bloombits.go

// 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 types

import (
	"encoding/binary"
	tmtypes "github.com/tendermint/tendermint/types"
	dbm "github.com/tendermint/tm-db"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/bitutil"
	"github.com/ethereum/go-ethereum/core/bloombits"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/ethdb"
)

const (
	// bloomServiceThreads is the number of goroutines used globally by an Ethereum
	// instance to service bloombits lookups for all running filters.
	BloomServiceThreads = 16

	// bloomFilterThreads is the number of goroutines used locally per filter to
	// multiplex requests onto the global servicing goroutines.
	BloomFilterThreads = 3

	// bloomRetrievalBatch is the maximum number of bloom bit retrievals to service
	// in a single batch.
	BloomRetrievalBatch = 16

	// bloomRetrievalWait is the maximum time to wait for enough bloom bit requests
	// to accumulate request an entire batch (avoiding hysteresis).
	BloomRetrievalWait = time.Duration(0)

	// BloomBitsBlocks is the number of blocks a single bloom bit section vector
	// contains on the server side.
	BloomBitsBlocks uint64 = 4096
)

const (
	// bloomThrottling is the time to wait between processing two consecutive index
	// sections. It's useful during chain upgrades to prevent disk overload.
	bloomThrottling = 100 * time.Millisecond

	bloomDir              = "bloom"
	FlagEnableBloomFilter = "enable-bloom-filter"
)

var (
	bloomBitsPrefix = []byte("B") // bloomBitsPrefix + bit (uint16 big endian) + section (uint64 big endian) + hash -> bloom bits
)

// bloomIndexer implements a core.ChainIndexer, building up a rotated bloom bits index
// for the Ethereum header bloom filters, permitting blazing fast filtering.
type bloomIndexer struct {
	size    uint64               // section size to generate bloombits for
	db      dbm.DB               // database instance to write index data and metadata into
	gen     *bloombits.Generator // generator to rotate the bloom bits crating the bloom index
	section uint64               // Section is the section number being processed currently
	head    common.Hash          // Head is the hash of the last header processed
}

func initBloomIndexer(db dbm.DB) bloomIndexer {
	return bloomIndexer{
		db:   db,
		size: BloomBitsBlocks,
	}
}

// Reset implements core.ChainIndexerBackend, starting a new bloombits index
// section.
func (b *bloomIndexer) Reset(section uint64) error {
	gen, err := bloombits.NewGenerator(uint(b.size))
	b.gen, b.section, b.head = gen, section, common.Hash{}
	return err
}

// Process implements core.ChainIndexerBackend, adding a new header's bloom into
// the index.
func (b *bloomIndexer) Process(hash common.Hash, height uint64, bloom types.Bloom) error {
	// the initial height is 1 but it on ethereum is 0. so subtract 1
	b.gen.AddBloom(uint(height-b.section*b.size-uint64(tmtypes.GetStartBlockHeight())), bloom)
	b.head = hash
	return nil
}

// Commit implements core.ChainIndexerBackend, finalizing the bloom section and
// writing it out into the database.
func (b *bloomIndexer) Commit() error {
	batch := b.db.NewBatch()
	for i := 0; i < types.BloomBitLength; i++ {
		bits, err := b.gen.Bitset(uint(i))
		if err != nil {
			return err
		}
		WriteBloomBits(batch, uint(i), b.section, b.head, bitutil.CompressBytes(bits))
	}
	return batch.Write()
}

// bloomBitsKey = bloomBitsPrefix + bit (uint16 big endian) + section (uint64 big endian) + hash
func bloomBitsKey(bit uint, section uint64, hash common.Hash) []byte {
	key := append(append(bloomBitsPrefix, make([]byte, 10)...), hash.Bytes()...)

	binary.BigEndian.PutUint16(key[1:], uint16(bit))
	binary.BigEndian.PutUint64(key[3:], section)

	return key
}

// ReadBloomBits retrieves the compressed bloom bit vector belonging to the given
// section and bit index from the.
func ReadBloomBits(db ethdb.KeyValueReader, bit uint, section uint64, head common.Hash) ([]byte, error) {
	return db.Get(bloomBitsKey(bit, section, head))
}

// WriteBloomBits stores the compressed bloom bits vector belonging to the given
// section and bit index.
func WriteBloomBits(batch dbm.Batch, bit uint, section uint64, head common.Hash, bits []byte) {
	batch.Set(bloomBitsKey(bit, section, head), bits)
}