| 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 | struct CacheEntry {␊ |
| 34 | CICell ih;␊ |
| 35 | long time;␊ |
| 36 | long long offset;␊ |
| 37 | };␊ |
| 38 | typedef struct CacheEntry CacheEntry;␊ |
| 39 | ␊ |
| 40 | #define kCacheSize (0x100000)␊ |
| 41 | #define kCacheMinBlockSize (0x200)␊ |
| 42 | #define kCacheMaxBlockSize (0x4000)␊ |
| 43 | #define kCacheMaxEntries (kCacheSize / kCacheMinBlockSize)␊ |
| 44 | ␊ |
| 45 | static CICell gCacheIH;␊ |
| 46 | static long gCacheBlockSize;␊ |
| 47 | static long gCacheNumEntries;␊ |
| 48 | static long gCacheTime;␊ |
| 49 | ␊ |
| 50 | #ifdef __i386__␊ |
| 51 | static CacheEntry *gCacheEntries;␊ |
| 52 | static char *gCacheBuffer;␊ |
| 53 | #else␊ |
| 54 | static CacheEntry gCacheEntries[kCacheMaxEntries];␊ |
| 55 | static char gCacheBuffer[kCacheSize];␊ |
| 56 | #endif␊ |
| 57 | ␊ |
| 58 | #if CACHE_STATS␊ |
| 59 | unsigned long gCacheHits;␊ |
| 60 | unsigned long gCacheMisses;␊ |
| 61 | unsigned long gCacheEvicts;␊ |
| 62 | #endif␊ |
| 63 | ␊ |
| 64 | void CacheReset()␊ |
| 65 | {␊ |
| 66 | gCacheIH = NULL;␊ |
| 67 | }␊ |
| 68 | ␊ |
| 69 | void CacheInit( CICell ih, long blockSize )␊ |
| 70 | {␊ |
| 71 | #ifdef __i386__␊ |
| 72 | if ((ih == gCacheIH) && (blockSize == gCacheBlockSize))␊ |
| 73 | return;␊ |
| 74 | #endif␊ |
| 75 | ␊ |
| 76 | if ((blockSize < kCacheMinBlockSize) ||␊ |
| 77 | (blockSize >= kCacheMaxBlockSize))␊ |
| 78 | return;␊ |
| 79 | ␊ |
| 80 | gCacheBlockSize = blockSize;␊ |
| 81 | gCacheNumEntries = kCacheSize / gCacheBlockSize;␊ |
| 82 | gCacheTime = 0;␊ |
| 83 | ␊ |
| 84 | #if CACHE_STATS␊ |
| 85 | gCacheHits = 0;␊ |
| 86 | gCacheMisses = 0;␊ |
| 87 | gCacheEvicts = 0;␊ |
| 88 | #endif␊ |
| 89 | ␊ |
| 90 | gCacheIH = ih;␊ |
| 91 | ␊ |
| 92 | #ifdef __i386__␊ |
| 93 | if (!gCacheBuffer) gCacheBuffer = (char *) malloc(kCacheSize);␊ |
| 94 | if (!gCacheEntries) gCacheEntries = (CacheEntry *) malloc(kCacheMaxEntries * sizeof(CacheEntry));␊ |
| 95 | if ( !gCacheBuffer || !gCacheEntries )␊ |
| 96 | {␊ |
| 97 | gCacheIH = 0; // invalidate cache␊ |
| 98 | return;␊ |
| 99 | }␊ |
| 100 | #endif␊ |
| 101 | ␊ |
| 102 | bzero(gCacheEntries, kCacheMaxEntries * sizeof(CacheEntry));␊ |
| 103 | }␊ |
| 104 | ␊ |
| 105 | long CacheRead( CICell ih, char * buffer, long long offset,␊ |
| 106 | ␉ long length, long cache )␊ |
| 107 | {␊ |
| 108 | long cnt, oldestEntry = 0, oldestTime, loadCache = 0;␊ |
| 109 | CacheEntry *entry;␊ |
| 110 | ␊ |
| 111 | // See if the data can be cached.␊ |
| 112 | if (cache && (gCacheIH == ih) && (length == gCacheBlockSize)) {␊ |
| 113 | // Look for the data in the cache.␊ |
| 114 | for (cnt = 0; cnt < gCacheNumEntries; cnt++) {␊ |
| 115 | entry = &gCacheEntries[cnt];␊ |
| 116 | if ((entry->ih == ih) && (entry->offset == offset)) {␊ |
| 117 | entry->time = ++gCacheTime;␊ |
| 118 | break;␊ |
| 119 | }␊ |
| 120 | }␊ |
| 121 | ␊ |
| 122 | // If the data was found copy it to the caller.␊ |
| 123 | if (cnt != gCacheNumEntries) {␊ |
| 124 | bcopy(gCacheBuffer + cnt * gCacheBlockSize, buffer, gCacheBlockSize);␊ |
| 125 | #if CACHE_STATS␊ |
| 126 | gCacheHits++;␊ |
| 127 | #endif␊ |
| 128 | return gCacheBlockSize;␊ |
| 129 | }␊ |
| 130 | ␊ |
| 131 | // Could not find the data in the cache.␊ |
| 132 | loadCache = 1;␊ |
| 133 | }␊ |
| 134 | ␊ |
| 135 | // Read the data from the disk.␊ |
| 136 | Seek(ih, offset);␊ |
| 137 | Read(ih, (long)buffer, length);␊ |
| 138 | #if CACHE_STATS␊ |
| 139 | if (cache) gCacheMisses++;␊ |
| 140 | #endif␊ |
| 141 | ␊ |
| 142 | // Put the data from the disk in the cache if needed.␊ |
| 143 | if (loadCache) {␊ |
| 144 | // Find a free entry.␊ |
| 145 | oldestTime = gCacheTime;␊ |
| 146 | for (cnt = 0; cnt < gCacheNumEntries; cnt++) {␊ |
| 147 | entry = &gCacheEntries[cnt];␊ |
| 148 | ␊ |
| 149 | // Found a free entry.␊ |
| 150 | if (entry->ih == 0) break;␊ |
| 151 | ␊ |
| 152 | if (entry->time < oldestTime) {␊ |
| 153 | oldestTime = entry->time;␊ |
| 154 | oldestEntry = cnt;␊ |
| 155 | }␊ |
| 156 | }␊ |
| 157 | ␊ |
| 158 | // If no free entry was found, use the oldest.␊ |
| 159 | if (cnt == gCacheNumEntries) {␊ |
| 160 | cnt = oldestEntry;␊ |
| 161 | #if CACHE_STATS␊ |
| 162 | gCacheEvicts++;␊ |
| 163 | #endif␊ |
| 164 | }␊ |
| 165 | ␊ |
| 166 | // Copy the data from disk to the new entry.␊ |
| 167 | entry = &gCacheEntries[cnt];␊ |
| 168 | entry->ih = ih;␊ |
| 169 | entry->time = ++gCacheTime;␊ |
| 170 | entry->offset = offset;␊ |
| 171 | bcopy(buffer, gCacheBuffer + cnt * gCacheBlockSize, gCacheBlockSize);␊ |
| 172 | }␊ |
| 173 | ␊ |
| 174 | return length;␊ |
| 175 | }␊ |
| 176 | |
