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/* Copyright (C) 1995,1996, 1997, 2000, 2001 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#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);
#include "libguile/arbiters.x"
}
/*
Local Variables:
c-file-style: "gnu"
End:
*/
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