libguile/extensions.c

   1 /* extensions.c - registering and loading extensions.
   2  *
   3  * Copyright (C) 2001, 2006, 2009, 2010, 2011 Free Software Foundation, Inc.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public License
   7  * as published by the Free Software Foundation; either version 3 of
   8  * the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301 USA
  19  */
  20
  21 #ifdef HAVE_CONFIG_H
  22 #  include <config.h>
  23 #endif
  24
  25 #include <string.h>
  26
  27 #include "libguile/_scm.h"
  28 #include "libguile/strings.h"
  29 #include "libguile/gc.h"
  30 #include "libguile/dynl.h"
  31 #include "libguile/dynwind.h"
  32
  33 #include "libguile/extensions.h"
  34
  35 typedef struct extension_t
  36 {
  37   struct extension_t *next;
  38   const char *lib;
  39   const char *init;
  40   void (*func)(void *);
  41   void *data;
  42 } extension_t;
  43
  44 static extension_t *registered_extensions = NULL;
  45 static scm_i_pthread_mutex_t ext_lock = SCM_I_PTHREAD_MUTEX_INITIALIZER;
  46
  47 /* Register a LIB/INIT pair for use by `scm_load_extension'.  LIB is
  48    allowed to be NULL and then only INIT is used to identify the
  49    registered entry.  This is useful when you don't know the library
  50    name (which isn't really relevant anyway in a completely linked
  51    program) and you are sure that INIT is unique (which it must be for
  52    static linking).  Hmm, given this reasoning, what use is LIB
  53    anyway?
  54 */
  55
  56 void
  57 scm_c_register_extension (const char *lib, const char *init,
  58                           void (*func) (void *), void *data)
  59 {
  60   extension_t *ext = scm_malloc (sizeof(extension_t));
  61   if (lib)
  62     ext->lib = scm_strdup (lib);
  63   else
  64     ext->lib = NULL;
  65   ext->init = scm_strdup (init);
  66   ext->func = func;
  67   ext->data = data;
  68
  69   scm_i_pthread_mutex_lock (&ext_lock);
  70   ext->next = registered_extensions;
  71   registered_extensions = ext;
  72   scm_i_pthread_mutex_unlock (&ext_lock);
  73 }
  74
  75 static void
  76 load_extension (SCM lib, SCM init)
  77 {
  78   extension_t *head;
  79
  80   scm_i_pthread_mutex_lock (&ext_lock);
  81   head = registered_extensions;
  82   scm_i_pthread_mutex_unlock (&ext_lock);
  83
  84   /* Search the registry. */
  85   if (head != NULL)
  86     {
  87       extension_t *ext;
  88       char *clib, *cinit;
  89       int found = 0;
  90
  91       scm_dynwind_begin (0);
  92
  93       clib = scm_to_locale_string (lib);
  94       scm_dynwind_free (clib);
  95       cinit = scm_to_locale_string (init);
  96       scm_dynwind_free (cinit);
  97
  98       for (ext = head; ext; ext = ext->next)
  99         if ((ext->lib == NULL || !strcmp (ext->lib, clib))
 100             && !strcmp (ext->init, cinit))
 101           {
 102             ext->func (ext->data);
 103             found = 1;
 104             break;
 105           }
 106
 107       scm_dynwind_end ();
 108
 109       if (found)
 110         return;
 111     }
 112
 113   /* Dynamically link the library. */
 114 #if HAVE_MODULES
 115   scm_dynamic_call (init, scm_dynamic_link (lib));
 116 #else
 117   scm_misc_error ("load-extension",
 118                   "extension ~S:~S not registered and dynamic-link disabled",
 119                   scm_list_2 (init, lib));
 120 #endif
 121 }
 122
 123 void
 124 scm_c_load_extension (const char *lib, const char *init)
 125 {
 126   load_extension (scm_from_locale_string (lib), scm_from_locale_string (init));
 127 }
 128
 129 SCM_DEFINE (scm_load_extension, "load-extension", 2, 0, 0,
 130             (SCM lib, SCM init),
 131             "Load and initialize the extension designated by LIB and INIT.\n"
 132             "When there is no pre-registered function for LIB/INIT, this is\n"
 133             "equivalent to\n"
 134             "\n"
 135             "@lisp\n"
 136             "(dynamic-call INIT (dynamic-link LIB))\n"
 137             "@end lisp\n"
 138             "\n"
 139             "When there is a pre-registered function, that function is called\n"
 140             "instead.\n"
 141             "\n"
 142             "Normally, there is no pre-registered function.  This option exists\n"
 143             "only for situations where dynamic linking is unavailable or unwanted.\n"
 144             "In that case, you would statically link your program with the desired\n"
 145             "library, and register its init function right after Guile has been\n"
 146             "initialized.\n"
 147             "\n"
 148             "LIB should be a string denoting a shared library without any file type\n"
 149             "suffix such as \".so\".  The suffix is provided automatically.  It\n"
 150             "should also not contain any directory components.  Libraries that\n"
 151             "implement Guile Extensions should be put into the normal locations for\n"
 152             "shared libraries.  We recommend to use the naming convention\n"
 153             "libguile-bla-blum for a extension related to a module `(bla blum)'.\n"
 154             "\n"
 155             "The normal way for a extension to be used is to write a small Scheme\n"
 156             "file that defines a module, and to load the extension into this\n"
 157             "module.  When the module is auto-loaded, the extension is loaded as\n"
 158             "well.  For example,\n"
 159             "\n"
 160             "@lisp\n"
 161             "(define-module (bla blum))\n"
 162             "\n"
 163             "(load-extension \"libguile-bla-blum\" \"bla_init_blum\")\n"
 164             "@end lisp")
 165 #define FUNC_NAME s_scm_load_extension
 166 {
 167   load_extension (lib, init);
 168   return SCM_UNSPECIFIED;
 169 }
 170 #undef FUNC_NAME
 171
 172 void
 173 scm_init_extensions ()
 174 {
 175 #include "libguile/extensions.x"
 176 }
 177
 178 /*
 179   Local Variables:
 180   c-file-style: "gnu"
 181   End:
 182 */