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// Copyright 2017 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 accounts
import (
"reflect"
"sort"
"sync"
"github.com/dexon-foundation/dexon/event"
)
// Manager is an overarching account manager that can communicate with various
// backends for signing transactions.
type Manager struct {
backends map[reflect.Type][]Backend // Index of backends currently registered
updaters []event.Subscription // Wallet update subscriptions for all backends
updates chan WalletEvent // Subscription sink for backend wallet changes
wallets []Wallet // Cache of all wallets from all registered backends
feed event.Feed // Wallet feed notifying of arrivals/departures
quit chan chan error
lock sync.RWMutex
}
// NewManager creates a generic account manager to sign transaction via various
// supported backends.
func NewManager(backends ...Backend) *Manager {
// Retrieve the initial list of wallets from the backends and sort by URL
var wallets []Wallet
for _, backend := range backends {
wallets = merge(wallets, backend.Wallets()...)
}
// Subscribe to wallet notifications from all backends
updates := make(chan WalletEvent, 4*len(backends))
subs := make([]event.Subscription, len(backends))
for i, backend := range backends {
subs[i] = backend.Subscribe(updates)
}
// Assemble the account manager and return
am := &Manager{
backends: make(map[reflect.Type][]Backend),
updaters: subs,
updates: updates,
wallets: wallets,
quit: make(chan chan error),
}
for _, backend := range backends {
kind := reflect.TypeOf(backend)
am.backends[kind] = append(am.backends[kind], backend)
}
go am.update()
return am
}
// Close terminates the account manager's internal notification processes.
func (am *Manager) Close() error {
errc := make(chan error)
am.quit <- errc
return <-errc
}
// update is the wallet event loop listening for notifications from the backends
// and updating the cache of wallets.
func (am *Manager) update() {
// Close all subscriptions when the manager terminates
defer func() {
am.lock.Lock()
for _, sub := range am.updaters {
sub.Unsubscribe()
}
am.updaters = nil
am.lock.Unlock()
}()
// Loop until termination
for {
select {
case event := <-am.updates:
// Wallet event arrived, update local cache
am.lock.Lock()
switch event.Kind {
case WalletArrived:
am.wallets = merge(am.wallets, event.Wallet)
case WalletDropped:
am.wallets = drop(am.wallets, event.Wallet)
}
am.lock.Unlock()
// Notify any listeners of the event
am.feed.Send(event)
case errc := <-am.quit:
// Manager terminating, return
errc <- nil
return
}
}
}
// Backends retrieves the backend(s) with the given type from the account manager.
func (am *Manager) Backends(kind reflect.Type) []Backend {
return am.backends[kind]
}
// Wallets returns all signer accounts registered under this account manager.
func (am *Manager) Wallets() []Wallet {
am.lock.RLock()
defer am.lock.RUnlock()
cpy := make([]Wallet, len(am.wallets))
copy(cpy, am.wallets)
return cpy
}
// Wallet retrieves the wallet associated with a particular URL.
func (am *Manager) Wallet(url string) (Wallet, error) {
am.lock.RLock()
defer am.lock.RUnlock()
parsed, err := parseURL(url)
if err != nil {
return nil, err
}
for _, wallet := range am.Wallets() {
if wallet.URL() == parsed {
return wallet, nil
}
}
return nil, ErrUnknownWallet
}
// Find attempts to locate the wallet corresponding to a specific account. Since
// accounts can be dynamically added to and removed from wallets, this method has
// a linear runtime in the number of wallets.
func (am *Manager) Find(account Account) (Wallet, error) {
am.lock.RLock()
defer am.lock.RUnlock()
for _, wallet := range am.wallets {
if wallet.Contains(account) {
return wallet, nil
}
}
return nil, ErrUnknownAccount
}
// Subscribe creates an async subscription to receive notifications when the
// manager detects the arrival or departure of a wallet from any of its backends.
func (am *Manager) Subscribe(sink chan<- WalletEvent) event.Subscription {
return am.feed.Subscribe(sink)
}
// merge is a sorted analogue of append for wallets, where the ordering of the
// origin list is preserved by inserting new wallets at the correct position.
//
// The original slice is assumed to be already sorted by URL.
func merge(slice []Wallet, wallets ...Wallet) []Wallet {
for _, wallet := range wallets {
n := sort.Search(len(slice), func(i int) bool { return slice[i].URL().Cmp(wallet.URL()) >= 0 })
if n == len(slice) {
slice = append(slice, wallet)
continue
}
slice = append(slice[:n], append([]Wallet{wallet}, slice[n:]...)...)
}
return slice
}
// drop is the couterpart of merge, which looks up wallets from within the sorted
// cache and removes the ones specified.
func drop(slice []Wallet, wallets ...Wallet) []Wallet {
for _, wallet := range wallets {
n := sort.Search(len(slice), func(i int) bool { return slice[i].URL().Cmp(wallet.URL()) >= 0 })
if n == len(slice) {
// Wallet not found, may happen during startup
continue
}
slice = append(slice[:n], slice[n+1:]...)
}
return slice
}
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