Import guile-1.8 as multiple upstream tarball component

[lilypond.git] / guile18 / libguile / extensions.c

diff --git a/guile18/libguile/extensions.c b/guile18/libguile/extensions.c
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+/* extensions.c - registering and loading extensions.
+ *
+ * Copyright (C) 2001, 2006 Free Software Foundation, Inc.
+ * 
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <string.h>
+
+#include "libguile/_scm.h"
+#include "libguile/strings.h"
+#include "libguile/gc.h"
+#include "libguile/dynl.h"
+#include "libguile/dynwind.h"
+
+#include "libguile/extensions.h"
+
+typedef struct extension_t
+{
+  struct extension_t *next;
+  const char *lib;
+  const char *init;
+  void (*func)(void *);
+  void *data;
+} extension_t;
+
+static extension_t *registered_extensions;
+
+/* Register a LIB/INIT pair for use by `scm_load_extension'.  LIB is
+   allowed to be NULL and then only INIT is used to identify the
+   registered entry.  This is useful when you don't know the library
+   name (which isn't really relevant anyway in a completely linked
+   program) and you are sure that INIT is unique (which it must be for
+   static linking).  Hmm, given this reasoning, what use is LIB
+   anyway?
+*/
+
+void
+scm_c_register_extension (const char *lib, const char *init,
+                         void (*func) (void *), void *data)
+{
+  extension_t *ext = scm_malloc (sizeof(extension_t));
+  if (lib)
+    ext->lib = scm_strdup (lib);
+  else
+    ext->lib = NULL;
+  ext->init = scm_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. */
+  if (registered_extensions != NULL)
+    {
+      extension_t *ext;
+      char *clib, *cinit;
+      int found = 0;
+
+      scm_dynwind_begin (0);
+
+      clib = scm_to_locale_string (lib);
+      scm_dynwind_free (clib);
+      cinit = scm_to_locale_string (init);
+      scm_dynwind_free (cinit);
+
+      for (ext = registered_extensions; ext; ext = ext->next)
+       if ((ext->lib == NULL || !strcmp (ext->lib, clib))
+           && !strcmp (ext->init, cinit))
+         {
+           ext->func (ext->data);
+            found = 1;
+           break;
+         }
+
+      scm_dynwind_end ();
+
+      if (found)
+        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_from_locale_string (lib), scm_from_locale_string (init));
+}
+
+SCM_DEFINE (scm_load_extension, "load-extension", 2, 0, 0,
+           (SCM lib, SCM init),
+           "Load and initialize the extension designated by LIB and INIT.\n"
+           "When there is no pre-registered function for LIB/INIT, this is\n"
+           "equivalent to\n"
+           "\n"
+           "@lisp\n"
+           "(dynamic-call INIT (dynamic-link LIB))\n"
+           "@end lisp\n"
+           "\n"
+           "When there is a pre-registered function, that function is called\n"
+           "instead.\n"
+           "\n"
+           "Normally, there is no pre-registered function.  This option exists\n"
+           "only for situations where dynamic linking is unavailable or unwanted.\n"
+           "In that case, you would statically link your program with the desired\n"
+           "library, and register its init function right after Guile has been\n"
+           "initialized.\n"
+           "\n"
+           "LIB should be a string denoting a shared library without any file type\n"
+           "suffix such as \".so\".  The suffix is provided automatically.  It\n"
+           "should also not contain any directory components.  Libraries that\n"
+           "implement Guile Extensions should be put into the normal locations for\n"
+           "shared libraries.  We recommend to use the naming convention\n"
+           "libguile-bla-blum for a extension related to a module `(bla blum)'.\n"
+           "\n"
+           "The normal way for a extension to be used is to write a small Scheme\n"
+           "file that defines a module, and to load the extension into this\n"
+           "module.  When the module is auto-loaded, the extension is loaded as\n"
+           "well.  For example,\n"
+           "\n"
+           "@lisp\n"
+           "(define-module (bla blum))\n"
+           "\n"
+           "(load-extension \"libguile-bla-blum\" \"bla_init_blum\")\n"
+           "@end lisp")
+#define FUNC_NAME s_scm_load_extension
+{
+  load_extension (lib, init);
+  return SCM_UNSPECIFIED;
+}
+#undef FUNC_NAME
+
+void
+scm_init_extensions ()
+{
+  registered_extensions = NULL;
+#include "libguile/extensions.x"
+}
+
+/*
+  Local Variables:
+  c-file-style: "gnu"
+  End:
+*/