98 lines
2.2 KiB
Go
98 lines
2.2 KiB
Go
// Copyright 2014 Prometheus Team
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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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package model
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import (
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"bytes"
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"hash"
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"hash/fnv"
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)
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// SeparatorByte is a byte that cannot occur in valid UTF-8 sequences and is
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// used to separate label names, label values, and other strings from each other
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// when calculating their combined hash value (aka signature aka fingerprint).
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const SeparatorByte byte = 255
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var (
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// cache the signature of an empty label set.
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emptyLabelSignature = fnv.New64a().Sum64()
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hashAndBufPool = make(chan *hashAndBuf, 1024)
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)
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type hashAndBuf struct {
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h hash.Hash64
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b bytes.Buffer
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}
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func getHashAndBuf() *hashAndBuf {
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select {
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case hb := <-hashAndBufPool:
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return hb
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default:
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return &hashAndBuf{h: fnv.New64a()}
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}
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}
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func putHashAndBuf(hb *hashAndBuf) {
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select {
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case hashAndBufPool <- hb:
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default:
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}
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}
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// LabelsToSignature returns a unique signature (i.e., fingerprint) for a given
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// label set.
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func LabelsToSignature(labels map[string]string) uint64 {
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if len(labels) == 0 {
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return emptyLabelSignature
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}
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var result uint64
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hb := getHashAndBuf()
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defer putHashAndBuf(hb)
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for k, v := range labels {
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hb.b.WriteString(k)
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hb.b.WriteByte(SeparatorByte)
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hb.b.WriteString(v)
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hb.h.Write(hb.b.Bytes())
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result ^= hb.h.Sum64()
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hb.h.Reset()
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hb.b.Reset()
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}
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return result
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}
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// LabelValuesToSignature returns a unique signature (i.e., fingerprint) for the
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// values of a given label set.
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func LabelValuesToSignature(labels map[string]string) uint64 {
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if len(labels) == 0 {
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return emptyLabelSignature
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}
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var result uint64
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hb := getHashAndBuf()
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defer putHashAndBuf(hb)
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for _, v := range labels {
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hb.b.WriteString(v)
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hb.h.Write(hb.b.Bytes())
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result ^= hb.h.Sum64()
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hb.h.Reset()
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hb.b.Reset()
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}
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return result
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}
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