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mmap_cache.h  view on Meta::CPAN

 * - Find the hash slot for the key
 * 
 * For get's:
 * 
 * - Use linear probing to find correct key, or empty slot
 * 
 * For set's:
 * 
 * - Use linear probing to find empty slot
 * - If not enough free slots, do an 'expunge' run
 * - Store key/value at FreeData offset, update, and store in slot
 * - If not enough space at FreeData offset, do an 'expunge' run
 *    then store data
 * 
 * For delete's:
 * 
 * - Use linear probing to find correct key, or empty slot
 * - Set slot to empty (data cleaned up in expunge run)
 * 
 * An expunge run consists of:
 * 
 * - Scan slots to find used key/value parts. Remove older items
 * - If ratio used/free slots too high, increase slot count
 * - Compact key/value data into one memory block
 * - Restore and update offsets in slots
 * 
*/

#include <stdint.h>

/* Main cache structure passed as a pointer to each function */
typedef struct mmap_cache mmap_cache;

/* Iterator structure for iterating over items in cache */
typedef struct mmap_cache_it mmap_cache_it;

/* Unsigned 32 bit integer */
typedef uint32_t MU32;

/* Unsigned 64 bit integer */
typedef uint64_t MU64;

/* Magic value for no p_cur */
#define NOPAGE (~(MU32)0)

/* Allow overriding "time" for tests */
void mmc_set_time_override(MU32);

/* Initialisation/closing/error functions */
mmap_cache * mmc_new();
int mmc_init(mmap_cache *);
int mmc_set_param(mmap_cache *, char *, char *);
int mmc_get_param(mmap_cache *, char *);
int mmc_close(mmap_cache *);
char * mmc_error(mmap_cache *);

/* Functions for find/locking a page */
int mmc_hash(mmap_cache *, void *, int, MU32 *, MU32 *);
int mmc_lock(mmap_cache *, MU32);
int mmc_unlock(mmap_cache *);
int mmc_is_locked(mmap_cache *);

/* Functions for getting/setting/deleting values in current page */
int mmc_read(mmap_cache *, MU32, void *, int, void **, int *, MU32 *, MU32 *);
int mmc_write(mmap_cache *, MU32, void *, int, void *, int, MU32, MU32);
int mmc_delete(mmap_cache *, MU32, void *, int, MU32 *);

/* Functions of expunging values in current page */
int mmc_calc_expunge(mmap_cache *, int, int, MU32 *, MU32 ***);
int mmc_do_expunge(mmap_cache *, int, MU32, MU32 **);

/* Functions for iterating over items in a cache */
mmap_cache_it * mmc_iterate_new(mmap_cache *);
MU32 * mmc_iterate_next(mmap_cache_it *);
void mmc_iterate_close(mmap_cache_it *);

/* Retrieve details of a cache page/entry */
void mmc_get_details(mmap_cache *, MU32 *, void **, int *, void **, int *, MU32 *, MU32 *, MU32 *);
void mmc_get_page_details(mmap_cache * cache, MU32 * nreads, MU32 * nreadhits);
void mmc_reset_page_details(mmap_cache * cache);

/* Internal functions */
int _mmc_set_error(mmap_cache *, int, char *, ...);
void _mmc_init_page(mmap_cache *, MU32);

MU32 * _mmc_find_slot(mmap_cache * , MU32 , void *, int, int );
void _mmc_delete_slot(mmap_cache * , MU32 *);

int _mmc_check_expunge(mmap_cache * , int);

int  _mmc_test_page(mmap_cache *);
int  _mmc_dump_page(mmap_cache *);