blob: 69cebadf1e56701c2445158e36935da16ac09ff8 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
|
/*
* Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.internal.storage.file;
import java.lang.ref.SoftReference;
import org.eclipse.jgit.storage.file.WindowCacheConfig;
class DeltaBaseCache {
private static final int CACHE_SZ = 1024;
static final SoftReference<Entry> DEAD;
private static int hash(long position) {
return (((int) position) << 22) >>> 22;
}
private static volatile int defaultMaxByteCount;
private final int maxByteCount;
private final Slot[] cache;
private Slot lruHead;
private Slot lruTail;
private int openByteCount;
static {
DEAD = new SoftReference<>(null);
reconfigure(new WindowCacheConfig());
}
static void reconfigure(WindowCacheConfig cfg) {
defaultMaxByteCount = cfg.getDeltaBaseCacheLimit();
}
DeltaBaseCache() {
maxByteCount = defaultMaxByteCount;
cache = new Slot[CACHE_SZ];
}
Entry get(Pack pack, long position) {
Slot e = cache[hash(position)];
if (e == null)
return null;
if (e.provider == pack && e.position == position) {
final Entry buf = e.data.get();
if (buf != null) {
moveToHead(e);
return buf;
}
}
return null;
}
void store(final Pack pack, final long position,
final byte[] data, final int objectType) {
if (data.length > maxByteCount)
return; // Too large to cache.
Slot e = cache[hash(position)];
if (e == null) {
e = new Slot();
cache[hash(position)] = e;
} else {
clearEntry(e);
}
openByteCount += data.length;
releaseMemory();
e.provider = pack;
e.position = position;
e.sz = data.length;
e.data = new SoftReference<>(new Entry(data, objectType));
moveToHead(e);
}
private void releaseMemory() {
while (openByteCount > maxByteCount && lruTail != null) {
final Slot currOldest = lruTail;
final Slot nextOldest = currOldest.lruPrev;
clearEntry(currOldest);
currOldest.lruPrev = null;
currOldest.lruNext = null;
if (nextOldest == null)
lruHead = null;
else
nextOldest.lruNext = null;
lruTail = nextOldest;
}
}
private void moveToHead(Slot e) {
unlink(e);
e.lruPrev = null;
e.lruNext = lruHead;
if (lruHead != null)
lruHead.lruPrev = e;
else
lruTail = e;
lruHead = e;
}
private void unlink(Slot e) {
final Slot prev = e.lruPrev;
final Slot next = e.lruNext;
if (prev != null)
prev.lruNext = next;
if (next != null)
next.lruPrev = prev;
}
private void clearEntry(Slot e) {
openByteCount -= e.sz;
e.provider = null;
e.data = DEAD;
e.sz = 0;
}
static class Entry {
final byte[] data;
final int type;
Entry(byte[] aData, int aType) {
data = aData;
type = aType;
}
}
private static class Slot {
Slot lruPrev;
Slot lruNext;
Pack provider;
long position;
int sz;
SoftReference<Entry> data = DEAD;
}
}
|
