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h2database
Commits
66b7ede9
提交
66b7ede9
authored
12 年前
作者:
Thomas Mueller
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电子邮件补丁
差异文件
LIRS cache: guard against bad hash functions.
上级
68956a78
隐藏空白字符变更
内嵌
并排
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1 个修改的文件
包含
16 行增加
和
8 行删除
+16
-8
CacheLIRS.java
h2/src/tools/org/h2/dev/store/btree/CacheLIRS.java
+16
-8
没有找到文件。
h2/src/tools/org/h2/dev/store/btree/CacheLIRS.java
浏览文件 @
66b7ede9
...
...
@@ -19,8 +19,7 @@ import java.util.Set;
* costly to acquire, for example file content.
* <p>
* This implementation is not multi-threading save. Null keys or null values are
* not allowed. There is no guard against bad hash functions, so it is important
* to the hash function of the key is good. The map fill factor is at most 75%.
* not allowed. The map fill factor is at most 75%.
* <p>
* Each entry is assigned a distinct memory size, and the cache will try to use
* at most the specified amount of memory. The memory unit is not relevant,
...
...
@@ -269,7 +268,7 @@ public class CacheLIRS<K, V> extends AbstractMap<K, V> implements Map<K, V> {
e
.
key
=
key
;
e
.
value
=
value
;
e
.
memory
=
memory
;
int
index
=
key
.
hashCode
()
&
mask
;
int
index
=
getIndex
(
key
)
;
e
.
mapNext
=
entries
[
index
];
entries
[
index
]
=
e
;
usedMemory
+=
memory
;
...
...
@@ -283,6 +282,15 @@ public class CacheLIRS<K, V> extends AbstractMap<K, V> implements Map<K, V> {
return
old
;
}
private
int
getIndex
(
Object
key
)
{
int
hash
=
key
.
hashCode
();
// Doug Lea's supplemental secondaryHash function (inlined)
// to protect against hash codes that don't differ in low order bits
hash
^=
(
hash
>>>
20
)
^
(
hash
>>>
12
);
hash
^=
(
hash
>>>
7
)
^
(
hash
>>>
4
);
return
hash
&
mask
;
}
/**
* Remove an entry. Both resident and non-resident entries can be removed.
*
...
...
@@ -290,8 +298,7 @@ public class CacheLIRS<K, V> extends AbstractMap<K, V> implements Map<K, V> {
* @return the old value, or null if there is no resident entry
*/
public
V
remove
(
Object
key
)
{
int
hash
=
key
.
hashCode
();
int
index
=
hash
&
mask
;
int
index
=
getIndex
(
key
);
Entry
<
K
,
V
>
e
=
entries
[
index
];
if
(
e
==
null
)
{
return
null
;
...
...
@@ -397,8 +404,8 @@ public class CacheLIRS<K, V> extends AbstractMap<K, V> implements Map<K, V> {
* @return the entry (might be a non-resident)
*/
private
Entry
<
K
,
V
>
find
(
Object
key
)
{
int
hash
=
key
.
hashCode
(
);
Entry
<
K
,
V
>
e
=
entries
[
hash
&
mask
];
int
index
=
getIndex
(
key
);
Entry
<
K
,
V
>
e
=
entries
[
index
];
while
(
e
!=
null
&&
!
e
.
key
.
equals
(
key
))
{
e
=
e
.
mapNext
;
}
...
...
@@ -484,7 +491,8 @@ public class CacheLIRS<K, V> extends AbstractMap<K, V> implements Map<K, V> {
}
/**
* Check whether there is a resident entry for the given key.
* Check whether there is a resident entry for the given key. This method
* does not adjusts the internal state of the cache.
*
* @param key the key (may not be null)
* @return true if there is a resident entry
...
...
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