* box-dynamic: New directory, implements the box type in a shared

library (aka extension)

	Thanks to Thomas Wawrzinek for patching box.c into an extension!

examples/box-dynamic/box.c

@@ -0,0 +1,128 @@
+/* examples/box-dynamic/box.c
+ * 
+ *	Copyright (C) 1998,2001 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
+ */
+
+/* Include all needed declarations.  */
+#include <libguile.h>
+
+
+/* The type code for the newly created smob type will be stored into
+   this variable.  It has the prefix `scm_tc16_' to make it usable
+   with the SCM_VALIDATE_SMOB macro below.  */
+static scm_bits_t scm_tc16_box;
+
+
+/* This function is responsible for marking all SCM objects included
+   in the smob.  */
+static SCM
+mark_box (SCM b)
+{
+  /* Since we have only one SCM object to protect, we simply return it
+     and the caller with mark it.  */
+  return SCM_CELL_OBJECT_1 (b);
+}
+
+
+/* Print a textual represenation of the smob to a given port.  */
+static int
+print_box (SCM b, SCM port, scm_print_state *pstate)
+{
+  SCM value = SCM_CELL_OBJECT_1 (b);
+
+  scm_puts ("#<box ", port);
+  scm_write (value, port);
+  scm_puts (">", port);
+
+  /* Non-zero means success.  */
+  return 1;
+}
+
+
+/* This defines the primitve `make-box', which returns a new smob of
+   type `box', initialized to `#f'.  */
+static SCM
+#define FUNC_NAME "make-box"
+make_box (void)
+{
+  /* This macro creates the new objects, stores the value `#f' into it
+     and returns it to the caller.  */
+  SCM_RETURN_NEWSMOB (scm_tc16_box, SCM_BOOL_F);
+}
+#undef FUNC_NAME
+
+
+/* This is the primitive `box-ref' which returns the object stored in
+   the box.  */
+static SCM
+box_ref (SCM b)
+#define FUNC_NAME "box-ref"
+{
+  /* First, we have to ensure that the user really gave us a box
+     objects.  The macro SCM_VALIDATE_SMOB will do all what is needed.
+     The parameters are interpreted as follows: 
+
+     1: The position of the checked variable in the parameter list.
+     b: The passed parameter.
+     box: Concatenated with the fixed prefix scm_tc16_, names the type
+          code for the expected smob type.  */
+  SCM_VALIDATE_SMOB (1, b, box);
+
+  /* Fetch the object from the box and return it.  */
+  return SCM_CELL_OBJECT_1 (b);
+}
+#undef FUNC_NAME
+
+
+/* Primitive which stores an arbitrary value into a box.  */
+static SCM
+box_set_x (SCM b, SCM value)
+#define FUNC_NAME "box-set!"
+{
+  SCM_VALIDATE_SMOB (1, b, box);
+
+  /* Set the cell number 1 of the smob to the given value.  */
+  SCM_SET_CELL_OBJECT_1 (b, value);
+
+  /* When this constant is returned, the REPL will not print the
+     returned value.  All procedures in Guile which are documented as
+     returning `and unspecified value' actually return this value.  */
+  return SCM_UNSPECIFIED;
+}
+#undef FUNC_NAME
+
+
+/* Create and initialize the new smob type, and register the
+   primitives with the interpreter library.
+   
+   To be called with (load-extension "libbox" "scm_init_box")
+   from a script.
+*/
+void
+scm_init_box ()
+{
+  scm_tc16_box = scm_make_smob_type ("box", 0);
+  scm_set_smob_mark (scm_tc16_box, mark_box);
+  scm_set_smob_print (scm_tc16_box, print_box);
+
+  scm_c_define_gsubr ("make-box", 0, 0, 0, make_box);
+  scm_c_define_gsubr ("box-set!", 2, 0, 0, box_set_x);
+  scm_c_define_gsubr ("box-ref", 1, 0, 0, box_ref);
+}
+
+/* End of file.  */