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/* 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_t_bits 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 will 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. */
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