libguile/continuations.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 "stackchk.h"
  46 #ifdef DEBUG_EXTENSIONS
  47 #include "debug.h"
  48 #endif
  49 #include "dynwind.h"
  50
  51 #include "continuations.h"
  52 \f
  53
  54 /* {Continuations}
  55  */
  56
  57 static char s_cont[] = "continuation";
  58
  59 #ifdef __STDC__
  60 SCM
  61 scm_make_cont (SCM * answer)
  62 #else
  63 SCM
  64 scm_make_cont (answer)
  65      SCM * answer;
  66 #endif
  67 {
  68   long j;
  69   SCM cont;
  70
  71 #ifdef CHEAP_CONTINUATIONS
  72   SCM_NEWCELL (cont);
  73   *answer = cont;
  74   SCM_DEFER_INTS;
  75   SCM_SETJMPBUF (cont, scm_must_malloc ((long) sizeof (regs), s_cont));
  76   SCM_CAR (cont) = scm_tc7_contin;
  77   SCM_DYNENV (cont) = scm_dynwinds;
  78   SCM_THROW_VALUE = SCM_EOL;
  79   SCM_BASE (cont) = SCM_BASE (rootcont);
  80   SCM_SEQ (cont) = SCM_SEQ (rootcont);
  81   SCM_ALLOW_INTS;
  82 #else
  83   register SCM_STACKITEM *src, *dst;
  84
  85 #if 0
  86   {
  87     SCM winds;
  88
  89     for (winds = scm_dynwinds; winds != SCM_EOL; winds = SCM_CDR (winds))
  90       {
  91         if (SCM_INUMP (SCM_CAR (winds)))
  92           {
  93             scm_relocate_chunk_to_heap (SCM_CAR (winds));
  94           }
  95       }
  96   }
  97 #endif
  98
  99   SCM_NEWCELL (cont);
 100   *answer = cont;
 101   SCM_DEFER_INTS;
 102   SCM_FLUSH_REGISTER_WINDOWS;
 103   j = scm_stack_size (SCM_BASE (scm_rootcont));
 104   SCM_SETJMPBUF (cont,
 105              scm_must_malloc ((long) (sizeof (regs) + j * sizeof (SCM_STACKITEM)),
 106                               s_cont));
 107   SCM_SETLENGTH (cont, j, scm_tc7_contin);
 108   SCM_DYNENV (cont) = scm_dynwinds;
 109   SCM_THROW_VALUE (cont) = SCM_EOL;
 110   src = SCM_BASE (cont) = SCM_BASE (scm_rootcont);
 111   SCM_SEQ (cont) = SCM_SEQ (scm_rootcont);
 112   SCM_ALLOW_INTS;
 113 #ifndef SCM_STACK_GROWS_UP
 114   src -= SCM_LENGTH (cont);
 115 #endif /* ndef SCM_STACK_GROWS_UP */
 116   dst = (SCM_STACKITEM *) (SCM_CHARS (cont) + sizeof (regs));
 117   for (j = SCM_LENGTH (cont); 0 <= --j;)
 118     *dst++ = *src++;
 119 #endif /* def CHEAP_CONTINUATIONS */
 120 #ifdef DEBUG_EXTENSIONS
 121   SCM_DFRAME (cont) = last_debug_info_frame;
 122 #endif
 123   return cont;
 124 }
 125
 126
 127 void scm_dynthrow PROTO ((SCM *a));
 128
 129 /* Grow the stack so that there is room */
 130 /* to copy in the continuation.  Then */
 131 #ifndef CHEAP_CONTINUATIONS
 132 #ifdef __STDC__
 133 static void
 134 grow_throw (SCM *a)
 135 #else
 136 static void
 137 grow_throw (a)
 138      SCM *a;
 139 #endif
 140 {                               /* retry the throw. */
 141   SCM growth[100];
 142   growth[0] = a[0];
 143   growth[1] = a[1];
 144   growth[2] = a[2] + 1;
 145   growth[3] = (SCM) a;
 146   scm_dynthrow (growth);
 147 }
 148 #endif /* ndef CHEAP_CONTINUATIONS */
 149
 150 #ifdef __STDC__
 151 void
 152 scm_dynthrow (SCM *a)
 153 #else
 154 void
 155 scm_dynthrow (a)
 156      SCM *a;
 157 #endif
 158 {
 159   SCM cont = a[0], val = a[1];
 160 #ifndef CHEAP_CONTINUATIONS
 161   register long j;
 162   register SCM_STACKITEM *src, *dst = SCM_BASE (scm_rootcont);
 163 #ifdef SCM_STACK_GROWS_UP
 164   if (a[2] && (a - ((SCM *) a[3]) < 100))
 165 #else
 166   if (a[2] && (((SCM *) a[3]) - a < 100))
 167 #endif
 168     fputs ("grow_throw: check if SCM growth[100]; being optimized out\n",
 169            stderr);
 170   /* if (a[2]) fprintf(stderr, " ct = %ld, dist = %ld\n",
 171                           a[2], (((SCM *)a[3]) - a)); */
 172 #ifdef SCM_STACK_GROWS_UP
 173   if (SCM_PTR_GE (dst + SCM_LENGTH (cont), (SCM_STACKITEM *) & a))
 174     grow_throw (a);
 175 #else
 176   dst -= SCM_LENGTH (cont);
 177   if (SCM_PTR_LE (dst, (SCM_STACKITEM *) & a))
 178     grow_throw (a);
 179 #endif /* def SCM_STACK_GROWS_UP */
 180   SCM_FLUSH_REGISTER_WINDOWS;
 181   src = (SCM_STACKITEM *) (SCM_CHARS (cont) + sizeof (regs));
 182   for (j = SCM_LENGTH (cont); 0 <= --j;)
 183     *dst++ = *src++;
 184 #ifdef sparc                    /* clear out stack up to this stackframe */
 185   /* maybe this would help, maybe not */
 186 /*      bzero((void *)&a, sizeof(SCM_STACKITEM) * (((SCM_STACKITEM *)&a) -
 187                                                (dst - SCM_LENGTH(cont)))) */
 188 #endif
 189 #endif /* ndef CHEAP_CONTINUATIONS */
 190 #ifdef DEBUG_EXTENSIONS
 191   last_debug_info_frame = SCM_DFRAME (cont);
 192 #endif
 193   SCM_THROW_VALUE(cont) = val;
 194   longjmp (SCM_JMPBUF (cont), 1);
 195 }
 196
 197 #ifdef __STDC__
 198 SCM
 199 scm_call_continuation (SCM cont, SCM val)
 200 #else
 201 SCM
 202 scm_call_continuation (cont, val)
 203      SCM cont;
 204      SCM val;
 205 #endif
 206 {
 207   SCM a[3];
 208   a[0] = cont;
 209   a[1] = val;
 210   a[2] = 0;
 211   if (   (SCM_SEQ (cont) != SCM_SEQ (scm_rootcont))
 212       || (SCM_BASE (cont) != SCM_BASE (scm_rootcont)))  /* base compare not needed */
 213     scm_wta (cont, "continuation from wrong top level", s_cont);
 214
 215   scm_dowinds (SCM_DYNENV (cont),
 216                scm_ilength (scm_dynwinds) - scm_ilength (SCM_DYNENV (cont)));
 217
 218   scm_dynthrow (a);
 219   return SCM_UNSPECIFIED; /* not reached */
 220 }
 221
 222
 223 #ifdef __STDC__
 224 void
 225 scm_init_continuations (void)
 226 #else
 227 void
 228 scm_init_continuations ()
 229 #endif
 230 {
 231 #include "continuations.x"
 232 }
 233