include/mpool.h

root/include/mpool.h
/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1991, 1993, 1994
 *      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. 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.
 */

#ifndef _MPOOL_H_
#define _MPOOL_H_

#include <sys/queue.h>

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

/* The BKT structures are the elements of the queues. */
typedef struct _bkt {
        TAILQ_ENTRY(_bkt) hq;           /* hash queue */
        TAILQ_ENTRY(_bkt) q;            /* lru queue */
        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 */
#define MPOOL_INUSE     0x04            /* page address is valid */
        u_int8_t flags;                 /* flags */
} BKT;

typedef struct MPOOL {
        TAILQ_HEAD(_lqh, _bkt) lqh;     /* lru queue head */
                                        /* hash queue array */
        TAILQ_HEAD(_hqh, _bkt) hqh[HASHSIZE];
        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 */
        unsigned long   pagesize;       /* file page size */
        int     fd;                     /* file descriptor */
                                        /* page in conversion routine */
        void    (*pgin)(void *, pgno_t, void *);
                                        /* page out conversion routine */
        void    (*pgout)(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;

#define MPOOL_IGNOREPIN 0x01            /* Ignore if the page is pinned. */
#define MPOOL_PAGE_REQUEST      0x01    /* Allocate a new page with a
                                           specific page number. */
#define MPOOL_PAGE_NEXT         0x02    /* Allocate a new page with the next
                                          page number. */

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

#endif
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