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52 lines
1.7 KiB
52 lines
1.7 KiB
// Copyright 2024 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 dedupelabels |
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package labels |
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import ( |
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"github.com/cespare/xxhash/v2" |
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) |
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// StableHash is a labels hashing implementation which is guaranteed to not change over time. |
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// This function should be used whenever labels hashing backward compatibility must be guaranteed. |
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func StableHash(ls Labels) uint64 { |
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// Use xxhash.Sum64(b) for fast path as it's faster. |
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b := make([]byte, 0, 1024) |
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for pos := 0; pos < len(ls.data); { |
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name, newPos := decodeString(ls.syms, ls.data, pos) |
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value, newPos := decodeString(ls.syms, ls.data, newPos) |
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if len(b)+len(name)+len(value)+2 >= cap(b) { |
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// If labels entry is 1KB+, hash the rest of them via Write(). |
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h := xxhash.New() |
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_, _ = h.Write(b) |
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for pos < len(ls.data) { |
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name, pos = decodeString(ls.syms, ls.data, pos) |
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value, pos = decodeString(ls.syms, ls.data, pos) |
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_, _ = h.WriteString(name) |
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_, _ = h.Write(seps) |
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_, _ = h.WriteString(value) |
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_, _ = h.Write(seps) |
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} |
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return h.Sum64() |
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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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pos = newPos |
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} |
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return xxhash.Sum64(b) |
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}
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