libguile/arbiters.c

   1 /*      Copyright (C) 1995,1996 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  16  *
  17  * As a special exception, the Free Software Foundation gives permission
  18  * for additional uses of the text contained in its release of GUILE.
  19  *
  20  * The exception is that, if you link the GUILE library with other files
  21  * to produce an executable, this does not by itself cause the
  22  * resulting executable to be covered by the GNU General Public License.
  23  * Your use of that executable is in no way restricted on account of
  24  * linking the GUILE library code into it.
  25  *
  26  * This exception does not however invalidate any other reasons why
  27  * the executable file might be covered by the GNU General Public License.
  28  *
  29  * This exception applies only to the code released by the
  30  * Free Software Foundation under the name GUILE.  If you copy
  31  * code from other Free Software Foundation releases into a copy of
  32  * GUILE, as the General Public License permits, the exception does
  33  * not apply to the code that you add in this way.  To avoid misleading
  34  * anyone as to the status of such modified files, you must delete
  35  * this exception notice from them.
  36  *
  37  * If you write modifications of your own for GUILE, it is your choice
  38  * whether to permit this exception to apply to your modifications.
  39  * If you do not wish that, delete this exception notice.
  40  */
  41 \f
  42
  43 #include <stdio.h>
  44 #include "_scm.h"
  45 #include "smob.h"
  46
  47 #include "arbiters.h"
  48
  49 \f
  50 /* {Arbiters}
  51  *
  52  * These procedures implement synchronization primitives.  Processors
  53  * with an atomic test-and-set instruction can use it here (and not
  54  * SCM_DEFER_INTS).
  55  */
  56
  57 static long scm_tc16_arbiter;
  58
  59
  60 static int
  61 prinarb (exp, port, pstate)
  62      SCM exp;
  63      SCM port;
  64      scm_print_state *pstate;
  65 {
  66   scm_gen_puts (scm_regular_string, "#<arbiter ", port);
  67   if (SCM_CAR (exp) & (1L << 16))
  68     scm_gen_puts (scm_regular_string, "locked ", port);
  69   scm_iprin1 (SCM_CDR (exp), port, pstate);
  70   scm_gen_putc ('>', port);
  71   return !0;
  72 }
  73
  74 static scm_smobfuns arbsmob =
  75 {
  76   scm_markcdr, scm_free0, prinarb, 0
  77 };
  78
  79 SCM_PROC(s_make_arbiter, "make-arbiter", 1, 0, 0, scm_make_arbiter);
  80
  81 SCM
  82 scm_make_arbiter (name)
  83      SCM name;
  84 {
  85   register SCM z;
  86   SCM_NEWCELL (z);
  87   SCM_SETCDR (z, name);
  88   SCM_SETCAR (z, scm_tc16_arbiter);
  89   return z;
  90 }
  91
  92 SCM_PROC(s_try_arbiter, "try-arbiter", 1, 0, 0, scm_try_arbiter);
  93
  94 SCM
  95 scm_try_arbiter (arb)
  96      SCM arb;
  97 {
  98   SCM_ASSERT ((SCM_TYP16 (arb) == scm_tc16_arbiter), arb, SCM_ARG1, s_try_arbiter);
  99   SCM_DEFER_INTS;
 100   if (SCM_CAR (arb) & (1L << 16))
 101     arb = SCM_BOOL_F;
 102   else
 103     {
 104       SCM_SETCAR (arb, scm_tc16_arbiter | (1L << 16));
 105       arb = SCM_BOOL_T;
 106     }
 107   SCM_ALLOW_INTS;
 108   return arb;
 109 }
 110
 111
 112 SCM_PROC(s_release_arbiter, "release-arbiter", 1, 0, 0, scm_release_arbiter);
 113
 114 SCM
 115 scm_release_arbiter (arb)
 116      SCM arb;
 117 {
 118   SCM_ASSERT ((SCM_TYP16 (arb) == scm_tc16_arbiter), arb, SCM_ARG1, s_release_arbiter);
 119   if (!(SCM_CAR (arb) & (1L << 16)))
 120     return SCM_BOOL_F;
 121   SCM_SETCAR (arb, scm_tc16_arbiter);
 122   return SCM_BOOL_T;
 123 }
 124
 125
 126
 127 void
 128 scm_init_arbiters ()
 129 {
 130   scm_tc16_arbiter = scm_newsmob (&arbsmob);
 131 #include "arbiters.x"
 132 }
 133