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/*
* This file is part of the sn package.
* Distribution of sn is covered by the GNU GPL. See file COPYING.
* Copyright 1998-2000 Harold Tay.
* Copyright 2000- Patrik Rdman.
*/
/*
* Generic caching module. Not very sophisticated, but very heavily
* used to avoid repeated object construction/deconstruction.
*/
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "cache.h"
static const char ver_ctrl_id[] = "$Id: cache.c 29 2004-04-24 23:02:38Z patrik $";
/* Max number of caches (of possibly different types of object)
that we can handle */
#ifndef CACHE_MAX
#define CACHE_MAX 4
#endif
struct entry {
void *object;
struct entry *prev;
struct entry *next;
};
struct table {
int maxsize;
int (*cmp) (void *, void *);
void (*freeobj) (void *);
int (*isstale) (void *);
struct entry *entries;
struct entry *freelist;
struct entry *freeblocks;
int hit;
int miss;
};
struct table table[CACHE_MAX] = { { 0, }, };
int cache_init (int max, int (*cmp) (void *, void *),
void (*freeobj) (void *),
int (*isstale) (void *))
{
int i;
int j;
if (max <= 1 || NULL == cmp || NULL == freeobj)
{
errno = EINVAL;
return -1;
}
for (i = 0; i < CACHE_MAX; i++)
if (0 == table[i].maxsize)
break;
if (CACHE_MAX == i)
{
errno = ENFILE;
return -1;
}
table[i].freeblocks = calloc(max, sizeof (struct entry));
if (NULL == table[i].freeblocks)
return -1;
for (j = 0; j < max - 1; j++)
table[i].freeblocks[j].next = &table[i].freeblocks[j + 1];
table[i].freelist = table[i].freeblocks;
table[i].maxsize = max;
table[i].cmp = cmp;
table[i].freeobj = freeobj;
table[i].isstale = isstale; /* This is permitted to be NULL */
table[i].hit = table[i].miss = 0;
return i;
}
/* Either get a free entry from the freelist, or remove the
last of the entries list */
static struct entry *new_entry (int desc)
{
struct entry *ep;
if ((ep = table[desc].freelist))
table[desc].freelist = ep->next;
else
{
for (ep = table[desc].entries; ep->next; ep = ep->next) ;
ep->prev->next = NULL;
table[desc].freeobj(ep->object);
}
ep->prev = ep->next = NULL;
ep->object = NULL;
return ep;
}
void cache_fin (int desc)
{
struct entry *ep;
struct entry *tmp;
void (*freeobj) (void *) = table[desc].freeobj;
for (ep = table[desc].entries; ep; ep = tmp)
{
(*freeobj) (ep->object);
tmp = ep->next;
}
free(table[desc].freeblocks);
memset(&table[desc], 0, sizeof (struct table));
}
void *cache_find (int desc, void *object)
{
register struct table *tp = &table[desc];
int (*cmp) (void *, void *) = tp->cmp;
int (*isstale) (void *) = tp->isstale;
struct entry *head = table[desc].entries;
register struct entry *ep;
for (ep = head; ep; ep = ep->next)
if (isstale && (*isstale) (ep->object))
{
if (ep->prev)
ep->prev->next = ep->next;
else
tp->entries = ep->next;
if (ep->next)
ep->next->prev = ep->prev;
ep->next = NULL;
(*tp->freeobj) (ep->object);
ep->next = tp->freelist;
tp->freelist = ep;
}
else if (0 == (*cmp) (object, ep->object))
{
/* Once found, move it to the head of the list */
if (ep != tp->entries)
{
ep->prev->next = ep->next;
if (ep->next)
ep->next->prev = ep->prev;
tp->entries->prev = ep;
ep->next = tp->entries;
tp->entries = ep;
ep->prev = NULL;
}
tp->hit++;
return tp->entries->object;
}
tp->miss++;
return NULL;
}
void cache_stat (int desc, int *hit, int *miss)
{
if (hit)
*hit = table[desc].hit;
if (miss)
*miss = table[desc].miss;
}
/* Return the first item in the cache. To be used as a hint.
Should we be checking for staleness here? */
void *cache_top (int desc)
{
return table[desc].entries->object;
}
/* Since new_entry() uses only pre-allocated memory, this function
cannot fail. */
void cache_insert (int desc, void *object)
{
register struct entry *ep;
ep = new_entry(desc);
ep->object = object;
ep->next = table[desc].entries;
if (table[desc].entries)
table[desc].entries->prev = ep;
table[desc].entries = ep;
}
void cache_invalidate (int desc, void *objp)
{
struct entry *ep;
struct entry *tmp;
for (ep = table[desc].entries; ep; ep = tmp)
if (0 == (*table[desc].cmp) (objp, ep->object))
{
if (ep->next)
ep->next->prev = ep->prev;
if (ep->prev)
ep->prev->next = ep->next;
else
table[desc].entries = ep->next;
(*table[desc].freeobj) (ep->object);
tmp = ep->next;
ep->object = NULL;
ep->prev = NULL;
ep->next = table[desc].freelist;
table[desc].freelist = ep;
break;
}
else
tmp = ep->next;
}
#ifdef CACHE_DEBUG
void cache_dump (int desc, void (*printer) (void *))
{
struct entry *ep;
for (ep = table[desc].entries; ep; ep = ep->next)
(*printer) (ep->object);
}
#endif /* CACHE_DEBUG */
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