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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package traceviewer
import (
"fmt"
"html/template"
"math"
"strings"
"time"
)
// TimeHistogram is an high-dynamic-range histogram for durations.
type TimeHistogram struct {
Count int
Buckets []int
MinBucket, MaxBucket int
}
// Five buckets for every power of 10.
var logDiv = math.Log(math.Pow(10, 1.0/5))
// Add adds a single sample to the histogram.
func (h *TimeHistogram) Add(d time.Duration) {
var bucket int
if d > 0 {
bucket = int(math.Log(float64(d)) / logDiv)
}
if len(h.Buckets) <= bucket {
h.Buckets = append(h.Buckets, make([]int, bucket-len(h.Buckets)+1)...)
h.Buckets = h.Buckets[:cap(h.Buckets)]
}
h.Buckets[bucket]++
if bucket < h.MinBucket || h.MaxBucket == 0 {
h.MinBucket = bucket
}
if bucket > h.MaxBucket {
h.MaxBucket = bucket
}
h.Count++
}
// BucketMin returns the minimum duration value for a provided bucket.
func (h *TimeHistogram) BucketMin(bucket int) time.Duration {
return time.Duration(math.Exp(float64(bucket) * logDiv))
}
// ToHTML renders the histogram as HTML.
func (h *TimeHistogram) ToHTML(urlmaker func(min, max time.Duration) string) template.HTML {
if h == nil || h.Count == 0 {
return template.HTML("")
}
const barWidth = 400
maxCount := 0
for _, count := range h.Buckets {
if count > maxCount {
maxCount = count
}
}
w := new(strings.Builder)
fmt.Fprintf(w, `<table>`)
for i := h.MinBucket; i <= h.MaxBucket; i++ {
// Tick label.
if h.Buckets[i] > 0 {
fmt.Fprintf(w, `<tr><td class="histoTime" align="right"><a href=%s>%s</a></td>`, urlmaker(h.BucketMin(i), h.BucketMin(i+1)), h.BucketMin(i))
} else {
fmt.Fprintf(w, `<tr><td class="histoTime" align="right">%s</td>`, h.BucketMin(i))
}
// Bucket bar.
width := h.Buckets[i] * barWidth / maxCount
fmt.Fprintf(w, `<td><div style="width:%dpx;background:blue;position:relative"> </div></td>`, width)
// Bucket count.
fmt.Fprintf(w, `<td align="right"><div style="position:relative">%d</div></td>`, h.Buckets[i])
fmt.Fprintf(w, "</tr>\n")
}
// Final tick label.
fmt.Fprintf(w, `<tr><td align="right">%s</td></tr>`, h.BucketMin(h.MaxBucket+1))
fmt.Fprintf(w, `</table>`)
return template.HTML(w.String())
}
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