Copyright 2017, OpenCensus Authors Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

package stats

import (
	
	
)
Measure represents a single numeric value to be tracked and recorded. For example, latency, request bytes, and response bytes could be measures to collect from a server. Measures by themselves have no outside effects. In order to be exported, the measure needs to be used in a View. If no Views are defined over a measure, there is very little cost in recording it.
Name returns the name of this measure. Measure names are globally unique (among all libraries linked into your program). We recommend prefixing the measure name with a domain name relevant to your project or application. Measure names are never sent over the wire or exported to backends. They are only used to create Views.
	Name() string
Description returns the human-readable description of this measure.
	Description() string
Unit returns the units for the values this measure takes on. Units are encoded according to the case-sensitive abbreviations from the Unified Code for Units of Measure: http://unitsofmeasure.org/ucum.html
	Unit() string
}
measureDescriptor is the untyped descriptor associated with each measure. Int64Measure and Float64Measure wrap measureDescriptor to provide typed recording APIs. Two Measures with the same name will have the same measureDescriptor.
type measureDescriptor struct {
	subs int32 // access atomically

	name        string
	description string
	unit        string
}

func ( *measureDescriptor) () {
	atomic.StoreInt32(&.subs, 1)
}

func ( *measureDescriptor) () bool {
	return atomic.LoadInt32(&.subs) == 1
}

var (
	mu       sync.RWMutex
	measures = make(map[string]*measureDescriptor)
)

func (, ,  string) *measureDescriptor {
	mu.Lock()
	defer mu.Unlock()

	if ,  := measures[];  {
		return 
	}
	 := &measureDescriptor{
		name:        ,
		description: ,
		unit:        ,
	}
	measures[] = 
	return 
}
Measurement is the numeric value measured when recording stats. Each measure provides methods to create measurements of their kind. For example, Int64Measure provides M to convert an int64 into a measurement.
type Measurement struct {
	v    float64
	m    Measure
	desc *measureDescriptor
}
Value returns the value of the Measurement as a float64.
func ( Measurement) () float64 {
	return .v
}
Measure returns the Measure from which this Measurement was created.
func ( Measurement) () Measure {
	return .m