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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
// 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 <>.
package core
import (
// BlockValidator is responsible for validating block headers, uncles and
// processed state.
// BlockValidator implements Validator.
type BlockValidator struct {
config *params.ChainConfig // Chain configuration options
bc *BlockChain // Canonical block chain
engine consensus.Engine // Consensus engine used for validating
// NewBlockValidator returns a new block validator which is safe for re-use
func NewBlockValidator(config *params.ChainConfig, blockchain *BlockChain, engine consensus.Engine) *BlockValidator {
validator := &BlockValidator{
config: config,
engine: engine,
bc: blockchain,
return validator
// ValidateBody validates the given block's uncles and verifies the block
// header's transaction and uncle roots. The headers are assumed to be already
// validated at this point.
func (v *BlockValidator) ValidateBody(block *types.Block) error {
// Check whether the block's known, and if not, that it's linkable
if v.bc.HasBlockAndState(block.Hash(), block.NumberU64()) {
return ErrKnownBlock
// Header validity is known at this point, check the uncles and transactions
header := block.Header()
if err := v.engine.VerifyUncles(v.bc, block); err != nil {
return err
if hash := types.CalcUncleHash(block.Uncles()); hash != header.UncleHash {
return fmt.Errorf("uncle root hash mismatch: have %x, want %x", hash, header.UncleHash)
if hash := types.DeriveSha(block.Transactions()); hash != header.TxHash {
return fmt.Errorf("transaction root hash mismatch: have %x, want %x", hash, header.TxHash)
if !v.bc.HasBlockAndState(block.ParentHash(), block.NumberU64()-1) {
if !v.bc.HasBlock(block.ParentHash(), block.NumberU64()-1) {
return consensus.ErrUnknownAncestor
return consensus.ErrPrunedAncestor
return nil
// ValidateState validates the various changes that happen after a state
// transition, such as amount of used gas, the receipt roots and the state root
// itself. ValidateState returns a database batch if the validation was a success
// otherwise nil and an error is returned.
func (v *BlockValidator) ValidateState(block *types.Block, statedb *state.StateDB, receipts types.Receipts, usedGas uint64) error {
header := block.Header()
if block.GasUsed() != usedGas {
return fmt.Errorf("invalid gas used (remote: %d local: %d)", block.GasUsed(), usedGas)
// Validate the received block's bloom with the one derived from the generated receipts.
// For valid blocks this should always validate to true.
rbloom := types.CreateBloom(receipts)
if rbloom != header.Bloom {
return fmt.Errorf("invalid bloom (remote: %x local: %x)", header.Bloom, rbloom)
// Tre receipt Trie's root (R = (Tr [[H1, R1], ... [Hn, R1]]))
receiptSha := types.DeriveSha(receipts)
if receiptSha != header.ReceiptHash {
return fmt.Errorf("invalid receipt root hash (remote: %x local: %x)", header.ReceiptHash, receiptSha)
// Validate the state root against the received state root and throw
// an error if they don't match.
if root := statedb.IntermediateRoot(v.config.IsEIP158(header.Number)); header.Root != root {
return fmt.Errorf("invalid merkle root (remote: %x local: %x)", header.Root, root)
return nil
// CalcGasLimit computes the gas limit of the next block after parent. It aims
// to keep the baseline gas above the provided floor, and increase it towards the
// ceil if the blocks are full. If the ceil is exceeded, it will always decrease
// the gas allowance.
func CalcGasLimit(parent *types.Block, gasFloor, gasCeil uint64) uint64 {
// contrib = (parentGasUsed * 3 / 2) / 1024
contrib := (parent.GasUsed() + parent.GasUsed()/2) / params.GasLimitBoundDivisor
// decay = parentGasLimit / 1024 -1
decay := parent.GasLimit()/params.GasLimitBoundDivisor - 1
strategy: gasLimit of block-to-mine is set based on parent's
gasUsed value. if parentGasUsed > parentGasLimit * (2/3) then we
increase it, otherwise lower it (or leave it unchanged if it's right
at that usage) the amount increased/decreased depends on how far away
from parentGasLimit * (2/3) parentGasUsed is.
limit := parent.GasLimit() - decay + contrib
if limit < params.MinGasLimit {
limit = params.MinGasLimit
// If we're outside our allowed gas range, we try to hone towards them
if limit < gasFloor {
limit = parent.GasLimit() + decay
if limit > gasFloor {
limit = gasFloor
} else if limit > gasCeil {
limit = parent.GasLimit() - decay
if limit < gasCeil {
limit = gasCeil
return limit
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