Chameleon

Chameleon Svn Source Tree

Root/tags/2.3/i386/libsaio/cache.c

Source at commit HEAD created 4 years 9 months ago.
By ifabio, Few update to kernelPatcher (Credits to CrazyBirdy)
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␊
33struct CacheEntry {␊
34␉CICell ih;␊
35␉long time;␊
36␉long long offset;␊
37};␊
38typedef struct CacheEntry CacheEntry;␊
39␊
40#define kCacheSize (0x100000)␊
41#define kCacheMinBlockSize (0x200)␊
42#define kCacheMaxBlockSize (0x8000)␊
43#define kCacheMaxEntries (kCacheSize / kCacheMinBlockSize)␊
44␊
45static CICell gCacheIH;␊
46static u_int32_t gCacheBlockSize;␊
47static long gCacheNumEntries;␊
48static 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␊
64void CacheReset()␊
65{␊
66␉gCacheIH = NULL;␊
67}␊
68␊
69void CacheInit( CICell ih, u_int32_t blockSize )␊
70{␊
71#ifdef __i386__␊
72␉if ((ih == gCacheIH) && (blockSize == gCacheBlockSize))␊
73␉{␊
74␉␉return;␊
75␉}␊
76#endif␊
77␊
78␉if ((blockSize < kCacheMinBlockSize) || (blockSize > kCacheMaxBlockSize))␊
79␉{␊
80␉␉return;␊
81␉}␊
82␊
83␉gCacheBlockSize = blockSize;␊
84␉gCacheNumEntries = kCacheSize / gCacheBlockSize;␊
85␉gCacheTime = 0;␊
86 ␊
87#if CACHE_STATS␊
88␉gCacheHits␉= 0;␊
89␉gCacheMisses␉= 0;␊
90␉gCacheEvicts␉= 0;␊
91#endif␊
92␊
93 gCacheIH = ih;␊
94␊
95#ifdef __i386__␊
96␉if (!gCacheBuffer)␊
97␉{␊
98␉␉gCacheBuffer = (char *) malloc(kCacheSize);␊
99␉}␊
100␊
101␉if (!gCacheEntries)␊
102␉{␊
103␉␉gCacheEntries = (CacheEntry *) malloc(kCacheMaxEntries * sizeof(CacheEntry));␊
104␉}␊
105␊
106␉if (!gCacheBuffer || !gCacheEntries)␊
107␉{␊
108␉␉gCacheIH = 0; // invalidate cache␊
109␉␉return;␊
110␉}␊
111#endif␊
112␊
113␉bzero(gCacheEntries, kCacheMaxEntries * sizeof(CacheEntry));␊
114}␊
115␊
116u_int32_t CacheRead(CICell ih, char * buffer, long long offset, u_int32_t length, long cache)␊
117{␊
118␉long cnt, oldestEntry = 0, oldestTime, loadCache = 0;␊
119␉CacheEntry *entry;␊
120␊
121␉// See if the data can be cached.␊
122␉if (cache && (gCacheIH == ih) && (length == gCacheBlockSize))␊
123␉{␊
124␉␉// Look for the data in the cache.␊
125␉␉for (cnt = 0; cnt < gCacheNumEntries; cnt++)␊
126␉␉{␊
127␉␉␉entry = &gCacheEntries[cnt];␊
128␊
129␉␉␉if ((entry->ih == ih) && (entry->offset == offset))␊
130␉␉␉{␊
131␉␉␉␉entry->time = ++gCacheTime;␊
132␉␉␉␉break;␊
133␉␉␉}␊
134␉␉}␊
135␊
136␉␉// If the data was found copy it to the caller.␊
137␉␉if (cnt != gCacheNumEntries)␊
138␉␉{␊
139␉␉␉bcopy(gCacheBuffer + cnt * gCacheBlockSize, buffer, gCacheBlockSize);␊
140#if CACHE_STATS␊
141␉␉␉gCacheHits++;␊
142#endif␊
143␉␉␉return gCacheBlockSize;␊
144␉␉}␊
145␊
146␉␉// Could not find the data in the cache.␊
147␉␉loadCache = 1;␊
148␉}␊
149␊
150␉// Read the data from the disk.␊
151␉Seek(ih, offset);␊
152␉Read(ih, (long)buffer, length);␊
153␊
154#if CACHE_STATS␊
155␉if (cache)␊
156␉{␊
157␉␉gCacheMisses++;␊
158␉}␊
159#endif␊
160␊
161␉// Put the data from the disk in the cache if needed.␊
162␉if (loadCache)␊
163␉{␊
164␉␉// Find a free entry.␊
165␉␉oldestTime = gCacheTime;␊
166␊
167␉␉for (cnt = 0; cnt < gCacheNumEntries; cnt++)␊
168␉␉{␊
169␉␉␉entry = &gCacheEntries[cnt];␊
170␊
171␉␉␉// Found a free entry.␊
172␉␉␉if (entry->ih == 0)␊
173␉␉␉{␊
174␉␉␉␉break;␊
175␉␉␉}␊
176␊
177␉␉␉if (entry->time < oldestTime)␊
178␉␉␉{␊
179␉␉␉␉oldestTime = entry->time;␊
180␉␉␉␉oldestEntry = cnt;␊
181␉␉␉}␊
182␉␉}␊
183␊
184␉␉// If no free entry was found, use the oldest.␊
185␉␉if (cnt == gCacheNumEntries)␊
186␉␉{␊
187␉␉␉cnt = oldestEntry;␊
188#if CACHE_STATS␊
189␉␉␉gCacheEvicts++;␊
190#endif␊
191␉␉}␊
192␊
193␉␉// Copy the data from disk to the new entry.␊
194␉␉entry = &gCacheEntries[cnt];␊
195␉␉entry->ih = ih;␊
196␉␉entry->time = ++gCacheTime;␊
197␉␉entry->offset = offset;␊
198␉␉bcopy(buffer, gCacheBuffer + cnt * gCacheBlockSize, gCacheBlockSize);␊
199␉}␊
200␊
201␉return length;␊
202}␊
203

Archive Download this file

Revision: HEAD