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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 filters implements an ethereum filtering system for block,
// transactions and log events.
package filters
import (
"fmt"
"sync"
"time"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/event"
)
// FilterType determines the type of filter and is used to put the filter in to
// the correct bucket when added.
type FilterType byte
const (
ChainFilter FilterType = iota // new block events filter
PendingTxFilter // pending transaction filter
LogFilter // new or removed log filter
PendingLogFilter // pending log filter
)
// 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 {
filterMu sync.RWMutex
filterId int
chainFilters map[int]*Filter
pendingTxFilters map[int]*Filter
logFilters map[int]*Filter
pendingLogFilters map[int]*Filter
// generic is an ugly hack for Get
generic map[int]*Filter
sub event.Subscription
}
// NewFilterSystem returns a newly allocated filter manager
func NewFilterSystem(mux *event.TypeMux) *FilterSystem {
fs := &FilterSystem{
chainFilters: make(map[int]*Filter),
pendingTxFilters: make(map[int]*Filter),
logFilters: make(map[int]*Filter),
pendingLogFilters: make(map[int]*Filter),
generic: make(map[int]*Filter),
}
fs.sub = mux.Subscribe(
core.PendingLogsEvent{},
core.RemovedLogsEvent{},
core.ChainEvent{},
core.TxPreEvent{},
vm.Logs(nil),
)
go fs.filterLoop()
return fs
}
// Stop quits the filter loop required for polling events
func (fs *FilterSystem) Stop() {
fs.sub.Unsubscribe()
}
// Acquire filter system maps lock, required to force lock acquisition
// sequence with filterMu acquired first to avoid deadlocks by callbacks
func (fs *FilterSystem) Lock() {
fs.filterMu.Lock()
}
// Release filter system maps lock
func (fs *FilterSystem) Unlock() {
fs.filterMu.Unlock()
}
// Add adds a filter to the filter manager
// Expects filterMu to be locked.
func (fs *FilterSystem) Add(filter *Filter, filterType FilterType) (int, error) {
id := fs.filterId
filter.created = time.Now()
switch filterType {
case ChainFilter:
fs.chainFilters[id] = filter
case PendingTxFilter:
fs.pendingTxFilters[id] = filter
case LogFilter:
fs.logFilters[id] = filter
case PendingLogFilter:
fs.pendingLogFilters[id] = filter
default:
return 0, fmt.Errorf("unknown filter type %v", filterType)
}
fs.generic[id] = filter
fs.filterId++
return id, nil
}
// Remove removes a filter by filter id
// Expects filterMu to be locked.
func (fs *FilterSystem) Remove(id int) {
delete(fs.chainFilters, id)
delete(fs.pendingTxFilters, id)
delete(fs.logFilters, id)
delete(fs.pendingLogFilters, id)
delete(fs.generic, id)
}
func (fs *FilterSystem) Get(id int) *Filter {
fs.filterMu.RLock()
defer fs.filterMu.RUnlock()
return fs.generic[id]
}
// filterLoop waits for specific events from ethereum and fires their handlers
// when the filter matches the requirements.
func (fs *FilterSystem) filterLoop() {
for event := range fs.sub.Chan() {
switch ev := event.Data.(type) {
case core.ChainEvent:
fs.filterMu.RLock()
for _, filter := range fs.chainFilters {
if filter.BlockCallback != nil && !filter.created.After(event.Time) {
filter.BlockCallback(ev.Block, ev.Logs)
}
}
fs.filterMu.RUnlock()
case core.TxPreEvent:
fs.filterMu.RLock()
for _, filter := range fs.pendingTxFilters {
if filter.TransactionCallback != nil && !filter.created.After(event.Time) {
filter.TransactionCallback(ev.Tx)
}
}
fs.filterMu.RUnlock()
case vm.Logs:
fs.filterMu.RLock()
for _, filter := range fs.logFilters {
if filter.LogCallback != nil && !filter.created.After(event.Time) {
for _, log := range filter.FilterLogs(ev) {
filter.LogCallback(log, false)
}
}
}
fs.filterMu.RUnlock()
case core.RemovedLogsEvent:
fs.filterMu.RLock()
for _, filter := range fs.logFilters {
if filter.LogCallback != nil && !filter.created.After(event.Time) {
for _, removedLog := range filter.FilterLogs(ev.Logs) {
filter.LogCallback(removedLog, true)
}
}
}
fs.filterMu.RUnlock()
case core.PendingLogsEvent:
fs.filterMu.RLock()
for _, filter := range fs.pendingLogFilters {
if filter.LogCallback != nil && !filter.created.After(event.Time) {
for _, pendingLog := range ev.Logs {
filter.LogCallback(pendingLog, false)
}
}
}
fs.filterMu.RUnlock()
}
}
}
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