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
  46 \f
  47 /* {Arbiters}
  48  *
  49  * These procedures implement synchronization primitives.  Processors
  50  * with an atomic test-and-set instruction can use it here (and not
  51  * SCM_DEFER_INTS).
  52  */
  53
  54 static long scm_tc16_arbiter;
  55
  56 #ifdef __STDC__
  57 static int
  58 prinarb (SCM exp, SCM port, int writing)
  59 #else
  60 static int
  61 prinarb (exp, port, writing)
  62      SCM exp;
  63      SCM port;
  64      int writing;
  65 #endif
  66 {
  67   scm_gen_puts (scm_regular_string, "#<arbiter ", port);
  68   if (SCM_CAR (exp) & (1L << 16))
  69     scm_gen_puts (scm_regular_string, "locked ", port);
  70   scm_iprin1 (SCM_CDR (exp), port, writing);
  71   scm_gen_putc ('>', port);
  72   return !0;
  73 }
  74
  75 static scm_smobfuns arbsmob =
  76 {
  77   scm_markcdr, scm_free0, prinarb, 0
  78 };
  79
  80 SCM_PROC(s_make_arbiter, "make-arbiter", 1, 0, 0, scm_make_arbiter);
  81 #ifdef __STDC__
  82 SCM
  83 scm_make_arbiter (SCM name)
  84 #else
  85 SCM
  86 scm_make_arbiter (name)
  87      SCM name;
  88 #endif
  89 {
  90   register SCM z;
  91   SCM_NEWCELL (z);
  92   SCM_CDR (z) = name;
  93   SCM_CAR (z) = scm_tc16_arbiter;
  94   return z;
  95 }
  96
  97 SCM_PROC(s_try_arbiter, "try-arbiter", 1, 0, 0, scm_try_arbiter);
  98 #ifdef __STDC__
  99 SCM
 100 scm_try_arbiter (SCM arb)
 101 #else
 102 SCM
 103 scm_try_arbiter (arb)
 104      SCM arb;
 105 #endif
 106 {
 107   SCM_ASSERT ((SCM_TYP16 (arb) == scm_tc16_arbiter), arb, SCM_ARG1, s_try_arbiter);
 108   SCM_DEFER_INTS;
 109   if (SCM_CAR (arb) & (1L << 16))
 110     arb = SCM_BOOL_F;
 111   else
 112     {
 113       SCM_CAR (arb) = scm_tc16_arbiter | (1L << 16);
 114       arb = SCM_BOOL_T;
 115     }
 116   SCM_ALLOW_INTS;
 117   return arb;
 118 }
 119
 120
 121 SCM_PROC(s_release_arbiter, "release-arbiter", 1, 0, 0, scm_release_arbiter);
 122 #ifdef __STDC__
 123 SCM
 124 scm_release_arbiter (SCM arb)
 125 #else
 126 SCM
 127 scm_release_arbiter (arb)
 128      SCM arb;
 129 #endif
 130 {
 131   SCM_ASSERT ((SCM_TYP16 (arb) == scm_tc16_arbiter), arb, SCM_ARG1, s_release_arbiter);
 132   if (!(SCM_CAR (arb) & (1L << 16)))
 133     return SCM_BOOL_F;
 134   SCM_CAR (arb) = scm_tc16_arbiter;
 135   return SCM_BOOL_T;
 136 }
 137
 138
 139 #ifdef __STDC__
 140 void
 141 scm_init_arbiters (void)
 142 #else
 143 void
 144 scm_init_arbiters ()
 145 #endif
 146 {
 147   scm_tc16_arbiter = scm_newsmob (&arbsmob);
 148 #include "arbiters.x"
 149 }
 150