Launcher, app/base, sentry, update service

internal/updater/locker.go

@@ -0,0 +1,50 @@
+// Copyright (c) 2020 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package updater
+
+import (
+	"sync/atomic"
+
+	"github.com/pkg/errors"
+)
+
+var ErrOperationOngoing = errors.New("the operation is already ongoing")
+
+// locker is an easy way to ensure we only perform one update at a time.
+type locker struct {
+	ongoing atomic.Value
+}
+
+func newLocker() *locker {
+	l := &locker{}
+
+	l.ongoing.Store(false)
+
+	return l
+}
+
+func (l *locker) doOnce(fn func() error) error {
+	if l.ongoing.Load().(bool) {
+		return ErrOperationOngoing
+	}
+
+	l.ongoing.Store(true)
+	defer func() { l.ongoing.Store(false) }()
+
+	return fn()
+}