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@ -18,9 +18,8 @@ import ( |
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"encoding/json" |
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"encoding/json" |
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"sort" |
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"sort" |
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"strconv" |
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"strconv" |
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"unsafe" |
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"github.com/cespare/xxhash" |
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"github.com/cespare/xxhash/v2" |
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) |
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) |
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// Well-known label names used by Prometheus components.
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// Well-known label names used by Prometheus components.
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@ -135,39 +134,19 @@ func (ls Labels) MatchLabels(on bool, names ...string) Labels { |
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return matchedLabels |
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return matchedLabels |
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} |
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} |
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// noEscape hides a pointer from escape analysis. noEscape is
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// the identity function but escape analysis doesn't think the
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// output depends on the input. noEscape is inlined and currently
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// compiles down to zero instructions.
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// USE CAREFULLY!
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// This was copied from the runtime; see issues 23382 and 7921.
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//go:nosplit
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//go:nocheckptr
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func noEscape(p unsafe.Pointer) unsafe.Pointer { |
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x := uintptr(p) |
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return unsafe.Pointer(x ^ 0) //nolint:staticcheck
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} |
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//go:nosplit
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//go:checkptr
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func noAllocBytes(buf string) []byte { |
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return *(*[]byte)(unsafe.Pointer(&buf)) |
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} |
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// Hash returns a hash value for the label set.
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// Hash returns a hash value for the label set.
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func (ls Labels) Hash() uint64 { |
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func (ls Labels) Hash() uint64 { |
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// xxhash.Sum64(b) for fast path as it's faster.
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b := make([]byte, 0, 1024) |
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b := make([]byte, 0, 1024) |
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for i, v := range ls { |
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for i, v := range ls { |
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if len(b)+len(v.Name)+len(v.Value)+2 >= cap(b) { |
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if len(b)+len(v.Name)+len(v.Value)+2 >= cap(b) { |
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// If labels entry is 1KB+ allocate do not allocate whole entry.
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// If labels entry is 1KB+ allocate do not allocate whole entry.
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h := xxhash.New() |
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h := xxhash.New() |
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// This allows b to be still on stack and reused. This is safe as xxhash.x
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_, _ = h.Write(b) |
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// is never used outside of this function.
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_, _ = h.Write(*(*[]byte)(noEscape(unsafe.Pointer(&b)))) |
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for _, v := range ls[i:] { |
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for _, v := range ls[i:] { |
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_, _ = h.Write(noAllocBytes(v.Name)) |
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_, _ = h.WriteString(v.Name) |
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_, _ = h.Write(seps) |
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_, _ = h.Write(seps) |
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_, _ = h.Write(noAllocBytes(v.Value)) |
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_, _ = h.WriteString(v.Value) |
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_, _ = h.Write(seps) |
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_, _ = h.Write(seps) |
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} |
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} |
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return h.Sum64() |
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return h.Sum64() |
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Bartlomiej Plotka
5 years ago