mirror of
https://github.com/prometheus/statsd_exporter.git
synced 2024-11-13 10:51:06 +00:00
86 lines
2.5 KiB
Go
86 lines
2.5 KiB
Go
// Copyright 2020 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 mapper
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import (
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"strings"
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"unicode/utf8"
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)
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// EscapeMetricName replaces invalid characters in the metric name with "_"
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// Valid characters are a-z, A-Z, 0-9, and _
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func EscapeMetricName(metricName string) string {
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metricLen := len(metricName)
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if metricLen == 0 {
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return ""
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}
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escaped := false
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var sb strings.Builder
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// If a metric starts with a digit, allocate the memory and prepend an
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// underscore.
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if metricName[0] >= '0' && metricName[0] <= '9' {
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escaped = true
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sb.Grow(metricLen + 1)
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sb.WriteByte('_')
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}
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// This is an character replacement method optimized for this limited
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// use case. It is much faster than using a regex.
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offset := 0
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var prevChar rune
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for i, c := range metricName {
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// Seek forward, skipping valid characters until we find one that needs
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// to be replaced, then add all the characters we've seen so far to the
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// string.Builder.
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if (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
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(c >= '0' && c <= '9') || (c == '_') {
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// Character is valid, so skip over it without doing anything.
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} else {
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// Double-dashes are allowed if there is a corresponding mapping.
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// For consistency, double-dashes should also be allowed in the default case.
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if c == '-' && prevChar == '-' {
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offset = i + utf8.RuneLen(c)
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continue
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}
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if !escaped {
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// Up until now we've been lazy and avoided actually allocating
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// memory. Unfortunately we've now determined this string needs
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// escaping, so allocate the buffer for the whole string.
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escaped = true
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sb.Grow(metricLen)
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}
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sb.WriteString(metricName[offset:i])
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offset = i + utf8.RuneLen(c)
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sb.WriteByte('_')
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}
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prevChar = c
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}
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if !escaped {
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// This is the happy path where nothing had to be escaped, so we can
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// avoid doing anything.
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return metricName
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}
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if offset < metricLen {
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sb.WriteString(metricName[offset:])
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}
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return sb.String()
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}
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