[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 "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_apply (in_guard, SCM_EOL, SCM_EOL);
  scm_dynwinds = scm_acons (in_guard, out_guard, scm_dynwinds);
  ans = scm_apply (thunk, SCM_EOL, SCM_EOL);
  scm_dynwinds = SCM_CDR (scm_dynwinds);
  scm_apply (out_guard, 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_TYP16_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 scm_bits_t tc16_guards;

static int
guards_print (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, (scm_bits_t) before, 
		(scm_bits_t) after, (scm_bits_t) 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 glocs, SCM vals)
{
  SCM tmp;
  while (SCM_NIMP (vals))
    {
      tmp = SCM_GLOC_VAL (SCM_CAR (glocs));
      SCM_GLOC_SET_VAL (SCM_CAR (glocs), 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_EQ_P (to, scm_dynwinds));
  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 ("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
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
0f2d19dd JB	46
a0599745 MD	47	#include "libguile/_scm.h"
	48	#include "libguile/eval.h"
	49	#include "libguile/alist.h"
	50	#include "libguile/fluids.h"
	51	#include "libguile/ports.h"
	52	#include "libguile/smob.h"
0f2d19dd	53
a0599745	54	#include "libguile/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,
1e6808ea MG	73	(SCM in_guard, SCM thunk, SCM out_guard),
	74	"All three arguments must be 0-argument procedures.\n"
	75	"@var{in_guard} is called, then @var{thunk}, then\n"
	76	"@var{out_guard}.\n"
	77	"\n"
	78	"If, any time during the execution of @var{thunk}, the\n"
	79	"continuation of the @code{dynamic_wind} expression is escaped\n"
	80	"non-locally, @var{out_guard} is called. If the continuation of\n"
	81	"the dynamic-wind is re-entered, @var{in_guard} is called. Thus\n"
	82	"@var{in_guard} and @var{out_guard} may be called any number of\n"
	83	"times.\n"
	84	"@lisp\n"
b380b885	85	"(define x 'normal-binding)\n"
1e6808ea	86	"@result{} x\n"
b380b885 MD	87	"(define a-cont (call-with-current-continuation \n"
	88	" (lambda (escape)\n"
	89	" (let ((old-x x))\n"
	90	" (dynamic-wind\n"
	91	" ;; in-guard:\n"
	92	" ;;\n"
1e6808ea MG	93	" (lambda () (set! x 'special-binding))\n"
1e6808ea MG	94	"\n"
b380b885 MD	95	" ;; thunk\n"
	96	" ;;\n"
	97	" (lambda () (display x) (newline)\n"
	98	" (call-with-current-continuation escape)\n"
	99	" (display x) (newline)\n"
1e6808ea MG	100	" x)\n"
1e6808ea MG	101	"\n"
b380b885 MD	102	" ;; out-guard:\n"
b380b885 MD	103	" ;;\n"
1e6808ea MG	104	" (lambda () (set! x old-x)))))))\n"
1e6808ea MG	105	"\n"
b380b885 MD	106	";; Prints: \n"
	107	"special-binding\n"
	108	";; Evaluates to:\n"
1e6808ea	109	"@result{} a-cont\n"
b380b885	110	"x\n"
1e6808ea	111	"@result{} normal-binding\n"
b380b885 MD	112	"(a-cont #f)\n"
	113	";; Prints:\n"
	114	"special-binding\n"
	115	";; Evaluates to:\n"
1e6808ea	116	"@result{} a-cont ;; the value of the (define a-cont...)\n"
b380b885	117	"x\n"
1e6808ea	118	"@result{} normal-binding\n"
b380b885 MD	119	"a-cont\n"
b380b885 MD	120	"@result{} special-binding\n"
1e6808ea	121	"@end lisp")
1bbd0b84	122	#define FUNC_NAME s_scm_dynamic_wind
0f2d19dd JB	123	{
0f2d19dd JB	124	SCM ans;
1e6808ea MG	125	SCM_ASSERT (SCM_NFALSEP (scm_thunk_p (out_guard)),
1e6808ea MG	126	out_guard,
1bbd0b84	127	SCM_ARG3, FUNC_NAME);
1e6808ea MG	128	scm_apply (in_guard, SCM_EOL, SCM_EOL);
	129	scm_dynwinds = scm_acons (in_guard, out_guard, scm_dynwinds);
	130	ans = scm_apply (thunk, SCM_EOL, SCM_EOL);
0f2d19dd	131	scm_dynwinds = SCM_CDR (scm_dynwinds);
1e6808ea	132	scm_apply (out_guard, SCM_EOL, SCM_EOL);
0f2d19dd JB	133	return ans;
0f2d19dd JB	134	}
1bbd0b84	135	#undef FUNC_NAME
0f2d19dd	136
3346a90f MD	137	/* The implementation of a C-callable dynamic-wind,
	138	* scm_internal_dynamic_wind, requires packaging of C pointers in a
	139	* smob. Objects of this type are pushed onto the dynwind chain.
	140	*/
	141
e841c3e0	142	#define SCM_GUARDSP(obj) SCM_TYP16_PREDICATE (tc16_guards, obj)
bd47429e MD	143	#define SCM_BEFORE_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 1))
	144	#define SCM_AFTER_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 2))
	145	#define SCM_GUARD_DATA(obj) ((void *) SCM_CELL_WORD (obj, 3))
3346a90f	146
e841c3e0	147	static scm_bits_t tc16_guards;
3346a90f	148
3346a90f	149	static int
e841c3e0	150	guards_print (SCM exp, SCM port, scm_print_state *pstate)
3346a90f MD	151	{
3346a90f MD	152	scm_puts ("#<guards ", port);
f1267706	153	scm_intprint (SCM_UNPACK (SCM_CDR (exp)), 16, port);
3346a90f MD	154	scm_putc ('>', port);
	155	return 1;
	156	}
	157
3346a90f MD	158	SCM
	159	scm_internal_dynamic_wind (scm_guard_t before,
	160	scm_inner_t inner,
	161	scm_guard_t after,
	162	void *inner_data,
	163	void *guard_data)
	164	{
	165	SCM guards, ans;
3346a90f	166	before (guard_data);
843524cc DH	167	SCM_NEWSMOB3 (guards, tc16_guards, (scm_bits_t) before,
843524cc DH	168	(scm_bits_t) after, (scm_bits_t) guard_data);
3346a90f MD	169	scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
	170	ans = inner (inner_data);
	171	scm_dynwinds = SCM_CDR (scm_dynwinds);
	172	after (guard_data);
	173	return ans;
	174	}
1cc91f1b	175
c2654ef0	176	#ifdef GUILE_DEBUG
a1ec6916	177	SCM_DEFINE (scm_wind_chain, "wind-chain", 0, 0, 0,
1bbd0b84	178	(),
156149ad MG	179	"Return the current wind chain. The wind chain contains all\n"
	180	"information required by @code{dynamic-wind} to call its\n"
	181	"argument thunks when entering/exiting its scope.")
1bbd0b84	182	#define FUNC_NAME s_scm_wind_chain
c2654ef0 MD	183	{
	184	return scm_dynwinds;
	185	}
1bbd0b84	186	#undef FUNC_NAME
c2654ef0 MD	187	#endif
c2654ef0 MD	188
6778caf9 MD	189	static void
	190	scm_swap_bindings (SCM glocs, SCM vals)
	191	{
	192	SCM tmp;
	193	while (SCM_NIMP (vals))
	194	{
	195	tmp = SCM_GLOC_VAL (SCM_CAR (glocs));
86d31dfe	196	SCM_GLOC_SET_VAL (SCM_CAR (glocs), SCM_CAR (vals));
6778caf9 MD	197	SCM_SETCAR (vals, tmp);
	198	glocs = SCM_CDR (glocs);
	199	vals = SCM_CDR (vals);
	200	}
	201	}
c2654ef0	202
0f2d19dd	203	void
6e8d25a6	204	scm_dowinds (SCM to, long delta)
0f2d19dd JB	205	{
0f2d19dd JB	206	tail:
843524cc	207	if (SCM_EQ_P (to, scm_dynwinds));
0f2d19dd JB	208	else if (0 > delta)
	209	{
	210	SCM wind_elt;
	211	SCM wind_key;
	212
	213	scm_dowinds (SCM_CDR (to), 1 + delta);
	214	wind_elt = SCM_CAR (to);
	215	#if 0
	216	if (SCM_INUMP (wind_elt))
	217	{
	218	scm_cross_dynwind_binding_scope (wind_elt, 0);
	219	}
	220	else
	221	#endif
	222	{
	223	wind_key = SCM_CAR (wind_elt);
6778caf9 MD	224	/* key = #t \| symbol \| thunk \| list of glocs \| list of fluids */
6778caf9 MD	225	if (SCM_NIMP (wind_key))
b3460a50	226	{
6778caf9 MD	227	if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
6778caf9 MD	228	scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
4725c298 MD	229	else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
	230	scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
	231	else if (SCM_GUARDSP (wind_key))
	232	SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	233	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
	234	scm_apply (wind_key, SCM_EOL, SCM_EOL);
b3460a50	235	}
0f2d19dd JB	236	}
	237	scm_dynwinds = to;
	238	}
	239	else
	240	{
	241	SCM from;
	242	SCM wind_elt;
	243	SCM wind_key;
	244
	245	from = SCM_CDR (SCM_CAR (scm_dynwinds));
	246	wind_elt = SCM_CAR (scm_dynwinds);
	247	scm_dynwinds = SCM_CDR (scm_dynwinds);
	248	#if 0
	249	if (SCM_INUMP (wind_elt))
	250	{
	251	scm_cross_dynwind_binding_scope (wind_elt, 0);
	252	}
	253	else
	254	#endif
	255	{
	256	wind_key = SCM_CAR (wind_elt);
6778caf9	257	if (SCM_NIMP (wind_key))
b3460a50	258	{
6778caf9 MD	259	if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
6778caf9 MD	260	scm_swap_bindings (wind_key, from);
4725c298 MD	261	else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
	262	scm_swap_fluids_reverse (wind_key, from);
	263	else if (SCM_GUARDSP (wind_key))
	264	SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
	265	else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
	266	scm_apply (from, SCM_EOL, SCM_EOL);
b3460a50	267	}
0f2d19dd JB	268	}
	269	delta--;
	270	goto tail; /* scm_dowinds(to, delta-1); */
	271	}
	272	}
	273
	274
1cc91f1b	275
0f2d19dd JB	276	void
0f2d19dd JB	277	scm_init_dynwind ()
0f2d19dd	278	{
e841c3e0 KN	279	tc16_guards = scm_make_smob_type ("guards", 0);
e841c3e0 KN	280	scm_set_smob_print (tc16_guards, guards_print);
8dc9439f	281	#ifndef SCM_MAGIC_SNARFER
a0599745	282	#include "libguile/dynwind.x"
8dc9439f	283	#endif
0f2d19dd	284	}
89e00824 ML	285
	286	/*
	287	Local Variables:
	288	c-file-style: "gnu"
	289	End:
	290	*/