| 1 | /*␊ |
| 2 | * Copyright (c) 2000-2003 Apple Computer, Inc. All rights reserved.␊ |
| 3 | *␊ |
| 4 | * @APPLE_LICENSE_HEADER_START@␊ |
| 5 | * ␊ |
| 6 | * The contents of this file constitute Original Code as defined in and␊ |
| 7 | * are subject to the Apple Public Source License Version 2.0 (the␊ |
| 8 | * "License"). You may not use this file except in compliance with the␊ |
| 9 | * License. Please obtain a copy of the License at␊ |
| 10 | * http://www.apple.com/publicsource and read it before using this file.␊ |
| 11 | * ␊ |
| 12 | * This Original Code and all software distributed under the License are␊ |
| 13 | * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER␊ |
| 14 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,␊ |
| 15 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,␊ |
| 16 | * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the␊ |
| 17 | * License for the specific language governing rights and limitations␊ |
| 18 | * under the License.␊ |
| 19 | * ␊ |
| 20 | * @APPLE_LICENSE_HEADER_END@␊ |
| 21 | */␊ |
| 22 | /*␊ |
| 23 | * cache.c - A simple cache for file systems meta-data.␊ |
| 24 | *␊ |
| 25 | * Copyright (c) 2000 Apple Computer, Inc.␊ |
| 26 | *␊ |
| 27 | * DRI: Josh de Cesare␊ |
| 28 | */␊ |
| 29 | ␊ |
| 30 | #include <sl.h>␊ |
| 31 | // #include <fs.h>␊ |
| 32 | ␊ |
| 33 | typedef struct CacheEntry {␊ |
| 34 | ␉CICell ih;␊ |
| 35 | ␉long time;␊ |
| 36 | ␉long long offset;␊ |
| 37 | } CacheEntry;␊ |
| 38 | ␊ |
| 39 | #define kCacheSize (0x100000)␊ |
| 40 | #define kCacheMinBlockSize (0x200)␊ |
| 41 | #define kCacheMaxBlockSize (0x8000)␊ |
| 42 | #define kCacheMaxEntries (kCacheSize / kCacheMinBlockSize)␊ |
| 43 | ␊ |
| 44 | static CICell gCacheIH;␊ |
| 45 | static long gCacheBlockSize;␊ |
| 46 | static long gCacheNumEntries;␊ |
| 47 | static long gCacheTime;␊ |
| 48 | ␊ |
| 49 | #ifdef __i386__␊ |
| 50 | ␉static CacheEntry *gCacheEntries;␊ |
| 51 | ␉static char *gCacheBuffer;␊ |
| 52 | #else␊ |
| 53 | ␉static CacheEntry gCacheEntries[kCacheMaxEntries];␊ |
| 54 | ␉static char gCacheBuffer[kCacheSize];␊ |
| 55 | #endif␊ |
| 56 | ␊ |
| 57 | #if CACHE_STATS␊ |
| 58 | ␉unsigned long gCacheHits;␊ |
| 59 | ␉unsigned long gCacheMisses;␊ |
| 60 | ␉unsigned long gCacheEvicts;␊ |
| 61 | #endif␊ |
| 62 | ␊ |
| 63 | void CacheReset()␊ |
| 64 | {␊ |
| 65 | ␉gCacheIH = NULL;␊ |
| 66 | }␊ |
| 67 | ␊ |
| 68 | void CacheInit( CICell ih, long blockSize )␊ |
| 69 | {␊ |
| 70 | #ifdef __i386__␊ |
| 71 | ␉if ((ih == gCacheIH) && (blockSize == gCacheBlockSize))␊ |
| 72 | ␉{␊ |
| 73 | ␉␉return;␊ |
| 74 | ␉}␊ |
| 75 | #endif␊ |
| 76 | ␊ |
| 77 | ␉if ((blockSize < kCacheMinBlockSize) || (blockSize > kCacheMaxBlockSize))␊ |
| 78 | ␉{␊ |
| 79 | ␉␉return;␊ |
| 80 | ␉}␊ |
| 81 | ␊ |
| 82 | ␉gCacheBlockSize = blockSize;␊ |
| 83 | ␉gCacheNumEntries = kCacheSize / gCacheBlockSize;␊ |
| 84 | ␉gCacheTime = 0;␊ |
| 85 | ␊ |
| 86 | #if CACHE_STATS␊ |
| 87 | ␉gCacheHits␉= 0;␊ |
| 88 | ␉gCacheMisses␉= 0;␊ |
| 89 | ␉gCacheEvicts␉= 0;␊ |
| 90 | #endif␊ |
| 91 | ␊ |
| 92 | gCacheIH = ih;␊ |
| 93 | ␊ |
| 94 | #ifdef __i386__␊ |
| 95 | ␉if (!gCacheBuffer)␊ |
| 96 | ␉{␊ |
| 97 | ␉␉gCacheBuffer = (char *) malloc(kCacheSize);␊ |
| 98 | ␉}␊ |
| 99 | ␊ |
| 100 | ␉if (!gCacheEntries)␊ |
| 101 | ␉{␊ |
| 102 | ␉␉gCacheEntries = (CacheEntry *) malloc(kCacheMaxEntries * sizeof(CacheEntry));␊ |
| 103 | ␉}␊ |
| 104 | ␊ |
| 105 | ␉if (!gCacheBuffer || !gCacheEntries)␊ |
| 106 | ␉{␊ |
| 107 | ␉␉gCacheIH = 0; // invalidate cache␊ |
| 108 | ␉␉return;␊ |
| 109 | ␉}␊ |
| 110 | #endif␊ |
| 111 | ␊ |
| 112 | ␉bzero(gCacheEntries, kCacheMaxEntries * sizeof(CacheEntry));␊ |
| 113 | }␊ |
| 114 | ␊ |
| 115 | long CacheRead(CICell ih, char * buffer, long long offset, long length, long cache)␊ |
| 116 | {␊ |
| 117 | ␉long cnt, oldestEntry = 0, oldestTime, loadCache = 0;␊ |
| 118 | ␉CacheEntry *entry;␊ |
| 119 | ␊ |
| 120 | ␉// See if the data can be cached.␊ |
| 121 | ␉if (cache && (gCacheIH == ih) && (length == gCacheBlockSize))␊ |
| 122 | ␉{␊ |
| 123 | ␉␉// Look for the data in the cache.␊ |
| 124 | ␉␉for (cnt = 0; cnt < gCacheNumEntries; cnt++)␊ |
| 125 | ␉␉{␊ |
| 126 | ␉␉␉entry = &gCacheEntries[cnt];␊ |
| 127 | ␊ |
| 128 | ␉␉␉if ((entry->ih == ih) && (entry->offset == offset))␊ |
| 129 | ␉␉␉{␊ |
| 130 | ␉␉␉␉entry->time = ++gCacheTime;␊ |
| 131 | ␉␉␉␉break;␊ |
| 132 | ␉␉␉}␊ |
| 133 | ␉␉}␊ |
| 134 | ␊ |
| 135 | ␉␉// If the data was found copy it to the caller.␊ |
| 136 | ␉␉if (cnt != gCacheNumEntries)␊ |
| 137 | ␉␉{␊ |
| 138 | ␉␉␉bcopy(gCacheBuffer + cnt * gCacheBlockSize, buffer, gCacheBlockSize);␊ |
| 139 | #if CACHE_STATS␊ |
| 140 | ␉␉␉gCacheHits++;␊ |
| 141 | #endif␊ |
| 142 | ␉␉␉return gCacheBlockSize;␊ |
| 143 | ␉␉}␊ |
| 144 | ␊ |
| 145 | ␉␉// Could not find the data in the cache.␊ |
| 146 | ␉␉loadCache = 1;␊ |
| 147 | ␉}␊ |
| 148 | ␊ |
| 149 | ␉// Read the data from the disk.␊ |
| 150 | ␉Seek(ih, offset);␊ |
| 151 | ␉Read(ih, (long)buffer, length);␊ |
| 152 | ␊ |
| 153 | #if CACHE_STATS␊ |
| 154 | ␉if (cache)␊ |
| 155 | ␉{␊ |
| 156 | ␉␉gCacheMisses++;␊ |
| 157 | ␉}␊ |
| 158 | #endif␊ |
| 159 | ␊ |
| 160 | ␉// Put the data from the disk in the cache if needed.␊ |
| 161 | ␉if (loadCache)␊ |
| 162 | ␉{␊ |
| 163 | ␉␉// Find a free entry.␊ |
| 164 | ␉␉oldestTime = gCacheTime;␊ |
| 165 | ␊ |
| 166 | ␉␉for (cnt = 0; cnt < gCacheNumEntries; cnt++)␊ |
| 167 | ␉␉{␊ |
| 168 | ␉␉␉entry = &gCacheEntries[cnt];␊ |
| 169 | ␊ |
| 170 | ␉␉␉// Found a free entry.␊ |
| 171 | ␉␉␉if (entry->ih == 0)␊ |
| 172 | ␉␉␉{␊ |
| 173 | ␉␉␉␉break;␊ |
| 174 | ␉␉␉}␊ |
| 175 | ␊ |
| 176 | ␉␉␉if (entry->time < oldestTime)␊ |
| 177 | ␉␉␉{␊ |
| 178 | ␉␉␉␉oldestTime = entry->time;␊ |
| 179 | ␉␉␉␉oldestEntry = cnt;␊ |
| 180 | ␉␉␉}␊ |
| 181 | ␉␉}␊ |
| 182 | ␊ |
| 183 | ␉␉// If no free entry was found, use the oldest.␊ |
| 184 | ␉␉if (cnt == gCacheNumEntries)␊ |
| 185 | ␉␉{␊ |
| 186 | ␉␉␉cnt = oldestEntry;␊ |
| 187 | #if CACHE_STATS␊ |
| 188 | ␉␉␉gCacheEvicts++;␊ |
| 189 | #endif␊ |
| 190 | ␉␉}␊ |
| 191 | ␊ |
| 192 | ␉␉// Copy the data from disk to the new entry.␊ |
| 193 | ␉␉entry = &gCacheEntries[cnt];␊ |
| 194 | ␉␉entry->ih = ih;␊ |
| 195 | ␉␉entry->time = ++gCacheTime;␊ |
| 196 | ␉␉entry->offset = offset;␊ |
| 197 | ␉␉bcopy(buffer, gCacheBuffer + cnt * gCacheBlockSize, gCacheBlockSize);␊ |
| 198 | ␉}␊ |
| 199 | ␊ |
| 200 | ␉return length;␊ |
| 201 | }␊ |
| 202 | |
