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282 lines
8.1 KiB
C
282 lines
8.1 KiB
C
/* Copyright (C) 1995, 1996, 1998, 1999, 2000 Free Software Foundation, Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this software; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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* As a special exception, the Free Software Foundation gives permission
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* for additional uses of the text contained in its release of GUILE.
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*
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* The exception is that, if you link the GUILE library with other files
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* to produce an executable, this does not by itself cause the
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* resulting executable to be covered by the GNU General Public License.
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* Your use of that executable is in no way restricted on account of
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* linking the GUILE library code into it.
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*
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* This exception does not however invalidate any other reasons why
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* the executable file might be covered by the GNU General Public License.
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*
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* This exception applies only to the code released by the
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* Free Software Foundation under the name GUILE. If you copy
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* code from other Free Software Foundation releases into a copy of
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* GUILE, as the General Public License permits, the exception does
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* not apply to the code that you add in this way. To avoid misleading
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* anyone as to the status of such modified files, you must delete
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* this exception notice from them.
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*
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* If you write modifications of your own for GUILE, it is your choice
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* whether to permit this exception to apply to your modifications.
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* If you do not wish that, delete this exception notice. */
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/* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
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gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
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#include <stdio.h>
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#include "_scm.h"
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#include "eval.h"
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#include "alist.h"
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#include "fluids.h"
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#include "ports.h"
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#include "smob.h"
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#include "dynwind.h"
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/* {Dynamic wind}
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Things that can be on the wind list:
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(enter-proc . leave-proc) dynamic-wind
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(tag . jmpbuf) catch
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(tag . lazy-catch) lazy-catch
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tag is either a symbol or a boolean
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((fluid ...) . (value ...)) with-fluids
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*/
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SCM_DEFINE (scm_dynamic_wind, "dynamic-wind", 3, 0, 0,
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(SCM thunk1, SCM thunk2, SCM thunk3),
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"All three arguments must be 0-argument procedures.\n\n"
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"@var{in-guard} is called, then @var{thunk}, then @var{out-guard}.\n\n"
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"If, any time during the execution of @var{thunk}, the continuation\n"
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"of the @code{dynamic-wind} expression is escaped non-locally, @var{out-guard}\n"
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"is called. If the continuation of the dynamic-wind is re-entered,\n"
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"@var{in-guard} is called. Thus @var{in-guard} and @var{out-guard} may\n"
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"be called any number of times.\n\n"
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"@example\n"
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"(define x 'normal-binding)\n"
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"@result{} x\n\n"
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"(define a-cont (call-with-current-continuation \n"
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" (lambda (escape)\n"
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" (let ((old-x x))\n"
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" (dynamic-wind\n"
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" ;; in-guard:\n"
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" ;;\n"
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" (lambda () (set! x 'special-binding))\n\n"
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" ;; thunk\n"
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" ;;\n"
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" (lambda () (display x) (newline)\n"
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" (call-with-current-continuation escape)\n"
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" (display x) (newline)\n"
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" x)\n\n"
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" ;; out-guard:\n"
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" ;;\n"
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" (lambda () (set! x old-x)))))))\n\n"
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";; Prints: \n"
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"special-binding\n"
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";; Evaluates to:\n"
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"@result{} a-cont\n\n"
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"x\n"
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"@result{} normal-binding\n\n"
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"(a-cont #f)\n"
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";; Prints:\n"
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"special-binding\n"
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";; Evaluates to:\n"
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"@result{} a-cont ;; the value of the (define a-cont...)\n\n"
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"x\n"
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"@result{} normal-binding\n\n"
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"a-cont\n"
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"@result{} special-binding\n"
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"@end example\n"
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"")
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#define FUNC_NAME s_scm_dynamic_wind
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{
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SCM ans;
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SCM_ASSERT (SCM_NFALSEP (scm_thunk_p (thunk3)),
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thunk3,
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SCM_ARG3, FUNC_NAME);
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scm_apply (thunk1, SCM_EOL, SCM_EOL);
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scm_dynwinds = scm_acons (thunk1, thunk3, scm_dynwinds);
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ans = scm_apply (thunk2, SCM_EOL, SCM_EOL);
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scm_dynwinds = SCM_CDR (scm_dynwinds);
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scm_apply (thunk3, SCM_EOL, SCM_EOL);
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return ans;
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}
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#undef FUNC_NAME
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/* The implementation of a C-callable dynamic-wind,
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* scm_internal_dynamic_wind, requires packaging of C pointers in a
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* smob. Objects of this type are pushed onto the dynwind chain.
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*/
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#define SCM_GUARDSP(obj) SCM_SMOB_PREDICATE (tc16_guards, obj)
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#define SCM_BEFORE_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 1))
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#define SCM_AFTER_GUARD(obj) ((scm_guard_t) SCM_CELL_WORD (obj, 2))
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#define SCM_GUARD_DATA(obj) ((void *) SCM_CELL_WORD (obj, 3))
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static long tc16_guards;
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static int
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printguards (SCM exp, SCM port, scm_print_state *pstate)
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{
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scm_puts ("#<guards ", port);
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scm_intprint (SCM_UNPACK (SCM_CDR (exp)), 16, port);
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scm_putc ('>', port);
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return 1;
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}
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SCM
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scm_internal_dynamic_wind (scm_guard_t before,
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scm_inner_t inner,
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scm_guard_t after,
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void *inner_data,
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void *guard_data)
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{
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SCM guards, ans;
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before (guard_data);
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SCM_NEWSMOB3 (guards, tc16_guards, before, after, guard_data);
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scm_dynwinds = scm_acons (guards, SCM_BOOL_F, scm_dynwinds);
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ans = inner (inner_data);
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scm_dynwinds = SCM_CDR (scm_dynwinds);
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after (guard_data);
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return ans;
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}
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#ifdef GUILE_DEBUG
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SCM_DEFINE (scm_wind_chain, "wind-chain", 0, 0, 0,
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(),
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"")
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#define FUNC_NAME s_scm_wind_chain
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{
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return scm_dynwinds;
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}
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#undef FUNC_NAME
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#endif
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static void
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scm_swap_bindings (SCM glocs, SCM vals)
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{
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SCM tmp;
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while (SCM_NIMP (vals))
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{
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tmp = SCM_GLOC_VAL (SCM_CAR (glocs));
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SCM_SETCDR (SCM_PACK (SCM_UNPACK (SCM_CAR (glocs)) - 1L),
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SCM_CAR (vals));
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SCM_SETCAR (vals, tmp);
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glocs = SCM_CDR (glocs);
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vals = SCM_CDR (vals);
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}
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}
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void
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scm_dowinds (SCM to, long delta)
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{
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tail:
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if (scm_dynwinds == to);
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else if (0 > delta)
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{
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SCM wind_elt;
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SCM wind_key;
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scm_dowinds (SCM_CDR (to), 1 + delta);
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wind_elt = SCM_CAR (to);
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#if 0
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if (SCM_INUMP (wind_elt))
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{
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scm_cross_dynwind_binding_scope (wind_elt, 0);
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}
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else
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#endif
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{
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wind_key = SCM_CAR (wind_elt);
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/* key = #t | symbol | thunk | list of glocs | list of fluids */
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if (SCM_NIMP (wind_key))
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{
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if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
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scm_swap_bindings (wind_key, SCM_CDR (wind_elt));
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else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
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scm_swap_fluids (wind_key, SCM_CDR (wind_elt));
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else if (SCM_GUARDSP (wind_key))
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SCM_BEFORE_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
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else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
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scm_apply (wind_key, SCM_EOL, SCM_EOL);
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}
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}
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scm_dynwinds = to;
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}
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else
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{
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SCM from;
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SCM wind_elt;
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SCM wind_key;
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from = SCM_CDR (SCM_CAR (scm_dynwinds));
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wind_elt = SCM_CAR (scm_dynwinds);
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scm_dynwinds = SCM_CDR (scm_dynwinds);
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#if 0
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if (SCM_INUMP (wind_elt))
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{
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scm_cross_dynwind_binding_scope (wind_elt, 0);
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}
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else
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#endif
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{
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wind_key = SCM_CAR (wind_elt);
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if (SCM_NIMP (wind_key))
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{
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if (SCM_TYP3 (wind_key) == scm_tc3_cons_gloc)
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scm_swap_bindings (wind_key, from);
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else if (SCM_TYP3 (wind_key) == scm_tc3_cons)
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scm_swap_fluids_reverse (wind_key, from);
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else if (SCM_GUARDSP (wind_key))
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SCM_AFTER_GUARD (wind_key) (SCM_GUARD_DATA (wind_key));
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else if (SCM_TYP3 (wind_key) == scm_tc3_closure)
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scm_apply (from, SCM_EOL, SCM_EOL);
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}
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}
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delta--;
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goto tail; /* scm_dowinds(to, delta-1); */
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}
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}
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void
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scm_init_dynwind ()
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{
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tc16_guards = scm_make_smob_type_mfpe ("guards", 0,
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NULL, scm_free0, printguards, NULL);
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#include "dynwind.x"
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}
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/*
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Local Variables:
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c-file-style: "gnu"
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End:
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*/
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