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Joey Armstrong5f51f2e2023-01-17 17:06:26 -05001// Copyright The OpenTelemetry Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package label
16
17// Iterator allows iterating over the set of labels in order,
18// sorted by key.
19type Iterator struct {
20 storage *Set
21 idx int
22}
23
24// MergeIterator supports iterating over two sets of labels while
25// eliminating duplicate values from the combined set. The first
26// iterator value takes precedence.
27type MergeItererator struct {
28 one oneIterator
29 two oneIterator
30 current KeyValue
31}
32
33type oneIterator struct {
34 iter Iterator
35 done bool
36 label KeyValue
37}
38
39// Next moves the iterator to the next position. Returns false if there
40// are no more labels.
41func (i *Iterator) Next() bool {
42 i.idx++
43 return i.idx < i.Len()
44}
45
46// Label returns current KeyValue. Must be called only after Next returns
47// true.
48func (i *Iterator) Label() KeyValue {
49 kv, _ := i.storage.Get(i.idx)
50 return kv
51}
52
53// Attribute is a synonym for Label().
54func (i *Iterator) Attribute() KeyValue {
55 return i.Label()
56}
57
58// IndexedLabel returns current index and label. Must be called only
59// after Next returns true.
60func (i *Iterator) IndexedLabel() (int, KeyValue) {
61 return i.idx, i.Label()
62}
63
64// Len returns a number of labels in the iterator's `*Set`.
65func (i *Iterator) Len() int {
66 return i.storage.Len()
67}
68
69// ToSlice is a convenience function that creates a slice of labels
70// from the passed iterator. The iterator is set up to start from the
71// beginning before creating the slice.
72func (i *Iterator) ToSlice() []KeyValue {
73 l := i.Len()
74 if l == 0 {
75 return nil
76 }
77 i.idx = -1
78 slice := make([]KeyValue, 0, l)
79 for i.Next() {
80 slice = append(slice, i.Label())
81 }
82 return slice
83}
84
85// NewMergeIterator returns a MergeIterator for merging two label sets
86// Duplicates are resolved by taking the value from the first set.
87func NewMergeIterator(s1, s2 *Set) MergeItererator {
88 mi := MergeItererator{
89 one: makeOne(s1.Iter()),
90 two: makeOne(s2.Iter()),
91 }
92 return mi
93}
94
95func makeOne(iter Iterator) oneIterator {
96 oi := oneIterator{
97 iter: iter,
98 }
99 oi.advance()
100 return oi
101}
102
103func (oi *oneIterator) advance() {
104 if oi.done = !oi.iter.Next(); !oi.done {
105 oi.label = oi.iter.Label()
106 }
107}
108
109// Next returns true if there is another label available.
110func (m *MergeItererator) Next() bool {
111 if m.one.done && m.two.done {
112 return false
113 }
114 if m.one.done {
115 m.current = m.two.label
116 m.two.advance()
117 return true
118 }
119 if m.two.done {
120 m.current = m.one.label
121 m.one.advance()
122 return true
123 }
124 if m.one.label.Key == m.two.label.Key {
125 m.current = m.one.label // first iterator label value wins
126 m.one.advance()
127 m.two.advance()
128 return true
129 }
130 if m.one.label.Key < m.two.label.Key {
131 m.current = m.one.label
132 m.one.advance()
133 return true
134 }
135 m.current = m.two.label
136 m.two.advance()
137 return true
138}
139
140// Label returns the current value after Next() returns true.
141func (m *MergeItererator) Label() KeyValue {
142 return m.current
143}