Update vendor github.com/cavaliercoder/grab

vendor/github.com/cavaliercoder/grab/bps/bps.go

@@ -0,0 +1,54 @@
+/*
+Package bps provides gauges for calculating the Bytes Per Second transfer rate
+of data streams.
+*/
+package bps
+
+import (
+	"context"
+	"time"
+)
+
+// Gauge is the common interface for all BPS gauges in this package. Given a
+// set of samples over time, each gauge type can be used to measure the Bytes
+// Per Second transfer rate of a data stream.
+//
+// All samples must monotonically increase in timestamp and value. Each sample
+// should represent the total number of bytes sent in a stream, rather than
+// accounting for the number sent since the last sample.
+//
+// To ensure a gauge can report progress as quickly as possible, take an initial
+// sample when your stream first starts.
+//
+// All gauge implementations are safe for concurrent use.
+type Gauge interface {
+	// Sample adds a new sample of the progress of the monitored stream.
+	Sample(t time.Time, n int64)
+
+	// BPS returns the calculated Bytes Per Second rate of the monitored stream.
+	BPS() float64
+}
+
+// SampleFunc is used by Watch to take periodic samples of a monitored stream.
+type SampleFunc func() (n int64)
+
+// Watch will periodically call the given SampleFunc to sample the progress of
+// a monitored stream and update the given gauge. SampleFunc should return the
+// total number of bytes transferred by the stream since it started.
+//
+// Watch is a blocking call and should typically be called in a new goroutine.
+// To prevent the goroutine from leaking, make sure to cancel the given context
+// once the stream is completed or canceled.
+func Watch(ctx context.Context, g Gauge, f SampleFunc, interval time.Duration) {
+	g.Sample(time.Now(), f())
+	t := time.NewTicker(interval)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case now := <-t.C:
+			g.Sample(now, f())
+		}
+	}
+}