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/* $OpenBSD: cache.c,v 1.3 2004/12/15 05:09:06 jfb Exp $ */
/*
* Copyright (c) 2004 Jean-Francois Brousseau <jfb@openbsd.org>
* 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. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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.
*/
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/time.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include "log.h"
#include "rcs.h"
#define RCS_CACHE_BUCKETS 256
struct rcs_cachent {
u_int rc_hits;
u_int8_t rc_hash;
RCSFILE *rc_rfp;
struct timeval rc_atime;
TAILQ_ENTRY(rcs_cachent) rc_list;
TAILQ_ENTRY(rcs_cachent) rc_lru;
};
static u_int8_t rcs_cache_hash (const char *);
TAILQ_HEAD(rcs_cachebkt, rcs_cachent) rcs_cache[RCS_CACHE_BUCKETS];
TAILQ_HEAD(rcs_lruhead, rcs_cachent) rcs_cache_lru;
u_int rcs_cache_maxent;
u_int rcs_cache_nbent;
/*
* rcs_cache_init()
*
* Initialize the RCS file data cache.
* Returns 0 on success, -1 on failure.
*/
int
rcs_cache_init(u_int maxent)
{
u_int i;
for (i = 0; i < RCS_CACHE_BUCKETS; i++)
TAILQ_INIT(&rcs_cache[i]);
TAILQ_INIT(&rcs_cache_lru);
rcs_cache_maxent = maxent;
rcs_cache_nbent = 0;
return (0);
}
/*
* rcs_cache_destroy()
*/
void
rcs_cache_destroy(void)
{
}
/*
* rcs_cache_fetch()
*
*/
RCSFILE*
rcs_cache_fetch(const char *path)
{
u_int8_t hash;
struct rcs_cachent *rcp;
RCSFILE *rfp;
rfp = NULL;
hash = rcs_cache_hash(path);
TAILQ_FOREACH(rcp, &(rcs_cache[hash]), rc_list) {
if (strcmp(path, rcp->rc_rfp->rf_path) == 0) {
rfp = rcp->rc_rfp;
break;
}
}
if (rcp != NULL) {
(void)gettimeofday(&(rcp->rc_atime), NULL);
rcp->rc_hits++;
/* move this item back at the end of the LRU */
TAILQ_REMOVE(&rcs_cache_lru, rcp, rc_lru);
TAILQ_INSERT_TAIL(&rcs_cache_lru, rcp, rc_lru);
/* increment reference count for caller */
rfp->rf_ref++;
}
return (rfp);
}
/*
* rcs_cache_store()
*
* Store the RCSFILE <rfp> in the RCS file cache. By storing the file, its
* reference count gets incremented for the cache reference, so the caller
* should still rcs_close() the file once they are done with it.
* Returns 0 on success, or -1 on failure.
*/
int
rcs_cache_store(RCSFILE *rfp)
{
struct rcs_cachent *rcp, *old_rcp;
/* don't store the same element twice */
if (rcs_cache_fetch(rfp->rf_path) != NULL)
return (0);
rcp = (struct rcs_cachent *)malloc(sizeof(*rcp));
if (rcp == NULL) {
cvs_log(LP_ERRNO, "failed to allocate RCS cache entry");
return (-1);
}
rcp->rc_hits = 0;
rcp->rc_rfp = rfp;
rfp->rf_ref++;
rcp->rc_hash = rcs_cache_hash(rfp->rf_path);
rcs_cache_nbent++;
if (rcs_cache_nbent == rcs_cache_maxent) {
/* ditch the oldest entry in the LRU */
old_rcp = TAILQ_FIRST(&rcs_cache_lru);
TAILQ_REMOVE(&rcs_cache_lru, old_rcp, rc_lru);
TAILQ_REMOVE(&(rcs_cache[old_rcp->rc_hash]), old_rcp, rc_list);
/* free our reference */
rcs_close(old_rcp->rc_rfp);
free(old_rcp);
}
TAILQ_INSERT_TAIL(&(rcs_cache[rcp->rc_hash]), rcp, rc_list);
TAILQ_INSERT_TAIL(&rcs_cache_lru, rcp, rc_lru);
return (0);
}
/*
* rcs_cache_hash()
*
* Hash the <path> string.
*/
static u_int8_t
rcs_cache_hash(const char *path)
{
const char *sp;
u_int8_t hash;
hash = 0;
for (sp = path; *sp != '\0'; sp++)
hash ^= (*sp << 3) ^ (*sp >> 2);
return (hash);
}
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