1 /* Copyright (C) 1995,1996,1998,1999,2000,2001, 2003, 2004, 2006, 2008 Free Software Foundation, Inc.
3 * This library is free software; you can redistribute it and/or
4 * modify it under the terms of the GNU Lesser General Public
5 * License as published by the Free Software Foundation; either
6 * version 2.1 of the License, or (at your option) any later version.
8 * This library 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 GNU
11 * Lesser General Public License for more details.
13 * You should have received a copy of the GNU Lesser General Public
14 * License along with this library; if not, write to the Free Software
15 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
27 #include "libguile/_scm.h"
28 #include "libguile/eval.h"
29 #include "libguile/alist.h"
30 #include "libguile/fluids.h"
31 #include "libguile/ports.h"
32 #include "libguile/smob.h"
34 #include "libguile/dynwind.h"
39 Things that can be on the wind list:
43 (enter-proc . leave-proc) dynamic-wind
45 (tag . pre-unwind-data) throw-handler / lazy-catch
46 tag is either a symbol or a boolean
52 SCM_DEFINE (scm_dynamic_wind, "dynamic-wind", 3, 0, 0,
53 (SCM in_guard, SCM thunk, SCM out_guard),
54 "All three arguments must be 0-argument procedures.\n"
55 "@var{in_guard} is called, then @var{thunk}, then\n"
58 "If, any time during the execution of @var{thunk}, the\n"
59 "continuation of the @code{dynamic_wind} expression is escaped\n"
60 "non-locally, @var{out_guard} is called. If the continuation of\n"
61 "the dynamic-wind is re-entered, @var{in_guard} is called. Thus\n"
62 "@var{in_guard} and @var{out_guard} may be called any number of\n"
65 "(define x 'normal-binding)\n"
67 "(define a-cont (call-with-current-continuation\n"
73 " (lambda () (set! x 'special-binding))\n"
77 " (lambda () (display x) (newline)\n"
78 " (call-with-current-continuation escape)\n"
79 " (display x) (newline)\n"
84 " (lambda () (set! x old-x)))))))\n"
91 "@result{} normal-binding\n"
96 "@result{} a-cont ;; the value of the (define a-cont...)\n"
98 "@result{} normal-binding\n"
100 "@result{} special-binding\n"
102 #define FUNC_NAME s_scm_dynamic_wind
105 SCM_ASSERT (scm_is_true (scm_thunk_p (out_guard)),
107 SCM_ARG3, FUNC_NAME);
108 scm_call_0 (in_guard);
109 old_winds = scm_i_dynwinds ();
110 scm_i_set_dynwinds (scm_acons (in_guard, out_guard, old_winds));
111 ans = scm_call_0 (thunk);
112 scm_i_set_dynwinds (old_winds);
113 scm_call_0 (out_guard);
119 scm_internal_dynamic_wind (scm_t_guard before,
127 scm_dynwind_begin (SCM_F_DYNWIND_REWINDABLE);
128 scm_dynwind_rewind_handler (before, guard_data, SCM_F_WIND_EXPLICITLY);
129 scm_dynwind_unwind_handler (after, guard_data, SCM_F_WIND_EXPLICITLY);
130 ans = inner (inner_data);
135 /* Frames and winders. */
137 static scm_t_bits tc16_frame;
138 #define FRAME_P(f) SCM_SMOB_PREDICATE (tc16_frame, (f))
140 #define FRAME_F_REWINDABLE (1 << 0)
141 #define FRAME_REWINDABLE_P(f) (SCM_SMOB_FLAGS(f) & FRAME_F_REWINDABLE)
143 static scm_t_bits tc16_winder;
144 #define WINDER_P(w) SCM_SMOB_PREDICATE (tc16_winder, (w))
145 #define WINDER_PROC(w) ((void (*)(void *))SCM_SMOB_DATA (w))
146 #define WINDER_DATA(w) ((void *)SCM_SMOB_DATA_2 (w))
148 #define WINDER_F_EXPLICIT (1 << 0)
149 #define WINDER_F_REWIND (1 << 1)
150 #define WINDER_F_MARK (1 << 2)
151 #define WINDER_EXPLICIT_P(w) (SCM_SMOB_FLAGS(w) & WINDER_F_EXPLICIT)
152 #define WINDER_REWIND_P(w) (SCM_SMOB_FLAGS(w) & WINDER_F_REWIND)
153 #define WINDER_MARK_P(w) (SCM_SMOB_FLAGS(w) & WINDER_F_MARK)
156 scm_dynwind_begin (scm_t_dynwind_flags flags)
159 SCM_NEWSMOB (f, tc16_frame, 0);
160 if (flags & SCM_F_DYNWIND_REWINDABLE)
161 SCM_SET_SMOB_FLAGS (f, FRAME_F_REWINDABLE);
162 scm_i_set_dynwinds (scm_cons (f, scm_i_dynwinds ()));
166 scm_dynwind_end (void)
170 /* Unwind upto and including the next frame entry. We can only
171 encounter #<winder> entries on the way.
174 winds = scm_i_dynwinds ();
175 while (scm_is_pair (winds))
177 SCM entry = SCM_CAR (winds);
178 winds = SCM_CDR (winds);
180 scm_i_set_dynwinds (winds);
185 assert (WINDER_P (entry));
186 if (!WINDER_REWIND_P (entry) && WINDER_EXPLICIT_P (entry))
187 WINDER_PROC(entry) (WINDER_DATA (entry));
196 if (WINDER_MARK_P (w))
197 return SCM_PACK (WINDER_DATA (w));
202 scm_dynwind_unwind_handler (void (*proc) (void *), void *data,
203 scm_t_wind_flags flags)
206 SCM_NEWSMOB2 (w, tc16_winder, (scm_t_bits) proc, (scm_t_bits) data);
207 if (flags & SCM_F_WIND_EXPLICITLY)
208 SCM_SET_SMOB_FLAGS (w, WINDER_F_EXPLICIT);
209 scm_i_set_dynwinds (scm_cons (w, scm_i_dynwinds ()));
213 scm_dynwind_rewind_handler (void (*proc) (void *), void *data,
214 scm_t_wind_flags flags)
217 SCM_NEWSMOB2 (w, tc16_winder, (scm_t_bits) proc, (scm_t_bits) data);
218 SCM_SET_SMOB_FLAGS (w, WINDER_F_REWIND);
219 scm_i_set_dynwinds (scm_cons (w, scm_i_dynwinds ()));
220 if (flags & SCM_F_WIND_EXPLICITLY)
225 scm_dynwind_unwind_handler_with_scm (void (*proc) (SCM), SCM data,
226 scm_t_wind_flags flags)
229 scm_t_bits fl = ((flags&SCM_F_WIND_EXPLICITLY)? WINDER_F_EXPLICIT : 0);
230 SCM_NEWSMOB2 (w, tc16_winder, (scm_t_bits) proc, SCM_UNPACK (data));
231 SCM_SET_SMOB_FLAGS (w, fl | WINDER_F_MARK);
232 scm_i_set_dynwinds (scm_cons (w, scm_i_dynwinds ()));
236 scm_dynwind_rewind_handler_with_scm (void (*proc) (SCM), SCM data,
237 scm_t_wind_flags flags)
240 SCM_NEWSMOB2 (w, tc16_winder, (scm_t_bits) proc, SCM_UNPACK (data));
241 SCM_SET_SMOB_FLAGS (w, WINDER_F_REWIND | WINDER_F_MARK);
242 scm_i_set_dynwinds (scm_cons (w, scm_i_dynwinds ()));
243 if (flags & SCM_F_WIND_EXPLICITLY)
248 scm_dynwind_free (void *mem)
250 scm_dynwind_unwind_handler (free, mem, SCM_F_WIND_EXPLICITLY);
254 SCM_DEFINE (scm_wind_chain, "wind-chain", 0, 0, 0,
256 "Return the current wind chain. The wind chain contains all\n"
257 "information required by @code{dynamic-wind} to call its\n"
258 "argument thunks when entering/exiting its scope.")
259 #define FUNC_NAME s_scm_wind_chain
261 return scm_i_dynwinds ();
267 scm_swap_bindings (SCM vars, SCM vals)
270 while (SCM_NIMP (vals))
272 tmp = SCM_VARIABLE_REF (SCM_CAR (vars));
273 SCM_VARIABLE_SET (SCM_CAR (vars), SCM_CAR (vals));
274 SCM_SETCAR (vals, tmp);
275 vars = SCM_CDR (vars);
276 vals = SCM_CDR (vals);
281 scm_dowinds (SCM to, long delta)
283 scm_i_dowinds (to, delta, NULL, NULL);
287 scm_i_dowinds (SCM to, long delta, void (*turn_func) (void *), void *data)
290 if (scm_is_eq (to, scm_i_dynwinds ()))
300 scm_i_dowinds (SCM_CDR (to), 1 + delta, turn_func, data);
301 wind_elt = SCM_CAR (to);
303 if (FRAME_P (wind_elt))
305 if (!FRAME_REWINDABLE_P (wind_elt))
306 scm_misc_error ("dowinds",
307 "cannot invoke continuation from this context",
310 else if (WINDER_P (wind_elt))
312 if (WINDER_REWIND_P (wind_elt))
313 WINDER_PROC (wind_elt) (WINDER_DATA (wind_elt));
317 wind_key = SCM_CAR (wind_elt);
318 /* key = #t | symbol | thunk | list of variables */
319 if (SCM_NIMP (wind_key))
321 if (scm_is_pair (wind_key))
323 if (SCM_VARIABLEP (SCM_CAR (wind_key)))
324 scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
326 else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
327 scm_call_0 (wind_key);
331 scm_i_set_dynwinds (to);
339 wind = scm_i_dynwinds ();
340 wind_elt = SCM_CAR (wind);
341 scm_i_set_dynwinds (SCM_CDR (wind));
343 if (FRAME_P (wind_elt))
347 else if (WINDER_P (wind_elt))
349 if (!WINDER_REWIND_P (wind_elt))
350 WINDER_PROC (wind_elt) (WINDER_DATA (wind_elt));
354 wind_key = SCM_CAR (wind_elt);
355 if (SCM_NIMP (wind_key))
357 if (scm_is_pair (wind_key))
359 if (SCM_VARIABLEP (SCM_CAR (wind_key)))
360 scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
362 else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
363 scm_call_0 (SCM_CDR (wind_elt));
368 goto tail; /* scm_dowinds(to, delta-1); */
375 tc16_frame = scm_make_smob_type ("frame", 0);
377 tc16_winder = scm_make_smob_type ("winder", 0);
378 scm_set_smob_mark (tc16_winder, winder_mark);
380 #include "libguile/dynwind.x"