104 lines
2.5 KiB
C
104 lines
2.5 KiB
C
/* -*-comment-start: "//";comment-end:""-*-
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* Mes --- Maxwell Equations of Software
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* Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
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*
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* This file is part of Mes.
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*
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* Mes is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* Mes is distributed in the hope that it will be useful, but
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* 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 Mes. If not, see <http://www.gnu.org/licenses/>.
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*/
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#define CACHE_SIZE 30
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#define ENV_HEAD 15
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#if! ENV_CACHE
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SCM cache_invalidate (SCM x){}
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SCM cache_invalidate_range (SCM p,SCM a){}
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SCM cache_save (SCM p){}
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SCM cache_lookup (SCM x){}
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#else // ENV_CACHE
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SCM env_cache_cars[CACHE_SIZE];
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SCM env_cache_cdrs[CACHE_SIZE];
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int cache_threshold = 0;
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SCM
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cache_save (SCM p)
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{
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int n = g_cells[car (p)].hits;
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if (n < cache_threshold) return cell_unspecified;
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int j = -1;
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for (int i=0; i < CACHE_SIZE; i++) {
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if (!env_cache_cars[i]) {
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j = i;
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break;
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}
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if (env_cache_cars[i] == car (p)) return cell_unspecified;
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if (n > g_cells[env_cache_cars[i]].hits) {
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n = g_cells[env_cache_cars[i]].hits;
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j = i;
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}
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}
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if (j >= 0) {
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cache_threshold = g_cells[car (p)].hits;
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env_cache_cars[j] = car (p);
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env_cache_cdrs[j] = cdr (p);
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}
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return cell_unspecified;
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}
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SCM
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cache_lookup (SCM x)
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{
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for (int i=0; i < CACHE_SIZE; i++) {
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if (!env_cache_cars[i]) break;
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if (env_cache_cars[i] == x) return env_cache_cdrs[i];
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}
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return cell_undefined;
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}
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SCM
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cache_invalidate (SCM x)
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{
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for (int i=0; i < CACHE_SIZE; i++) {
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if (env_cache_cars[i] == x) {
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env_cache_cars[i] = 0;
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break;
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}
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}
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return cell_unspecified;
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}
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SCM
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cache_invalidate_range (SCM p, SCM a)
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{
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do {
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cache_invalidate (caar (p));
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p = cdr (p);
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} while (p != a);
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return cell_unspecified;
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}
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SCM
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assq_ref_cache (SCM x, SCM a) ///((internal))
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{
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g_cells[x].hits++;
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SCM c = cache_lookup (x);
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if (c != cell_undefined) return c;
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int i = 0;
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while (a != cell_nil && x != CAAR (a)) {i++;a = cdr (a);}
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if (a == cell_nil) return cell_undefined;
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if (i>ENV_HEAD) cache_save (car (a));
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return cdar (a);
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}
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#endif // ENV_CACHE
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