include/mpool.h

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)mpool.h     8.1 (Berkeley) 6/2/93
 */

/*
 * The memory pool scheme is a simple one.  Each in memory page is referenced
 * by a bucket which is threaded in three ways.  All active pages are threaded
 * on a hash chain (hashed by the page number) and an lru chain.  Inactive
 * pages are threaded on a free chain.  Each reference to a memory pool is
 * handed an MPOOL which is the opaque cookie passed to all of the memory
 * routines.
 */
#define HASHSIZE        128
#define HASHKEY(pgno)   ((pgno - 1) % HASHSIZE)

/* The BKT structures are the elements of the lists. */
typedef struct BKT {
        struct BKT      *hnext;         /* next hash bucket */
        struct BKT      *hprev;         /* previous hash bucket */
        struct BKT      *cnext;         /* next free/lru bucket */
        struct BKT      *cprev;         /* previous free/lru bucket */
        void            *page;          /* page */
        pgno_t          pgno;           /* page number */

#define MPOOL_DIRTY     0x01            /* page needs to be written */
#define MPOOL_PINNED    0x02            /* page is pinned into memory */
        unsigned long   flags;          /* flags */
} BKT;

/* The BKTHDR structures are the heads of the lists. */
typedef struct BKTHDR {
        struct BKT      *hnext;         /* next hash bucket */
        struct BKT      *hprev;         /* previous hash bucket */
        struct BKT      *cnext;         /* next free/lru bucket */
        struct BKT      *cprev;         /* previous free/lru bucket */
} BKTHDR;

typedef struct MPOOL {
        BKTHDR  free;                   /* The free list. */
        BKTHDR  lru;                    /* The LRU list. */
        BKTHDR  hashtable[HASHSIZE];    /* Hashed list by page number. */
        pgno_t  curcache;               /* Current number of cached pages. */
        pgno_t  maxcache;               /* Max number of cached pages. */
        pgno_t  npages;                 /* Number of pages in the file. */
        u_long  pagesize;               /* File page size. */
        int     fd;                     /* File descriptor. */
                                        /* Page in conversion routine. */
        void    (*pgin) __P((void *, pgno_t, void *));
                                        /* Page out conversion routine. */
        void    (*pgout) __P((void *, pgno_t, void *));
        void    *pgcookie;              /* Cookie for page in/out routines. */
#ifdef STATISTICS
        unsigned long   cachehit;
        unsigned long   cachemiss;
        unsigned long   pagealloc;
        unsigned long   pageflush;
        unsigned long   pageget;
        unsigned long   pagenew;
        unsigned long   pageput;
        unsigned long   pageread;
        unsigned long   pagewrite;
#endif
} MPOOL;

#ifdef __MPOOLINTERFACE_PRIVATE
/* Macros to insert/delete into/from hash chain. */
#define rmhash(bp) { \
        (bp)->hprev->hnext = (bp)->hnext; \
        (bp)->hnext->hprev = (bp)->hprev; \
}
#define inshash(bp, pg) { \
        hp = &mp->hashtable[HASHKEY(pg)]; \
        (bp)->hnext = hp->hnext; \
        (bp)->hprev = (struct BKT *)hp; \
        hp->hnext->hprev = (bp); \
        hp->hnext = (bp); \
}

/* Macros to insert/delete into/from lru and free chains. */
#define rmchain(bp) { \
        (bp)->cprev->cnext = (bp)->cnext; \
        (bp)->cnext->cprev = (bp)->cprev; \
}
#define inschain(bp, dp) { \
        (bp)->cnext = (dp)->cnext; \
        (bp)->cprev = (struct BKT *)(dp); \
        (dp)->cnext->cprev = (bp); \
        (dp)->cnext = (bp); \
}
#endif

__BEGIN_DECLS
MPOOL   *mpool_open __P((DBT *, int, pgno_t, pgno_t));
void     mpool_filter __P((MPOOL *, void (*)(void *, pgno_t, void *),
            void (*)(void *, pgno_t, void *), void *));
void    *mpool_new __P((MPOOL *, pgno_t *));
void    *mpool_get __P((MPOOL *, pgno_t, u_int));
int      mpool_put __P((MPOOL *, void *, u_int));
int      mpool_sync __P((MPOOL *));
int      mpool_close __P((MPOOL *));
#ifdef STATISTICS
void     mpool_stat __P((MPOOL *));
#endif
__END_DECLS