Rename Repository -> Folder, Node -> Device (fixes #739)

internal/model/deviceactivity.go

@@ -0,0 +1,51 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package model
+
+import (
+	"sync"
+
+	"github.com/syncthing/syncthing/internal/protocol"
+)
+
+// 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),
+	}
+}
+
+func (m deviceActivity) leastBusy(availability []protocol.DeviceID) protocol.DeviceID {
+	m.mut.Lock()
+	var low int = 2<<30 - 1
+	var selected protocol.DeviceID
+	for _, device := range availability {
+		if usage := m.act[device]; usage < low {
+			low = usage
+			selected = device
+		}
+	}
+	m.mut.Unlock()
+	return selected
+}
+
+func (m deviceActivity) using(device protocol.DeviceID) {
+	m.mut.Lock()
+	defer m.mut.Unlock()
+	m.act[device]++
+}
+
+func (m deviceActivity) done(device protocol.DeviceID) {
+	m.mut.Lock()
+	defer m.mut.Unlock()
+	m.act[device]--
+}