func (m *MeasuredWriter) BytesPer(perPeriod time.Duration) uint64 {
	return uint64(m.rate.Rate(perPeriod))
}
BytesPer tells the rate per period at which bytes were written since last
measurement.
package iocontrol
import (
	"io"
	"time"
)
type MeasuredWriter struct {
	wrap io.Writer
	rate *rateCounter
}
func NewMeasuredWriter(w io.Writer) *MeasuredWriter {
	return &MeasuredWriter{wrap: w, rate: newCounter()}
}