labels.go

// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package collectd // import "github.com/open-telemetry/opentelemetry-collector-contrib/internal/collectd"

import (
	"strings"
)

// LabelsFromName tries to pull out dimensions out of name in the format
// "name[k=v,f=x]-more_name".
// For the example above it would return "name-more_name" and extract dimensions
// (k,v) and (f,x).
// If something unexpected is encountered it returns the original metric name.
//
// The code tries to avoid allocation by using local slices and avoiding calls
// to functions like strings.Slice.
func LabelsFromName(val *string) (metricName string, labels map[string]string) {
	metricName = *val
	index := strings.Index(*val, "[")
	if index > -1 {
		left := (*val)[:index]
		rest := (*val)[index+1:]
		index = strings.Index(rest, "]")
		if index > -1 {
			working := make(map[string]string)
			dimensions := rest[:index]
			rest = rest[index+1:]
			cindex := strings.Index(dimensions, ",")
			prev := 0
			for {
				if cindex < prev {
					cindex = len(dimensions)
				}
				piece := dimensions[prev:cindex]
				tindex := strings.Index(piece, "=")
				if tindex == -1 || strings.Contains(piece[tindex+1:], "=") {
					return
				}
				working[piece[:tindex]] = piece[tindex+1:]
				if cindex == len(dimensions) {
					break
				}
				prev = cindex + 1
				cindex = strings.Index(dimensions[prev:], ",") + prev
			}
			labels = working
			metricName = left + rest
		}
	}
	return
}