gen/libsaio/cache.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /* cache */
  25
  26 #import "cache.h"
  27 #import "libsa.h"
  28
  29 cache_t *cacheInit(
  30     int nitems,
  31     int item_size
  32 )
  33 {
  34     cache_t *cp;
  35     item_size += sizeof(item_t);
  36     cp = (cache_t *)malloc(sizeof(cache_t) + nitems * item_size);
  37     cp->nitems = nitems;
  38     cp->item_size = item_size;
  39     return cp;
  40 }
  41
  42 /*
  43  * Either find an item in the cache, or find where it should go.
  44  * Returns 1 if found, 0 if not found.
  45  * This function assumes that if you find an empty slot, you will use it;
  46  * therefore, empty slots returned are marked valid.
  47  */
  48 int cacheFind(
  49     cache_t *cp,
  50     int key1,
  51     int key2,
  52     char **ip
  53 )
  54 {
  55     item_t *iip, *min_p;
  56     int i,j;
  57
  58     for(i=j=0, iip = min_p = (item_t *)cp->storage; i < cp->nitems; i++) {
  59         if (iip->referenced && (iip->key1 == key1) && (iip->key2 == key2)) {
  60             *ip = iip->storage;
  61             if (iip->referenced < 65535)
  62                 iip->referenced++;
  63             return 1;
  64         }
  65         if (iip->referenced < min_p->referenced) {
  66             min_p = iip;
  67             j = i;
  68         }
  69         iip = (item_t *)((char *)iip + cp->item_size);
  70     }
  71     *ip = min_p->storage;
  72     min_p->referenced = 1;
  73     min_p->key1 = key1;
  74     min_p->key2 = key2;
  75     return 0;
  76 }
  77
  78 /*
  79  * Flush the cache.
  80  */
  81 void cacheFlush(
  82     cache_t *cp
  83 )
  84 {
  85     int i;
  86     item_t *ip;
  87
  88     if (cp == 0)
  89         return;
  90     for(i=0, ip = (item_t *)cp->storage; i < cp->nitems; i++) {
  91         ip->referenced = 0;
  92         ip = (item_t *)((char *)ip + cp->item_size);
  93     }
  94 }