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filter.go
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filter.go
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// (c) 2019-2020, Ava Labs, Inc.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// 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"
"errors"
"fmt"
"math/big"
"github.com/ava-labs/subnet-evm/core/bloombits"
"github.com/ava-labs/subnet-evm/core/types"
"github.com/ava-labs/subnet-evm/rpc"
"github.com/ethereum/go-ethereum/common"
)
// Filter can be used to retrieve and filter logs.
type Filter struct {
sys *FilterSystem
addresses []common.Address
topics [][]common.Hash
block *common.Hash // Block hash if filtering a single block
begin, end int64 // Range interval if filtering multiple blocks
matcher *bloombits.Matcher
}
// NewRangeFilter creates a new filter which uses a bloom filter on blocks to
// figure out whether a particular block is interesting or not.
func (sys *FilterSystem) NewRangeFilter(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)
}
size, _ := sys.backend.BloomStatus()
// Create a generic filter and convert it into a range filter
filter := newFilter(sys, addresses, topics)
filter.matcher = bloombits.NewMatcher(size, filters)
filter.begin = begin
filter.end = end
return filter
}
// NewBlockFilter creates a new filter which directly inspects the contents of
// a block to figure out whether it is interesting or not.
func (sys *FilterSystem) NewBlockFilter(block common.Hash, addresses []common.Address, topics [][]common.Hash) *Filter {
// Create a generic filter and convert it into a block filter
filter := newFilter(sys, addresses, topics)
filter.block = &block
return filter
}
// newFilter creates a generic filter that can either filter based on a block hash,
// or based on range queries. The search criteria needs to be explicitly set.
func newFilter(sys *FilterSystem, addresses []common.Address, topics [][]common.Hash) *Filter {
return &Filter{
sys: sys,
addresses: addresses,
topics: topics,
}
}
// 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) {
// If we're doing singleton block filtering, execute and return
if f.block != nil {
header, err := f.sys.backend.HeaderByHash(ctx, *f.block)
if err != nil {
return nil, err
}
if header == nil {
return nil, errors.New("unknown block")
}
return f.blockLogs(ctx, header)
}
// Disallow blocks past the last accepted block if the backend does not
// allow unfinalized queries.
allowUnfinalizedQueries := f.sys.backend.IsAllowUnfinalizedQueries()
acceptedBlock := f.sys.backend.LastAcceptedBlock()
if !allowUnfinalizedQueries && acceptedBlock != nil {
lastAccepted := acceptedBlock.Number().Int64()
if f.begin >= 0 && f.begin > lastAccepted {
return nil, fmt.Errorf("requested from block %d after last accepted block %d", f.begin, lastAccepted)
}
if f.end >= 0 && f.end > lastAccepted {
return nil, fmt.Errorf("requested to block %d after last accepted block %d", f.end, lastAccepted)
}
}
var (
beginPending = f.begin == rpc.PendingBlockNumber.Int64()
endPending = f.end == rpc.PendingBlockNumber.Int64()
endSet = f.end >= 0
)
// special case for pending logs
if beginPending && !endPending {
return nil, errInvalidBlockRange
}
// Short-cut if all we care about is pending logs
if beginPending && endPending {
return nil, nil
}
resolveSpecial := func(number int64) (int64, error) {
var hdr *types.Header
switch number {
case rpc.LatestBlockNumber.Int64(), rpc.PendingBlockNumber.Int64():
// we should return head here since we've already captured
// that we need to get the pending logs in the pending boolean above
hdr, _ = f.sys.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
if hdr == nil {
return 0, errors.New("latest header not found")
}
case rpc.FinalizedBlockNumber.Int64():
hdr, _ = f.sys.backend.HeaderByNumber(ctx, rpc.FinalizedBlockNumber)
if hdr == nil {
return 0, errors.New("finalized header not found")
}
case rpc.SafeBlockNumber.Int64():
hdr, _ = f.sys.backend.HeaderByNumber(ctx, rpc.SafeBlockNumber)
if hdr == nil {
return 0, errors.New("safe header not found")
}
default:
return number, nil
}
return hdr.Number.Int64(), nil
}
var err error
// range query need to resolve the special begin/end block number
if f.begin, err = resolveSpecial(f.begin); err != nil {
return nil, err
}
if f.end, err = resolveSpecial(f.end); err != nil {
return nil, err
}
// When querying unfinalized data without a populated end block, it is
// possible that the begin will be greater than the end.
//
// We error in this case to prevent a bad UX where the caller thinks there
// are no logs from the specified beginning to end (when in reality there may
// be some).
if endSet && f.end < f.begin {
return nil, fmt.Errorf("begin block %d is greater than end block %d", f.begin, f.end)
}
// If the requested range of blocks exceeds the maximum number of blocks allowed by the backend
// return an error instead of searching for the logs.
if maxBlocks := f.sys.backend.GetMaxBlocksPerRequest(); f.end-f.begin >= maxBlocks && maxBlocks > 0 {
return nil, fmt.Errorf("requested too many blocks from %d to %d, maximum is set to %d", f.begin, f.end, maxBlocks)
}
// Gather all indexed logs, and finish with non indexed ones
logChan, errChan := f.rangeLogsAsync(ctx)
var logs []*types.Log
for {
select {
case log := <-logChan:
logs = append(logs, log)
case err := <-errChan:
if err != nil {
// if an error occurs during extraction, we do return the extracted data
return logs, err
}
return logs, nil
}
}
}
// rangeLogsAsync retrieves block-range logs that match the filter criteria asynchronously,
// it creates and returns two channels: one for delivering log data, and one for reporting errors.
func (f *Filter) rangeLogsAsync(ctx context.Context) (chan *types.Log, chan error) {
var (
logChan = make(chan *types.Log)
errChan = make(chan error)
)
go func() {
defer func() {
close(errChan)
close(logChan)
}()
// Gather all indexed logs, and finish with non indexed ones
var (
end = uint64(f.end)
size, sections = f.sys.backend.BloomStatus()
err error
)
if indexed := sections * size; indexed > uint64(f.begin) {
if indexed > end {
indexed = end + 1
}
if err = f.indexedLogs(ctx, indexed-1, logChan); err != nil {
errChan <- err
return
}
}
if err := f.unindexedLogs(ctx, end, logChan); err != nil {
errChan <- err
return
}
errChan <- nil
}()
return logChan, errChan
}
// 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, logChan chan *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 err
}
defer session.Close()
f.sys.backend.ServiceFilter(ctx, session)
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 err
}
f.begin = int64(number) + 1
// Retrieve the suggested block and pull any truly matching logs
header, err := f.sys.backend.HeaderByNumber(ctx, rpc.BlockNumber(number))
if header == nil || err != nil {
return err
}
found, err := f.checkMatches(ctx, header)
if err != nil {
return err
}
for _, log := range found {
logChan <- log
}
case <-ctx.Done():
return ctx.Err()
}
}
}
// unindexedLogs returns the logs matching the filter criteria based on raw block
// iteration and bloom matching.
func (f *Filter) unindexedLogs(ctx context.Context, end uint64, logChan chan *types.Log) error {
for ; f.begin <= int64(end); f.begin++ {
header, err := f.sys.backend.HeaderByNumber(ctx, rpc.BlockNumber(f.begin))
if header == nil || err != nil {
return err
}
found, err := f.blockLogs(ctx, header)
if err != nil {
return err
}
for _, log := range found {
select {
case logChan <- log:
case <-ctx.Done():
return ctx.Err()
}
}
}
return nil
}
// blockLogs returns the logs matching the filter criteria within a single block.
func (f *Filter) blockLogs(ctx context.Context, header *types.Header) ([]*types.Log, error) {
if bloomFilter(header.Bloom, f.addresses, f.topics) {
return f.checkMatches(ctx, header)
}
return nil, 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) ([]*types.Log, error) {
logsList, err := f.sys.getLogs(ctx, header.Hash(), header.Number.Uint64())
if err != nil {
return nil, err
}
unfiltered := types.FlattenLogs(logsList)
logs := filterLogs(unfiltered, nil, nil, f.addresses, f.topics)
if len(logs) == 0 {
return nil, nil
}
// Most backends will deliver un-derived logs, but check nevertheless.
if len(logs) > 0 && logs[0].TxHash != (common.Hash{}) {
return logs, nil
}
// We have matching logs, check if we need to resolve full logs via the light client
receipts, err := f.sys.backend.GetReceipts(ctx, header.Hash())
if err != nil {
return nil, err
}
unfiltered = unfiltered[:0]
for _, receipt := range receipts {
unfiltered = append(unfiltered, receipt.Logs...)
}
logs = filterLogs(unfiltered, nil, nil, f.addresses, f.topics)
return logs, nil
}
// includes returns true if the element is present in the list.
func includes[T comparable](things []T, element T) bool {
for _, thing := range things {
if thing == element {
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 check = func(log *types.Log) bool {
if fromBlock != nil && fromBlock.Int64() >= 0 && fromBlock.Uint64() > log.BlockNumber {
return false
}
if toBlock != nil && toBlock.Int64() >= 0 && toBlock.Uint64() < log.BlockNumber {
return false
}
if len(addresses) > 0 && !includes(addresses, log.Address) {
return false
}
// If the to filtered topics is greater than the amount of topics in logs, skip.
if len(topics) > len(log.Topics) {
return false
}
for i, sub := range topics {
if len(sub) == 0 {
continue // empty rule set == wildcard
}
if !includes(sub, log.Topics[i]) {
return false
}
}
return true
}
var ret []*types.Log
for _, log := range logs {
if check(log) {
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
}