vendor/go.opencensus.io/internal/tagencoding/tagencoding.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

// Copyright 2017, OpenCensus Authors
//
// 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 tagencoding contains the tag encoding
// used interally by the stats collector.
package tagencoding // import "go.opencensus.io/internal/tagencoding"

type Values struct {
    Buffer     []byte
    WriteIndex int
    ReadIndex  int
}

func (vb *Values) growIfRequired(expected int) {
    if len(vb.Buffer)-vb.WriteIndex < expected {
        tmp := make([]byte, 2*(len(vb.Buffer)+1)+expected)
        copy(tmp, vb.Buffer)
        vb.Buffer = tmp
    }
}

func (vb *Values) WriteValue(v []byte) {
    length := len(v) & 0xff
    vb.growIfRequired(1 + length)

    // writing length of v
    vb.Buffer[vb.WriteIndex] = byte(length)
    vb.WriteIndex++

    if length == 0 {
        // No value was encoded for this key
        return
    }

    // writing v
    copy(vb.Buffer[vb.WriteIndex:], v[:length])
    vb.WriteIndex += length
}

// ReadValue is the helper method to read the values when decoding valuesBytes to a map[Key][]byte.
func (vb *Values) ReadValue() []byte {
    // read length of v
    length := int(vb.Buffer[vb.ReadIndex])
    vb.ReadIndex++
    if length == 0 {
        // No value was encoded for this key
        return nil
    }

    // read value of v
    v := make([]byte, length)
    endIdx := vb.ReadIndex + length
    copy(v, vb.Buffer[vb.ReadIndex:endIdx])
    vb.ReadIndex = endIdx
    return v
}

func (vb *Values) Bytes() []byte {
    return vb.Buffer[:vb.WriteIndex]
}