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

/*	Copyright (C) 1995, 1996, 1998, 1999, 2000 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 "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.\n\n"
	    "@var{in-guard} is called, then @var{thunk}, then @var{out-guard}.\n\n"
	    "If, any time during the execution of @var{thunk}, the continuation\n"
	    "of the @code{dynamic-wind} expression is escaped non-locally, @var{out-guard}\n"
	    "is called.   If the continuation of the dynamic-wind is re-entered,\n"
	    "@var{in-guard} is called.   Thus @var{in-guard} and @var{out-guard} may\n"
	    "be called any number of times.\n\n"
	    "@example\n"
	    "(define x 'normal-binding)\n"
	    "@result{} x\n\n"
	    "(define a-cont  (call-with-current-continuation \n"
	    "		  (lambda (escape)\n"
	    "		     (let ((old-x x))\n"
	    "		       (dynamic-wind\n"
	    "			  ;; in-guard:\n"
	    "			  ;;\n"
	    "			  (lambda () (set! x 'special-binding))\n\n"
	    "			  ;; thunk\n"
	    "			  ;;\n"
	    "		 	  (lambda () (display x) (newline)\n"
	    "				     (call-with-current-continuation escape)\n"
	    "				     (display x) (newline)\n"
	    "				     x)\n\n"
	    "			  ;; out-guard:\n"
	    "			  ;;\n"
	    "			  (lambda () (set! x old-x)))))))\n\n"
	    ";; Prints: \n"
	    "special-binding\n"
	    ";; Evaluates to:\n"
	    "@result{} a-cont\n\n"
	    "x\n"
	    "@result{} normal-binding\n\n"
	    "(a-cont #f)\n"
	    ";; Prints:\n"
	    "special-binding\n"
	    ";; Evaluates to:\n"
	    "@result{} a-cont  ;; the value of the (define a-cont...)\n\n"
	    "x\n"
	    "@result{} normal-binding\n\n"
	    "a-cont\n"
	    "@result{} special-binding\n"
	    "@end example\n"
	    "")
#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.
 */

#define SCM_GUARDSP(obj) SCM_SMOB_PREDICATE (tc16_guards, obj)
#define SCM_BEFORE_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 1))
#define SCM_AFTER_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 2))
#define SCM_GUARD_DATA(obj) ((void *) SCM_CELL_WORD (obj, 3))

static long tc16_guards;

static int
printguards (SCM exp, SCM port, scm_print_state *pstate)
{
  scm_puts ("#<guards ", port);
  scm_intprint (SCM_UNPACK (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;
  before (guard_data);
  SCM_NEWSMOB3 (guards, tc16_guards, before, after, guard_data);
  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", 0,
                                         NULL, scm_free0, printguards, NULL);
#include "dynwind.x"
}
Commit	Line	Data
bd47429e	1	/* Copyright (C) 1995, 1996, 1998, 1999, 2000 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	52	#include "smob.h"
0f2d19dd	53
20e6290e	54	#include "dynwind.h"
0f2d19dd JB	55	\f
	56
	57	/* {Dynamic wind}
b3460a50 MV	58
	59	Things that can be on the wind list:
	60
	61	(enter-proc . leave-proc) dynamic-wind
	62	(tag . jmpbuf) catch
	63	(tag . lazy-catch) lazy-catch
	64	tag is either a symbol or a boolean
	65
	66	((fluid ...) . (value ...)) with-fluids
	67
	68	*/
0f2d19dd JB	69
	70
	71
3b3b36dd	72	SCM_DEFINE (scm_dynamic_wind, "dynamic-wind", 3, 0, 0,
1bbd0b84	73	(SCM thunk1, SCM thunk2, SCM thunk3),
b380b885 MD	74	"All three arguments must be 0-argument procedures.\n\n"
	75	"@var{in-guard} is called, then @var{thunk}, then @var{out-guard}.\n\n"
	76	"If, any time during the execution of @var{thunk}, the continuation\n"
	77	"of the @code{dynamic-wind} expression is escaped non-locally, @var{out-guard}\n"
	78	"is called. If the continuation of the dynamic-wind is re-entered,\n"
	79	"@var{in-guard} is called. Thus @var{in-guard} and @var{out-guard} may\n"
	80	"be called any number of times.\n\n"
	81	"@example\n"
	82	"(define x 'normal-binding)\n"
	83	"@result{} x\n\n"
	84	"(define a-cont (call-with-current-continuation \n"
	85	" (lambda (escape)\n"
	86	" (let ((old-x x))\n"
	87	" (dynamic-wind\n"
	88	" ;; in-guard:\n"
	89	" ;;\n"
	90	" (lambda () (set! x 'special-binding))\n\n"
	91	" ;; thunk\n"
	92	" ;;\n"
	93	" (lambda () (display x) (newline)\n"
	94	" (call-with-current-continuation escape)\n"
	95	" (display x) (newline)\n"
	96	" x)\n\n"
	97	" ;; out-guard:\n"
	98	" ;;\n"
	99	" (lambda () (set! x old-x)))))))\n\n"
	100	";; Prints: \n"
	101	"special-binding\n"
	102	";; Evaluates to:\n"
	103	"@result{} a-cont\n\n"
	104	"x\n"
	105	"@result{} normal-binding\n\n"
	106	"(a-cont #f)\n"
	107	";; Prints:\n"
	108	"special-binding\n"
	109	";; Evaluates to:\n"
	110	"@result{} a-cont ;; the value of the (define a-cont...)\n\n"
	111	"x\n"
	112	"@result{} normal-binding\n\n"
	113	"a-cont\n"
	114	"@result{} special-binding\n"
	115	"@end example\n"
	116	"")
1bbd0b84	117	#define FUNC_NAME s_scm_dynamic_wind
0f2d19dd JB	118	{
0f2d19dd JB	119	SCM ans;
6778caf9 MD	120	SCM_ASSERT (SCM_NFALSEP (scm_thunk_p (thunk3)),
6778caf9 MD	121	thunk3,
1bbd0b84	122	SCM_ARG3, FUNC_NAME);
0f2d19dd JB	123	scm_apply (thunk1, SCM_EOL, SCM_EOL);
	124	scm_dynwinds = scm_acons (thunk1, thunk3, scm_dynwinds);
	125	ans = scm_apply (thunk2, SCM_EOL, SCM_EOL);
	126	scm_dynwinds = SCM_CDR (scm_dynwinds);
	127	scm_apply (thunk3, SCM_EOL, SCM_EOL);
	128	return ans;
	129	}
1bbd0b84	130	#undef FUNC_NAME
0f2d19dd	131
3346a90f MD	132	/* The implementation of a C-callable dynamic-wind,
	133	* scm_internal_dynamic_wind, requires packaging of C pointers in a
	134	* smob. Objects of this type are pushed onto the dynwind chain.
	135	*/
	136
bd47429e MD	137	#define SCM_GUARDSP(obj) SCM_SMOB_PREDICATE (tc16_guards, obj)
	138	#define SCM_BEFORE_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 1))
	139	#define SCM_AFTER_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 2))
	140	#define SCM_GUARD_DATA(obj) ((void *) SCM_CELL_WORD (obj, 3))
3346a90f MD	141
	142	static long tc16_guards;
	143
3346a90f MD	144	static int
	145	printguards (SCM exp, SCM port, scm_print_state *pstate)
	146	{
	147	scm_puts ("#<guards ", port);
f1267706	148	scm_intprint (SCM_UNPACK (SCM_CDR (exp)), 16, port);
3346a90f MD	149	scm_putc ('>', port);
	150	return 1;
	151	}
	152
3346a90f MD	153	SCM
	154	scm_internal_dynamic_wind (scm_guard_t before,
	155	scm_inner_t inner,
	156	scm_guard_t after,
	157	void *inner_data,
	158	void *guard_data)
	159	{
	160	SCM guards, ans;
3346a90f	161	before (guard_data);
bd47429e	162	SCM_NEWSMOB3 (guards, tc16_guards, before, after, guard_data);
3346a90f MD	163	scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
	164	ans = inner (inner_data);
	165	scm_dynwinds = SCM_CDR (scm_dynwinds);
	166	after (guard_data);
	167	return ans;
	168	}
1cc91f1b	169
c2654ef0	170	#ifdef GUILE_DEBUG
a1ec6916	171	SCM_DEFINE (scm_wind_chain, "wind-chain", 0, 0, 0,
1bbd0b84	172	(),
b380b885	173	"")
1bbd0b84	174	#define FUNC_NAME s_scm_wind_chain
c2654ef0 MD	175	{
	176	return scm_dynwinds;
	177	}
1bbd0b84	178	#undef FUNC_NAME
c2654ef0 MD	179	#endif
c2654ef0 MD	180
6778caf9 MD	181	static void
	182	scm_swap_bindings (SCM glocs, SCM vals)
	183	{
	184	SCM tmp;
	185	while (SCM_NIMP (vals))
	186	{
	187	tmp = SCM_GLOC_VAL (SCM_CAR (glocs));
	188	SCM_SETCDR (SCM_CAR (glocs) - 1L, SCM_CAR (vals));
	189	SCM_SETCAR (vals, tmp);
	190	glocs = SCM_CDR (glocs);
	191	vals = SCM_CDR (vals);
	192	}
	193	}
c2654ef0	194
0f2d19dd	195	void
6e8d25a6	196	scm_dowinds (SCM to, long delta)
0f2d19dd JB	197	{
	198	tail:
	199	if (scm_dynwinds == to);
	200	else if (0 > delta)
	201	{
	202	SCM wind_elt;
	203	SCM wind_key;
	204
	205	scm_dowinds (SCM_CDR (to), 1 + delta);
	206	wind_elt = SCM_CAR (to);
	207	#if 0
	208	if (SCM_INUMP (wind_elt))
	209	{
	210	scm_cross_dynwind_binding_scope (wind_elt, 0);
	211	}
	212	else
	213	#endif
	214	{
	215	wind_key = SCM_CAR (wind_elt);
6778caf9 MD	216	/* key = #t \| symbol \| thunk \| list of glocs \| list of fluids */
6778caf9 MD	217	if (SCM_NIMP (wind_key))
b3460a50	218	{
6778caf9 MD	219	if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
6778caf9 MD	220	scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
4725c298 MD	221	else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
	222	scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
	223	else if (SCM_GUARDSP (wind_key))
	224	SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	225	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
	226	scm_apply (wind_key, SCM_EOL, SCM_EOL);
b3460a50	227	}
0f2d19dd JB	228	}
	229	scm_dynwinds = to;
	230	}
	231	else
	232	{
	233	SCM from;
	234	SCM wind_elt;
	235	SCM wind_key;
	236
	237	from = SCM_CDR (SCM_CAR (scm_dynwinds));
	238	wind_elt = SCM_CAR (scm_dynwinds);
	239	scm_dynwinds = SCM_CDR (scm_dynwinds);
	240	#if 0
	241	if (SCM_INUMP (wind_elt))
	242	{
	243	scm_cross_dynwind_binding_scope (wind_elt, 0);
	244	}
	245	else
	246	#endif
	247	{
	248	wind_key = SCM_CAR (wind_elt);
6778caf9	249	if (SCM_NIMP (wind_key))
b3460a50	250	{
6778caf9 MD	251	if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
6778caf9 MD	252	scm_swap_bindings (wind_key, from);
4725c298 MD	253	else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
	254	scm_swap_fluids_reverse (wind_key, from);
	255	else if (SCM_GUARDSP (wind_key))
	256	SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	257	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
	258	scm_apply (from, SCM_EOL, SCM_EOL);
b3460a50	259	}
0f2d19dd JB	260	}
	261	delta--;
	262	goto tail; /* scm_dowinds(to, delta-1); */
	263	}
	264	}
	265
	266
1cc91f1b	267
0f2d19dd JB	268	void
0f2d19dd JB	269	scm_init_dynwind ()
0f2d19dd	270	{
bd47429e MD	271	tc16_guards = scm_make_smob_type_mfpe ("guards", 0,
bd47429e MD	272	NULL, scm_free0, printguards, NULL);
0f2d19dd JB	273	#include "dynwind.x"
0f2d19dd JB	274	}