|
1
5 package org.h2.util;
6
7 import java.sql.SQLException  ;
8
9 public abstract class HashBase {
10 protected int mask, len, size, deletedCount, level;
11 protected boolean zeroKey;
12 private int maxSize, minSize, maxDeleted;
13 private static final int MAX_LOAD = 90;
14
15 public HashBase() {
16 reset(2);
17 }
18
19 public int size() {
20 return size + (zeroKey ? 1 : 0);
21 }
22
23 protected void checkSizePut() throws SQLException {
24 if(deletedCount > size) {
25 rehash(level);
26 }
27 if(size + deletedCount >= maxSize) {
28 rehash(level+1);
29 }
30 }
31
32 protected void checkSizeRemove() throws SQLException {
33 if(size < minSize && level>0) {
34 rehash(level-1);
35 } else if(deletedCount > maxDeleted) {
36 rehash(level);
37 }
38 }
39
40 protected abstract void rehash(int newLevel) throws SQLException ;
41
42 protected void reset(int newLevel) {
43 minSize = size * 3 / 4;
44 size = 0;
45 level = newLevel;
46 len = 2 << level;
47 mask = len - 1;
48 maxSize = (int)(len * MAX_LOAD / 100L);
49 deletedCount = 0;
50 maxDeleted = 20 + len / 2;
51 }
52
53 protected int getIndex(int hash) {
54 return hash & mask;
55 }
56
57 }
58 |
Popular Tags |
Java API By Example, From Geeks To Geeks.