[bpt/guile.git] / libguile / dynwind.c

/*	Copyright (C) 1995, 1996, 1998, 1999 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 */

\f

#include <stdio.h>
#include "_scm.h"
#include "eval.h"
#include "alist.h"
#include "fluids.h"
#include "genio.h"
#include "smob.h"

#include "dynwind.h"
\f

/* {Dynamic wind}
 
   Things that can be on the wind list:

   (enter-proc . leave-proc)     dynamic-wind
   (tag . jmpbuf)                catch
   (tag . lazy-catch)            lazy-catch
     tag is either a symbol or a boolean

   ((fluid ...) . (value ...))   with-fluids

*/


SCM_DEFINE (scm_dynamic_wind, "dynamic-wind", 3, 0, 0,
           (SCM thunk1, SCM thunk2, SCM thunk3),
"All three arguments must be 0-argument procedures.

@var{in-guard} is called, then @var{thunk}, then @var{out-guard}.

If, any time during the execution of @var{thunk}, the continuation
of the @code{dynamic-wind} expression is escaped non-locally, @var{out-guard}
is called.   If the continuation of the dynamic-wind is re-entered,
@var{in-guard} is called.   Thus @var{in-guard} and @var{out-guard} may
be called any number of times.

@example
(define x 'normal-binding)
@result{} x

(define a-cont  (call-with-current-continuation 
		  (lambda (escape)
		     (let ((old-x x))
		       (dynamic-wind
			  ;; in-guard:
			  ;;
			  (lambda () (set! x 'special-binding))

			  ;; thunk
			  ;;
		 	  (lambda () (display x) (newline)
				     (call-with-current-continuation escape)
				     (display x) (newline)
				     x)

			  ;; out-guard:
			  ;;
			  (lambda () (set! x old-x)))))))

;; Prints: 
special-binding
;; Evaluates to:
@result{} a-cont

x
@result{} normal-binding

(a-cont #f)
;; Prints:
special-binding
;; Evaluates to:
@result{} a-cont  ;; the value of the (define a-cont...)

x
@result{} normal-binding

a-cont
@result{} special-binding
@end example
")
#define FUNC_NAME s_scm_dynamic_wind
{
  SCM ans;
  SCM_ASSERT (SCM_NFALSEP (scm_thunk_p (thunk3)),
	      thunk3,
	      SCM_ARG3, FUNC_NAME);
  scm_apply (thunk1, SCM_EOL, SCM_EOL);
  scm_dynwinds = scm_acons (thunk1, thunk3, scm_dynwinds);
  ans = scm_apply (thunk2, SCM_EOL, SCM_EOL);
  scm_dynwinds = SCM_CDR (scm_dynwinds);
  scm_apply (thunk3, SCM_EOL, SCM_EOL);
  return ans;
}
#undef FUNC_NAME

/* The implementation of a C-callable dynamic-wind,
 * scm_internal_dynamic_wind, requires packaging of C pointers in a
 * smob.  Objects of this type are pushed onto the dynwind chain.
 */

typedef struct guardsmem {
  scm_guard_t before;
  scm_guard_t after;
  void *data;
} guardsmem;

#define SCM_GUARDSMEM(obj) ((guardsmem *) SCM_CDR (obj))
#define SCM_BEFORE_GUARD(obj) (SCM_GUARDSMEM (obj)->before)
#define SCM_AFTER_GUARD(obj) (SCM_GUARDSMEM (obj)->after)
#define SCM_GUARD_DATA(obj) (SCM_GUARDSMEM (obj)->data)
#define SCM_GUARDSP(obj) (SCM_NIMP(obj) && (SCM_CAR (obj) == tc16_guards))

static long tc16_guards;

static scm_sizet
freeguards (SCM guards)
{
  scm_must_free ((char *) SCM_CDR (guards));
  return sizeof (guardsmem);
}

static int
printguards (SCM exp, SCM port, scm_print_state *pstate)
{
  scm_puts ("#<guards ", port);
  scm_intprint (SCM_CDR (exp), 16, port);
  scm_putc ('>', port);
  return 1;
}

SCM
scm_internal_dynamic_wind (scm_guard_t before,
			   scm_inner_t inner,
			   scm_guard_t after,
			   void *inner_data,
			   void *guard_data)
{
  SCM guards, ans;
  guardsmem *g;
  before (guard_data);
  g = (guardsmem *) scm_must_malloc (sizeof (*g), "guards");
  g->before = before;
  g->after = after;
  g->data = guard_data;
  SCM_NEWSMOB (guards, tc16_guards, g);
  scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
  ans = inner (inner_data);
  scm_dynwinds = SCM_CDR (scm_dynwinds);
  after (guard_data);
  return ans;
}

#ifdef GUILE_DEBUG
SCM_DEFINE (scm_wind_chain, "wind-chain", 0, 0, 0, 
            (),
"")
#define FUNC_NAME s_scm_wind_chain
{
  return scm_dynwinds;
}
#undef FUNC_NAME
#endif

static void
scm_swap_bindings (SCM glocs, SCM vals)
{
  SCM tmp;
  while (SCM_NIMP (vals))
    {
      tmp = SCM_GLOC_VAL (SCM_CAR (glocs));
      SCM_SETCDR (SCM_CAR (glocs) - 1L, SCM_CAR (vals));
      SCM_SETCAR (vals, tmp);
      glocs = SCM_CDR (glocs);
      vals = SCM_CDR (vals);
    }
}

void 
scm_dowinds (SCM to, long delta)
{
 tail:
  if (scm_dynwinds == to);
  else if (0 > delta)
    {
      SCM wind_elt;
      SCM wind_key;

      scm_dowinds (SCM_CDR (to), 1 + delta);
      wind_elt = SCM_CAR (to);
#if 0
      if (SCM_INUMP (wind_elt))
	{
	  scm_cross_dynwind_binding_scope (wind_elt, 0);
	}
      else
#endif
	{
	  wind_key = SCM_CAR (wind_elt);
	  /* key = #t | symbol | thunk | list of glocs | list of fluids */
	  if (SCM_NIMP (wind_key))
	    {
	      if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
		scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
	      else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
		scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
	      else if (SCM_GUARDSP (wind_key))
		SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	      else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
		scm_apply (wind_key, SCM_EOL, SCM_EOL);
	    }
	}
      scm_dynwinds = to;
    }
  else
    {
      SCM from;
      SCM wind_elt;
      SCM wind_key;

      from = SCM_CDR (SCM_CAR (scm_dynwinds));
      wind_elt = SCM_CAR (scm_dynwinds);
      scm_dynwinds = SCM_CDR (scm_dynwinds);
#if 0
      if (SCM_INUMP (wind_elt))
	{
	  scm_cross_dynwind_binding_scope (wind_elt, 0);
	}
      else
#endif
	{
	  wind_key = SCM_CAR (wind_elt);
	  if (SCM_NIMP (wind_key))
	    {
	      if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
		scm_swap_bindings (wind_key, from);
	      else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
		scm_swap_fluids_reverse (wind_key, from);
	      else if (SCM_GUARDSP (wind_key))
		SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	      else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
		scm_apply (from, SCM_EOL, SCM_EOL);
	    }
	}
      delta--;
      goto tail;		/* scm_dowinds(to, delta-1); */
    }
}


void
scm_init_dynwind ()
{
  tc16_guards = scm_make_smob_type_mfpe ("guards", sizeof (struct guardsmem),
                                        NULL, freeguards, printguards, NULL);
#include "dynwind.x"
}
Commit	Line	Data
78a0461a	1	/* Copyright (C) 1995, 1996, 1998, 1999 Free Software Foundation, Inc.
0f2d19dd JB	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
82892bed JB	15	* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
82892bed JB	16	* Boston, MA 02111-1307 USA
0f2d19dd JB	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.
82892bed	40	* If you do not wish that, delete this exception notice. */
1bbd0b84 GB	41
	42	/* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
	43	gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
	44
0f2d19dd JB	45	\f
	46
	47	#include <stdio.h>
	48	#include "_scm.h"
20e6290e JB	49	#include "eval.h"
20e6290e JB	50	#include "alist.h"
b3460a50	51	#include "fluids.h"
3346a90f MD	52	#include "genio.h"
3346a90f MD	53	#include "smob.h"
0f2d19dd	54
20e6290e	55	#include "dynwind.h"
0f2d19dd JB	56	\f
	57
	58	/* {Dynamic wind}
b3460a50 MV	59
	60	Things that can be on the wind list:
	61
	62	(enter-proc . leave-proc) dynamic-wind
	63	(tag . jmpbuf) catch
	64	(tag . lazy-catch) lazy-catch
	65	tag is either a symbol or a boolean
	66
	67	((fluid ...) . (value ...)) with-fluids
	68
	69	*/
0f2d19dd JB	70
	71
	72
3b3b36dd	73	SCM_DEFINE (scm_dynamic_wind, "dynamic-wind", 3, 0, 0,
1bbd0b84	74	(SCM thunk1, SCM thunk2, SCM thunk3),
4079f87e GB	75	"All three arguments must be 0-argument procedures.
	76
	77	@var{in-guard} is called, then @var{thunk}, then @var{out-guard}.
	78
	79	If, any time during the execution of @var{thunk}, the continuation
	80	of the @code{dynamic-wind} expression is escaped non-locally, @var{out-guard}
	81	is called. If the continuation of the dynamic-wind is re-entered,
	82	@var{in-guard} is called. Thus @var{in-guard} and @var{out-guard} may
	83	be called any number of times.
	84
	85	@example
	86	(define x 'normal-binding)
	87	@result{} x
	88
	89	(define a-cont (call-with-current-continuation
	90	(lambda (escape)
	91	(let ((old-x x))
	92	(dynamic-wind
	93	;; in-guard:
	94	;;
	95	(lambda () (set! x 'special-binding))
	96
	97	;; thunk
	98	;;
	99	(lambda () (display x) (newline)
	100	(call-with-current-continuation escape)
	101	(display x) (newline)
	102	x)
	103
	104	;; out-guard:
	105	;;
	106	(lambda () (set! x old-x)))))))
	107
	108	;; Prints:
	109	special-binding
	110	;; Evaluates to:
	111	@result{} a-cont
	112
	113	x
	114	@result{} normal-binding
	115
	116	(a-cont #f)
	117	;; Prints:
	118	special-binding
	119	;; Evaluates to:
	120	@result{} a-cont ;; the value of the (define a-cont...)
	121
	122	x
	123	@result{} normal-binding
	124
	125	a-cont
	126	@result{} special-binding
	127	@end example
	128	")
1bbd0b84	129	#define FUNC_NAME s_scm_dynamic_wind
0f2d19dd JB	130	{
0f2d19dd JB	131	SCM ans;
6778caf9 MD	132	SCM_ASSERT (SCM_NFALSEP (scm_thunk_p (thunk3)),
6778caf9 MD	133	thunk3,
1bbd0b84	134	SCM_ARG3, FUNC_NAME);
0f2d19dd JB	135	scm_apply (thunk1, SCM_EOL, SCM_EOL);
	136	scm_dynwinds = scm_acons (thunk1, thunk3, scm_dynwinds);
	137	ans = scm_apply (thunk2, SCM_EOL, SCM_EOL);
	138	scm_dynwinds = SCM_CDR (scm_dynwinds);
	139	scm_apply (thunk3, SCM_EOL, SCM_EOL);
	140	return ans;
	141	}
1bbd0b84	142	#undef FUNC_NAME
0f2d19dd	143
3346a90f MD	144	/* The implementation of a C-callable dynamic-wind,
	145	* scm_internal_dynamic_wind, requires packaging of C pointers in a
	146	* smob. Objects of this type are pushed onto the dynwind chain.
	147	*/
	148
	149	typedef struct guardsmem {
	150	scm_guard_t before;
	151	scm_guard_t after;
	152	void *data;
	153	} guardsmem;
	154
	155	#define SCM_GUARDSMEM(obj) ((guardsmem *) SCM_CDR (obj))
	156	#define SCM_BEFORE_GUARD(obj) (SCM_GUARDSMEM (obj)->before)
	157	#define SCM_AFTER_GUARD(obj) (SCM_GUARDSMEM (obj)->after)
	158	#define SCM_GUARD_DATA(obj) (SCM_GUARDSMEM (obj)->data)
d3a6bc94	159	#define SCM_GUARDSP(obj) (SCM_NIMP(obj) && (SCM_CAR (obj) == tc16_guards))
3346a90f MD	160
	161	static long tc16_guards;
	162
	163	static scm_sizet
	164	freeguards (SCM guards)
	165	{
	166	scm_must_free ((char *) SCM_CDR (guards));
	167	return sizeof (guardsmem);
	168	}
	169
	170	static int
	171	printguards (SCM exp, SCM port, scm_print_state *pstate)
	172	{
	173	scm_puts ("#<guards ", port);
	174	scm_intprint (SCM_CDR (exp), 16, port);
	175	scm_putc ('>', port);
	176	return 1;
	177	}
	178
3346a90f MD	179	SCM
	180	scm_internal_dynamic_wind (scm_guard_t before,
	181	scm_inner_t inner,
	182	scm_guard_t after,
	183	void *inner_data,
	184	void *guard_data)
	185	{
	186	SCM guards, ans;
	187	guardsmem *g;
	188	before (guard_data);
3346a90f MD	189	g = (guardsmem ) scm_must_malloc (sizeof (g), "guards");
	190	g->before = before;
	191	g->after = after;
	192	g->data = guard_data;
23a62151	193	SCM_NEWSMOB (guards, tc16_guards, g);
3346a90f MD	194	scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
	195	ans = inner (inner_data);
	196	scm_dynwinds = SCM_CDR (scm_dynwinds);
	197	after (guard_data);
	198	return ans;
	199	}
1cc91f1b	200
c2654ef0	201	#ifdef GUILE_DEBUG
a1ec6916	202	SCM_DEFINE (scm_wind_chain, "wind-chain", 0, 0, 0,
1bbd0b84 GB	203	(),
	204	"")
	205	#define FUNC_NAME s_scm_wind_chain
c2654ef0 MD	206	{
	207	return scm_dynwinds;
	208	}
1bbd0b84	209	#undef FUNC_NAME
c2654ef0 MD	210	#endif
c2654ef0 MD	211
6778caf9 MD	212	static void
	213	scm_swap_bindings (SCM glocs, SCM vals)
	214	{
	215	SCM tmp;
	216	while (SCM_NIMP (vals))
	217	{
	218	tmp = SCM_GLOC_VAL (SCM_CAR (glocs));
	219	SCM_SETCDR (SCM_CAR (glocs) - 1L, SCM_CAR (vals));
	220	SCM_SETCAR (vals, tmp);
	221	glocs = SCM_CDR (glocs);
	222	vals = SCM_CDR (vals);
	223	}
	224	}
c2654ef0	225
0f2d19dd	226	void
6e8d25a6	227	scm_dowinds (SCM to, long delta)
0f2d19dd JB	228	{
	229	tail:
	230	if (scm_dynwinds == to);
	231	else if (0 > delta)
	232	{
	233	SCM wind_elt;
	234	SCM wind_key;
	235
	236	scm_dowinds (SCM_CDR (to), 1 + delta);
	237	wind_elt = SCM_CAR (to);
	238	#if 0
	239	if (SCM_INUMP (wind_elt))
	240	{
	241	scm_cross_dynwind_binding_scope (wind_elt, 0);
	242	}
	243	else
	244	#endif
	245	{
	246	wind_key = SCM_CAR (wind_elt);
6778caf9 MD	247	/* key = #t \| symbol \| thunk \| list of glocs \| list of fluids */
6778caf9 MD	248	if (SCM_NIMP (wind_key))
b3460a50	249	{
6778caf9 MD	250	if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
6778caf9 MD	251	scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
4725c298 MD	252	else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
	253	scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
	254	else if (SCM_GUARDSP (wind_key))
	255	SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	256	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
	257	scm_apply (wind_key, SCM_EOL, SCM_EOL);
b3460a50	258	}
0f2d19dd JB	259	}
	260	scm_dynwinds = to;
	261	}
	262	else
	263	{
	264	SCM from;
	265	SCM wind_elt;
	266	SCM wind_key;
	267
	268	from = SCM_CDR (SCM_CAR (scm_dynwinds));
	269	wind_elt = SCM_CAR (scm_dynwinds);
	270	scm_dynwinds = SCM_CDR (scm_dynwinds);
	271	#if 0
	272	if (SCM_INUMP (wind_elt))
	273	{
	274	scm_cross_dynwind_binding_scope (wind_elt, 0);
	275	}
	276	else
	277	#endif
	278	{
	279	wind_key = SCM_CAR (wind_elt);
6778caf9	280	if (SCM_NIMP (wind_key))
b3460a50	281	{
6778caf9 MD	282	if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
6778caf9 MD	283	scm_swap_bindings (wind_key, from);
4725c298 MD	284	else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
	285	scm_swap_fluids_reverse (wind_key, from);
	286	else if (SCM_GUARDSP (wind_key))
	287	SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	288	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
	289	scm_apply (from, SCM_EOL, SCM_EOL);
b3460a50	290	}
0f2d19dd JB	291	}
	292	delta--;
	293	goto tail; /* scm_dowinds(to, delta-1); */
	294	}
	295	}
	296
	297
1cc91f1b	298
0f2d19dd JB	299	void
0f2d19dd JB	300	scm_init_dynwind ()
0f2d19dd	301	{
23a62151 MD	302	tc16_guards = scm_make_smob_type_mfpe ("guards", sizeof (struct guardsmem),
23a62151 MD	303	NULL, freeguards, printguards, NULL);
0f2d19dd JB	304	#include "dynwind.x"
0f2d19dd JB	305	}