libguile/dynwind.c

   1 /*      Copyright (C) 1995, 1996, 1998, 1999 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_ASSERT (SCM_NFALSEP (scm_thunk_p (thunk3)),
  79               thunk3,
  80               SCM_ARG3, s_dynamic_wind);
  81   scm_apply (thunk1, SCM_EOL, SCM_EOL);
  82   scm_dynwinds = scm_acons (thunk1, thunk3, scm_dynwinds);
  83   ans = scm_apply (thunk2, SCM_EOL, SCM_EOL);
  84   scm_dynwinds = SCM_CDR (scm_dynwinds);
  85   scm_apply (thunk3, SCM_EOL, SCM_EOL);
  86   return ans;
  87 }
  88
  89 /* The implementation of a C-callable dynamic-wind,
  90  * scm_internal_dynamic_wind, requires packaging of C pointers in a
  91  * smob.  Objects of this type are pushed onto the dynwind chain.
  92  */
  93
  94 typedef struct guardsmem {
  95   scm_guard_t before;
  96   scm_guard_t after;
  97   void *data;
  98 } guardsmem;
  99
 100 #define SCM_GUARDSMEM(obj) ((guardsmem *) SCM_CDR (obj))
 101 #define SCM_BEFORE_GUARD(obj) (SCM_GUARDSMEM (obj)->before)
 102 #define SCM_AFTER_GUARD(obj) (SCM_GUARDSMEM (obj)->after)
 103 #define SCM_GUARD_DATA(obj) (SCM_GUARDSMEM (obj)->data)
 104 #define SCM_GUARDSP(obj) (SCM_CAR (obj) == tc16_guards)
 105
 106 static long tc16_guards;
 107
 108 static scm_sizet
 109 freeguards (SCM guards)
 110 {
 111   scm_must_free ((char *) SCM_CDR (guards));
 112   return sizeof (guardsmem);
 113 }
 114
 115 static int
 116 printguards (SCM exp, SCM port, scm_print_state *pstate)
 117 {
 118   scm_puts ("#<guards ", port);
 119   scm_intprint (SCM_CDR (exp), 16, port);
 120   scm_putc ('>', port);
 121   return 1;
 122 }
 123
 124 SCM
 125 scm_internal_dynamic_wind (scm_guard_t before,
 126                            scm_inner_t inner,
 127                            scm_guard_t after,
 128                            void *inner_data,
 129                            void *guard_data)
 130 {
 131   SCM guards, ans;
 132   guardsmem *g;
 133   before (guard_data);
 134   g = (guardsmem *) scm_must_malloc (sizeof (*g), "guards");
 135   g->before = before;
 136   g->after = after;
 137   g->data = guard_data;
 138   SCM_NEWSMOB (guards, tc16_guards, g);
 139   scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
 140   ans = inner (inner_data);
 141   scm_dynwinds = SCM_CDR (scm_dynwinds);
 142   after (guard_data);
 143   return ans;
 144 }
 145
 146 #ifdef GUILE_DEBUG
 147 SCM_PROC (s_wind_chain, "wind-chain", 0, 0, 0, scm_wind_chain);
 148
 149 SCM
 150 scm_wind_chain ()
 151 {
 152   return scm_dynwinds;
 153 }
 154 #endif
 155
 156 static void
 157 scm_swap_bindings (SCM glocs, SCM vals)
 158 {
 159   SCM tmp;
 160   while (SCM_NIMP (vals))
 161     {
 162       tmp = SCM_GLOC_VAL (SCM_CAR (glocs));
 163       SCM_SETCDR (SCM_CAR (glocs) - 1L, SCM_CAR (vals));
 164       SCM_SETCAR (vals, tmp);
 165       glocs = SCM_CDR (glocs);
 166       vals = SCM_CDR (vals);
 167     }
 168 }
 169
 170 void
 171 scm_dowinds (to, delta)
 172      SCM to;
 173      long delta;
 174 {
 175  tail:
 176   if (scm_dynwinds == to);
 177   else if (0 > delta)
 178     {
 179       SCM wind_elt;
 180       SCM wind_key;
 181
 182       scm_dowinds (SCM_CDR (to), 1 + delta);
 183       wind_elt = SCM_CAR (to);
 184 #if 0
 185       if (SCM_INUMP (wind_elt))
 186         {
 187           scm_cross_dynwind_binding_scope (wind_elt, 0);
 188         }
 189       else
 190 #endif
 191         {
 192           wind_key = SCM_CAR (wind_elt);
 193           /* key = #t | symbol | thunk | list of glocs | list of fluids */
 194           if (SCM_NIMP (wind_key))
 195             {
 196               if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
 197                 scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
 198               else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
 199                 scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
 200               else if (SCM_GUARDSP (wind_key))
 201                 SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
 202               else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
 203                 scm_apply (wind_key, SCM_EOL, SCM_EOL);
 204             }
 205         }
 206       scm_dynwinds = to;
 207     }
 208   else
 209     {
 210       SCM from;
 211       SCM wind_elt;
 212       SCM wind_key;
 213
 214       from = SCM_CDR (SCM_CAR (scm_dynwinds));
 215       wind_elt = SCM_CAR (scm_dynwinds);
 216       scm_dynwinds = SCM_CDR (scm_dynwinds);
 217 #if 0
 218       if (SCM_INUMP (wind_elt))
 219         {
 220           scm_cross_dynwind_binding_scope (wind_elt, 0);
 221         }
 222       else
 223 #endif
 224         {
 225           wind_key = SCM_CAR (wind_elt);
 226           if (SCM_NIMP (wind_key))
 227             {
 228               if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
 229                 scm_swap_bindings (wind_key, from);
 230               else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
 231                 scm_swap_fluids_reverse (wind_key, from);
 232               else if (SCM_GUARDSP (wind_key))
 233                 SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
 234               else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
 235                 scm_apply (from, SCM_EOL, SCM_EOL);
 236             }
 237         }
 238       delta--;
 239       goto tail;                /* scm_dowinds(to, delta-1); */
 240     }
 241 }
 242
 243
 244
 245 void
 246 scm_init_dynwind ()
 247 {
 248   tc16_guards = scm_make_smob_type_mfpe ("guards", sizeof (struct guardsmem),
 249                                         NULL, freeguards, printguards, NULL);
 250 #include "dynwind.x"
 251 }