mes/cache.c
Jan Nieuwenhuizen f26c7222b2 core: Split-off cache, display, reader.
* mes.c: Remove cache, display, reader functions.
* cache.c: New file.
* display.c: New file.
* reader.c: New file.
2016-12-12 20:35:19 +01:00

104 lines
2.5 KiB
C

/* -*-comment-start: "//";comment-end:""-*-
* Mes --- Maxwell Equations of Software
* Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
*
* This file is part of Mes.
*
* Mes 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 3 of the License, or (at
* your option) any later version.
*
* Mes 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 Mes. If not, see <http://www.gnu.org/licenses/>.
*/
#define CACHE_SIZE 30
#define ENV_HEAD 15
#if! ENV_CACHE
SCM cache_invalidate (SCM x){}
SCM cache_invalidate_range (SCM p,SCM a){}
SCM cache_save (SCM p){}
SCM cache_lookup (SCM x){}
#else // ENV_CACHE
SCM env_cache_cars[CACHE_SIZE];
SCM env_cache_cdrs[CACHE_SIZE];
int cache_threshold = 0;
SCM
cache_save (SCM p)
{
int n = g_cells[car (p)].hits;
if (n < cache_threshold) return cell_unspecified;
int j = -1;
for (int i=0; i < CACHE_SIZE; i++) {
if (!env_cache_cars[i]) {
j = i;
break;
}
if (env_cache_cars[i] == car (p)) return cell_unspecified;
if (n > g_cells[env_cache_cars[i]].hits) {
n = g_cells[env_cache_cars[i]].hits;
j = i;
}
}
if (j >= 0) {
cache_threshold = g_cells[car (p)].hits;
env_cache_cars[j] = car (p);
env_cache_cdrs[j] = cdr (p);
}
return cell_unspecified;
}
SCM
cache_lookup (SCM x)
{
for (int i=0; i < CACHE_SIZE; i++) {
if (!env_cache_cars[i]) break;
if (env_cache_cars[i] == x) return env_cache_cdrs[i];
}
return cell_undefined;
}
SCM
cache_invalidate (SCM x)
{
for (int i=0; i < CACHE_SIZE; i++) {
if (env_cache_cars[i] == x) {
env_cache_cars[i] = 0;
break;
}
}
return cell_unspecified;
}
SCM
cache_invalidate_range (SCM p, SCM a)
{
do {
cache_invalidate (caar (p));
p = cdr (p);
} while (p != a);
return cell_unspecified;
}
SCM
assq_ref_cache (SCM x, SCM a) ///((internal))
{
g_cells[x].hits++;
SCM c = cache_lookup (x);
if (c != cell_undefined) return c;
int i = 0;
while (a != cell_nil && x != CAAR (a)) {i++;a = cdr (a);}
if (a == cell_nil) return cell_undefined;
if (i>ENV_HEAD) cache_save (car (a));
return cdar (a);
}
#endif // ENV_CACHE