syncthing/model/suppressor.go

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// Copyright (C) 2014 Jakob Borg and other contributors. All rights reserved.
// Use of this source code is governed by an MIT-style license that can be
// found in the LICENSE file.
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package model
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import (
"os"
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"sync"
"time"
)
const (
MaxChangeHistory = 4
)
type change struct {
size int64
when time.Time
}
type changeHistory struct {
changes []change
next int64
prevSup bool
}
type suppressor struct {
sync.Mutex
changes map[string]changeHistory
threshold int64 // bytes/s
}
func (h changeHistory) bandwidth(t time.Time) int64 {
if len(h.changes) == 0 {
return 0
}
var t0 = h.changes[0].when
if t == t0 {
return 0
}
var bw float64
for _, c := range h.changes {
bw += float64(c.size)
}
return int64(bw / t.Sub(t0).Seconds())
}
func (h *changeHistory) append(size int64, t time.Time) {
c := change{size, t}
if len(h.changes) == MaxChangeHistory {
h.changes = h.changes[1:MaxChangeHistory]
}
h.changes = append(h.changes, c)
}
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func (s *suppressor) Suppress(name string, fi os.FileInfo) (cur, prev bool) {
return s.suppress(name, fi.Size(), time.Now())
}
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func (s *suppressor) suppress(name string, size int64, t time.Time) (bool, bool) {
s.Lock()
if s.changes == nil {
s.changes = make(map[string]changeHistory)
}
h := s.changes[name]
sup := h.bandwidth(t) > s.threshold
prevSup := h.prevSup
h.prevSup = sup
if !sup {
h.append(size, t)
}
s.changes[name] = h
s.Unlock()
return sup, prevSup
}