61 lines
1.6 KiB
Go
61 lines
1.6 KiB
Go
// Copyright 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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package labels
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import (
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"bytes"
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"math"
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"strconv"
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"sync"
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)
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// floatFormatBufPool is exclusively used in FormatOpenMetricsFloat.
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var floatFormatBufPool = sync.Pool{
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New: func() any {
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// To contain at most 17 digits and additional syntax for a float64.
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b := make([]byte, 0, 24)
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return &b
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},
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}
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// FormatOpenMetricsFloat works like the usual Go string formatting of a float
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// but appends ".0" if the resulting number would otherwise contain neither a
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// "." nor an "e".
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func FormatOpenMetricsFloat(f float64) string {
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// A few common cases hardcoded.
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switch {
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case f == 1:
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return "1.0"
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case f == 0:
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return "0.0"
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case f == -1:
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return "-1.0"
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case math.IsNaN(f):
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return "NaN"
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case math.IsInf(f, +1):
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return "+Inf"
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case math.IsInf(f, -1):
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return "-Inf"
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}
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bp := floatFormatBufPool.Get().(*[]byte)
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defer floatFormatBufPool.Put(bp)
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*bp = strconv.AppendFloat((*bp)[:0], f, 'g', -1, 64)
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if bytes.ContainsAny(*bp, "e.") {
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return string(*bp)
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}
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*bp = append(*bp, '.', '0')
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return string(*bp)
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}
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