vendor: revendor for gRPC

vendor/google.golang.org/grpc/benchmark/stats/stats.go

@@ -0,0 +1,116 @@
+package stats
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"math"
+	"time"
+)
+
+// Stats is a simple helper for gathering additional statistics like histogram
+// during benchmarks. This is not thread safe.
+type Stats struct {
+	numBuckets int
+	unit       time.Duration
+	min, max   int64
+	histogram  *Histogram
+
+	durations durationSlice
+	dirty     bool
+}
+
+type durationSlice []time.Duration
+
+// NewStats creates a new Stats instance. If numBuckets is not positive,
+// the default value (16) will be used.
+func NewStats(numBuckets int) *Stats {
+	if numBuckets <= 0 {
+		numBuckets = 16
+	}
+	return &Stats{
+		// Use one more bucket for the last unbounded bucket.
+		numBuckets: numBuckets + 1,
+		durations:  make(durationSlice, 0, 100000),
+	}
+}
+
+// Add adds an elapsed time per operation to the stats.
+func (stats *Stats) Add(d time.Duration) {
+	stats.durations = append(stats.durations, d)
+	stats.dirty = true
+}
+
+// Clear resets the stats, removing all values.
+func (stats *Stats) Clear() {
+	stats.durations = stats.durations[:0]
+	stats.histogram = nil
+	stats.dirty = false
+}
+
+// maybeUpdate updates internal stat data if there was any newly added
+// stats since this was updated.
+func (stats *Stats) maybeUpdate() {
+	if !stats.dirty {
+		return
+	}
+
+	stats.min = math.MaxInt64
+	stats.max = 0
+	for _, d := range stats.durations {
+		if stats.min > int64(d) {
+			stats.min = int64(d)
+		}
+		if stats.max < int64(d) {
+			stats.max = int64(d)
+		}
+	}
+
+	// Use the largest unit that can represent the minimum time duration.
+	stats.unit = time.Nanosecond
+	for _, u := range []time.Duration{time.Microsecond, time.Millisecond, time.Second} {
+		if stats.min <= int64(u) {
+			break
+		}
+		stats.unit = u
+	}
+
+	// Adjust the min/max according to the new unit.
+	stats.min /= int64(stats.unit)
+	stats.max /= int64(stats.unit)
+	numBuckets := stats.numBuckets
+	if n := int(stats.max - stats.min + 1); n < numBuckets {
+		numBuckets = n
+	}
+	stats.histogram = NewHistogram(HistogramOptions{
+		NumBuckets: numBuckets,
+		// max-min(lower bound of last bucket) = (1 + growthFactor)^(numBuckets-2) * baseBucketSize.
+		GrowthFactor:   math.Pow(float64(stats.max-stats.min), 1/float64(numBuckets-2)) - 1,
+		BaseBucketSize: 1.0,
+		MinValue:       stats.min})
+
+	for _, d := range stats.durations {
+		stats.histogram.Add(int64(d / stats.unit))
+	}
+
+	stats.dirty = false
+}
+
+// Print writes textual output of the Stats.
+func (stats *Stats) Print(w io.Writer) {
+	stats.maybeUpdate()
+
+	if stats.histogram == nil {
+		fmt.Fprint(w, "Histogram (empty)\n")
+	} else {
+		fmt.Fprintf(w, "Histogram (unit: %s)\n", fmt.Sprintf("%v", stats.unit)[1:])
+		stats.histogram.Print(w)
+	}
+}
+
+// String returns the textual output of the Stats as string.
+func (stats *Stats) String() string {
+	var b bytes.Buffer
+	stats.Print(&b)
+	return b.String()
+}