
+            text = (char *) malloc(sizeof(char) * 486); /** A long string follows! **/
+            sprintf(text, "%s", "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 corre
ct amount.  The boy gives him back two of his own pennies and then the big shiny quarter that is his prize. -RICHH");
+

+            if (perl_match(text, "m/quarter/")) /** Does text contain 'quarter'? **/
+              printf("perl_match: Text contains the word 'quarter'.\n\n");
+            else
+              printf("perl_match: Text doesn't contain the word 'quarter'.\n\n");
+
+            if (perl_match(text, "m/eighth/")) /** Does text contain 'eighth'? **/
+              printf("perl_match: Text contains the word 'eighth'.\n\n");
+            else
+              printf("perl_match: Text doesn't contain the word 'eighth'.\n\n");
+
+                                              /** Match all occurrences of /wi../ **/
+
+
+
+
30/Jan/96                perl 5.003 with                        9
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+            num_matches = perl_matches(text, "m/(wi..)/g", &matches);
+
+            printf("perl_matches: m/(wi..)/g found %d matches...\n", num_matches);
+            for (i = 0; i < num_matches; i++)
+              printf("match: %s\n", matches[i]);
+            printf("\n");
+            for (i = 0; i < num_matches; i++) {
+              free(matches[i]);
+            }
+            free(matches);
+
+                                              /** Remove all vowels from text **/
+            num_matches = perl_substitute(&text, "s/[aeiou]//gi");
+            if (num_matches) {
+              printf("perl_substitute: s/[aeiou]//gi...%d substitutions made.\n",
+               num_matches);
+              printf("Now text is: %s\n\n", text);
+            }
+
+                                              /** Attempt a substitution
+            if (!perl_substitute(&text, "s/Perl/C/")) {
+              printf("perl_substitute: s/Perl/C...No substitution made.\n\n");
+            }
+
+            free(text);
+
+            perl_destruct(my_perl);
+            perl_free(my_perl);
+          }
+
+       which produces the output
+
+          perl_match: Text contains the word 'quarter'.
+
+          perl_match: Text doesn't contain the word 'eighth'.
+
+          perl_matches: m/(wi..)/g found 2 matches...
+          match: will
+          match: with
+
+          perl_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 s
qzy 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
+

+          perl_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
+
+
+
+
30/Jan/96                perl 5.003 with                       10
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+       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 the perlguts
+       manpage.
+
+       Then you'll need to know how to manipulate the Perl stack.
+       That's described in the perlcall manpage.
+
+       Once you've understood those, embedding Perl in C is easy.
+
+       Since C has no built-in function for integer
+       exponentiation, let's make Perl's ** operator available to
+       it (this is less useful than it sounds, since Perl
+       implements ** with C's pow() function).  First I'll create
+       a stub exponentiation function in power.pl:
+
+           sub expo {
+               my ($a, $b) = @_;
+               return $a ** $b;
+           }
+
+       Now I'll create a C program, power.c, with a function
+       PerlPower() that contains all the perlguts necessary to
+       push the two arguments into expo() and to pop the return
+       value out.  Take a deep breath...
+
+
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30/Jan/96                perl 5.003 with                       11
+

+
+
+
+
+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+           #include <stdio.h>
+           #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 */
+             perl_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[2];
+
+             my_perl = perl_alloc();
+             perl_construct( my_perl );
+
+             my_argv[1] = (char *) malloc(10);
+             sprintf(my_argv[1], "power.pl");
+
+             perl_parse(my_perl, NULL, argc, my_argv, env);
+
+             PerlPower(3, 4);                      /*** Compute 3 ** 4 ***/
+
+             perl_destruct(my_perl);
+             perl_free(my_perl);
+           }
+
+
+       Compile and run:
+
+           % cc -o power power.c -L/usr/local/lib/perl5/alpha-dec_osf/CORE
+           -I/usr/local/lib/perl5/alpha-dec_osf/CORE -lperl -lm
+
+           % power
+           3 to the 4th power is 81.
+
+
+
+
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+
PERLEMBED(1)     Perl Programmers Reference Guide    PERLEMBED(1)
+

+
+
MORAL
+
       You can sometimes write faster code in C, but you can
+       always write code faster in Perl.  Since you can use each
+       from the other, combine them as you wish.
+
+
AUTHOR
+
       Jon Orwant <orwant@media.mit.edu>, with contributions from
+       Tim Bunce, Tom Christiansen, Dov Grobgeld, and Ilya
+       Zakharevich.
+
+       December 18, 1995
+
+       Some of this material is excerpted from my book: Perl 5
+       Interactive, Waite Group Press, 1996 (ISBN 1-57169-064-6)
+       and appears courtesy of Waite Group Press.
+
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+

+ + + + +
+Top + +Master Index + +Keywords + +Functions +
+
+

+

+ +This manual page was brought to you by mjl_man V-2.0 -- cgit v1.2.3-54-g00ecf