mirror of
https://github.com/prometheus/prometheus.git
synced 2024-11-09 23:24:05 -08:00
labels: shrink by making internals a single string
This commit adds an alternate implementation for `labels.Labels`, behind
a build tag `stringlabels`.
Instead of storing label names and values as individual strings, they
are all concatenated into one string in this format:
[len][name0][len][value0][len][name1][len][value1]...
The lengths are varint encoded so usually a single byte.
The previous `[]string` had 24 bytes of overhead for the slice and 16
for each label name and value; this one has 16 bytes overhead plus 1
for each name and value.
In `ScratchBuilder.Overwrite` and `Labels.Hash` we use an unsafe
conversion from string to byte slice. `Overwrite` is explicitly unsafe,
but for `Hash` this is a pure performance hack.
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham
parent
3f7ba22bde
commit
6136ae67e0
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@ -11,6 +11,8 @@
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//go:build !stringlabels
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package labels
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import (
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787
model/labels/labels_string.go
Normal file
787
model/labels/labels_string.go
Normal file
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@ -0,0 +1,787 @@
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// Copyright 2017 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//go:build stringlabels
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package labels
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import (
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"bytes"
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"encoding/json"
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"reflect"
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"sort"
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"strconv"
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"unsafe"
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"github.com/cespare/xxhash/v2"
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"github.com/prometheus/common/model"
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)
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// Well-known label names used by Prometheus components.
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const (
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MetricName = "__name__"
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AlertName = "alertname"
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BucketLabel = "le"
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InstanceName = "instance"
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)
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var seps = []byte{'\xff'}
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// Label is a key/value pair of strings.
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type Label struct {
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Name, Value string
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}
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// Labels is implemented by a single flat string holding name/value pairs.
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// Each name and value is preceded by its length in varint encoding.
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// Names are in order.
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type Labels struct {
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data string
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}
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type labelSlice []Label
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func (ls labelSlice) Len() int { return len(ls) }
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func (ls labelSlice) Swap(i, j int) { ls[i], ls[j] = ls[j], ls[i] }
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func (ls labelSlice) Less(i, j int) bool { return ls[i].Name < ls[j].Name }
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func decodeSize(data string, index int) (int, int) {
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var size int
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for shift := uint(0); ; shift += 7 {
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// Just panic if we go of the end of data, since all Labels strings are constructed internally and
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// malformed data indicates a bug, or memory corruption.
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b := data[index]
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index++
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size |= int(b&0x7F) << shift
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if b < 0x80 {
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break
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}
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}
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return size, index
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}
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func decodeString(data string, index int) (string, int) {
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var size int
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size, index = decodeSize(data, index)
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return data[index : index+size], index + size
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}
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func (ls Labels) String() string {
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var b bytes.Buffer
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b.WriteByte('{')
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for i := 0; i < len(ls.data); {
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if i > 0 {
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b.WriteByte(',')
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b.WriteByte(' ')
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}
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var name, value string
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name, i = decodeString(ls.data, i)
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value, i = decodeString(ls.data, i)
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b.WriteString(name)
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b.WriteByte('=')
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b.WriteString(strconv.Quote(value))
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}
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b.WriteByte('}')
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return b.String()
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}
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// Bytes returns ls as a byte slice.
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// It uses non-printing characters and so should not be used for printing.
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func (ls Labels) Bytes(buf []byte) []byte {
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if cap(buf) < len(ls.data) {
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buf = make([]byte, len(ls.data))
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} else {
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buf = buf[:len(ls.data)]
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}
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copy(buf, ls.data)
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return buf
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}
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// MarshalJSON implements json.Marshaler.
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func (ls Labels) MarshalJSON() ([]byte, error) {
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return json.Marshal(ls.Map())
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}
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// UnmarshalJSON implements json.Unmarshaler.
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func (ls *Labels) UnmarshalJSON(b []byte) error {
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var m map[string]string
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if err := json.Unmarshal(b, &m); err != nil {
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return err
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}
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*ls = FromMap(m)
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return nil
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}
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// MarshalYAML implements yaml.Marshaler.
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func (ls Labels) MarshalYAML() (interface{}, error) {
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return ls.Map(), nil
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}
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// IsZero implements yaml.IsZeroer - if we don't have this then 'omitempty' fields are always omitted.
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func (ls Labels) IsZero() bool {
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return len(ls.data) == 0
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}
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// UnmarshalYAML implements yaml.Unmarshaler.
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func (ls *Labels) UnmarshalYAML(unmarshal func(interface{}) error) error {
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var m map[string]string
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if err := unmarshal(&m); err != nil {
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return err
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}
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*ls = FromMap(m)
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return nil
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}
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// MatchLabels returns a subset of Labels that matches/does not match with the provided label names based on the 'on' boolean.
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// If on is set to true, it returns the subset of labels that match with the provided label names and its inverse when 'on' is set to false.
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// TODO: This is only used in printing an error message
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func (ls Labels) MatchLabels(on bool, names ...string) Labels {
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b := NewBuilder(ls)
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if on {
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b.Keep(names...)
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} else {
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b.Del(MetricName)
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b.Del(names...)
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}
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return b.Labels(EmptyLabels())
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}
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// Hash returns a hash value for the label set.
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// Note: the result is not guaranteed to be consistent across different runs of Prometheus.
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func (ls Labels) Hash() uint64 {
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return xxhash.Sum64(yoloBytes(ls.data))
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}
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// HashForLabels returns a hash value for the labels matching the provided names.
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// 'names' have to be sorted in ascending order.
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func (ls Labels) HashForLabels(b []byte, names ...string) (uint64, []byte) {
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b = b[:0]
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j := 0
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for i := 0; i < len(ls.data); {
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var name, value string
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name, i = decodeString(ls.data, i)
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value, i = decodeString(ls.data, i)
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for j < len(names) && names[j] < name {
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j++
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}
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if j == len(names) {
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break
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}
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if name == names[j] {
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b = append(b, name...)
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b = append(b, seps[0])
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b = append(b, value...)
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b = append(b, seps[0])
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}
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}
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return xxhash.Sum64(b), b
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}
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// HashWithoutLabels returns a hash value for all labels except those matching
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// the provided names.
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// 'names' have to be sorted in ascending order.
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func (ls Labels) HashWithoutLabels(b []byte, names ...string) (uint64, []byte) {
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b = b[:0]
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j := 0
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for i := 0; i < len(ls.data); {
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var name, value string
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name, i = decodeString(ls.data, i)
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value, i = decodeString(ls.data, i)
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for j < len(names) && names[j] < name {
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j++
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}
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if name == MetricName || (j < len(names) && name == names[j]) {
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continue
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}
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b = append(b, name...)
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b = append(b, seps[0])
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b = append(b, value...)
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b = append(b, seps[0])
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}
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return xxhash.Sum64(b), b
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}
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// BytesWithLabels is just as Bytes(), but only for labels matching names.
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// 'names' have to be sorted in ascending order.
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func (ls Labels) BytesWithLabels(buf []byte, names ...string) []byte {
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b := buf[:0]
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j := 0
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for pos := 0; pos < len(ls.data); {
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lName, newPos := decodeString(ls.data, pos)
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_, newPos = decodeString(ls.data, newPos)
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for j < len(names) && names[j] < lName {
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j++
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}
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if j == len(names) {
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break
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}
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if lName == names[j] {
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b = append(b, ls.data[pos:newPos]...)
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}
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pos = newPos
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}
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return b
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}
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// BytesWithoutLabels is just as Bytes(), but only for labels not matching names.
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// 'names' have to be sorted in ascending order.
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func (ls Labels) BytesWithoutLabels(buf []byte, names ...string) []byte {
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b := buf[:0]
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j := 0
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for pos := 0; pos < len(ls.data); {
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lName, newPos := decodeString(ls.data, pos)
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_, newPos = decodeString(ls.data, newPos)
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for j < len(names) && names[j] < lName {
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j++
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}
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if j == len(names) || lName != names[j] {
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b = append(b, ls.data[pos:newPos]...)
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}
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pos = newPos
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}
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return b
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}
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// Copy returns a copy of the labels.
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func (ls Labels) Copy() Labels {
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buf := append([]byte{}, ls.data...)
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return Labels{data: yoloString(buf)}
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}
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// Get returns the value for the label with the given name.
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// Returns an empty string if the label doesn't exist.
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func (ls Labels) Get(name string) string {
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for i := 0; i < len(ls.data); {
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var lName, lValue string
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lName, i = decodeString(ls.data, i)
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lValue, i = decodeString(ls.data, i)
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if lName == name {
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return lValue
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}
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}
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return ""
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}
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// Has returns true if the label with the given name is present.
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func (ls Labels) Has(name string) bool {
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for i := 0; i < len(ls.data); {
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var lName string
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lName, i = decodeString(ls.data, i)
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_, i = decodeString(ls.data, i)
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if lName == name {
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return true
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}
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}
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return false
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}
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// HasDuplicateLabelNames returns whether ls has duplicate label names.
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// It assumes that the labelset is sorted.
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func (ls Labels) HasDuplicateLabelNames() (string, bool) {
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var lName, prevName string
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for i := 0; i < len(ls.data); {
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lName, i = decodeString(ls.data, i)
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_, i = decodeString(ls.data, i)
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if lName == prevName {
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return lName, true
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}
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prevName = lName
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}
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return "", false
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}
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// WithoutEmpty returns the labelset without empty labels.
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// May return the same labelset.
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func (ls Labels) WithoutEmpty() Labels {
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for pos := 0; pos < len(ls.data); {
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_, newPos := decodeString(ls.data, pos)
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lValue, newPos := decodeString(ls.data, newPos)
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if lValue != "" {
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pos = newPos
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continue
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}
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// Do not copy the slice until it's necessary.
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// TODO: could optimise the case where all blanks are at the end.
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// Note: we size the new buffer on the assumption there is exactly one blank value.
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buf := make([]byte, pos, pos+(len(ls.data)-newPos))
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copy(buf, ls.data[:pos]) // copy the initial non-blank labels
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pos = newPos // move past the first blank value
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for pos < len(ls.data) {
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var newPos int
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_, newPos = decodeString(ls.data, pos)
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lValue, newPos = decodeString(ls.data, newPos)
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if lValue != "" {
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buf = append(buf, ls.data[pos:newPos]...)
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}
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pos = newPos
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}
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return Labels{data: yoloString(buf)}
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}
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return ls
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}
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// IsValid checks if the metric name or label names are valid.
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func (ls Labels) IsValid() bool {
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err := ls.Validate(func(l Label) error {
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if l.Name == model.MetricNameLabel && !model.IsValidMetricName(model.LabelValue(l.Value)) {
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return strconv.ErrSyntax
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}
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if !model.LabelName(l.Name).IsValid() || !model.LabelValue(l.Value).IsValid() {
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return strconv.ErrSyntax
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}
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return nil
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})
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return err == nil
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}
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// Equal returns whether the two label sets are equal.
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func Equal(ls, o Labels) bool {
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return ls.data == o.data
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}
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// Map returns a string map of the labels.
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func (ls Labels) Map() map[string]string {
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m := make(map[string]string, len(ls.data)/10)
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for i := 0; i < len(ls.data); {
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var lName, lValue string
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lName, i = decodeString(ls.data, i)
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lValue, i = decodeString(ls.data, i)
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m[lName] = lValue
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}
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return m
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}
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// EmptyLabels returns an empty Labels value, for convenience.
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func EmptyLabels() Labels {
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return Labels{}
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}
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func yoloString(b []byte) string {
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return *((*string)(unsafe.Pointer(&b)))
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}
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func yoloBytes(s string) (b []byte) {
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*(*string)(unsafe.Pointer(&b)) = s
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(*reflect.SliceHeader)(unsafe.Pointer(&b)).Cap = len(s)
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return
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}
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// New returns a sorted Labels from the given labels.
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// The caller has to guarantee that all label names are unique.
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func New(ls ...Label) Labels {
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sort.Sort(labelSlice(ls))
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size := labelsSize(ls)
|
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buf := make([]byte, size)
|
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marshalLabelsToSizedBuffer(ls, buf)
|
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return Labels{data: yoloString(buf)}
|
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}
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// FromMap returns new sorted Labels from the given map.
|
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func FromMap(m map[string]string) Labels {
|
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l := make([]Label, 0, len(m))
|
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for k, v := range m {
|
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l = append(l, Label{Name: k, Value: v})
|
||||
}
|
||||
return New(l...)
|
||||
}
|
||||
|
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// FromStrings creates new labels from pairs of strings.
|
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func FromStrings(ss ...string) Labels {
|
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if len(ss)%2 != 0 {
|
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panic("invalid number of strings")
|
||||
}
|
||||
ls := make([]Label, 0, len(ss)/2)
|
||||
for i := 0; i < len(ss); i += 2 {
|
||||
ls = append(ls, Label{Name: ss[i], Value: ss[i+1]})
|
||||
}
|
||||
|
||||
sort.Sort(labelSlice(ls))
|
||||
return New(ls...)
|
||||
}
|
||||
|
||||
// Compare compares the two label sets.
|
||||
// The result will be 0 if a==b, <0 if a < b, and >0 if a > b.
|
||||
// TODO: replace with Less function - Compare is never needed.
|
||||
// TODO: just compare the underlying strings when we don't need alphanumeric sorting.
|
||||
func Compare(a, b Labels) int {
|
||||
l := len(a.data)
|
||||
if len(b.data) < l {
|
||||
l = len(b.data)
|
||||
}
|
||||
|
||||
ia, ib := 0, 0
|
||||
for ia < l {
|
||||
var aName, bName string
|
||||
aName, ia = decodeString(a.data, ia)
|
||||
bName, ib = decodeString(b.data, ib)
|
||||
if aName != bName {
|
||||
if aName < bName {
|
||||
return -1
|
||||
}
|
||||
return 1
|
||||
}
|
||||
var aValue, bValue string
|
||||
aValue, ia = decodeString(a.data, ia)
|
||||
bValue, ib = decodeString(b.data, ib)
|
||||
if aValue != bValue {
|
||||
if aValue < bValue {
|
||||
return -1
|
||||
}
|
||||
return 1
|
||||
}
|
||||
}
|
||||
// If all labels so far were in common, the set with fewer labels comes first.
|
||||
return len(a.data) - len(b.data)
|
||||
}
|
||||
|
||||
// Copy labels from b on top of whatever was in ls previously, reusing memory or expanding if needed.
|
||||
func (ls *Labels) CopyFrom(b Labels) {
|
||||
ls.data = b.data // strings are immutable
|
||||
}
|
||||
|
||||
// IsEmpty returns true if ls represents an empty set of labels.
|
||||
func (ls Labels) IsEmpty() bool {
|
||||
return len(ls.data) == 0
|
||||
}
|
||||
|
||||
// Len returns the number of labels; it is relatively slow.
|
||||
func (ls Labels) Len() int {
|
||||
count := 0
|
||||
for i := 0; i < len(ls.data); {
|
||||
var size int
|
||||
size, i = decodeSize(ls.data, i)
|
||||
i += size
|
||||
size, i = decodeSize(ls.data, i)
|
||||
i += size
|
||||
count++
|
||||
}
|
||||
return count
|
||||
}
|
||||
|
||||
// Range calls f on each label.
|
||||
func (ls Labels) Range(f func(l Label)) {
|
||||
for i := 0; i < len(ls.data); {
|
||||
var lName, lValue string
|
||||
lName, i = decodeString(ls.data, i)
|
||||
lValue, i = decodeString(ls.data, i)
|
||||
f(Label{Name: lName, Value: lValue})
|
||||
}
|
||||
}
|
||||
|
||||
// Validate calls f on each label. If f returns a non-nil error, then it returns that error cancelling the iteration.
|
||||
func (ls Labels) Validate(f func(l Label) error) error {
|
||||
for i := 0; i < len(ls.data); {
|
||||
var lName, lValue string
|
||||
lName, i = decodeString(ls.data, i)
|
||||
lValue, i = decodeString(ls.data, i)
|
||||
err := f(Label{Name: lName, Value: lValue})
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
// InternStrings calls intern on every string value inside ls, replacing them with what it returns.
|
||||
func (ls *Labels) InternStrings(intern func(string) string) {
|
||||
ls.data = intern(ls.data)
|
||||
}
|
||||
|
||||
// ReleaseStrings calls release on every string value inside ls.
|
||||
func (ls Labels) ReleaseStrings(release func(string)) {
|
||||
release(ls.data)
|
||||
}
|
||||
|
||||
// Builder allows modifying Labels.
|
||||
type Builder struct {
|
||||
base Labels
|
||||
del []string
|
||||
add []Label
|
||||
}
|
||||
|
||||
// NewBuilder returns a new LabelsBuilder.
|
||||
func NewBuilder(base Labels) *Builder {
|
||||
b := &Builder{
|
||||
del: make([]string, 0, 5),
|
||||
add: make([]Label, 0, 5),
|
||||
}
|
||||
b.Reset(base)
|
||||
return b
|
||||
}
|
||||
|
||||
// Reset clears all current state for the builder.
|
||||
func (b *Builder) Reset(base Labels) {
|
||||
b.base = base
|
||||
b.del = b.del[:0]
|
||||
b.add = b.add[:0]
|
||||
for i := 0; i < len(base.data); {
|
||||
var lName, lValue string
|
||||
lName, i = decodeString(base.data, i)
|
||||
lValue, i = decodeString(base.data, i)
|
||||
if lValue == "" {
|
||||
b.del = append(b.del, lName)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Del deletes the label of the given name.
|
||||
func (b *Builder) Del(ns ...string) *Builder {
|
||||
for _, n := range ns {
|
||||
for i, a := range b.add {
|
||||
if a.Name == n {
|
||||
b.add = append(b.add[:i], b.add[i+1:]...)
|
||||
}
|
||||
}
|
||||
b.del = append(b.del, n)
|
||||
}
|
||||
return b
|
||||
}
|
||||
|
||||
// Keep removes all labels from the base except those with the given names.
|
||||
func (b *Builder) Keep(ns ...string) *Builder {
|
||||
Outer:
|
||||
for i := 0; i < len(b.base.data); {
|
||||
var lName string
|
||||
lName, i = decodeString(b.base.data, i)
|
||||
_, i = decodeString(b.base.data, i)
|
||||
for _, n := range ns {
|
||||
if lName == n {
|
||||
continue Outer
|
||||
}
|
||||
}
|
||||
b.del = append(b.del, lName)
|
||||
}
|
||||
return b
|
||||
}
|
||||
|
||||
// Set the name/value pair as a label. A value of "" means delete that label.
|
||||
func (b *Builder) Set(n, v string) *Builder {
|
||||
if v == "" {
|
||||
// Empty labels are the same as missing labels.
|
||||
return b.Del(n)
|
||||
}
|
||||
for i, a := range b.add {
|
||||
if a.Name == n {
|
||||
b.add[i].Value = v
|
||||
return b
|
||||
}
|
||||
}
|
||||
b.add = append(b.add, Label{Name: n, Value: v})
|
||||
|
||||
return b
|
||||
}
|
||||
|
||||
// Labels returns the labels from the builder, adding them to res if non-nil.
|
||||
// Argument res can be the same as b.base, if caller wants to overwrite that slice.
|
||||
// If no modifications were made, the original labels are returned.
|
||||
func (b *Builder) Labels(res Labels) Labels {
|
||||
if len(b.del) == 0 && len(b.add) == 0 {
|
||||
return b.base
|
||||
}
|
||||
|
||||
sort.Sort(labelSlice(b.add))
|
||||
sort.Strings(b.del)
|
||||
a, d := 0, 0
|
||||
|
||||
buf := make([]byte, 0, len(b.base.data)) // TODO: see if we can re-use the buffer from res.
|
||||
for pos := 0; pos < len(b.base.data); {
|
||||
oldPos := pos
|
||||
var lName string
|
||||
lName, pos = decodeString(b.base.data, pos)
|
||||
_, pos = decodeString(b.base.data, pos)
|
||||
for d < len(b.del) && b.del[d] < lName {
|
||||
d++
|
||||
}
|
||||
if d < len(b.del) && b.del[d] == lName {
|
||||
continue // This label has been deleted.
|
||||
}
|
||||
for ; a < len(b.add) && b.add[a].Name < lName; a++ {
|
||||
buf = appendLabelTo(buf, &b.add[a]) // Insert label that was not in the base set.
|
||||
}
|
||||
if a < len(b.add) && b.add[a].Name == lName {
|
||||
buf = appendLabelTo(buf, &b.add[a])
|
||||
a++
|
||||
continue // This label has been replaced.
|
||||
}
|
||||
buf = append(buf, b.base.data[oldPos:pos]...)
|
||||
}
|
||||
// We have come to the end of the base set; add any remaining labels.
|
||||
for ; a < len(b.add); a++ {
|
||||
buf = appendLabelTo(buf, &b.add[a])
|
||||
}
|
||||
return Labels{data: yoloString(buf)}
|
||||
}
|
||||
|
||||
func marshalLabelsToSizedBuffer(lbls []Label, data []byte) int {
|
||||
i := len(data)
|
||||
for index := len(lbls) - 1; index >= 0; index-- {
|
||||
size := marshalLabelToSizedBuffer(&lbls[index], data[:i])
|
||||
i -= size
|
||||
}
|
||||
return len(data) - i
|
||||
}
|
||||
|
||||
func marshalLabelToSizedBuffer(m *Label, data []byte) int {
|
||||
i := len(data)
|
||||
i -= len(m.Value)
|
||||
copy(data[i:], m.Value)
|
||||
i = encodeSize(data, i, len(m.Value))
|
||||
i -= len(m.Name)
|
||||
copy(data[i:], m.Name)
|
||||
i = encodeSize(data, i, len(m.Name))
|
||||
return len(data) - i
|
||||
}
|
||||
|
||||
func sizeVarint(x uint64) (n int) {
|
||||
// Most common case first
|
||||
if x < 1<<7 {
|
||||
return 1
|
||||
}
|
||||
if x >= 1<<56 {
|
||||
return 9
|
||||
}
|
||||
if x >= 1<<28 {
|
||||
x >>= 28
|
||||
n = 4
|
||||
}
|
||||
if x >= 1<<14 {
|
||||
x >>= 14
|
||||
n += 2
|
||||
}
|
||||
if x >= 1<<7 {
|
||||
n++
|
||||
}
|
||||
return n + 1
|
||||
}
|
||||
|
||||
func encodeVarint(data []byte, offset int, v uint64) int {
|
||||
offset -= sizeVarint(v)
|
||||
base := offset
|
||||
for v >= 1<<7 {
|
||||
data[offset] = uint8(v&0x7f | 0x80)
|
||||
v >>= 7
|
||||
offset++
|
||||
}
|
||||
data[offset] = uint8(v)
|
||||
return base
|
||||
}
|
||||
|
||||
// Special code for the common case that a size is less than 128
|
||||
func encodeSize(data []byte, offset, v int) int {
|
||||
if v < 1<<7 {
|
||||
offset--
|
||||
data[offset] = uint8(v)
|
||||
return offset
|
||||
}
|
||||
return encodeVarint(data, offset, uint64(v))
|
||||
}
|
||||
|
||||
func labelsSize(lbls []Label) (n int) {
|
||||
// we just encode name/value/name/value, without any extra tags or length bytes
|
||||
for _, e := range lbls {
|
||||
n += labelSize(&e)
|
||||
}
|
||||
return n
|
||||
}
|
||||
|
||||
func labelSize(m *Label) (n int) {
|
||||
// strings are encoded as length followed by contents.
|
||||
l := len(m.Name)
|
||||
n += l + sizeVarint(uint64(l))
|
||||
l = len(m.Value)
|
||||
n += l + sizeVarint(uint64(l))
|
||||
return n
|
||||
}
|
||||
|
||||
func appendLabelTo(buf []byte, m *Label) []byte {
|
||||
size := labelSize(m)
|
||||
sizeRequired := len(buf) + size
|
||||
if cap(buf) >= sizeRequired {
|
||||
buf = buf[:sizeRequired]
|
||||
} else {
|
||||
bufSize := cap(buf)
|
||||
// Double size of buffer each time it needs to grow, to amortise copying cost.
|
||||
for bufSize < sizeRequired {
|
||||
bufSize = bufSize*2 + 1
|
||||
}
|
||||
newBuf := make([]byte, sizeRequired, bufSize)
|
||||
copy(newBuf, buf)
|
||||
buf = newBuf
|
||||
}
|
||||
marshalLabelToSizedBuffer(m, buf)
|
||||
return buf
|
||||
}
|
||||
|
||||
// ScratchBuilder allows efficient construction of a Labels from scratch.
|
||||
type ScratchBuilder struct {
|
||||
add []Label
|
||||
output Labels
|
||||
overwriteBuffer []byte
|
||||
}
|
||||
|
||||
// NewScratchBuilder creates a ScratchBuilder initialized for Labels with n entries.
|
||||
func NewScratchBuilder(n int) ScratchBuilder {
|
||||
return ScratchBuilder{add: make([]Label, 0, n)}
|
||||
}
|
||||
|
||||
func (b *ScratchBuilder) Reset() {
|
||||
b.add = b.add[:0]
|
||||
b.output = EmptyLabels()
|
||||
}
|
||||
|
||||
// Add a name/value pair.
|
||||
// Note if you Add the same name twice you will get a duplicate label, which is invalid.
|
||||
func (b *ScratchBuilder) Add(name, value string) {
|
||||
b.add = append(b.add, Label{Name: name, Value: value})
|
||||
}
|
||||
|
||||
// Sort the labels added so far by name.
|
||||
func (b *ScratchBuilder) Sort() {
|
||||
sort.Sort(labelSlice(b.add))
|
||||
}
|
||||
|
||||
// Asssign is for when you already have a Labels which you want this ScratchBuilder to return.
|
||||
func (b *ScratchBuilder) Assign(l Labels) {
|
||||
b.output = l
|
||||
}
|
||||
|
||||
// Labels returns the name/value pairs added as a Labels object. Calling Add() after Labels() has no effect.
|
||||
// Note: if you want them sorted, call Sort() first.
|
||||
func (b *ScratchBuilder) Labels() Labels {
|
||||
if b.output.IsEmpty() {
|
||||
size := labelsSize(b.add)
|
||||
buf := make([]byte, size)
|
||||
marshalLabelsToSizedBuffer(b.add, buf)
|
||||
b.output = Labels{data: yoloString(buf)}
|
||||
}
|
||||
return b.output
|
||||
}
|
||||
|
||||
// Write the newly-built Labels out to ls, reusing an internal buffer.
|
||||
// Callers must ensure that there are no other references to ls.
|
||||
func (b *ScratchBuilder) Overwrite(ls *Labels) {
|
||||
size := labelsSize(b.add)
|
||||
if size <= cap(b.overwriteBuffer) {
|
||||
b.overwriteBuffer = b.overwriteBuffer[:size]
|
||||
} else {
|
||||
b.overwriteBuffer = make([]byte, size)
|
||||
}
|
||||
marshalLabelsToSizedBuffer(b.add, b.overwriteBuffer)
|
||||
ls.data = yoloString(b.overwriteBuffer)
|
||||
}
|
||||
Loading…
Reference in a new issue