Compiling your C program

C プログラムのコンパイル
Adding a Perl interpreter to your C program

C プログラムに Perl インタプリタを追加
Calling a Perl subroutine from your C program

C プログラムから Perl 関数を呼び出し
Evaluating a Perl statement from your C program

C プログラムから Perl 文を評価
Performing Perl pattern matches and substitutions from your C program

C プログラムから Perl パターンマッチと置換を処理
Fiddling with the Perl stack from your C program

C プログラムから Perl スタックを操作
Maintaining a persistent interpreter

持続するインタプリタの維持
Maintaining multiple interpreter instances

複数のインタプリタインスタンスを管理
Using Perl modules, which themselves use C libraries, from your C program

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
Embedding Perl under Win32

Win32 で Perl の埋め込み

Compiling your C program 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.)

たとえこのドキュメントに書かれているスクリプトのコンパイルに失敗しても, あなたは一人ではありません. 大事なルール: プログラムは PERL をコンパイルしたのとまったく同じ手順でコンパイルしなさい. (大声でごめんなさい)

Also, every C program that uses Perl must link in the 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 (/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.)

また, Perl を利用する全ての C プログラムは perl ライブラリとリンクしなければなりません. それは何? ってあなたは尋ねるかもしれません. Perl 自身は C で書かれています; perl ライブラリはあなたの perl 実行形式(/usr/bin/perl 若しくはそれに類するもの)を作るのに使われた Cプログラムをコンパイルしたもののコレクションです. (正確には: Perl があなたのマシンでコンパイルされているか, 適切にインストールされて居るのでなければ, あなたの C プログラムから Perl を利用することはできません -- つまり lib ディレクトリをコピーしないまま Perl 実行形式を別のマシンへとコピーしてもうまくいきません.)

When you use Perl from C, your C program will--usually--allocate, "run", and deallocate a PerlInterpreter object, which is defined by the perl library.

C から Perl を利用するとき, C プログラムでは--通常--perlライブラリで定義されている PerlInterpreter オブジェクトを確保し, "実行"し, そして破棄するでしょう.

If your copy of Perl is recent enough to contain this documentation (version 5.002 or later), then the perl library (and EXTERN.h and perl.h, which you'll also need) will reside in a directory that looks like this:

あなたの Perl がこのドキュメントを含んでいる程度に十分新しい(version 5.002以降)のであれば, perl ライブラリ (及び必要となる EXTERN.h 及び perl.h)は次のようなディレクトリに於かれているでしょう:

    /usr/local/lib/perl5/your_architecture_here/CORE

or perhaps just

若しくは単に

    /usr/local/lib/perl5/CORE

or maybe something like

それか次のようかもしれません

    /usr/opt/perl5/CORE

Execute this statement for a hint about where to find CORE:

次の文を実行すると CORE を探す手がかりになるでしょう:

    perl -MConfig -e 'print $Config{archlib}'

Here's how you'd compile the example in the next section, "Adding a Perl interpreter to your C program", on my Linux box:

ここに, 次のセクション, "Adding a Perl interpreter to your C program" の例を私の Linux box でどうやってコンパイルするかを記しておきます:

    % 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:

(1行で書いてください.) 古い 5.003_05 の動いている私の DEC Alpha ではこのおまじないは少し違います.

    % 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 perl -V command and pay special attention to the "cc" and "ccflags" information.

何を付け加えるべきかわかりますか? あなたの Perl が 5.001 以降であれば, perl -V コマンドを実行して "cc" と "ccflags" に表示される情報をよく見てください.

You'll have to choose the appropriate compiler (cc, gcc, et al.) for your machine: perl -MConfig -e 'print $Config{cc}' will tell you what to use.

あなたのマシンに適切なコンパイラ(cc, gcc, その他)を選ぶ必要があります: perl -MConfig -e 'print $Config{cc}' が何を使うべきか教えてくれるでしょう.

You'll also have to choose the appropriate 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 and perl.h, you need to change the path following the -I.

またマシンに適切なライブラリディレクトリ(/usr/local/lib/...) を選ぶ必要もあります. もしコンパイラが何らかの関数が未定義だとか, -lperl が見つからないだとかいうようなら, -L で指定されているパスを変更する必要があるでしょう. もし EXTERN.h 及び perl.h が見つからないというのなら, -I で指定されているパスを変更する必要があるでしょう.

You may have to add extra libraries as well. Which ones? Perhaps those printed by

追加のライブラリを同じように追加する必要があるかもしれません. 何をって? たぶん次のコマンドで出力されるでしょう

   perl -MConfig -e 'print $Config{libs}'

Provided your perl binary was properly configured and installed the ExtUtils::Embed module will determine all of this information for you:

提供されているあなたの perl バイナリが適切に設定及びインストールされているのなら, これら全ての情報は ExtUtils::Embed モジュールが教えてくれます:

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

If the 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.)

もし ExtUtils::Embed モジュールが Perl 配布物に含まれていなければ, http://www.perl.com/perl/CPAN/modules/by-module/ExtUtils/ から入手できます (もしこのドキュメントが Perl 配布物に含まれていたのなら, あなたの 5.004 以降を実行しているのでもう持っているでしょう.)

The 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.

CPAN にある ExtUtils::Embed キットにはこのドキュメントにある例やテストの全てのソース, 加えて他の例や便利な情報も含まれています.

Adding a Perl interpreter to your C program C プログラムに Perl インタプリタを追加

In a sense, perl (the C program) is a good example of embedding Perl (the language), so I'll demonstrate embedding with miniperlmain.c, included in the source distribution. Here's a bastardized, nonportable version of miniperlmain.c containing the essentials of embedding:

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 miniperlmain.c を作ってみましょう. ここでは 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)
    {
	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 env pointer. Normally handed to perl_parse as its final argument, env here is replaced by 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; since PERL_SYS_INIT3() may change env, it may be more appropriate to provide env as an argument to perl_parse().

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 perl_parse に最後の引数で渡されますが, ここでの env は現在の環境を使うことを示すために NULL に置き換えています. PERL_SYS_INIT3() 及び PERL_SYS_TERM() は Perl インタプリタの実行に必要なCランタイム環境の, システムに関連したチューンナップを提供します; PERL_SYS_INIT3() は env を変更することがあるので, perl_parse() の引数に env を提供した方が良いでしょう.

Now compile this program (I'll call it interp.c) into an executable:

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 interp.c としています):

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

After a successful compilation, you'll be able to use interp just like perl itself:

コンパイルが正常に終了すると 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

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.

perl_run よ呼び出す前に 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.

Calling a Perl subroutine from your C program 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 call_* functions documented in perlcall [CPAN]. In this example we'll use call_argv.

That's shown below, in a program I'll call 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 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 perlcall [CPAN].

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 `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 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 NULL-terminated args list passed to call_argv. For other data types, or to examine return values, you'll need to manipulate the Perl stack. That's demonstrated in "Fiddling with the Perl stack from your C program".

Evaluating a Perl statement from your C program 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 perlapi 内 "eval_sv" [CPAN] and perlapi 内 "eval_pv" [CPAN].

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 perlfunc 内 "use" [CPAN], perlfunc 内 "require" [CPAN], and perlfunc 内 "do" [CPAN] to include external Perl files.

eval_pv 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.

   #include <EXTERN.h>
   #include <perl.h>

   static PerlInterpreter *my_perl;

   main (int argc, char **argv, char **env)
   {
       STRLEN n_a;
       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", 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);
       PERL_SYS_TERM();
   }

All of those strange functions with sv in their names help convert Perl scalars to C types. They're described in perlguts [CPAN] and perlapi [CPAN].

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

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 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.

Performing Perl pattern matches and substitutions from your C program C プログラムから Perl パターンマッチと置換を処理

The 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: match(), substitute(), and matches().

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, match(), substitute(), 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., m/clasp/ or /\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 SV and an =~ operation (e.g., s/bob/robert/g or tr[A-Z][a-z]), substitute() modifies the string within the SV as according to the operation, returning the number of substitutions made.

   int matches(SV *string, char *pattern, AV **matches);

Given an SV, a pattern, and a pointer to an empty AV, matches() evaluates $string =~ $pattern in a list context, and fills in matches with the array elements, returning the number of matches found.

Here's a sample program, 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;
     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)
 {
     char *embedding[] = { "", "-e", "0" };
     AV *match_list;
     I32 num_matches, i;
     SV *text;
     STRLEN n_a;

     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(1099,0);
     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(*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);
     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.

Fiddling with the Perl stack from your C program 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 perlguts [CPAN] and perlapi [CPAN].

Then you'll need to know how to manipulate the Perl stack. That's described in perlcall [CPAN].

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 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...

    #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.

Maintaining a persistent interpreter 持続するインタプリタの維持

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.

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.

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 main. We knew exactly what code would be run, and assumed we could avoid variable collisions and outrageous symbol table growth.

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 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.

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.

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.

If the file is pulled in by perl_parse(), compiled into a newly constructed interpreter, and subsequently cleaned out with perl_destruct() afterwards, you're shielded from most namespace troubles.

もしファイルが 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 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.

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 perlfunc 内 "eval" [CPAN]. 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 perlapi 内 "call_argv" [CPAN], We'll call the subroutine Embed::Persistent::eval_file which lives in the file persistent.pl and pass the filename and boolean cleanup/cache flag as arguments.

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 perlfunc 内 "eval" [CPAN] 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, perlapi 内 "call_argv" [CPAN] をつかって, persistent.pl にある 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.

Note that the process will continue to grow for each file that it uses. In addition, there might be AUTOLOADed 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 perlfunc 内 "my" [CPAN] whenever possible.

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, 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 perlfunc 内 "my" [CPAN] 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

 #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;
     STRLEN n_a;

     PERL_SYS_INIT3(&argc,&argv,&env);
     if((my_perl = perl_alloc()) == NULL) {
        fprintf(stderr, "no memory!");
        exit(1);
     }
     perl_construct(my_perl);

     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(ERRSV,n_a));
        }
     }

     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

Execution of END blocks END ブロックの実行

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 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 perl_destruct will return the exit value.

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, 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 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.

Maintaining multiple interpreter instances 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 before the next interpreter is constructed. By default, when perl is not built with any special options, the global variable PL_perl_destruct_level is set to 0, since extra cleaning isn't usually needed when a program only ever creates a single interpreter in its entire lifetime.

Setting PL_perl_destruct_level to 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 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 PL_perl_destruct_level is needed because perl_construct resets it to 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 -Dusemultiplicity or the options -Dusethreads -Duseithreads when building perl. By default, enabling one of these Configure options sets the per-interpreter global variable PL_perl_destruct_level to 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 -Dusemultiplicity option otherwise some interpreter variables may not be initialized correctly between consecutive runs and your application may crash.

Using -Dusethreads -Duseithreads rather than -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, *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 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

Using Perl modules, which themselves use C libraries, from your C program 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

If you've played with the examples above and tried to embed a script that use()s a Perl module (such as Socket) which itself uses a C or C++ library, this probably happened:

もしこれまでの例を遊んできていて, (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 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. )

What's wrong?

なにがいけなかったのでしょう?

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 perl_parse(), handing it NULL for the second argument:

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, 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);

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 perlmain.c to see how Perl does this:

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. 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);
 }

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 Module::bootstrap() and is invoked when you say use Module. In turn, this hooks into an XSUB, boot_Module, which creates a Perl counterpart for each of the extension's XSUBs. Don't worry about this part; leave that to the xsubpp and extension authors. If your extension is dynamically loaded, DynaLoader creates 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.

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 Module::bootstrap() の名前を持ち, use Module したときに呼び出されます. 次に, これは XSUB, 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 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 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.

Once you have this code, slap it into the second argument of perl_parse():

このコードを作れば, あとは 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);

Then compile:

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"'

ExtUtils::Embed can also automate writing the xs_init glue code.

ExtUtils::Embed は 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`

Consult perlxs [CPAN], perlguts [CPAN], and perlapi [CPAN] for more details.

詳細は perlxs [CPAN], perlguts [CPAN], perlapi [CPAN] を参照してください.

Embedding Perl under Win32 Win32 での Perl 埋め込み

In general, all of the source code shown here should work unmodified under Windows.

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.

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 genmake, which generates a simple makefile to build a program from a single C source file. It can be used like this:

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 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}"

You may wish to use a more robust environment such as the Microsoft Developer Studio. In this case, run this to generate perlxsi.c:

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

Create a new project and Insert -> Files into Project: perlxsi.c, perl.lib, and your own source files, e.g. interp.c. Typically you'll find perl.lib in C:\perl\lib\CORE, if not, you should see the CORE directory relative to perl -V:archlib. The studio will also need this path so it knows where to find Perl include files. This path can be added via the Tools -> Options -> Directories menu. Finally, select Build -> Build interp.exe and you're ready to go.

あたらしいプロジェクトを作成し, 挿入 -> 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 C:\perl\lib\CORE にあるでしょう. もしここになければ perl -V:archlib にある 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.

Hiding Perl_

If you completely hide the short forms 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 perlguts 内 "Background and PERL_IMPLICIT_CONTEXT for the explanation of the C<aTHX_>." [CPAN] ) 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.)

MORAL 精神

You can sometimes write faster code in C, but you can always write code faster in Perl. Because you can use each from the other, combine them as you wish.

Cを使うことで より速いコードを書けますが, Perlなら常に 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.

AUTHOR 著者

Jon Orwant <orwant@media.mit.edu> and Doug MacEachern <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.

COPYRIGHT 著作権

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.

TRANSALTE TO JAPANESE 和訳

 山科 氷魚 (YAMASHINA Hio) <hio@hio.jp>

Original distribution is perl VERSION 5.8.8. Translated on 2008-02-18 (perl-5.8.0, 2003-06-18)

原典: perl VERSION 5.8.8. 翻訳日: 2008-02-18 (perl-5.8.0, 2003-06-18)

perlembed - how to embed perl in your C program

索引

AUTHOR 著者
Adding a Perl interpreter to your C program C プログラムに Perl インタプリタを追加
COPYRIGHT 著作権
Calling a Perl subroutine from your C program C プログラムから Perl 関数を呼び出し
Compiling your C program 作成した C プログラムのコンパイル
DESCRIPTION 説明
Embedding Perl under Win32 Win32 での Perl 埋め込み
Evaluating a Perl statement from your C program C プログラムから Perl 文を評価
Execution of END blocks END ブロックの実行
Fiddling with the Perl stack from your C program C プログラムから Perl スタックを操作
Hiding Perl_
MORAL 精神
Maintaining a persistent interpreter 持続するインタプリタの維持
Maintaining multiple interpreter instances 複数のインタプリタインスタンスの管理
NAME 名前
PREAMBLE 前書き
Performing Perl pattern matches and substitutions from your C program C プログラムから Perl パターンマッチと置換を処理
ROADMAP 道のり
TRANSALTE TO JAPANESE 和訳
Use C from C?
Use C from Perl?
Use Perl from C?
Use Perl from Perl?
Use a Unix program from Perl?
Using Perl modules, which themselves use C libraries, from your C program 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

perlembed - how to embed perl in your C program