75 lines
1.7 KiB
Go
75 lines
1.7 KiB
Go
package labels
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import "sort"
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type Label struct {
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Key, Value string
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}
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// The Labels type represents a set of labels, sorted by Key.
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type Labels []Label
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// Merge merges other with the current set, replacing any matching keys from other.
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func (ls *Labels) Merge(other Labels) {
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var list []Label
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i, j := 0, 0
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for i < len(*ls) && j < len(other) {
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if (*ls)[i].Key < other[j].Key {
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list = append(list, (*ls)[i])
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i++
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} else if (*ls)[i].Key > other[j].Key {
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list = append(list, other[j])
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j++
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} else {
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// equal, then "other" replaces existing key
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list = append(list, other[j])
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i++
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j++
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}
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}
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if i < len(*ls) {
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list = append(list, (*ls)[i:]...)
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} else if j < len(other) {
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list = append(list, other[j:]...)
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}
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*ls = list
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}
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// New takes an even number of strings representing key-value pairs
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// and creates a new slice of Labels. Duplicates are removed, however,
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// there is no guarantee which will be removed
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func New(args ...string) Labels {
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if len(args)%2 != 0 {
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panic("uneven number of arguments to label.Labels")
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}
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var labels Labels
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for i := 0; i+1 < len(args); i += 2 {
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labels = append(labels, Label{Key: args[i], Value: args[i+1]})
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}
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sort.Slice(labels, func(i, j int) bool {
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return labels[i].Key < labels[j].Key
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})
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// deduplicate
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// loop invariant: labels[:i] has no duplicates
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for i := 0; i < len(labels)-1; i++ {
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j := i + 1
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// find all duplicate keys
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for j < len(labels) && labels[i].Key == labels[j].Key {
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j++
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}
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d := (j - 1) - i // number of duplicate keys
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if d > 0 {
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// copy over duplicate keys in order to maintain loop invariant
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copy(labels[i+1:], labels[j:])
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labels = labels[:len(labels)-d]
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}
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}
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return labels
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}
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