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

/* Copyright (C) 1995,1996,1998,1999,2000,2001 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.  */


\f

#include "libguile/_scm.h"
#include "libguile/eval.h"
#include "libguile/alist.h"
#include "libguile/fluids.h"
#include "libguile/ports.h"
#include "libguile/smob.h"

#include "libguile/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 in_guard, SCM thunk, SCM out_guard),
	    "All three arguments must be 0-argument procedures.\n"
	    "@var{in_guard} is called, then @var{thunk}, then\n"
	    "@var{out_guard}.\n"
	    "\n"
	    "If, any time during the execution of @var{thunk}, the\n"
	    "continuation of the @code{dynamic_wind} expression is escaped\n"
	    "non-locally, @var{out_guard} is called.  If the continuation of\n"
	    "the dynamic-wind is re-entered, @var{in_guard} is called.  Thus\n"
	    "@var{in_guard} and @var{out_guard} may be called any number of\n"
	    "times.\n"
	    "@lisp\n"
	    "(define x 'normal-binding)\n"
	    "@result{} x\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"
	    "x\n"
	    "@result{} normal-binding\n"
	    "(a-cont #f)\n"
	    ";; Prints:\n"
	    "special-binding\n"
	    ";; Evaluates to:\n"
	    "@result{} a-cont  ;; the value of the (define a-cont...)\n"
	    "x\n"
	    "@result{} normal-binding\n"
	    "a-cont\n"
	    "@result{} special-binding\n"
	    "@end lisp")
#define FUNC_NAME s_scm_dynamic_wind
{
  SCM ans;
  SCM_ASSERT (SCM_NFALSEP (scm_thunk_p (out_guard)),
	      out_guard,
	      SCM_ARG3, FUNC_NAME);
  scm_call_0 (in_guard);
  scm_dynwinds = scm_acons (in_guard, out_guard, scm_dynwinds);
  ans = scm_call_0 (thunk);
  scm_dynwinds = SCM_CDR (scm_dynwinds);
  scm_call_0 (out_guard);
  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_TYP16_PREDICATE (tc16_guards, obj)
#define SCM_BEFORE_GUARD(obj) ((scm_t_guard) SCM_CELL_WORD (obj, 1))
#define SCM_AFTER_GUARD(obj) ((scm_t_guard) SCM_CELL_WORD (obj, 2))
#define SCM_GUARD_DATA(obj) ((void *) SCM_CELL_WORD (obj, 3))

static scm_t_bits tc16_guards;

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

SCM
scm_internal_dynamic_wind (scm_t_guard before,
			   scm_t_inner inner,
			   scm_t_guard after,
			   void *inner_data,
			   void *guard_data)
{
  SCM guards, ans;
  before (guard_data);
  SCM_NEWSMOB3 (guards, tc16_guards, (scm_t_bits) before, 
		(scm_t_bits) after, (scm_t_bits) 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, 
            (),
	    "Return the current wind chain. The wind chain contains all\n"
	    "information required by @code{dynamic-wind} to call its\n"
	    "argument thunks when entering/exiting its scope.")
#define FUNC_NAME s_scm_wind_chain
{
  return scm_dynwinds;
}
#undef FUNC_NAME
#endif

static void
scm_swap_bindings (SCM vars, SCM vals)
{
  SCM tmp;
  while (SCM_NIMP (vals))
    {
      tmp = SCM_VARIABLE_REF (SCM_CAR (vars));
      SCM_VARIABLE_SET (SCM_CAR (vars), SCM_CAR (vals));
      SCM_SETCAR (vals, tmp);
      vars = SCM_CDR (vars);
      vals = SCM_CDR (vals);
    }
}

void 
scm_dowinds (SCM to, long delta)
{
 tail:
  if (SCM_EQ_P (to, scm_dynwinds));
  else if (delta < 0)
    {
      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 variables | list of fluids */
	  if (SCM_NIMP (wind_key))
	    {
	      if (SCM_CONSP (wind_key))
		{
		  if (SCM_VARIABLEP (SCM_CAR (wind_key)))
		    scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
		  else if (SCM_FLUIDP (SCM_CAR (wind_key)))
		    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_call_0 (wind_key);
	    }
	}
      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_CONSP (wind_key))
		{
		  if (SCM_VARIABLEP (SCM_CAR (wind_key)))
		    scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
		  else if (SCM_FLUIDP (SCM_CAR (wind_key)))
		    scm_swap_fluids_reverse (wind_key, SCM_CDR (wind_elt));
		}
	      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_call_0 (from);
	    }
	}
      delta--;
      goto tail;		/* scm_dowinds(to, delta-1); */
    }
}


void
scm_init_dynwind ()
{
  tc16_guards = scm_make_smob_type ("guards", 0);
  scm_set_smob_print (tc16_guards, guards_print);
#ifndef SCM_MAGIC_SNARFER
#include "libguile/dynwind.x"
#endif
}

/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/
Commit	Line	Data
e81d98ec	1	/* Copyright (C) 1995,1996,1998,1999,2000,2001 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	41
1bbd0b84	42
0f2d19dd JB	43	\f
0f2d19dd JB	44
a0599745 MD	45	#include "libguile/_scm.h"
	46	#include "libguile/eval.h"
	47	#include "libguile/alist.h"
	48	#include "libguile/fluids.h"
	49	#include "libguile/ports.h"
	50	#include "libguile/smob.h"
0f2d19dd	51
a0599745	52	#include "libguile/dynwind.h"
0f2d19dd JB	53	\f
	54
	55	/* {Dynamic wind}
b3460a50 MV	56
	57	Things that can be on the wind list:
	58
	59	(enter-proc . leave-proc) dynamic-wind
	60	(tag . jmpbuf) catch
	61	(tag . lazy-catch) lazy-catch
	62	tag is either a symbol or a boolean
	63
	64	((fluid ...) . (value ...)) with-fluids
	65
	66	*/
0f2d19dd JB	67
	68
	69
3b3b36dd	70	SCM_DEFINE (scm_dynamic_wind, "dynamic-wind", 3, 0, 0,
1e6808ea MG	71	(SCM in_guard, SCM thunk, SCM out_guard),
	72	"All three arguments must be 0-argument procedures.\n"
	73	"@var{in_guard} is called, then @var{thunk}, then\n"
	74	"@var{out_guard}.\n"
	75	"\n"
	76	"If, any time during the execution of @var{thunk}, the\n"
	77	"continuation of the @code{dynamic_wind} expression is escaped\n"
	78	"non-locally, @var{out_guard} is called. If the continuation of\n"
	79	"the dynamic-wind is re-entered, @var{in_guard} is called. Thus\n"
	80	"@var{in_guard} and @var{out_guard} may be called any number of\n"
	81	"times.\n"
	82	"@lisp\n"
b380b885	83	"(define x 'normal-binding)\n"
1e6808ea	84	"@result{} x\n"
b380b885 MD	85	"(define a-cont (call-with-current-continuation \n"
	86	" (lambda (escape)\n"
	87	" (let ((old-x x))\n"
	88	" (dynamic-wind\n"
	89	" ;; in-guard:\n"
	90	" ;;\n"
1e6808ea MG	91	" (lambda () (set! x 'special-binding))\n"
1e6808ea MG	92	"\n"
b380b885 MD	93	" ;; thunk\n"
	94	" ;;\n"
	95	" (lambda () (display x) (newline)\n"
	96	" (call-with-current-continuation escape)\n"
	97	" (display x) (newline)\n"
1e6808ea MG	98	" x)\n"
1e6808ea MG	99	"\n"
b380b885 MD	100	" ;; out-guard:\n"
b380b885 MD	101	" ;;\n"
1e6808ea MG	102	" (lambda () (set! x old-x)))))))\n"
1e6808ea MG	103	"\n"
b380b885 MD	104	";; Prints: \n"
	105	"special-binding\n"
	106	";; Evaluates to:\n"
1e6808ea	107	"@result{} a-cont\n"
b380b885	108	"x\n"
1e6808ea	109	"@result{} normal-binding\n"
b380b885 MD	110	"(a-cont #f)\n"
	111	";; Prints:\n"
	112	"special-binding\n"
	113	";; Evaluates to:\n"
1e6808ea	114	"@result{} a-cont ;; the value of the (define a-cont...)\n"
b380b885	115	"x\n"
1e6808ea	116	"@result{} normal-binding\n"
b380b885 MD	117	"a-cont\n"
b380b885 MD	118	"@result{} special-binding\n"
1e6808ea	119	"@end lisp")
1bbd0b84	120	#define FUNC_NAME s_scm_dynamic_wind
0f2d19dd JB	121	{
0f2d19dd JB	122	SCM ans;
1e6808ea MG	123	SCM_ASSERT (SCM_NFALSEP (scm_thunk_p (out_guard)),
1e6808ea MG	124	out_guard,
1bbd0b84	125	SCM_ARG3, FUNC_NAME);
fdc28395	126	scm_call_0 (in_guard);
1e6808ea	127	scm_dynwinds = scm_acons (in_guard, out_guard, scm_dynwinds);
fdc28395	128	ans = scm_call_0 (thunk);
0f2d19dd	129	scm_dynwinds = SCM_CDR (scm_dynwinds);
fdc28395	130	scm_call_0 (out_guard);
0f2d19dd JB	131	return ans;
0f2d19dd JB	132	}
1bbd0b84	133	#undef FUNC_NAME
0f2d19dd	134
3346a90f MD	135	/* The implementation of a C-callable dynamic-wind,
	136	* scm_internal_dynamic_wind, requires packaging of C pointers in a
	137	* smob. Objects of this type are pushed onto the dynwind chain.
	138	*/
	139
e841c3e0	140	#define SCM_GUARDSP(obj) SCM_TYP16_PREDICATE (tc16_guards, obj)
92c2555f MV	141	#define SCM_BEFORE_GUARD(obj) ((scm_t_guard) SCM_CELL_WORD (obj, 1))
92c2555f MV	142	#define SCM_AFTER_GUARD(obj) ((scm_t_guard) SCM_CELL_WORD (obj, 2))
bd47429e	143	#define SCM_GUARD_DATA(obj) ((void *) SCM_CELL_WORD (obj, 3))
3346a90f	144
92c2555f	145	static scm_t_bits tc16_guards;
3346a90f	146
3346a90f	147	static int
e81d98ec	148	guards_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
3346a90f MD	149	{
3346a90f MD	150	scm_puts ("#<guards ", port);
f1267706	151	scm_intprint (SCM_UNPACK (SCM_CDR (exp)), 16, port);
3346a90f MD	152	scm_putc ('>', port);
	153	return 1;
	154	}
	155
3346a90f	156	SCM
92c2555f MV	157	scm_internal_dynamic_wind (scm_t_guard before,
	158	scm_t_inner inner,
	159	scm_t_guard after,
3346a90f MD	160	void *inner_data,
	161	void *guard_data)
	162	{
	163	SCM guards, ans;
3346a90f	164	before (guard_data);
92c2555f MV	165	SCM_NEWSMOB3 (guards, tc16_guards, (scm_t_bits) before,
92c2555f MV	166	(scm_t_bits) after, (scm_t_bits) guard_data);
3346a90f MD	167	scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
	168	ans = inner (inner_data);
	169	scm_dynwinds = SCM_CDR (scm_dynwinds);
	170	after (guard_data);
	171	return ans;
	172	}
1cc91f1b	173
c2654ef0	174	#ifdef GUILE_DEBUG
a1ec6916	175	SCM_DEFINE (scm_wind_chain, "wind-chain", 0, 0, 0,
1bbd0b84	176	(),
156149ad MG	177	"Return the current wind chain. The wind chain contains all\n"
	178	"information required by @code{dynamic-wind} to call its\n"
	179	"argument thunks when entering/exiting its scope.")
1bbd0b84	180	#define FUNC_NAME s_scm_wind_chain
c2654ef0 MD	181	{
	182	return scm_dynwinds;
	183	}
1bbd0b84	184	#undef FUNC_NAME
c2654ef0 MD	185	#endif
c2654ef0 MD	186
6778caf9	187	static void
904a077d	188	scm_swap_bindings (SCM vars, SCM vals)
6778caf9 MD	189	{
	190	SCM tmp;
	191	while (SCM_NIMP (vals))
	192	{
904a077d MV	193	tmp = SCM_VARIABLE_REF (SCM_CAR (vars));
904a077d MV	194	SCM_VARIABLE_SET (SCM_CAR (vars), SCM_CAR (vals));
6778caf9	195	SCM_SETCAR (vals, tmp);
904a077d	196	vars = SCM_CDR (vars);
6778caf9 MD	197	vals = SCM_CDR (vals);
	198	}
	199	}
c2654ef0	200
0f2d19dd	201	void
c014a02e	202	scm_dowinds (SCM to, long delta)
0f2d19dd JB	203	{
0f2d19dd JB	204	tail:
843524cc	205	if (SCM_EQ_P (to, scm_dynwinds));
1be6b49c	206	else if (delta < 0)
0f2d19dd JB	207	{
	208	SCM wind_elt;
	209	SCM wind_key;
	210
	211	scm_dowinds (SCM_CDR (to), 1 + delta);
	212	wind_elt = SCM_CAR (to);
	213	#if 0
	214	if (SCM_INUMP (wind_elt))
	215	{
	216	scm_cross_dynwind_binding_scope (wind_elt, 0);
	217	}
	218	else
	219	#endif
	220	{
	221	wind_key = SCM_CAR (wind_elt);
904a077d	222	/* key = #t \| symbol \| thunk \| list of variables \| list of fluids */
6778caf9	223	if (SCM_NIMP (wind_key))
b3460a50	224	{
904a077d MV	225	if (SCM_CONSP (wind_key))
	226	{
	227	if (SCM_VARIABLEP (SCM_CAR (wind_key)))
	228	scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
	229	else if (SCM_FLUIDP (SCM_CAR (wind_key)))
	230	scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
	231	}
4725c298 MD	232	else if (SCM_GUARDSP (wind_key))
	233	SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	234	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
fdc28395	235	scm_call_0 (wind_key);
b3460a50	236	}
0f2d19dd JB	237	}
	238	scm_dynwinds = to;
	239	}
	240	else
	241	{
	242	SCM from;
	243	SCM wind_elt;
	244	SCM wind_key;
	245
	246	from = SCM_CDR (SCM_CAR (scm_dynwinds));
	247	wind_elt = SCM_CAR (scm_dynwinds);
	248	scm_dynwinds = SCM_CDR (scm_dynwinds);
	249	#if 0
	250	if (SCM_INUMP (wind_elt))
	251	{
	252	scm_cross_dynwind_binding_scope (wind_elt, 0);
	253	}
	254	else
	255	#endif
	256	{
	257	wind_key = SCM_CAR (wind_elt);
6778caf9	258	if (SCM_NIMP (wind_key))
b3460a50	259	{
904a077d MV	260	if (SCM_CONSP (wind_key))
	261	{
	262	if (SCM_VARIABLEP (SCM_CAR (wind_key)))
	263	scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
	264	else if (SCM_FLUIDP (SCM_CAR (wind_key)))
	265	scm_swap_fluids_reverse (wind_key, SCM_CDR (wind_elt));
	266	}
4725c298 MD	267	else if (SCM_GUARDSP (wind_key))
	268	SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	269	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
fdc28395	270	scm_call_0 (from);
b3460a50	271	}
0f2d19dd JB	272	}
	273	delta--;
	274	goto tail; /* scm_dowinds(to, delta-1); */
	275	}
	276	}
	277
	278
1cc91f1b	279
0f2d19dd JB	280	void
0f2d19dd JB	281	scm_init_dynwind ()
0f2d19dd	282	{
e841c3e0 KN	283	tc16_guards = scm_make_smob_type ("guards", 0);
e841c3e0 KN	284	scm_set_smob_print (tc16_guards, guards_print);
8dc9439f	285	#ifndef SCM_MAGIC_SNARFER
a0599745	286	#include "libguile/dynwind.x"
8dc9439f	287	#endif
0f2d19dd	288	}
89e00824 ML	289
	290	/*
	291	Local Variables:
	292	c-file-style: "gnu"
	293	End:
	294	*/