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/* Copyright (C) 1995,1996, 1997, 2000 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
*
* As a special exception, the Free Software Foundation gives permission
* for additional uses of the text contained in its release of GUILE.
*
* The exception is that, if you link the GUILE library with other files
* to produce an executable, this does not by itself cause the
* resulting executable to be covered by the GNU General Public License.
* Your use of that executable is in no way restricted on account of
* linking the GUILE library code into it.
*
* This exception does not however invalidate any other reasons why
* the executable file might be covered by the GNU General Public License.
*
* This exception applies only to the code released by the
* Free Software Foundation under the name GUILE. If you copy
* code from other Free Software Foundation releases into a copy of
* GUILE, as the General Public License permits, the exception does
* not apply to the code that you add in this way. To avoid misleading
* anyone as to the status of such modified files, you must delete
* this exception notice from them.
*
* If you write modifications of your own for GUILE, it is your choice
* whether to permit this exception to apply to your modifications.
* If you do not wish that, delete this exception notice. */
/* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
#include "libguile/_scm.h"
#include "libguile/ports.h"
#include "libguile/smob.h"
#include "libguile/validate.h"
#include "libguile/arbiters.h"
/* {Arbiters}
*
* These procedures implement synchronization primitives. Processors
* with an atomic test-and-set instruction can use it here (and not
* SCM_DEFER_INTS).
*/
static scm_t_bits scm_tc16_arbiter;
#define SCM_ARB_LOCKED(arb) ((SCM_CELL_WORD_0 (arb)) & (1L << 16))
#define SCM_LOCK_ARB(arb) (SCM_SET_CELL_WORD_0 ((arb), scm_tc16_arbiter | (1L << 16)));
#define SCM_UNLOCK_ARB(arb) (SCM_SET_CELL_WORD_0 ((arb), scm_tc16_arbiter));
static int
arbiter_print (SCM exp, SCM port, scm_print_state *pstate)
{
scm_puts ("#<arbiter ", port);
if (SCM_ARB_LOCKED (exp))
scm_puts ("locked ", port);
scm_iprin1 (SCM_PACK (SCM_SMOB_DATA (exp)), port, pstate);
scm_putc ('>', port);
return !0;
}
SCM_DEFINE (scm_make_arbiter, "make-arbiter", 1, 0, 0,
(SCM name),
"Return an object of type arbiter and name @var{name}. Its\n"
"state is initially unlocked. Arbiters are a way to achieve\n"
"process synchronization.")
#define FUNC_NAME s_scm_make_arbiter
{
SCM_RETURN_NEWSMOB (scm_tc16_arbiter, SCM_UNPACK (name));
}
#undef FUNC_NAME
SCM_DEFINE (scm_try_arbiter, "try-arbiter", 1, 0, 0,
(SCM arb),
"Return @code{#t} and lock the arbiter @var{arb} if the arbiter\n"
"was unlocked. Otherwise, return @code{#f}.")
#define FUNC_NAME s_scm_try_arbiter
{
SCM_VALIDATE_SMOB (1, arb, arbiter);
SCM_DEFER_INTS;
if (SCM_ARB_LOCKED(arb))
arb = SCM_BOOL_F;
else
{
SCM_LOCK_ARB(arb);
arb = SCM_BOOL_T;
}
SCM_ALLOW_INTS;
return arb;
}
#undef FUNC_NAME
SCM_DEFINE (scm_release_arbiter, "release-arbiter", 1, 0, 0,
(SCM arb),
"Return @code{#t} and unlock the arbiter @var{arb} if the\n"
"arbiter was locked. Otherwise, return @code{#f}.")
#define FUNC_NAME s_scm_release_arbiter
{
SCM_VALIDATE_SMOB (1, arb, arbiter);
if (!SCM_ARB_LOCKED(arb))
return SCM_BOOL_F;
SCM_UNLOCK_ARB (arb);
return SCM_BOOL_T;
}
#undef FUNC_NAME
void
scm_init_arbiters ()
{
scm_tc16_arbiter = scm_make_smob_type ("arbiter", 0);
scm_set_smob_mark (scm_tc16_arbiter, scm_markcdr);
scm_set_smob_print (scm_tc16_arbiter, arbiter_print);
#ifndef SCM_MAGIC_SNARFER
#include "libguile/arbiters.x"
#endif
}
/*
Local Variables:
c-file-style: "gnu"
End:
*/
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