libguile/arbiters.c

   1 /*      Copyright (C) 1995,1996, 1997 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, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42 /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
  43    gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
  44
  45 \f
  46
  47 #include <stdio.h>
  48 #include "_scm.h"
  49 #include "smob.h"
  50 #include "genio.h"
  51
  52 #include "scm_validate.h"
  53 #include "arbiters.h"
  54
  55 \f
  56 /* {Arbiters}
  57  *
  58  * These procedures implement synchronization primitives.  Processors
  59  * with an atomic test-and-set instruction can use it here (and not
  60  * SCM_DEFER_INTS).
  61  */
  62
  63 static long scm_tc16_arbiter;
  64
  65
  66 static int
  67 prinarb (SCM exp, SCM port, scm_print_state *pstate)
  68 {
  69   scm_puts ("#<arbiter ", port);
  70   if (SCM_CAR (exp) & (1L << 16))
  71     scm_puts ("locked ", port);
  72   scm_iprin1 (SCM_CDR (exp), port, pstate);
  73   scm_putc ('>', port);
  74   return !0;
  75 }
  76
  77 SCM_DEFINE (scm_make_arbiter, "make-arbiter", 1, 0, 0,
  78            (SCM name),
  79 "")
  80 #define FUNC_NAME s_scm_make_arbiter
  81 {
  82   SCM_RETURN_NEWSMOB (scm_tc16_arbiter, name);
  83 }
  84 #undef FUNC_NAME
  85
  86 SCM_DEFINE (scm_try_arbiter, "try-arbiter", 1, 0, 0,
  87            (SCM arb),
  88 "")
  89 #define FUNC_NAME s_scm_try_arbiter
  90 {
  91   SCM_VALIDATE_SMOB (1,arb,arbiter);
  92   SCM_DEFER_INTS;
  93   if (SCM_CAR (arb) & (1L << 16))
  94     arb = SCM_BOOL_F;
  95   else
  96     {
  97       SCM_SETCAR (arb, scm_tc16_arbiter | (1L << 16));
  98       arb = SCM_BOOL_T;
  99     }
 100   SCM_ALLOW_INTS;
 101   return arb;
 102 }
 103 #undef FUNC_NAME
 104
 105
 106 SCM_DEFINE (scm_release_arbiter, "release-arbiter", 1, 0, 0,
 107            (SCM arb),
 108 "")
 109 #define FUNC_NAME s_scm_release_arbiter
 110 {
 111   SCM_VALIDATE_SMOB (1,arb,arbiter);
 112   if (!(SCM_CAR (arb) & (1L << 16)))
 113     return SCM_BOOL_F;
 114   SCM_SETCAR (arb, scm_tc16_arbiter);
 115   return SCM_BOOL_T;
 116 }
 117 #undef FUNC_NAME
 118
 119
 120
 121 void
 122 scm_init_arbiters ()
 123 {
 124   scm_tc16_arbiter = scm_make_smob_type_mfpe ("arbiter", 0,
 125                                               scm_markcdr, NULL, prinarb, NULL);
 126 #include "arbiters.x"
 127 }