-
Notifications
You must be signed in to change notification settings - Fork 2
/
btree.go
179 lines (159 loc) · 3.52 KB
/
btree.go
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
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
package glinq
import g "github.com/yoyofx/glinq/generic"
const maxChildren = 64 // must be even and > 2
//BTree a B-tree data structures
type BTree[K, V any] struct {
root *BTreeNode[K, V]
height int
n int
less g.LessFn[K]
}
type BTreeNode[K, V any] struct {
m int
children [maxChildren]entry[K, V]
}
type entry[K, V any] struct {
key K
val V
valid bool
next *BTreeNode[K, V]
}
// NewBTree New returns an empty B-tree.
func NewBTree[K, V any](less g.LessFn[K]) *BTree[K, V] {
return &BTree[K, V]{
root: &BTreeNode[K, V]{},
less: less,
}
}
// Size returns the number of elements in the tree.
func (t *BTree[K, V]) Size() int {
return t.n
}
// Get returns the value associated with 'key'.
func (t *BTree[K, V]) Get(key K) (V, bool) {
return t.search(t.root, key, t.height)
}
func (t *BTree[K, V]) search(x *BTreeNode[K, V], key K, height int) (V, bool) {
children := x.children
if height == 0 {
// leaf BTreeNode
for j := 0; j < x.m; j++ {
if g.Compare(key, children[j].key, t.less) == 0 {
return children[j].val, children[j].valid
}
}
} else {
// internal BTreeNode
for j := 0; j < x.m; j++ {
if x.m == j+1 || g.Compare(key, children[j+1].key, t.less) < 0 {
return t.search(children[j].next, key, height-1)
}
}
}
var v V
return v, false
}
// Put associates 'key' with 'val'.
func (t *BTree[K, V]) Put(key K, val V) {
u := t.insert(t.root, key, val, t.height, true)
t.n++
if u == nil {
return
}
n := &BTreeNode[K, V]{
m: 2,
}
n.children[0] = entry[K, V]{
key: t.root.children[0].key,
next: t.root,
}
n.children[1] = entry[K, V]{
key: u.children[0].key,
next: u,
}
t.root = n
t.height++
}
// Remove removes the value associated with 'key'.
func (t *BTree[K, V]) Remove(key K) {
_, ok := t.Get(key)
if !ok {
return
}
var v V
// insert a tombstone to remove an existing value
t.insert(t.root, key, v, t.height, false)
t.n--
}
func (t *BTree[K, V]) insert(h *BTreeNode[K, V], key K, val V, height int, valid bool) *BTreeNode[K, V] {
ent := entry[K, V]{
key: key,
val: val,
valid: valid,
}
var j int
if height == 0 {
// leaf BTreeNode
for j = 0; j < h.m; j++ {
if g.Compare(key, h.children[j].key, t.less) == 0 {
h.children[j].val = val
h.children[j].valid = valid
return nil
} else if g.Compare(key, h.children[j].key, t.less) < 0 {
break
}
}
} else {
// internal BTreeNode
for j = 0; j < h.m; j++ {
if (j+1 == h.m) || g.Compare(key, h.children[j+1].key, t.less) < 0 {
u := t.insert(h.children[j].next, key, val, height-1, valid)
if u == nil {
return nil
}
j++
ent.key = u.children[0].key
ent.valid = false
ent.next = u
break
}
}
}
for i := h.m; i > j; i-- {
h.children[i] = h.children[i-1]
}
h.children[j] = ent
h.m++
if h.m < maxChildren {
return nil
}
return t.split(h)
}
func (t *BTree[K, V]) split(h *BTreeNode[K, V]) *BTreeNode[K, V] {
n := &BTreeNode[K, V]{
m: maxChildren / 2,
}
h.m = maxChildren / 2
for j := 0; j < maxChildren/2; j++ {
n.children[j] = h.children[maxChildren/2+j]
}
return n
}
// Each calls 'fn' on every BTreeNode in the tree in order.
func (t *BTree[K, V]) Each(fn func(key K, val V)) {
t.each(t.root, t.height, fn)
}
func (t *BTree[K, V]) each(n *BTreeNode[K, V], height int, fn func(key K, val V)) {
if height == 0 {
for j := 0; j < n.m; j++ {
if !n.children[j].valid {
continue
}
fn(n.children[j].key, n.children[j].val)
}
} else {
for j := 0; j < n.m; j++ {
t.each(n.children[j].next, height-1, fn)
}
}
}