libguile/extensions.c

   1 /* extensions.c - registering and loading extensions.
   2  *
   3  * Copyright (C) 2001 Free Software Foundation, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2, or (at your option)
   8  * any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this software; see the file COPYING.  If not, write to
  17  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18  * Boston, MA 02111-1307 USA
  19  *
  20  * As a special exception, the Free Software Foundation gives permission
  21  * for additional uses of the text contained in its release of GUILE.
  22  *
  23  * The exception is that, if you link the GUILE library with other files
  24  * to produce an executable, this does not by itself cause the
  25  * resulting executable to be covered by the GNU General Public License.
  26  * Your use of that executable is in no way restricted on account of
  27  * linking the GUILE library code into it.
  28  *
  29  * This exception does not however invalidate any other reasons why
  30  * the executable file might be covered by the GNU General Public License.
  31  *
  32  * This exception applies only to the code released by the
  33  * Free Software Foundation under the name GUILE.  If you copy
  34  * code from other Free Software Foundation releases into a copy of
  35  * GUILE, as the General Public License permits, the exception does
  36  * not apply to the code that you add in this way.  To avoid misleading
  37  * anyone as to the status of such modified files, you must delete
  38  * this exception notice from them.
  39  *
  40  * If you write modifications of your own for GUILE, it is your choice
  41  * whether to permit this exception to apply to your modifications.
  42  * If you do not wish that, delete this exception notice.  */
  43
  44 #include "libguile/_scm.h"
  45 #include "libguile/strings.h"
  46 #include "libguile/gc.h"
  47 #include "libguile/dynl.h"
  48
  49 #include "libguile/extensions.h"
  50
  51 typedef struct extension_t
  52 {
  53   struct extension_t *next;
  54   const char *lib;
  55   const char *init;
  56   void (*func)(void *);
  57   void *data;
  58 } extension_t;
  59
  60 static extension_t *registered_extensions;
  61
  62 void
  63 scm_c_register_extension (const char *lib, const char *init,
  64                           void (*func) (void *), void *data)
  65 {
  66   extension_t *ext = scm_must_malloc (sizeof(extension_t),
  67                                            "scm_register_extension");
  68   ext->lib = scm_must_strdup (lib);
  69   ext->init = scm_must_strdup (init);
  70   ext->func = func;
  71   ext->data = data;
  72
  73   ext->next = registered_extensions;
  74   registered_extensions = ext;
  75 }
  76
  77 static void
  78 load_extension (SCM lib, SCM init)
  79 {
  80   /* Search the registry. */
  81   {
  82     extension_t *ext;
  83
  84     for (ext = registered_extensions; ext; ext = ext->next)
  85       if (!strcmp (ext->lib, SCM_STRING_CHARS (lib))
  86           && !strcmp (ext->init, SCM_STRING_CHARS (init)))
  87         {
  88           ext->func (ext->data);
  89           return;
  90         }
  91   }
  92
  93   /* Dynamically link the library. */
  94
  95   scm_dynamic_call (init, scm_dynamic_link (lib));
  96 }
  97
  98 void
  99 scm_c_load_extension (const char *lib, const char *init)
 100 {
 101   load_extension (scm_makfrom0str (lib), scm_makfrom0str (init));
 102 }
 103
 104 SCM_DEFINE (scm_load_extension, "load-extension", 2, 0, 0,
 105             (SCM lib, SCM init),
 106             "Load and initilize the extension designated by LIB and INIT."
 107 "When there is no pre-registered function for LIB/INIT, this is "
 108 "equivalent to "
 109 " "
 110 "   (dynamic-call INIT (dynamic-link LIB)) "
 111 " "
 112 "When there is a pre-registered function, that function is called "
 113 "instead. "
 114 " "
 115 "Normally, there is no pre-registered function.  This option exists "
 116 "only for situations where dynamic linking is unavailable or unwanted. "
 117 "In that case, you would statically link your program with the desired "
 118 "library, and register its init function right after Guile has been "
 119 "initialized. "
 120 " "
 121 "LIB should be a string denoting a shared library without any file type "
 122 "suffix such as \".so\".  The suffix is provided automatically.  It "
 123 "should also not contain any directory components.  Libraries that "
 124 "implement Guile Extensions should be put into the normal locations for "
 125 "shared libraries.  We recommend to use the naming convention "
 126 "libguile-bla-blum for a extension related to a module `(bla blum)'. "
 127 " "
 128 "The normal way for a extension to be used is to write a small Scheme "
 129 "file that defines a module, and to load the extension into this "
 130 "module.  When the module is auto-loaded, the extension is loaded as "
 131 "well.  For example, "
 132 " "
 133 "   (define-module (bla blum)) "
 134 " "
 135 "   (load-extension \"libguile-bla-blum\" \"bla_init_blum\")")
 136 #define FUNC_NAME s_scm_load_extension
 137 {
 138   SCM_VALIDATE_STRING (1, lib);
 139   SCM_VALIDATE_STRING (2, init);
 140   load_extension (lib, init);
 141   return SCM_UNSPECIFIED;
 142 }
 143 #undef FUNC_NAME
 144
 145 void
 146 scm_init_extensions ()
 147 {
 148   registered_extensions = NULL;
 149 #ifndef SCM_MAGIC_SNARFER
 150 #include "libguile/extensions.x"
 151 #endif
 152 }
 153
 154 /*
 155   Local Variables:
 156   c-file-style: "gnu"
 157   End:
 158 */