/* 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. */ #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" /* {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 ("#', 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 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 (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 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_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_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_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); #include "libguile/dynwind.x" } /* Local Variables: c-file-style: "gnu" End: */