// 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
import (
"context"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/bloombits"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/rpc"
)
type Backend interface {
ChainDb() ethdb.Database
EventMux() *event.TypeMux
HeaderByNumber(ctx context.Context, blockNr rpc.BlockNumber) (*types.Header, error)
GetReceipts(ctx context.Context, blockHash common.Hash) (types.Receipts, error)
SubscribeTxPreEvent(chan<- core.TxPreEvent) event.Subscription
SubscribeChainEvent(ch chan<- core.ChainEvent) event.Subscription
SubscribeRemovedLogsEvent(ch chan<- core.RemovedLogsEvent) event.Subscription
SubscribeLogsEvent(ch chan<- []*types.Log) event.Subscription
BloomStatus() (uint64, uint64)
ServiceFilter(ctx context.Context, session *bloombits.MatcherSession)
}
// Filter can be used to retrieve and filter logs.
type Filter struct {
backend Backend
db ethdb.Database
begin, end int64
addresses []common.Address
topics [][]common.Hash
matcher *bloombits.Matcher
}
// New creates a new filter which uses a bloom filter on blocks to figure out whether
// a particular block is interesting or not.
func New(backend Backend, begin, end int64, addresses []common.Address, topics [][]common.Hash) *Filter {
// Flatten the address and topic filter clauses into a single bloombits filter
// system. Since the bloombits are not positional, nil topics are permitted,
// which get flattened into a nil byte slice.
var filters [][][]byte
if len(addresses) > 0 {
filter := make([][]byte, len(addresses))
for i, address := range addresses {
filter[i] = address.Bytes()
}
filters = append(filters, filter)
}
for _, topicList := range topics {
filter := make([][]byte, len(topicList))
for i, topic := range topicList {
filter[i] = topic.Bytes()
}
filters = append(filters, filter)
}
// Assemble and return the filter
size, _ := backend.BloomStatus()
return &Filter{
backend: backend,
begin: begin,
end: end,
addresses: addresses,
topics: topics,
db: backend.ChainDb(),
matcher: bloombits.NewMatcher(size, filters),
}
}
// Logs searches the blockchain for matching log entries, returning all from the
// first block that contains matches, updating the start of the filter accordingly.
func (f *Filter) Logs(ctx context.Context) ([]*types.Log, error) {
// Figure out the limits of the filter range
header, _ := f.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
if header == nil {
return nil, nil
}
head := header.Number.Uint64()
if f.begin == -1 {
f.begin = int64(head)
}
end := uint64(f.end)
if f.end == -1 {
end = head
}
// Gather all indexed logs, and finish with non indexed ones
var (
logs []*types.Log
err error
)
size, sections := f.backend.BloomStatus()
if indexed := sections * size; indexed > uint64(f.begin) {
if indexed > end {
logs, err = f.indexedLogs(ctx, end)
} else {
logs, err = f.indexedLogs(ctx, indexed-1)
}
if err != nil {
return logs, err
}
}
rest, err := f.unindexedLogs(ctx, end)
logs = append(logs, rest...)
return logs, err
}
// indexedLogs returns the logs matching the filter criteria based on the bloom
// bits indexed available locally or via the network.
func (f *Filter) indexedLogs(ctx context.Context, end uint64) ([]*types.Log, error) {
// Create a matcher session and request servicing from the backend
matches := make(chan uint64, 64)
session, err := f.matcher.Start(ctx, uint64(f.begin), end, matches)
if err != nil {
return nil, err
}
defer session.Close()
f.backend.ServiceFilter(ctx, session)
// Iterate over the matches until exhausted or context closed
var logs []*types.Log
for {
select {
case number, ok := <-matches:
// Abort if all matches have been fulfilled
if !ok {
err := session.Error()
if err == nil {
f.begin = int64(end) + 1
}
return logs, err
}
f.begin = int64(number) + 1
// Retrieve the suggested block and pull any truly matching logs
header, err := f.backend.HeaderByNumber(ctx, rpc.BlockNumber(number))
if header == nil || err != nil {
return logs, err
}
found, err := f.checkMatches(ctx, header)
if err != nil {
return logs, err
}
logs = append(logs, found...)
case <-ctx.Done():
return logs, ctx.Err()
}
}
}
// indexedLogs returns the logs matching the filter criteria based on raw block
// iteration and bloom matching.
func (f *Filter) unindexedLogs(ctx context.Context, end uint64) ([]*types.Log, error) {
var logs []*types.Log
for ; f.begin <= int64(end); f.begin++ {
header, err := f.backend.HeaderByNumber(ctx, rpc.BlockNumber(f.begin))
if header == nil || err != nil {
return logs, err
}
if bloomFilter(header.Bloom, f.addresses, f.topics) {
found, err := f.checkMatches(ctx, header)
if err != nil {
return logs, err
}
logs = append(logs, found...)
}
}
return logs, nil
}
// checkMatches checks if the receipts belonging to the given header contain any log events that
// match the filter criteria. This function is called when the bloom filter signals a potential match.
func (f *Filter) checkMatches(ctx context.Context, header *types.Header) (logs []*types.Log, err error) {
// Get the logs of the block
receipts, err := f.backend.GetReceipts(ctx, header.Hash())
if err != nil {
return nil, err
}
var unfiltered []*types.Log
for _, receipt := range receipts {
unfiltered = append(unfiltered, receipt.Logs...)
}
logs = filterLogs(unfiltered, nil, nil, f.addresses, f.topics)
if len(logs) > 0 {
return logs, nil
}
return nil, nil
}
func includes(addresses []common.Address, a common.Address) bool {
for _, addr := range addresses {
if addr == a {
return true
}
}
return false
}
// filterLogs creates a slice of logs matching the given criteria.
func filterLogs(logs []*types.Log, fromBlock, toBlock *big.Int, addresses []common.Address, topics [][]common.Hash) []*types.Log {
var ret []*types.Log
Logs:
for _, log := range logs {
if fromBlock != nil && fromBlock.Int64() >= 0 && fromBlock.Uint64() > log.BlockNumber {
continue
}
if toBlock != nil && toBlock.Int64() >= 0 && toBlock.Uint64() < log.BlockNumber {
continue
}
if len(addresses) > 0 && !includes(addresses, log.Address) {
continue
}
// If the to filtered topics is greater than the amount of topics in logs, skip.
if len(topics) > len(log.Topics) {
continue Logs
}
for i, topics := range topics {
match := len(topics) == 0 // empty rule set == wildcard
for _, topic := range topics {
if log.Topics[i] == topic {
match = true
break
}
}
if !match {
continue Logs
}
}
ret = append(ret, log)
}
return ret
}
func bloomFilter(bloom types.Bloom, addresses []common.Address, topics [][]common.Hash) bool {
if len(addresses) > 0 {
var included bool
for _, addr := range addresses {
if types.BloomLookup(bloom, addr) {
included = true
break
}
}
if !included {
return false
}
}
for _, sub := range topics {
included := len(sub) == 0 // empty rule set == wildcard
for _, topic := range sub {
if types.BloomLookup(bloom, topic) {
included = true
break
}
}
if !included {
return false
}
}
return true
}
