libguile/continuations.c

   1 /*      Copyright (C) 1995,1996,1998 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 "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
  60 SCM
  61 scm_make_cont (answer)
  62      SCM * answer;
  63 {
  64   long j;
  65   SCM cont;
  66
  67 #ifdef CHEAP_CONTINUATIONS
  68   SCM_NEWCELL (cont);
  69   *answer = cont;
  70   SCM_ENTER_A_SECTION;
  71   SCM_SETJMPBUF (cont, scm_must_malloc ((long) sizeof (scm_contregs), s_cont));
  72   SCM_DYNENV (cont) = scm_dynwinds;
  73   SCM_THROW_VALUE = SCM_EOL;
  74   SCM_BASE (cont) = SCM_BASE (rootcont);
  75   SCM_SEQ (cont) = SCM_SEQ (rootcont);
  76   SCM_SETCAR (cont, scm_tc7_contin);
  77   SCM_EXIT_A_SECTION;
  78 #else
  79   register SCM_STACKITEM *src, *dst;
  80
  81 #if 0
  82   {
  83     SCM winds;
  84
  85     for (winds = scm_dynwinds; winds != SCM_EOL; winds = SCM_CDR (winds))
  86       {
  87         if (SCM_INUMP (SCM_CAR (winds)))
  88           {
  89             scm_relocate_chunk_to_heap (SCM_CAR (winds));
  90           }
  91       }
  92   }
  93 #endif
  94
  95   SCM_NEWCELL (cont);
  96   *answer = cont;
  97   SCM_ENTER_A_SECTION;
  98   SCM_FLUSH_REGISTER_WINDOWS;
  99   j = scm_stack_size (SCM_BASE (scm_rootcont));
 100   SCM_SETJMPBUF (cont,
 101              scm_must_malloc ((long) (sizeof (scm_contregs) + j * sizeof (SCM_STACKITEM)),
 102                               s_cont));
 103   SCM_DYNENV (cont) = scm_dynwinds;
 104   SCM_THROW_VALUE (cont) = SCM_EOL;
 105   src = SCM_BASE (cont) = SCM_BASE (scm_rootcont);
 106   SCM_SEQ (cont) = SCM_SEQ (scm_rootcont);
 107   SCM_SETLENGTH (cont, j, scm_tc7_contin);
 108   SCM_EXIT_A_SECTION;
 109 #ifndef SCM_STACK_GROWS_UP
 110   src -= SCM_LENGTH (cont);
 111 #endif /* ndef SCM_STACK_GROWS_UP */
 112   dst = (SCM_STACKITEM *) (SCM_CHARS (cont) + sizeof (scm_contregs));
 113   for (j = SCM_LENGTH (cont); 0 <= --j;)
 114     *dst++ = *src++;
 115 #endif /* def CHEAP_CONTINUATIONS */
 116 #ifdef DEBUG_EXTENSIONS
 117   SCM_DFRAME (cont) = scm_last_debug_frame;
 118 #endif
 119   return cont;
 120 }
 121
 122 /* Grow the stack so that there is room */
 123 /* to copy in the continuation.  Then */
 124 #ifndef CHEAP_CONTINUATIONS
 125
 126 static void grow_throw SCM_P ((SCM *a));
 127
 128 static void
 129 grow_throw (a)
 130      SCM *a;
 131 {                               /* retry the throw. */
 132   SCM growth[100];
 133   growth[0] = a[0];
 134   growth[1] = a[1];
 135   growth[2] = a[2] + 1;
 136   growth[3] = (SCM) a;
 137   scm_dynthrow (growth);
 138 }
 139 #endif /* ndef CHEAP_CONTINUATIONS */
 140
 141
 142 void
 143 scm_dynthrow (a)
 144      SCM *a;
 145 {
 146   SCM cont = a[0], val = a[1];
 147 #ifndef CHEAP_CONTINUATIONS
 148   register long j;
 149   register SCM_STACKITEM *src, *dst = SCM_BASE (scm_rootcont);
 150 #ifdef SCM_STACK_GROWS_UP
 151   if (a[2] && (a - ((SCM *) a[3]) < 100))
 152 #else
 153   if (a[2] && (((SCM *) a[3]) - a < 100))
 154 #endif
 155     fputs ("grow_throw: check if SCM growth[100]; being optimized out\n",
 156            stderr);
 157   /* if (a[2]) fprintf(stderr, " ct = %ld, dist = %ld\n",
 158                           a[2], (((SCM *)a[3]) - a)); */
 159 #ifdef SCM_STACK_GROWS_UP
 160   if (SCM_PTR_GE (dst + SCM_LENGTH (cont), (SCM_STACKITEM *) & a))
 161     grow_throw (a);
 162 #else
 163   dst -= SCM_LENGTH (cont);
 164   if (SCM_PTR_LE (dst, (SCM_STACKITEM *) & a))
 165     grow_throw (a);
 166 #endif /* def SCM_STACK_GROWS_UP */
 167   SCM_FLUSH_REGISTER_WINDOWS;
 168   src = (SCM_STACKITEM *) (SCM_CHARS (cont) + sizeof (scm_contregs));
 169   for (j = SCM_LENGTH (cont); 0 <= --j;)
 170     *dst++ = *src++;
 171 #ifdef sparc                    /* clear out stack up to this stackframe */
 172   /* maybe this would help, maybe not */
 173 /*      bzero((void *)&a, sizeof(SCM_STACKITEM) * (((SCM_STACKITEM *)&a) -
 174                                                (dst - SCM_LENGTH(cont)))) */
 175 #endif
 176 #endif /* ndef CHEAP_CONTINUATIONS */
 177 #ifdef DEBUG_EXTENSIONS
 178   scm_last_debug_frame = SCM_DFRAME (cont);
 179 #endif
 180   SCM_THROW_VALUE(cont) = val;
 181   longjmp (SCM_JMPBUF (cont), 1);
 182 }
 183
 184
 185 SCM
 186 scm_call_continuation (cont, val)
 187      SCM cont;
 188      SCM val;
 189 {
 190   SCM a[3];
 191   a[0] = cont;
 192   a[1] = val;
 193   a[2] = 0;
 194   if (   (SCM_SEQ (cont) != SCM_SEQ (scm_rootcont))
 195       || (SCM_BASE (cont) != SCM_BASE (scm_rootcont)))  /* base compare not needed */
 196     scm_wta (cont, "continuation from wrong top level", s_cont);
 197
 198   scm_dowinds (SCM_DYNENV (cont),
 199                scm_ilength (scm_dynwinds) - scm_ilength (SCM_DYNENV (cont)));
 200
 201   scm_dynthrow (a);
 202   return SCM_UNSPECIFIED; /* not reached */
 203 }
 204
 205
 206
 207 void
 208 scm_init_continuations ()
 209 {
 210 #include "continuations.x"
 211 }
 212