nmdb/cache.h

   1
   2 #ifndef _CACHE_H
   3 #define _CACHE_H
   4
   5 /* Generic cache layer. See cache.c for more information. */
   6
   7 #include <sys/types.h>          /* for size_t */
   8 #include <stdint.h>             /* for int64_t */
   9
  10
  11 #define CHAINLEN 4
  12
  13 struct cache {
  14         /* set directly by initialization */
  15         size_t numobjs;
  16         unsigned int flags;
  17
  18         /* calculated */
  19         size_t hashlen;
  20
  21         /* the cache data itself */
  22         struct cache_chain *table;
  23 };
  24
  25 struct cache_entry {
  26         unsigned char *key;
  27         unsigned char *val;
  28         size_t ksize;
  29         size_t vsize;
  30
  31         struct cache_entry *prev;
  32         struct cache_entry *next;
  33 };
  34
  35 struct cache_chain {
  36         size_t len;
  37
  38         /* the entries live inside the chain, to avoid allocation costs and
  39          * make it more cache-friendly */
  40         struct cache_entry entries[CHAINLEN];
  41
  42         /* these point to elements of the entries array */
  43         struct cache_entry *first;
  44         struct cache_entry *last;
  45 };
  46
  47
  48 struct cache *cache_create(size_t numobjs, unsigned int flags);
  49 int cache_free(struct cache *cd);
  50 int cache_get(struct cache *cd, const unsigned char *key, size_t ksize,
  51                 unsigned char **val, size_t *vsize);
  52 int cache_set(struct cache *cd, const unsigned char *k, size_t ksize,
  53                 const unsigned char *v, size_t vsize);
  54 int cache_del(struct cache *cd, const unsigned char *key, size_t ksize);
  55 int cache_cas(struct cache *cd, const unsigned char *key, size_t ksize,
  56                 const unsigned char *oldval, size_t ovsize,
  57                 const unsigned char *newval, size_t nvsize);
  58 int cache_incr(struct cache *cd, const unsigned char *key, size_t ksize,
  59                 int64_t increment, int64_t *newval);
  60
  61 #endif
  62