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// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package model
import (
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/sync"
)
// deviceActivity tracks the number of outstanding requests per device and can
// answer which device is least busy. It is safe for use from multiple
// goroutines.
type deviceActivity struct {
act map[protocol.DeviceID]int
mut sync.Mutex
}
func newDeviceActivity() *deviceActivity {
return &deviceActivity{
act: make(map[protocol.DeviceID]int),
mut: sync.NewMutex(),
}
}
// Returns the index of the least busy device, or -1 if all are too busy.
func (m *deviceActivity) leastBusy(availability []Availability) int {
m.mut.Lock()
low := 2<<30 - 1
best := -1
for i := range availability {
if usage := m.act[availability[i].ID]; usage < low {
low = usage
best = i
}
}
m.mut.Unlock()
return best
}
func (m *deviceActivity) using(availability Availability) {
m.mut.Lock()
m.act[availability.ID]++
m.mut.Unlock()
}
func (m *deviceActivity) done(availability Availability) {
m.mut.Lock()
m.act[availability.ID]--
m.mut.Unlock()
}
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