=for comment
  made from [perl-5.8.0] [pod/perlembed.pod]

=head1 名前

perlembed - C プログラムに perl を埋め込む

=head1 説明

=head2 前書き

あなたの欲しいのはどれ？

=over 5

=item B<Perl から C を使う>

L<perlxstut>, L<perlxs>, L<h2xs>, L<perlguts>, L<perlapi> を読みましょう.

=item B<Perl から Unix プログラムを使う>

バッククオート及び L<perlfunc> にある C<system> と C<exec> を読みましょう.

=item B<Perl から Perl を使う>

L<perlfunc/do> 及び L<perlfunc/eval>, L<perlfunc/require>, 
L<perlfunc/use> を読みましょう.

=item B<C から C を使う>

構成を考え直してみましょう.

=item <C から Perl を使う>

このままどうぞ...

=back

=head2 道のり

=over 5

=item *



C プログラムのコンパイル

=item *



C プログラムに Perl インタプリタを追加

=item *



C プログラムから Perl 関数を呼び出し

=item *



C プログラムから Perl 文を評価

=item *



C プログラムから Perl パターンマッチと置換を処理

=item *



C プログラムから Perl スタックを操作

=item *



持続するインタプリタの維持

=item *



複数のインタプリタインスタンスを管理

=item *



C プログラムからそれ自身が C ライブラリを使う Perl モジュールを使用

=item *



Win32 で Perl の埋め込み

=back

=head2 作成した C プログラムのコンパイル

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 C プログラムに Perl インタプリタを追加

ある意味においては, perl 実行形式自身が Perl 言語を埋め込んだ
C プログラムの良い例です. そこでソースディストリビューションに含まれる
I<miniperlmain.c> を作ってみましょう. ここでは I<miniperlmain.c> の
粗悪な, 可搬性の低いバージョンになりますが, 埋め込みの基本は抑えています.

    #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);
	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);
    }

C<env> ポインタは使っていないことに注意してください. 
通常 C<perl_parse> に最後の引数で渡されますが, ここでの C<env> は
現在の環境を使うことを示すために C<NULL> に置き換えています.

ではこのプログラムを実行形式へとコンパイルしてみましょう
(ここでは I<interp.c> としています):

    % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts`

コンパイルが正常に終了すると I<interp> を perl そのものと同じように
使うことができます:

    % interp
    print "Pretty Good Perl \n";
    print "10890 - 9801 is ", 10890 - 9801;
    <CTRL-D>
    Pretty Good Perl
    10890 - 9801 is 1089

又は

    % interp -e 'printf("%x", 3735928559)'
    deadbeef

I<perl_run> よ呼び出す前に I<argv[1]> のファイル名を置き換えることで
Perl スクリプトをファイルから読み込み実行することもできます.

=head2 C プログラムから Perl 関数を呼び出し

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 };
        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);
    }

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 C プログラムから Perl 文を評価

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)
   {
       STRLEN n_a;
       char *embedding[] = { "", "-e", "0" };

       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", FALSE)));

       /** Treat $a as a float **/
       eval_pv("$a = 3.14; $a **= 2", TRUE);
       printf("a = %f\n", SvNV(get_sv("a", FALSE)));

       /** Treat $a as a string **/
       eval_pv("$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> 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'd expression.  It is also
possible and in most cases a better strategy to fetch the return value
from I<eval_pv()> instead.  Example:


   ...
   STRLEN n_a;
   SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE);
   printf("%s\n", SvPV(val,n_a));
   ...

This way, we avoid namespace pollution by not creating global
variables and we've simplified our code as well.


=head2 C プログラムから Perl パターンマッチと置換を処理

I<eval_sv()> 関数を使って, Perl ソースである文字列を評価できます. 
そこでマッチと置換に"特化"した関数, I<match()>, I<substitute()>, 
I<matches()>を定義してみましょう.

   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<AV> at 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>

 /** 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;
     STRLEN n_a;

     PUSHMARK(SP);
     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_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_eval_sv(command, TRUE);
     SvREFCNT_dec(command);

     *string = get_sv("string", FALSE);
     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(1099, 0);
     I32 num_matches;
     STRLEN n_a;

     sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)",
 	      SvPV(string,n_a), pattern);

     my_eval_sv(command, TRUE);
     SvREFCNT_dec(command);

     *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();
     char *embedding[] = { "", "-e", "0" };
     AV *match_list;
     I32 num_matches, i;
     SV *text = NEWSV(1099,0);
     STRLEN n_a;

     perl_construct(my_perl);
     perl_parse(my_perl, NULL, 3, embedding, NULL);
     PL_exit_flags |= PERL_EXIT_DESTRUCT_END;

     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) {
 	printf("substitute: s/[aeiou]//gi...%d substitutions made.\n",
 	       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);
     perl_free(my_perl);
 }

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 C プログラムから Perl スタックを操作

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" };

      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);
    }

Compile and run:


    % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts`

    % power
    3 to the 4th power is 81.

=head2 持続するインタプリタの維持

対話的なそして/もしくは潜在的に長く実行されるアプリケーションを開発するとき, 
新しいインタプリタの確保構築を何回も行うのでなく, 
持続するインタプリタを維持させるのはよい考えです. 
その大きな理由はPerl が 一度のみメモリにロードされるコトから来る
スピードにあります.

しかしながら, 持続するインタプリタを使うのに当たって, 
ネームスペースや変数のスコープによる注意しなければなりません. 
これまでのサンプルでは, デフォルトのパッケージ C<main> を使ってきました. 
私たちはどんなコードが実行されるかを知ってます. 
そして変数の衝突やをひどいシンボルテーブルの増加を
避けることが出来たでしょう.

あなたのアプリケーションが時々いくつかの任意のファイルから Perl コードを
実行するサーバだとしてみましょう. 貴方のサーバではこれまでどんなコードが
実行されてきたのか知る方法はありません. 
これは, 非常に危険です.

もしファイルが C<perl_parse()> によって新しく構築されるインタプリタに
コンパイルされることで読み込まれるのなら, そして続いて C<perl_destruct()> に
よって後にクリアされるのなら, それは多くのネームスペースのトラブルから
守られるでしょう.

このシナリオで用いられるネームスペースの衝突を回避するもう１つの方法は, 
ファイル名からユニークと保証されるパッケージ名に変換して, 
そして L<perlfunc/eval> を実行することです. 後述のサンプルでは, 
それぞれのファイルは一度のみコンパイルされます. それか, 
アプリケーションは必要がなくなったときにファイルに関連する
シンボルテーブルをクリアする方法をとるかもしれません. その場合, 
L<perlapi/call_argv> をつかって, C<persistent.pl> にある 
C<Embed::Persistent::eval_file> 関数を, ファイル名とクリーンアップ
もしくはキャッシュどちらを行うかのの真偽値を引数にわたして
呼ぶことになるでしょう.

これを使う毎に, プロセスは成長し続けることに注意しましょう. 
加えて, C<AUTOLOAD> された関数やPerlのシンボルテーブルを成長させる
ほかの状況もあるでしょう. メモリの消費を最小にすることを保証するために
プロセスサイズの track を保ったり, ある程度の要求の後リスタートさせる
何らかの手法の追加を望むでしょう. また, 可能なときは常に変数を 
L<perlfunc/my> のスコープにしておきたいでしょう.

 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

 static PerlInterpreter *perl = NULL;

 int
 main(int argc, char **argv, char **env)
 {
     char *embedding[] = { "", "persistent.pl" };
     char *args[] = { "", DO_CLEAN, NULL };
     char filename [1024];
     int exitstatus = 0;
     STRLEN n_a;

     if((perl = perl_alloc()) == NULL) {
        fprintf(stderr, "no memory!");
        exit(1);
     }
     perl_construct(perl);

     exitstatus = perl_parse(perl, NULL, 2, embedding, NULL);
     PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
     if(!exitstatus) {
        exitstatus = perl_run(perl);

        while(printf("Enter file name: ") && gets(filename)) {

            /* 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(ERRSV,n_a));
        }
     }

     PL_perl_destruct_level = 0;
     perl_destruct(perl);
     perl_free(perl);
     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 END ブロックの実行

伝統的に, END ブロックは perl_run の最後に実行されてきました. 
これは, perl_run を呼び出さないアプリケーションにおいて問題となります. 
perl 5.7.2 以降において, C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END> と
することで新しい振る舞いを得ることが出来ます. これは, perl_parse が
失敗して C<perl_destruct> が復帰値を返しても END ブロックの実行を
有効にします.

=head2 複数のインタプリタインスタンスの管理

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:


 PL_perl_destruct_level = 1;

 while(1) {
     ...
     /* reset global variables here with PL_perl_destruct_level = 1 */
     perl_construct(my_perl);
     ...
     /* clean and reset _everything_ during perl_destruct */
     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.


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.


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 */
 /* 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 = perl_alloc(),
         *two_perl = perl_alloc();
     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:


 % 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 C プログラムからそれ自身が C プログラムを使う Perl モジュールの使用

もしこれまでの例を遊んできていて, (I<Socket> の様に
それ自身が C もしくは C++ ライブラリを使う) Perl モジュールを I<use()> する
スクリプトを埋め込もうとしたのなら, 次のようなことが起こるでしょう.

 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.)

 Socket モジュールをロードできません. 使用中の perl はダイナミック
 ローディングが無効になっています.
  (おそらく, ダイナミックローディングをサポートする, もしくは Socket
  モジュールを静的に組み込んでいる新しい perl 実行形式を作成しなければ
  ならないでしょう. )

なにがいけなかったのでしょう?

インタプリタは自分自身ではこれらのエクステンションとどう話せばいいのか
知りません. 
ちいさな接着剤が助けになります. 
これまで, I<perl_parse()> を呼んできましたが, その２番目の引数はNULLでした:

 perl_parse(my_perl, NULL, argc, my_argv, NULL);

ここは Perl と C/C++ ルーティンとの最初のコンタクトを生成するために挿入される
接着剤となるコードを示す場所です. 
I<perlmain.c> の一部から, これを Perl がどのように扱うかをみてみましょう.

 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);
 }

単純に, 作成している Perl 実行形式とリンクさせている各エクステンション
(そのマシンでの初期設定もしくは新しいエクステンションを追加したときに
決定されています)毎の, エクステンションのルーティンを組み込むために
生成される Perl 関数を置きます. 
通常, 関数名は I<Module::bootstrap()> の名前を持ち, 
I<use Module> したときに呼び出されます.
次に, これは XSUB, I<boot_Module> にフックします. 
これはエクステンションの XSUB に対応して作成されます. 
ここに関してはあまり悩まないで I<xsubpp> とエクステンションの
作者に任せておけば大丈夫です. 
もしエクステンションがダイナミックローディングされるのなら, 
DynaLoader が I<Module::bootstram()> を動的に生成します. 
実際には, DynaLoader が動いているのなら静的にリンクされているモジュールは
まずないでしょう.

このコードを作れば, あとは I<perl_parse()>の２番目の引数にこれを置くだけです.

 perl_parse(my_perl, xs_init, argc, my_argv, NULL);

そしてコンパイルします:

 % 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> は I<xs_init> コードの生成を自動化します.

 % 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`

詳細は L<perlxs>, L<perlguts>, L<perlapi> を参照してください.

=head1 Win32 での Perl 埋め込み

一般的に, これまで見てきたソースコードは Windows でも修正なしに使用できます.

しかし, 例に挙げていたコマンドラインについては注意が必要です. 
Win32 付属のコマンドシェルではバックスラッシュが昨日しません. 
CPAN にある ExtUtils::Embed キットには B<getnmake> というスクリプトが
付属しています. これをつかって１つの C ソースファイルからプログラムを
構築するために簡単な Makefile を生成することができます. 
次のようにして使います:

 C:\ExtUtils-Embed\eg> perl genmake interp.c
 C:\ExtUtils-Embed\eg> nmake
 C:\ExtUtils-Embed\eg> interp -e "print qq{I'm embedded in Win32!\n}"

Microsoft Developer Studio の様なもっと便利な環境を使いたいかもしれません. 
その様なときには perlxsi.c を生成するためにこれを実行します:

 perl -MExtUtils::Embed -e xsinit

あたらしいプロジェクトを作成し, 挿入 -X<>> ファイル: perlxsi.c, 
perl.lib, 自分のソースファイル. 典型的に perl.lib は
B<C:\perl\lib\CORE> にあるでしょう. もしここになければ C<perl -V:archlib> 
にある B<CORE> ディレクトリ を見てください. 
DevStudio は Perl インクルードがいるの位置も必要です. 
ツール -> オプション -> ディレクトリ メニューから追加してください. 
最後に ビルド -> ビルド interp.exe を選択しましょう.

=head1 精神

Cを使うことで I<より速いコードを書けます>が, 
Perlなら常に I<より速くコードを書けます>.
ほかにもいろいろ使えるので, 望むままに組み合わせてください.

=head1 著者

Jon Orwant <F<orwant@tpj.com>> and Doug MacEachern
<F<dougm@osf.org>>, 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.


July 22, 1998


=head1 著作権

Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant.  All
Rights Reserved.


Permission is granted to make and distribute verbatim copies of this
documentation provided the copyright notice and this permission notice are
preserved on all copies.


Permission is granted to copy and distribute modified versions of this
documentation under the conditions for verbatim copying, provided also
that they are marked clearly as modified versions, that the authors'
names and title are unchanged (though subtitles and additional
authors' names may be added), and that the entire resulting derived
work is distributed under the terms of a permission notice identical
to this one.


Permission is granted to copy and distribute translations of this
documentation into another language, under the above conditions for
modified versions.