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 /* Grow the stack so that there is room */
 127 /* to copy in the continuation.  Then */
 128 #ifndef CHEAP_CONTINUATIONS
 129 #ifdef __STDC__
 130 static void
 131 grow_throw (SCM *a)
 132 #else
 133 static void
 134 grow_throw (a)
 135      SCM *a;
 136 #endif
 137 {                               /* retry the throw. */
 138   SCM growth[100];
 139   growth[0] = a[0];
 140   growth[1] = a[1];
 141   growth[2] = a[2] + 1;
 142   growth[3] = (SCM) a;
 143   scm_dynthrow (growth);
 144 }
 145 #endif /* ndef CHEAP_CONTINUATIONS */
 146
 147 #ifdef __STDC__
 148 void
 149 scm_dynthrow (SCM *a)
 150 #else
 151 void
 152 scm_dynthrow (a)
 153      SCM *a;
 154 #endif
 155 {
 156   SCM cont = a[0], val = a[1];
 157 #ifndef CHEAP_CONTINUATIONS
 158   register long j;
 159   register SCM_STACKITEM *src, *dst = SCM_BASE (scm_rootcont);
 160 #ifdef SCM_STACK_GROWS_UP
 161   if (a[2] && (a - ((SCM *) a[3]) < 100))
 162 #else
 163   if (a[2] && (((SCM *) a[3]) - a < 100))
 164 #endif
 165     fputs ("grow_throw: check if SCM growth[100]; being optimized out\n",
 166            stderr);
 167   /* if (a[2]) fprintf(stderr, " ct = %ld, dist = %ld\n",
 168                           a[2], (((SCM *)a[3]) - a)); */
 169 #ifdef SCM_STACK_GROWS_UP
 170   if (SCM_PTR_GE (dst + SCM_LENGTH (cont), (SCM_STACKITEM *) & a))
 171     grow_throw (a);
 172 #else
 173   dst -= SCM_LENGTH (cont);
 174   if (SCM_PTR_LE (dst, (SCM_STACKITEM *) & a))
 175     grow_throw (a);
 176 #endif /* def SCM_STACK_GROWS_UP */
 177   SCM_FLUSH_REGISTER_WINDOWS;
 178   src = (SCM_STACKITEM *) (SCM_CHARS (cont) + sizeof (regs));
 179   for (j = SCM_LENGTH (cont); 0 <= --j;)
 180     *dst++ = *src++;
 181 #ifdef sparc                    /* clear out stack up to this stackframe */
 182   /* maybe this would help, maybe not */
 183 /*      bzero((void *)&a, sizeof(SCM_STACKITEM) * (((SCM_STACKITEM *)&a) -
 184                                                (dst - SCM_LENGTH(cont)))) */
 185 #endif
 186 #endif /* ndef CHEAP_CONTINUATIONS */
 187 #ifdef DEBUG_EXTENSIONS
 188   last_debug_info_frame = SCM_DFRAME (cont);
 189 #endif
 190   SCM_THROW_VALUE(cont) = val;
 191   longjmp (SCM_JMPBUF (cont), 1);
 192 }
 193
 194 #ifdef __STDC__
 195 SCM
 196 scm_call_continuation (SCM cont, SCM val)
 197 #else
 198 SCM
 199 scm_call_continuation (cont, val)
 200      SCM cont;
 201      SCM val;
 202 #endif
 203 {
 204   SCM a[3];
 205   a[0] = cont;
 206   a[1] = val;
 207   a[2] = 0;
 208   if (   (SCM_SEQ (cont) != SCM_SEQ (scm_rootcont))
 209       || (SCM_BASE (cont) != SCM_BASE (scm_rootcont)))  /* base compare not needed */
 210     scm_wta (cont, "continuation from wrong top level", s_cont);
 211
 212   scm_dowinds (SCM_DYNENV (cont),
 213                scm_ilength (scm_dynwinds) - scm_ilength (SCM_DYNENV (cont)));
 214
 215   scm_dynthrow (a);
 216   return SCM_UNSPECIFIED; /* not reached */
 217 }
 218
 219
 220 #ifdef __STDC__
 221 void
 222 scm_init_continuations (void)
 223 #else
 224 void
 225 scm_init_continuations ()
 226 #endif
 227 {
 228 #include "continuations.x"
 229 }
 230