1// 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 attribute // import "go.opentelemetry.io/otel/attribute" 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 MergeIterator 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 attribute. 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) MergeIterator { 88 mi := MergeIterator{ 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 *MergeIterator) 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 *MergeIterator) Label() KeyValue { 142 return m.current 143} 144