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iterator.go (4038B)

      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 
     15 package attribute // import "go.opentelemetry.io/otel/attribute"
     16 
     17 // Iterator allows iterating over the set of attributes in order, sorted by
     18 // key.
     19 type Iterator struct {
     20 	storage *Set
     21 	idx     int
     22 }
     23 
     24 // MergeIterator supports iterating over two sets of attributes while
     25 // eliminating duplicate values from the combined set. The first iterator
     26 // value takes precedence.
     27 type MergeIterator struct {
     28 	one     oneIterator
     29 	two     oneIterator
     30 	current KeyValue
     31 }
     32 
     33 type oneIterator struct {
     34 	iter Iterator
     35 	done bool
     36 	attr KeyValue
     37 }
     38 
     39 // Next moves the iterator to the next position. Returns false if there are no
     40 // more attributes.
     41 func (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.
     48 //
     49 // Deprecated: Use Attribute instead.
     50 func (i *Iterator) Label() KeyValue {
     51 	return i.Attribute()
     52 }
     53 
     54 // Attribute returns the current KeyValue of the Iterator. It must be called
     55 // only after Next returns true.
     56 func (i *Iterator) Attribute() KeyValue {
     57 	kv, _ := i.storage.Get(i.idx)
     58 	return kv
     59 }
     60 
     61 // IndexedLabel returns current index and attribute. Must be called only
     62 // after Next returns true.
     63 //
     64 // Deprecated: Use IndexedAttribute instead.
     65 func (i *Iterator) IndexedLabel() (int, KeyValue) {
     66 	return i.idx, i.Attribute()
     67 }
     68 
     69 // IndexedAttribute returns current index and attribute. Must be called only
     70 // after Next returns true.
     71 func (i *Iterator) IndexedAttribute() (int, KeyValue) {
     72 	return i.idx, i.Attribute()
     73 }
     74 
     75 // Len returns a number of attributes in the iterated set.
     76 func (i *Iterator) Len() int {
     77 	return i.storage.Len()
     78 }
     79 
     80 // ToSlice is a convenience function that creates a slice of attributes from
     81 // the passed iterator. The iterator is set up to start from the beginning
     82 // before creating the slice.
     83 func (i *Iterator) ToSlice() []KeyValue {
     84 	l := i.Len()
     85 	if l == 0 {
     86 		return nil
     87 	}
     88 	i.idx = -1
     89 	slice := make([]KeyValue, 0, l)
     90 	for i.Next() {
     91 		slice = append(slice, i.Attribute())
     92 	}
     93 	return slice
     94 }
     95 
     96 // NewMergeIterator returns a MergeIterator for merging two attribute sets.
     97 // Duplicates are resolved by taking the value from the first set.
     98 func NewMergeIterator(s1, s2 *Set) MergeIterator {
     99 	mi := MergeIterator{
    100 		one: makeOne(s1.Iter()),
    101 		two: makeOne(s2.Iter()),
    102 	}
    103 	return mi
    104 }
    105 
    106 func makeOne(iter Iterator) oneIterator {
    107 	oi := oneIterator{
    108 		iter: iter,
    109 	}
    110 	oi.advance()
    111 	return oi
    112 }
    113 
    114 func (oi *oneIterator) advance() {
    115 	if oi.done = !oi.iter.Next(); !oi.done {
    116 		oi.attr = oi.iter.Attribute()
    117 	}
    118 }
    119 
    120 // Next returns true if there is another attribute available.
    121 func (m *MergeIterator) Next() bool {
    122 	if m.one.done && m.two.done {
    123 		return false
    124 	}
    125 	if m.one.done {
    126 		m.current = m.two.attr
    127 		m.two.advance()
    128 		return true
    129 	}
    130 	if m.two.done {
    131 		m.current = m.one.attr
    132 		m.one.advance()
    133 		return true
    134 	}
    135 	if m.one.attr.Key == m.two.attr.Key {
    136 		m.current = m.one.attr // first iterator attribute value wins
    137 		m.one.advance()
    138 		m.two.advance()
    139 		return true
    140 	}
    141 	if m.one.attr.Key < m.two.attr.Key {
    142 		m.current = m.one.attr
    143 		m.one.advance()
    144 		return true
    145 	}
    146 	m.current = m.two.attr
    147 	m.two.advance()
    148 	return true
    149 }
    150 
    151 // Label returns the current value after Next() returns true.
    152 //
    153 // Deprecated: Use Attribute instead.
    154 func (m *MergeIterator) Label() KeyValue {
    155 	return m.current
    156 }
    157 
    158 // Attribute returns the current value after Next() returns true.
    159 func (m *MergeIterator) Attribute() KeyValue {
    160 	return m.current
    161 }