lib/libc/db/btree/lrucache.h

   1 /*-
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Mike Olson.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 /*
  38  * @(#)lrucache.h       5.1 (Berkeley) 1/23/91
  39  */
  40
  41 /*
  42  *  LRU list entries.  The head of the list is the most-recently requested
  43  *  block; the tail is the least-recently requested one.
  44  */
  45
  46 typedef struct LRU_ENT {
  47         char    *l_buffer;              /* buffer we return to user */
  48         int     l_pgno;                 /* logical page number */
  49         int     l_flags;                /* FREE and DIRTY bits */
  50         struct LRU_ENT  *l_prev;        /* predecessor in LRU list */
  51         struct LRU_ENT  *l_next;        /* successor in LRU list */
  52 } LRU_ENT;
  53
  54 /*
  55  *  Cache entries.  We use a hash table to avoid a linear walk of the LRU
  56  *  list when we need to look up blocks by number.  The hash table is
  57  *  chained.
  58  */
  59
  60 typedef struct CACHE_ENT {
  61         int                     c_pgno;
  62         LRU_ENT                 *c_lruent;
  63         struct CACHE_ENT        *c_chain;
  64 } CACHE_ENT;
  65
  66 /*
  67  *  The LRU cache structure.  The cache size (lru_csize) is the largest size
  68  *  the user wants us to grow to; current size (lru_cursz) is always less than
  69  *  or equal to lru_csize.  Note that we will grow the cache (lru_csize) if
  70  *  it's the only way that we can satisfy a user's block request.
  71  */
  72
  73 typedef struct LRUCACHE {
  74         int             lru_fd;
  75         int             lru_csize;
  76         int             lru_psize;
  77         int             lru_cursz;
  78         char            *lru_opaque;            /* passed to inproc, outproc */
  79         int             (*lru_inproc)();
  80         int             (*lru_outproc)();
  81         LRU_ENT         *lru_head;
  82         LRU_ENT         *lru_tail;
  83         CACHE_ENT       **lru_cache;
  84 } LRUCACHE;
  85
  86 #ifndef NULL
  87 #define NULL    0
  88 #endif /* ndef NULL */
  89
  90 /* this is the opaque type we return for LRU caches */
  91 typedef char    *LRU;
  92
  93 /* bits for l_flags in LRU_ENT structure */
  94 #define F_DIRTY         (1 << 0)
  95 #define F_FREE          (1 << 1)
  96
  97 /* lru module routines */
  98 extern CACHE_ENT        *lruhashget();
  99 extern CACHE_ENT        *lruhashput();
 100 extern int              lruhashdel();
 101 extern void             lruhead();
 102 extern int              lrugrow();
 103 extern LRU              lruinit();
 104 extern int              lruwrite();
 105 extern int              lrusync();
 106 extern char             *lruget();
 107 extern char             *lrugetnew();
 108 extern char             *lrugetpg();
 109 extern int              lrurelease();
 110 extern void             lrufree();