forked from ava-labs/subnet-evm
/
blockchain_iterator.go
184 lines (164 loc) · 5.11 KB
/
blockchain_iterator.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 core implements the Ethereum consensus protocol.
package core
import (
"context"
"errors"
"fmt"
"sync"
"github.com/MetalBlockchain/subnet-evm/core/types"
)
type blockAndState struct {
block *types.Block
hasState bool
err error
}
type blockChainIterator struct {
bc *BlockChain
nextReadBlockHeight uint64
nextBlockHeightToRead uint64
blocks []*blockAndState
blocksRead chan *blockAndState
heightsToRead chan uint64
wg sync.WaitGroup
closeOnce sync.Once
onClose chan struct{}
}
func newBlockChainIterator(bc *BlockChain, start uint64, parallelism int) *blockChainIterator {
i := &blockChainIterator{
bc: bc,
nextReadBlockHeight: start,
nextBlockHeightToRead: start,
blocks: make([]*blockAndState, parallelism),
blocksRead: make(chan *blockAndState),
heightsToRead: make(chan uint64),
onClose: make(chan struct{}),
}
i.wg.Add(parallelism)
// Start [parallelism] worker threads to read block information
for j := 0; j < parallelism; j++ {
// Start a goroutine to read incoming heights from [heightsToRead]
// fetch the corresponding block information and place it on the
// [blocksRead] channel.
go func() {
defer i.wg.Done()
for {
// Read heights in from [heightsToRead]
var height uint64
select {
case height = <-i.heightsToRead:
case <-i.onClose:
return
}
block := bc.GetBlockByNumber(height)
if block == nil {
select {
case i.blocksRead <- &blockAndState{err: fmt.Errorf("missing block:%d", height)}:
continue
case <-i.onClose:
return
}
}
select {
case i.blocksRead <- &blockAndState{block: block, hasState: bc.HasState(block.Root())}:
continue
case <-i.onClose:
return
}
}
}()
}
lastAccepted := i.bc.LastAcceptedBlock().NumberU64()
// populateReaders ie. adds task for [parallelism] threads
i.populateReaders(lastAccepted)
return i
}
// populateReaders adds the heights for the next [parallelism] blocks to
// [blocksToRead]. This is called piecewise to ensure that each of the blocks
// is read within Next and set in [blocks] before moving on to the next tranche
// of blocks.
func (i *blockChainIterator) populateReaders(lastAccepted uint64) {
maxHeightToRead := i.nextReadBlockHeight + uint64(len(i.blocks))
for {
if i.nextBlockHeightToRead > lastAccepted {
return
}
if maxHeightToRead <= i.nextBlockHeightToRead {
return
}
select {
case i.heightsToRead <- i.nextBlockHeightToRead:
i.nextBlockHeightToRead++
case <-i.onClose:
return
}
}
}
// Next retrieves the next consecutive block in the iteration
func (i *blockChainIterator) Next(ctx context.Context) (*types.Block, bool, error) {
lastAccepted := i.bc.LastAcceptedBlock().NumberU64()
if i.nextReadBlockHeight > lastAccepted {
return nil, false, errors.New("no more blocks")
}
i.populateReaders(lastAccepted)
nextIndex := int(i.nextReadBlockHeight % uint64(len(i.blocks)))
for {
nextBlock := i.blocks[nextIndex]
// If the nextBlock in the iteration has already been populated
// return the block immediately.
if nextBlock != nil {
i.blocks[nextIndex] = nil
i.nextReadBlockHeight++
i.populateReaders(lastAccepted)
return nextBlock.block, nextBlock.hasState, nil
}
// Otherwise, keep reading in block info from [blocksRead]
// and populate the [blocks] buffer until we hit the actual
// next block in the iteration.
select {
case block := <-i.blocksRead:
if block.err != nil {
i.Stop()
return nil, false, block.err
}
index := int(block.block.NumberU64() % uint64(len(i.blocks)))
i.blocks[index] = block
case <-ctx.Done():
return nil, false, ctx.Err()
case <-i.onClose:
return nil, false, errors.New("closed")
}
}
}
// Stop closes the [onClose] channel signalling all worker threads to exit
// and waits for all of the worker threads to finish.
func (i *blockChainIterator) Stop() {
i.closeOnce.Do(func() {
close(i.onClose)
})
i.wg.Wait()
}