guile/libguile/extensions.c

/* extensions.c - registering and loading extensions.
 *
 * Copyright (C) 2001 Free Software Foundation, Inc.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307 USA
 *
 * As a special exception, the Free Software Foundation gives permission
 * for additional uses of the text contained in its release of GUILE.
 *
 * The exception is that, if you link the GUILE library with other files
 * to produce an executable, this does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * Your use of that executable is in no way restricted on account of
 * linking the GUILE library code into it.
 *
 * This exception does not however invalidate any other reasons why
 * the executable file might be covered by the GNU General Public License.
 *
 * This exception applies only to the code released by the
 * Free Software Foundation under the name GUILE.  If you copy
 * code from other Free Software Foundation releases into a copy of
 * GUILE, as the General Public License permits, the exception does
 * not apply to the code that you add in this way.  To avoid misleading
 * anyone as to the status of such modified files, you must delete
 * this exception notice from them.
 *
 * If you write modifications of your own for GUILE, it is your choice
 * whether to permit this exception to apply to your modifications.
 * If you do not wish that, delete this exception notice.  */

#include "libguile/_scm.h"
#include "libguile/strings.h"
#include "libguile/gc.h"
#include "libguile/dynl.h"

#include "libguile/extensions.h"

struct extension {
  struct extension *next;
  const char *lib;
  const char *init;
  void (*func)(void *);
  void *data;
};

static struct extension *registered_extensions;

void
scm_c_register_extension (const char *lib, const char *init,
			  void (*func) (void *), void *data)
{
  struct extension *ext = scm_must_malloc (sizeof(struct extension),
					   "scm_register_extension");
  ext->lib = scm_must_strdup (lib);
  ext->init = scm_must_strdup (init);
  ext->func = func;
  ext->data = data;

  ext->next = registered_extensions;
  registered_extensions = ext;
}

static void
load_extension (SCM lib, SCM init)
{
  /* Search the registry. */
  {
    struct extension *ext;

    for (ext = registered_extensions; ext; ext = ext->next)
      if (!strcmp (ext->lib, SCM_STRING_CHARS (lib))
	  && !strcmp (ext->init, SCM_STRING_CHARS (init)))
	{
	  ext->func (ext->data);
	  return;
	}
  }

  /* Dynamically link the library. */

  scm_dynamic_call (init, scm_dynamic_link (lib));
}

void
scm_c_load_extension (const char *lib, const char *init)
{
  load_extension (scm_makfrom0str (lib), scm_makfrom0str (init));
}

SCM_DEFINE (scm_load_extension, "load-extension", 2, 0, 0,
	    (SCM lib, SCM init),
	    "Load and initilize the extension designated by LIB and INIT."
"When there is no pre-registered function for LIB/INIT, this is "
"equivalent to "
" "
"   (dynamic-call INIT (dynamic-link LIB)) "
" "
"When there is a pre-registered function, that function is called "
"instead. "
" "
"Normally, there is no pre-registered function.  This option exists "
"only for situations where dynamic linking is unavailable or unwanted. "
"In that case, you would statically link your program with the desired "
"library, and register its init function right after Guile has been "
"initialized. "
" "
"LIB should be a string denoting a shared library without any file type "
"suffix such as \".so\".  The suffix is provided automatically.  It "
"should also not contain any directory components.  Libraries that "
"implement Guile Extensions should be put into the normal locations for "
"shared libraries.  We recommend to use the naming convention "
"libguile-bla-blum for a extension related to a module `(bla blum)'. "
" "
"The normal way for a extension to be used is to write a small Scheme "
"file that defines a module, and to load the extension into this "
"module.  When the module is auto-loaded, the extension is loaded as "
"well.  For example, "
" "
"   (define-module (bla blum)) "
" "
"   (load-extension \"libguile-bla-blum\" \"bla_init_blum\")")
#define FUNC_NAME s_scm_load_extension
{
  SCM_VALIDATE_STRING (1, lib);
  SCM_VALIDATE_STRING (2, init);
  load_extension (lib, init);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

void
scm_init_extensions ()
{
  registered_extensions = NULL;
#ifndef SCM_MAGIC_SNARFER
#include "libguile/extensions.x"
#endif
}

/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/