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// Copyright The OpenTelemetry 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 label
// Iterator allows iterating over the set of labels in order,
// sorted by key.
type Iterator struct {
storage *Set
idx int
}
// MergeIterator supports iterating over two sets of labels while
// eliminating duplicate values from the combined set. The first
// iterator value takes precedence.
type MergeItererator struct {
one oneIterator
two oneIterator
current KeyValue
}
type oneIterator struct {
iter Iterator
done bool
label KeyValue
}
// Next moves the iterator to the next position. Returns false if there
// are no more labels.
func (i *Iterator) Next() bool {
i.idx++
return i.idx < i.Len()
}
// Label returns current KeyValue. Must be called only after Next returns
// true.
func (i *Iterator) Label() KeyValue {
kv, _ := i.storage.Get(i.idx)
return kv
}
// Attribute is a synonym for Label().
func (i *Iterator) Attribute() KeyValue {
return i.Label()
}
// IndexedLabel returns current index and label. Must be called only
// after Next returns true.
func (i *Iterator) IndexedLabel() (int, KeyValue) {
return i.idx, i.Label()
}
// Len returns a number of labels in the iterator's `*Set`.
func (i *Iterator) Len() int {
return i.storage.Len()
}
// ToSlice is a convenience function that creates a slice of labels
// from the passed iterator. The iterator is set up to start from the
// beginning before creating the slice.
func (i *Iterator) ToSlice() []KeyValue {
l := i.Len()
if l == 0 {
return nil
}
i.idx = -1
slice := make([]KeyValue, 0, l)
for i.Next() {
slice = append(slice, i.Label())
}
return slice
}
// NewMergeIterator returns a MergeIterator for merging two label sets
// Duplicates are resolved by taking the value from the first set.
func NewMergeIterator(s1, s2 *Set) MergeItererator {
mi := MergeItererator{
one: makeOne(s1.Iter()),
two: makeOne(s2.Iter()),
}
return mi
}
func makeOne(iter Iterator) oneIterator {
oi := oneIterator{
iter: iter,
}
oi.advance()
return oi
}
func (oi *oneIterator) advance() {
if oi.done = !oi.iter.Next(); !oi.done {
oi.label = oi.iter.Label()
}
}
// Next returns true if there is another label available.
func (m *MergeItererator) Next() bool {
if m.one.done && m.two.done {
return false
}
if m.one.done {
m.current = m.two.label
m.two.advance()
return true
}
if m.two.done {
m.current = m.one.label
m.one.advance()
return true
}
if m.one.label.Key == m.two.label.Key {
m.current = m.one.label // first iterator label value wins
m.one.advance()
m.two.advance()
return true
}
if m.one.label.Key < m.two.label.Key {
m.current = m.one.label
m.one.advance()
return true
}
m.current = m.two.label
m.two.advance()
return true
}
// Label returns the current value after Next() returns true.
func (m *MergeItererator) Label() KeyValue {
return m.current
}