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 "sl.h" //Azi:???␊ |
32 | //#include <fs.h>␊ |
33 | ␊ |
34 | struct CacheEntry {␊ |
35 | CICell ih;␊ |
36 | long time;␊ |
37 | long long offset;␊ |
38 | };␊ |
39 | typedef struct CacheEntry CacheEntry;␊ |
40 | ␊ |
41 | #define kCacheSize (0x100000)␊ |
42 | #define kCacheMinBlockSize (0x200)␊ |
43 | #define kCacheMaxBlockSize (0x8000)␊ |
44 | #define kCacheMaxEntries (kCacheSize / kCacheMinBlockSize)␊ |
45 | ␊ |
46 | static CICell gCacheIH;␊ |
47 | static long gCacheBlockSize;␊ |
48 | static long gCacheNumEntries;␊ |
49 | static long gCacheTime;␊ |
50 | ␊ |
51 | #ifdef __i386__␊ |
52 | static CacheEntry *gCacheEntries;␊ |
53 | static char *gCacheBuffer;␊ |
54 | #else␊ |
55 | static CacheEntry gCacheEntries[kCacheMaxEntries];␊ |
56 | static char gCacheBuffer[kCacheSize];␊ |
57 | #endif␊ |
58 | ␊ |
59 | #if CACHE_STATS␊ |
60 | unsigned long gCacheHits;␊ |
61 | unsigned long gCacheMisses;␊ |
62 | unsigned long gCacheEvicts;␊ |
63 | #endif␊ |
64 | ␊ |
65 | void CacheReset()␊ |
66 | {␊ |
67 | gCacheIH = NULL;␊ |
68 | }␊ |
69 | ␊ |
70 | void CacheInit( CICell ih, long blockSize )␊ |
71 | {␊ |
72 | #ifdef __i386__␊ |
73 | if ((ih == gCacheIH) && (blockSize == gCacheBlockSize))␊ |
74 | return;␊ |
75 | #endif␊ |
76 | ␊ |
77 | if ((blockSize < kCacheMinBlockSize) ||␊ |
78 | (blockSize > kCacheMaxBlockSize))␊ |
79 | return;␊ |
80 | ␊ |
81 | gCacheBlockSize = blockSize;␊ |
82 | gCacheNumEntries = kCacheSize / gCacheBlockSize;␊ |
83 | gCacheTime = 0;␊ |
84 | ␊ |
85 | #if CACHE_STATS␊ |
86 | gCacheHits = 0;␊ |
87 | gCacheMisses = 0;␊ |
88 | gCacheEvicts = 0;␊ |
89 | #endif␊ |
90 | ␊ |
91 | gCacheIH = ih;␊ |
92 | ␊ |
93 | #ifdef __i386__␊ |
94 | if (!gCacheBuffer) gCacheBuffer = (char *) malloc(kCacheSize);␊ |
95 | if (!gCacheEntries) gCacheEntries = (CacheEntry *) malloc(kCacheMaxEntries * sizeof(CacheEntry));␊ |
96 | if ( !gCacheBuffer || !gCacheEntries )␊ |
97 | {␊ |
98 | gCacheIH = 0; // invalidate cache␊ |
99 | return;␊ |
100 | }␊ |
101 | #endif␊ |
102 | ␊ |
103 | bzero(gCacheEntries, kCacheMaxEntries * sizeof(CacheEntry));␊ |
104 | }␊ |
105 | ␊ |
106 | long CacheRead( CICell ih, char * buffer, long long offset,␊ |
107 | ␉ long length, long cache )␊ |
108 | {␊ |
109 | long cnt, oldestEntry = 0, oldestTime, loadCache = 0;␊ |
110 | CacheEntry *entry;␊ |
111 | ␊ |
112 | // See if the data can be cached.␊ |
113 | if (cache && (gCacheIH == ih) && (length == gCacheBlockSize)) {␊ |
114 | // Look for the data in the cache.␊ |
115 | for (cnt = 0; cnt < gCacheNumEntries; cnt++) {␊ |
116 | entry = &gCacheEntries[cnt];␊ |
117 | if ((entry->ih == ih) && (entry->offset == offset)) {␊ |
118 | entry->time = ++gCacheTime;␊ |
119 | break;␊ |
120 | }␊ |
121 | }␊ |
122 | ␊ |
123 | // If the data was found copy it to the caller.␊ |
124 | if (cnt != gCacheNumEntries) {␊ |
125 | bcopy(gCacheBuffer + cnt * gCacheBlockSize, buffer, gCacheBlockSize);␊ |
126 | #if CACHE_STATS␊ |
127 | gCacheHits++;␊ |
128 | #endif␊ |
129 | return gCacheBlockSize;␊ |
130 | }␊ |
131 | ␊ |
132 | // Could not find the data in the cache.␊ |
133 | loadCache = 1;␊ |
134 | }␊ |
135 | ␊ |
136 | // Read the data from the disk.␊ |
137 | Seek(ih, offset);␊ |
138 | Read(ih, (long)buffer, length);␊ |
139 | #if CACHE_STATS␊ |
140 | if (cache) gCacheMisses++;␊ |
141 | #endif␊ |
142 | ␊ |
143 | // Put the data from the disk in the cache if needed.␊ |
144 | if (loadCache) {␊ |
145 | // Find a free entry.␊ |
146 | oldestTime = gCacheTime;␊ |
147 | for (cnt = 0; cnt < gCacheNumEntries; cnt++) {␊ |
148 | entry = &gCacheEntries[cnt];␊ |
149 | ␊ |
150 | // Found a free entry.␊ |
151 | if (entry->ih == 0) break;␊ |
152 | ␊ |
153 | if (entry->time < oldestTime) {␊ |
154 | oldestTime = entry->time;␊ |
155 | oldestEntry = cnt;␊ |
156 | }␊ |
157 | }␊ |
158 | ␊ |
159 | // If no free entry was found, use the oldest.␊ |
160 | if (cnt == gCacheNumEntries) {␊ |
161 | cnt = oldestEntry;␊ |
162 | #if CACHE_STATS␊ |
163 | gCacheEvicts++;␊ |
164 | #endif␊ |
165 | }␊ |
166 | ␊ |
167 | // Copy the data from disk to the new entry.␊ |
168 | entry = &gCacheEntries[cnt];␊ |
169 | entry->ih = ih;␊ |
170 | entry->time = ++gCacheTime;␊ |
171 | entry->offset = offset;␊ |
172 | bcopy(buffer, gCacheBuffer + cnt * gCacheBlockSize, gCacheBlockSize);␊ |
173 | }␊ |
174 | ␊ |
175 | return length;␊ |
176 | }␊ |
177 | |