diff options
Diffstat (limited to 'dex/downloader/api.go')
| -rw-r--r-- | dex/downloader/api.go | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/dex/downloader/api.go b/dex/downloader/api.go new file mode 100644 index 000000000..721818e75 --- /dev/null +++ b/dex/downloader/api.go @@ -0,0 +1,166 @@ +// Copyright 2015 The go-ethereum Authors +// This file is part of the go-ethereum library. +// +// The go-ethereum library is free software: you can redistribute it and/or modify +// it under the terms of the GNU Lesser General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// The go-ethereum library 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 Lesser General Public License for more details. +// +// You should have received a copy of the GNU Lesser General Public License +// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. + +package downloader + +import ( + "context" + "sync" + + ethereum "github.com/dexon-foundation/dexon" + "github.com/dexon-foundation/dexon/event" + "github.com/dexon-foundation/dexon/rpc" +) + +// PublicDownloaderAPI provides an API which gives information about the current synchronisation status. +// It offers only methods that operates on data that can be available to anyone without security risks. +type PublicDownloaderAPI struct { + d *Downloader + mux *event.TypeMux + installSyncSubscription chan chan interface{} + uninstallSyncSubscription chan *uninstallSyncSubscriptionRequest +} + +// NewPublicDownloaderAPI create a new PublicDownloaderAPI. The API has an internal event loop that +// listens for events from the downloader through the global event mux. In case it receives one of +// these events it broadcasts it to all syncing subscriptions that are installed through the +// installSyncSubscription channel. +func NewPublicDownloaderAPI(d *Downloader, m *event.TypeMux) *PublicDownloaderAPI { + api := &PublicDownloaderAPI{ + d: d, + mux: m, + installSyncSubscription: make(chan chan interface{}), + uninstallSyncSubscription: make(chan *uninstallSyncSubscriptionRequest), + } + + go api.eventLoop() + + return api +} + +// eventLoop runs a loop until the event mux closes. It will install and uninstall new +// sync subscriptions and broadcasts sync status updates to the installed sync subscriptions. +func (api *PublicDownloaderAPI) eventLoop() { + var ( + sub = api.mux.Subscribe(StartEvent{}, DoneEvent{}, FailedEvent{}) + syncSubscriptions = make(map[chan interface{}]struct{}) + ) + + for { + select { + case i := <-api.installSyncSubscription: + syncSubscriptions[i] = struct{}{} + case u := <-api.uninstallSyncSubscription: + delete(syncSubscriptions, u.c) + close(u.uninstalled) + case event := <-sub.Chan(): + if event == nil { + return + } + + var notification interface{} + switch event.Data.(type) { + case StartEvent: + notification = &SyncingResult{ + Syncing: true, + Status: api.d.Progress(), + } + case DoneEvent, FailedEvent: + notification = false + } + // broadcast + for c := range syncSubscriptions { + c <- notification + } + } + } +} + +// Syncing provides information when this nodes starts synchronising with the Ethereum network and when it's finished. +func (api *PublicDownloaderAPI) Syncing(ctx context.Context) (*rpc.Subscription, error) { + notifier, supported := rpc.NotifierFromContext(ctx) + if !supported { + return &rpc.Subscription{}, rpc.ErrNotificationsUnsupported + } + + rpcSub := notifier.CreateSubscription() + + go func() { + statuses := make(chan interface{}) + sub := api.SubscribeSyncStatus(statuses) + + for { + select { + case status := <-statuses: + notifier.Notify(rpcSub.ID, status) + case <-rpcSub.Err(): + sub.Unsubscribe() + return + case <-notifier.Closed(): + sub.Unsubscribe() + return + } + } + }() + + return rpcSub, nil +} + +// SyncingResult provides information about the current synchronisation status for this node. +type SyncingResult struct { + Syncing bool `json:"syncing"` + Status ethereum.SyncProgress `json:"status"` +} + +// uninstallSyncSubscriptionRequest uninstalles a syncing subscription in the API event loop. +type uninstallSyncSubscriptionRequest struct { + c chan interface{} + uninstalled chan interface{} +} + +// SyncStatusSubscription represents a syncing subscription. +type SyncStatusSubscription struct { + api *PublicDownloaderAPI // register subscription in event loop of this api instance + c chan interface{} // channel where events are broadcasted to + unsubOnce sync.Once // make sure unsubscribe logic is executed once +} + +// Unsubscribe uninstalls the subscription from the DownloadAPI event loop. +// The status channel that was passed to subscribeSyncStatus isn't used anymore +// after this method returns. +func (s *SyncStatusSubscription) Unsubscribe() { + s.unsubOnce.Do(func() { + req := uninstallSyncSubscriptionRequest{s.c, make(chan interface{})} + s.api.uninstallSyncSubscription <- &req + + for { + select { + case <-s.c: + // drop new status events until uninstall confirmation + continue + case <-req.uninstalled: + return + } + } + }) +} + +// SubscribeSyncStatus creates a subscription that will broadcast new synchronisation updates. +// The given channel must receive interface values, the result can either +func (api *PublicDownloaderAPI) SubscribeSyncStatus(status chan interface{}) *SyncStatusSubscription { + api.installSyncSubscription <- status + return &SyncStatusSubscription{api: api, c: status} +} |