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/* Copyright (C) 1995,1996,1998,2000,2001 Free Software Foundation, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307 USA
*
* As a special exception, the Free Software Foundation gives permission
* for additional uses of the text contained in its release of GUILE.
*
* The exception is that, if you link the GUILE library with other files
* to produce an executable, this does not by itself cause the
* resulting executable to be covered by the GNU General Public License.
* Your use of that executable is in no way restricted on account of
* linking the GUILE library code into it.
*
* This exception does not however invalidate any other reasons why
* the executable file might be covered by the GNU General Public License.
*
* This exception applies only to the code released by the
* Free Software Foundation under the name GUILE. If you copy
* code from other Free Software Foundation releases into a copy of
* GUILE, as the General Public License permits, the exception does
* not apply to the code that you add in this way. To avoid misleading
* anyone as to the status of such modified files, you must delete
* this exception notice from them.
*
* If you write modifications of your own for GUILE, it is your choice
* whether to permit this exception to apply to your modifications.
* If you do not wish that, delete this exception notice. */
/* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
#include <string.h>
#include "libguile/_scm.h"
#include "libguile/root.h"
#include "libguile/stackchk.h"
#include "libguile/smob.h"
#include "libguile/ports.h"
#include "libguile/dynwind.h"
#include "libguile/values.h"
#ifdef DEBUG_EXTENSIONS
#include "libguile/debug.h"
#endif
#include "libguile/validate.h"
#include "libguile/continuations.h"
/* {Continuations}
*/
scm_t_bits scm_tc16_continuation;
static SCM
continuation_mark (SCM obj)
{
scm_t_contregs *continuation = SCM_CONTREGS (obj);
scm_gc_mark (continuation->throw_value);
scm_mark_locations (continuation->stack, continuation->num_stack_items);
return continuation->dynenv;
}
static size_t
continuation_free (SCM obj)
{
scm_t_contregs *continuation = SCM_CONTREGS (obj);
/* stack array size is 1 if num_stack_items is 0 (rootcont). */
size_t extra_items = (continuation->num_stack_items > 0)
? (continuation->num_stack_items - 1)
: 0;
size_t bytes_free = sizeof (scm_t_contregs)
+ extra_items * sizeof (SCM_STACKITEM);
scm_must_free (continuation);
return bytes_free;
}
static int
continuation_print (SCM obj, SCM port, scm_print_state *state SCM_UNUSED)
{
scm_t_contregs *continuation = SCM_CONTREGS (obj);
scm_puts ("#<continuation ", port);
scm_intprint (continuation->num_stack_items, 10, port);
scm_puts (" @ ", port);
scm_intprint (SCM_CELL_WORD_1 (obj), 16, port);
scm_putc ('>', port);
return 1;
}
/* this may return more than once: the first time with the escape
procedure, then subsequently with the value to be passed to the
continuation. */
#define FUNC_NAME "scm_make_continuation"
SCM
scm_make_continuation (int *first)
{
volatile SCM cont;
scm_t_contregs *continuation;
scm_t_contregs *rootcont = SCM_CONTREGS (scm_rootcont);
long stack_size;
SCM_STACKITEM * src;
SCM_ENTER_A_SECTION;
SCM_FLUSH_REGISTER_WINDOWS;
stack_size = scm_stack_size (rootcont->base);
continuation = scm_must_malloc (sizeof (scm_t_contregs)
+ (stack_size - 1) * sizeof (SCM_STACKITEM),
FUNC_NAME);
continuation->num_stack_items = stack_size;
continuation->dynenv = scm_dynwinds;
continuation->throw_value = SCM_EOL;
continuation->base = src = rootcont->base;
continuation->seq = rootcont->seq;
#ifdef DEBUG_EXTENSIONS
continuation->dframe = scm_last_debug_frame;
#endif
SCM_NEWSMOB (cont, scm_tc16_continuation, continuation);
SCM_EXIT_A_SECTION;
#ifndef SCM_STACK_GROWS_UP
src -= stack_size;
#endif
memcpy (continuation->stack, src, sizeof (SCM_STACKITEM) * stack_size);
if (setjmp (continuation->jmpbuf))
{
*first = 0;
return continuation->throw_value;
}
else
{
*first = 1;
return cont;
}
}
#undef FUNC_NAME
static void scm_dynthrow (SCM, SCM);
/* Grow the stack by a fixed amount to provide space to copy in the
* continuation. Possibly this function has to be called several times
* recursively before enough space is available. Make sure the compiler does
* not optimize the growth array away by storing it's address into a global
* variable.
*/
scm_t_bits scm_i_dummy;
static void
grow_stack (SCM cont, SCM val)
{
scm_t_bits growth[100];
scm_i_dummy = (scm_t_bits) growth;
scm_dynthrow (cont, val);
}
/* Copy the continuation stack into the current stack. Calling functions from
* within this function is safe, since only stack frames below this function's
* own frame are overwritten. Thus, memcpy can be used for best performance.
*/
static void
copy_stack_and_call (scm_t_contregs *continuation, SCM val,
SCM_STACKITEM * dst)
{
memcpy (dst, continuation->stack,
sizeof (SCM_STACKITEM) * continuation->num_stack_items);
#ifdef DEBUG_EXTENSIONS
scm_last_debug_frame = continuation->dframe;
#endif
continuation->throw_value = val;
longjmp (continuation->jmpbuf, 1);
}
/* Call grow_stack until the stack space is large enough, then, as the current
* stack frame might get overwritten, let copy_stack_and_call perform the
* actual copying and continuation calling.
*/
static void
scm_dynthrow (SCM cont, SCM val)
{
scm_t_contregs *continuation = SCM_CONTREGS (cont);
SCM_STACKITEM * dst = SCM_BASE (scm_rootcont);
SCM_STACKITEM stack_top_element;
#ifdef SCM_STACK_GROWS_UP
if (SCM_PTR_GE (dst + continuation->num_stack_items, &stack_top_element))
grow_stack (cont, val);
#else
dst -= continuation->num_stack_items;
if (SCM_PTR_LE (dst, &stack_top_element))
grow_stack (cont, val);
#endif /* def SCM_STACK_GROWS_UP */
SCM_FLUSH_REGISTER_WINDOWS;
copy_stack_and_call (continuation, val, dst);
}
static SCM
continuation_apply (SCM cont, SCM args)
#define FUNC_NAME "continuation_apply"
{
scm_t_contregs *continuation = SCM_CONTREGS (cont);
scm_t_contregs *rootcont = SCM_CONTREGS (scm_rootcont);
if (continuation->seq != rootcont->seq
/* this base comparison isn't needed */
|| continuation->base != rootcont->base)
{
SCM_MISC_ERROR ("continuation from wrong top level: ~S",
SCM_LIST1 (cont));
}
scm_dowinds (continuation->dynenv,
scm_ilength (scm_dynwinds)
- scm_ilength (continuation->dynenv));
scm_dynthrow (cont, scm_values (args));
return SCM_UNSPECIFIED; /* not reached */
}
#undef FUNC_NAME
void
scm_init_continuations ()
{
scm_tc16_continuation = scm_make_smob_type ("continuation", 0);
scm_set_smob_mark (scm_tc16_continuation, continuation_mark);
scm_set_smob_free (scm_tc16_continuation, continuation_free);
scm_set_smob_print (scm_tc16_continuation, continuation_print);
scm_set_smob_apply (scm_tc16_continuation, continuation_apply, 0, 0, 1);
#ifndef SCM_MAGIC_SNARFER
#include "libguile/continuations.x"
#endif
}
/*
Local Variables:
c-file-style: "gnu"
End:
*/
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