libguile/dynwind.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, 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 \f
  42
  43 #include <stdio.h>
  44 #include "_scm.h"
  45 #include "eval.h"
  46 #include "alist.h"
  47 #include "fluids.h"
  48 #include "genio.h"
  49 #include "smob.h"
  50
  51 #include "dynwind.h"
  52 \f
  53
  54 /* {Dynamic wind}
  55
  56    Things that can be on the wind list:
  57
  58    (enter-proc . leave-proc)     dynamic-wind
  59    (tag . jmpbuf)                catch
  60    (tag . lazy-catch)            lazy-catch
  61      tag is either a symbol or a boolean
  62
  63    ((fluid ...) . (value ...))   with-fluids
  64
  65 */
  66
  67
  68
  69 SCM_PROC(s_dynamic_wind, "dynamic-wind", 3, 0, 0, scm_dynamic_wind);
  70
  71 SCM
  72 scm_dynamic_wind (thunk1, thunk2, thunk3)
  73      SCM thunk1;
  74      SCM thunk2;
  75      SCM thunk3;
  76 {
  77   SCM ans;
  78   scm_apply (thunk1, SCM_EOL, SCM_EOL);
  79   scm_dynwinds = scm_acons (thunk1, thunk3, scm_dynwinds);
  80   ans = scm_apply (thunk2, SCM_EOL, SCM_EOL);
  81   scm_dynwinds = SCM_CDR (scm_dynwinds);
  82   scm_apply (thunk3, SCM_EOL, SCM_EOL);
  83   return ans;
  84 }
  85
  86 /* The implementation of a C-callable dynamic-wind,
  87  * scm_internal_dynamic_wind, requires packaging of C pointers in a
  88  * smob.  Objects of this type are pushed onto the dynwind chain.
  89  */
  90
  91 typedef struct guardsmem {
  92   scm_guard_t before;
  93   scm_guard_t after;
  94   void *data;
  95 } guardsmem;
  96
  97 #define SCM_GUARDSMEM(obj) ((guardsmem *) SCM_CDR (obj))
  98 #define SCM_BEFORE_GUARD(obj) (SCM_GUARDSMEM (obj)->before)
  99 #define SCM_AFTER_GUARD(obj) (SCM_GUARDSMEM (obj)->after)
 100 #define SCM_GUARD_DATA(obj) (SCM_GUARDSMEM (obj)->data)
 101 #define SCM_GUARDSP(obj) (SCM_CAR (obj) == tc16_guards)
 102
 103 static long tc16_guards;
 104
 105 static scm_sizet
 106 freeguards (SCM guards)
 107 {
 108   scm_must_free ((char *) SCM_CDR (guards));
 109   return sizeof (guardsmem);
 110 }
 111
 112 static int
 113 printguards (SCM exp, SCM port, scm_print_state *pstate)
 114 {
 115   scm_puts ("#<guards ", port);
 116   scm_intprint (SCM_CDR (exp), 16, port);
 117   scm_putc ('>', port);
 118   return 1;
 119 }
 120
 121 static scm_smobfuns guardsmob = {
 122   scm_mark0,
 123   freeguards,
 124   printguards,
 125   0
 126 };
 127
 128 SCM
 129 scm_internal_dynamic_wind (scm_guard_t before,
 130                            scm_inner_t inner,
 131                            scm_guard_t after,
 132                            void *inner_data,
 133                            void *guard_data)
 134 {
 135   SCM guards, ans;
 136   guardsmem *g;
 137   before (guard_data);
 138   SCM_NEWCELL (guards);
 139   SCM_DEFER_INTS;
 140   g = (guardsmem *) scm_must_malloc (sizeof (*g), "guards");
 141   g->before = before;
 142   g->after = after;
 143   g->data = guard_data;
 144   SCM_SETCDR (guards, g);
 145   SCM_SETCAR (guards, tc16_guards);
 146   SCM_ALLOW_INTS;
 147   scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
 148   ans = inner (inner_data);
 149   scm_dynwinds = SCM_CDR (scm_dynwinds);
 150   after (guard_data);
 151   return ans;
 152 }
 153
 154 #ifdef GUILE_DEBUG
 155 SCM_PROC (s_wind_chain, "wind-chain", 0, 0, 0, scm_wind_chain);
 156
 157 SCM
 158 scm_wind_chain ()
 159 {
 160   return scm_dynwinds;
 161 }
 162 #endif
 163
 164
 165 void
 166 scm_dowinds (to, delta)
 167      SCM to;
 168      long delta;
 169 {
 170  tail:
 171   if (scm_dynwinds == to);
 172   else if (0 > delta)
 173     {
 174       SCM wind_elt;
 175       SCM wind_key;
 176
 177       scm_dowinds (SCM_CDR (to), 1 + delta);
 178       wind_elt = SCM_CAR (to);
 179 #if 0
 180       if (SCM_INUMP (wind_elt))
 181         {
 182           scm_cross_dynwind_binding_scope (wind_elt, 0);
 183         }
 184       else
 185 #endif
 186         {
 187           wind_key = SCM_CAR (wind_elt);
 188           if (!(SCM_NIMP (wind_key) && SCM_SYMBOLP (wind_key))
 189               && (wind_key != SCM_BOOL_F)
 190               && (wind_key != SCM_BOOL_T))
 191             {
 192               if (SCM_NIMP (wind_key) && SCM_CONSP (wind_key))
 193                 scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
 194               else if (SCM_NIMP (wind_key) && SCM_GUARDSP (wind_key))
 195                 SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
 196               else
 197                 scm_apply (wind_key, SCM_EOL, SCM_EOL);
 198             }
 199         }
 200       scm_dynwinds = to;
 201     }
 202   else
 203     {
 204       SCM from;
 205       SCM wind_elt;
 206       SCM wind_key;
 207
 208       from = SCM_CDR (SCM_CAR (scm_dynwinds));
 209       wind_elt = SCM_CAR (scm_dynwinds);
 210       scm_dynwinds = SCM_CDR (scm_dynwinds);
 211 #if 0
 212       if (SCM_INUMP (wind_elt))
 213         {
 214           scm_cross_dynwind_binding_scope (wind_elt, 0);
 215         }
 216       else
 217 #endif
 218         {
 219           wind_key = SCM_CAR (wind_elt);
 220           if (!(SCM_NIMP (wind_key) && SCM_SYMBOLP (wind_key))
 221               && (wind_key != SCM_BOOL_F)
 222               && (wind_key != SCM_BOOL_T))
 223             {
 224               if (SCM_NIMP (wind_key) && SCM_CONSP (wind_key))
 225                 scm_swap_fluids_reverse (wind_key, from);
 226               else if (SCM_NIMP (wind_key) && SCM_GUARDSP (wind_key))
 227                 SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
 228               else
 229                 scm_apply (from, SCM_EOL, SCM_EOL);
 230             }
 231         }
 232       delta--;
 233       goto tail;                /* scm_dowinds(to, delta-1); */
 234     }
 235 }
 236
 237
 238
 239 void
 240 scm_init_dynwind ()
 241 {
 242   tc16_guards = scm_newsmob (&guardsmob);
 243 #include "dynwind.x"
 244 }