-
Notifications
You must be signed in to change notification settings - Fork 4
/
reverse_bits.go
122 lines (103 loc) · 3.13 KB
/
reverse_bits.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
/*
Copyright 2017 Google Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package vindexes
import (
"bytes"
"encoding/binary"
"encoding/hex"
"fmt"
"math/bits"
"gopkg.in/src-d/go-vitess.v1/sqltypes"
"gopkg.in/src-d/go-vitess.v1/vt/key"
"gopkg.in/src-d/go-vitess.v1/vt/vterrors"
)
var (
_ Vindex = (*ReverseBits)(nil)
_ Reversible = (*ReverseBits)(nil)
)
// ReverseBits defines vindex that reverses the bits of a number.
// It's Unique, Reversible and Functional.
type ReverseBits struct {
name string
}
// NewReverseBits creates a new ReverseBits.
func NewReverseBits(name string, m map[string]string) (Vindex, error) {
return &ReverseBits{name: name}, nil
}
// String returns the name of the vindex.
func (vind *ReverseBits) String() string {
return vind.name
}
// Cost returns the cost of this index as 1.
func (vind *ReverseBits) Cost() int {
return 1
}
// IsUnique returns true since the Vindex is unique.
func (vind *ReverseBits) IsUnique() bool {
return true
}
// IsFunctional returns true since the Vindex is functional.
func (vind *ReverseBits) IsFunctional() bool {
return true
}
// Map returns the corresponding KeyspaceId values for the given ids.
func (vind *ReverseBits) Map(cursor VCursor, ids []sqltypes.Value) ([]key.Destination, error) {
out := make([]key.Destination, len(ids))
for i, id := range ids {
num, err := sqltypes.ToUint64(id)
if err != nil {
out[i] = key.DestinationNone{}
continue
}
out[i] = key.DestinationKeyspaceID(reverse(num))
}
return out, nil
}
// Verify returns true if ids maps to ksids.
func (vind *ReverseBits) Verify(_ VCursor, ids []sqltypes.Value, ksids [][]byte) ([]bool, error) {
out := make([]bool, len(ids))
for i := range ids {
num, err := sqltypes.ToUint64(ids[i])
if err != nil {
return nil, vterrors.Wrap(err, "reverseBits.Verify")
}
out[i] = bytes.Compare(reverse(num), ksids[i]) == 0
}
return out, nil
}
// ReverseMap returns the ids from ksids.
func (vind *ReverseBits) ReverseMap(_ VCursor, ksids [][]byte) ([]sqltypes.Value, error) {
reverseIds := make([]sqltypes.Value, 0, len(ksids))
for _, keyspaceID := range ksids {
val, err := unreverse(keyspaceID)
if err != nil {
return reverseIds, err
}
reverseIds = append(reverseIds, sqltypes.NewUint64(val))
}
return reverseIds, nil
}
func init() {
Register("reverse_bits", NewReverseBits)
}
func reverse(shardKey uint64) []byte {
reversed := make([]byte, 8)
binary.BigEndian.PutUint64(reversed, bits.Reverse64(shardKey))
return reversed
}
func unreverse(k []byte) (uint64, error) {
if len(k) != 8 {
return 0, fmt.Errorf("invalid keyspace id: %v", hex.EncodeToString(k))
}
return bits.Reverse64(binary.BigEndian.Uint64(k)), nil
}