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
|
package bitfield
import (
"math/bits"
)
var _ = Bitfield(Bitvector32{})
// Bitvector32 is a bitfield with a fixed defined size of 32. There is no length bit
// present in the underlying byte array.
type Bitvector32 []byte
const bitvector32ByteSize = 4
const bitvector32BitSize = bitvector32ByteSize * 8
// NewBitvector32 creates a new bitvector of size 32.
func NewBitvector32() Bitvector32 {
byteArray := [bitvector32ByteSize]byte{}
return byteArray[:]
}
// BitAt returns the bit value at the given index. If the index requested
// exceeds the number of bits in the bitvector, then this method returns false.
func (b Bitvector32) BitAt(idx uint64) bool {
// Out of bounds, must be false.
if idx >= b.Len() || len(b) != bitvector32ByteSize {
return false
}
i := uint8(1 << (idx % 8))
return b[idx/8]&i == i
}
// SetBitAt will set the bit at the given index to the given value. If the index
// requested exceeds the number of bits in the bitvector, then this method returns
// false.
func (b Bitvector32) SetBitAt(idx uint64, val bool) {
// Out of bounds, do nothing.
if idx >= b.Len() || len(b) != bitvector32ByteSize {
return
}
bit := uint8(1 << (idx % 8))
if val {
b[idx/8] |= bit
} else {
b[idx/8] &^= bit
}
}
// Len returns the number of bits in the bitvector.
func (b Bitvector32) Len() uint64 {
return bitvector32BitSize
}
// Count returns the number of 1s in the bitvector.
func (b Bitvector32) Count() uint64 {
if len(b) == 0 {
return 0
}
c := 0
for i, bt := range b {
if i >= bitvector32ByteSize {
break
}
c += bits.OnesCount8(bt)
}
return uint64(c)
}
// Bytes returns the bytes data representing the bitvector32.
func (b Bitvector32) Bytes() []byte {
if len(b) == 0 {
return []byte{}
}
ln := min(len(b), bitvector32ByteSize)
ret := make([]byte, ln)
copy(ret, b[:ln])
return ret[:]
}
// BitIndices returns the list of indices which are set to 1.
func (b Bitvector32) BitIndices() []int {
indices := make([]int, 0, bitvector32BitSize)
for i, bt := range b {
if i >= bitvector32ByteSize {
break
}
for j := 0; j < 8; j++ {
bit := byte(1 << uint(j))
if bt&bit == bit {
indices = append(indices, i*8+j)
}
}
}
return indices
}
|
