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// Copyright 2014 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 filters implements an ethereum filtering system for block,
// transactions and log events.
package filters
import (
"sync"
"time"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/event"
)
// FilterSystem manages filters that filter specific events such as
// block, transaction and log events. The Filtering system can be used to listen
// for specific LOG events fired by the EVM (Ethereum Virtual Machine).
type FilterSystem struct {
eventMux *event.TypeMux
filterMu sync.RWMutex
filterId int
filters map[int]*Filter
created map[int]time.Time
quit chan struct{}
}
// NewFilterSystem returns a newly allocated filter manager
func NewFilterSystem(mux *event.TypeMux) *FilterSystem {
fs := &FilterSystem{
eventMux: mux,
filters: make(map[int]*Filter),
created: make(map[int]time.Time),
}
go fs.filterLoop()
return fs
}
// Stop quits the filter loop required for polling events
func (fs *FilterSystem) Stop() {
close(fs.quit)
}
// Add adds a filter to the filter manager
func (fs *FilterSystem) Add(filter *Filter) (id int) {
fs.filterMu.Lock()
defer fs.filterMu.Unlock()
id = fs.filterId
fs.filters[id] = filter
fs.created[id] = time.Now()
fs.filterId++
return id
}
// Remove removes a filter by filter id
func (fs *FilterSystem) Remove(id int) {
fs.filterMu.Lock()
defer fs.filterMu.Unlock()
delete(fs.filters, id)
delete(fs.created, id)
}
// Get retrieves a filter installed using Add The filter may not be modified.
func (fs *FilterSystem) Get(id int) *Filter {
fs.filterMu.RLock()
defer fs.filterMu.RUnlock()
return fs.filters[id]
}
// filterLoop waits for specific events from ethereum and fires their handlers
// when the filter matches the requirements.
func (fs *FilterSystem) filterLoop() {
// Subscribe to events
eventCh := fs.eventMux.Subscribe(
//core.PendingBlockEvent{},
core.ChainEvent{},
core.TxPreEvent{},
vm.Logs(nil),
).Chan()
out:
for {
select {
case <-fs.quit:
break out
case event, ok := <-eventCh:
if !ok {
// Event subscription closed, set the channel to nil to stop spinning
eventCh = nil
continue
}
// A real event arrived, notify the registered filters
switch ev := event.Data.(type) {
case core.ChainEvent:
fs.filterMu.RLock()
for id, filter := range fs.filters {
if filter.BlockCallback != nil && fs.created[id].Before(event.Time) {
filter.BlockCallback(ev.Block, ev.Logs)
}
}
fs.filterMu.RUnlock()
case core.TxPreEvent:
fs.filterMu.RLock()
for id, filter := range fs.filters {
if filter.TransactionCallback != nil && fs.created[id].Before(event.Time) {
filter.TransactionCallback(ev.Tx)
}
}
fs.filterMu.RUnlock()
case vm.Logs:
fs.filterMu.RLock()
for id, filter := range fs.filters {
if filter.LogsCallback != nil && fs.created[id].Before(event.Time) {
msgs := filter.FilterLogs(ev)
if len(msgs) > 0 {
filter.LogsCallback(msgs)
}
}
}
fs.filterMu.RUnlock()
}
}
}
}
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