NetBSD/lib/libc/db/btree/lrucache.h

111 lines
3.7 KiB
C

/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Mike Olson.
*
* 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.
*/
/*
* @(#)lrucache.h 5.1 (Berkeley) 1/23/91
*/
/*
* LRU list entries. The head of the list is the most-recently requested
* block; the tail is the least-recently requested one.
*/
typedef struct LRU_ENT {
char *l_buffer; /* buffer we return to user */
int l_pgno; /* logical page number */
int l_flags; /* FREE and DIRTY bits */
struct LRU_ENT *l_prev; /* predecessor in LRU list */
struct LRU_ENT *l_next; /* successor in LRU list */
} LRU_ENT;
/*
* Cache entries. We use a hash table to avoid a linear walk of the LRU
* list when we need to look up blocks by number. The hash table is
* chained.
*/
typedef struct CACHE_ENT {
int c_pgno;
LRU_ENT *c_lruent;
struct CACHE_ENT *c_chain;
} CACHE_ENT;
/*
* The LRU cache structure. The cache size (lru_csize) is the largest size
* the user wants us to grow to; current size (lru_cursz) is always less than
* or equal to lru_csize. Note that we will grow the cache (lru_csize) if
* it's the only way that we can satisfy a user's block request.
*/
typedef struct LRUCACHE {
int lru_fd;
int lru_csize;
int lru_psize;
int lru_cursz;
char *lru_opaque; /* passed to inproc, outproc */
int (*lru_inproc)();
int (*lru_outproc)();
LRU_ENT *lru_head;
LRU_ENT *lru_tail;
CACHE_ENT **lru_cache;
} LRUCACHE;
#ifndef NULL
#define NULL 0
#endif /* ndef NULL */
/* this is the opaque type we return for LRU caches */
typedef char *LRU;
/* bits for l_flags in LRU_ENT structure */
#define F_DIRTY (1 << 0)
#define F_FREE (1 << 1)
/* lru module routines */
extern CACHE_ENT *lruhashget();
extern CACHE_ENT *lruhashput();
extern int lruhashdel();
extern void lruhead();
extern int lrugrow();
extern LRU lruinit();
extern int lruwrite();
extern int lrusync();
extern char *lruget();
extern char *lrugetnew();
extern char *lrugetpg();
extern int lrurelease();
extern void lrufree();