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// 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/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/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 an 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}
}
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