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42 lines
1 KiB
Go
42 lines
1 KiB
Go
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//go:build stringlabels
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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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var h *xxhash.Digest
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for i := 0; i < len(ls.data); {
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var v Label
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v.Name, i = decodeString(ls.data, i)
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v.Value, i = decodeString(ls.data, i)
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if h == nil && len(b)+len(v.Name)+len(v.Value)+2 >= cap(b) {
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// If labels entry is 1KB+, switch to Write API. Copy in the values up to this point.
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h = xxhash.New()
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_, _ = h.Write(b)
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}
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if h != nil {
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_, _ = h.WriteString(v.Name)
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_, _ = h.Write(seps)
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_, _ = h.WriteString(v.Value)
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_, _ = h.Write(seps)
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continue
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}
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b = append(b, v.Name...)
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b = append(b, seps[0])
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b = append(b, v.Value...)
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b = append(b, seps[0])
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}
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if h != nil {
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return h.Sum64()
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}
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return xxhash.Sum64(b)
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}
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