move multicall logic to struct

This commit is contained in:
Sina Mahmoodi 2023-10-10 16:34:48 +02:00
parent 2690445207
commit d1ce690e76
2 changed files with 350 additions and 306 deletions

View file

@ -19,7 +19,6 @@ package ethapi
import (
"context"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"math/big"
@ -1222,62 +1221,6 @@ func (s *BlockChainAPI) Call(ctx context.Context, args TransactionArgs, blockNrO
return result.Return(), result.Err
}
// CallBatch is a batch of calls to be simulated sequentially.
type CallBatch struct {
BlockOverrides *BlockOverrides
StateOverrides *StateOverride
Calls []TransactionArgs
}
type blockResult struct {
Number hexutil.Uint64 `json:"number"`
Hash common.Hash `json:"hash"`
Time hexutil.Uint64 `json:"timestamp"`
GasLimit hexutil.Uint64 `json:"gasLimit"`
GasUsed hexutil.Uint64 `json:"gasUsed"`
FeeRecipient common.Address `json:"feeRecipient"`
BaseFee *hexutil.Big `json:"baseFeePerGas"`
PrevRandao common.Hash `json:"prevRandao"`
Calls []callResult `json:"calls"`
}
func mcBlockResultFromHeader(header *types.Header, callResults []callResult) blockResult {
return blockResult{
Number: hexutil.Uint64(header.Number.Uint64()),
Hash: header.Hash(),
Time: hexutil.Uint64(header.Time),
GasLimit: hexutil.Uint64(header.GasLimit),
GasUsed: hexutil.Uint64(header.GasUsed),
FeeRecipient: header.Coinbase,
BaseFee: (*hexutil.Big)(header.BaseFee),
PrevRandao: header.MixDigest,
Calls: callResults,
}
}
type callResult struct {
ReturnValue hexutil.Bytes `json:"returnData"`
Logs []*types.Log `json:"logs"`
GasUsed hexutil.Uint64 `json:"gasUsed"`
Status hexutil.Uint64 `json:"status"`
Error *callError `json:"error,omitempty"`
}
func (r *callResult) MarshalJSON() ([]byte, error) {
type callResultAlias callResult
// Marshal logs to be an empty array instead of nil when empty
if r.Logs == nil {
r.Logs = []*types.Log{}
}
return json.Marshal((*callResultAlias)(r))
}
type multicallOpts struct {
BlockStateCalls []CallBatch
TraceTransfers bool
Validation bool
}
// MulticallV1 executes series of transactions on top of a base state.
// The transactions are packed into blocks. For each block, block header
// fields can be overridden. The state can also be overridden prior to
@ -1290,255 +1233,8 @@ func (s *BlockChainAPI) MulticallV1(ctx context.Context, opts multicallOpts, blo
n := rpc.BlockNumberOrHashWithNumber(rpc.LatestBlockNumber)
blockNrOrHash = &n
}
state, base, err := s.b.StateAndHeaderByNumberOrHash(ctx, *blockNrOrHash)
if state == nil || err != nil {
return nil, err
}
// Setup context so it may be cancelled before the calls completed
// or, in case of unmetered gas, setup a context with a timeout.
var (
cancel context.CancelFunc
timeout = s.b.RPCEVMTimeout()
blocks = opts.BlockStateCalls
)
if timeout > 0 {
ctx, cancel = context.WithTimeout(ctx, timeout)
} else {
ctx, cancel = context.WithCancel(ctx)
}
// Make sure the context is cancelled when the call has completed
// this makes sure resources are cleaned up.
defer cancel()
headers, err := makeHeaders(ctx, s.b.ChainConfig(), blocks, base)
if err != nil {
return nil, err
}
var (
results = make([]blockResult, len(blocks))
// Each tx and all the series of txes shouldn't consume more gas than cap
globalGasCap = s.b.RPCGasCap()
gp = new(core.GasPool).AddGas(globalGasCap)
header = base
blockContext = core.NewEVMBlockContext(header, NewChainContext(ctx, s.b), nil)
rules = s.b.ChainConfig().Rules(blockContext.BlockNumber, blockContext.Random != nil, blockContext.Time)
precompiles = vm.ActivePrecompiledContracts(rules).Copy()
numHashes = headers[len(headers)-1].Number.Uint64() - base.Number.Uint64() + 256
// Cache for the block hashes.
hashes = make([]common.Hash, numHashes)
)
for bi, block := range blocks {
header = headers[bi]
blockContext = core.NewEVMBlockContext(header, NewChainContext(ctx, s.b), nil)
// Respond to BLOCKHASH requests.
blockContext.GetHash = func(n uint64) common.Hash {
var (
h common.Hash
err error
)
h, hashes, err = getHash(ctx, n, base, headers, s.b, hashes)
if err != nil {
log.Warn(err.Error())
return common.Hash{}
}
return h
}
// State overrides are applied prior to execution of a block
if err := block.StateOverrides.Apply(state, precompiles); err != nil {
return nil, err
}
var (
gasUsed uint64
txes = make([]*types.Transaction, len(block.Calls))
callResults = make([]callResult, len(block.Calls))
)
for i, call := range block.Calls {
if call.Nonce == nil {
nonce := state.GetNonce(call.from())
call.Nonce = (*hexutil.Uint64)(&nonce)
}
// Let the call run wild unless explicitly specified.
if call.Gas == nil {
remaining := blockContext.GasLimit - gasUsed
call.Gas = (*hexutil.Uint64)(&remaining)
}
if call.GasPrice == nil && call.MaxFeePerGas == nil && call.MaxPriorityFeePerGas == nil {
call.MaxFeePerGas = (*hexutil.Big)(big.NewInt(0))
call.MaxPriorityFeePerGas = (*hexutil.Big)(big.NewInt(0))
}
// TODO: check chainID and against current header for london fees
if err := call.validateAll(); err != nil {
return nil, err
}
tx := call.ToTransaction(true)
txes[i] = tx
// TODO: repair log block hashes post execution.
vmConfig := &vm.Config{
NoBaseFee: true,
// Block hash will be repaired after execution.
Tracer: newTracer(opts.TraceTransfers, blockContext.BlockNumber.Uint64(), common.Hash{}, tx.Hash(), uint(i)),
}
result, err := applyMessage(ctx, s.b, call, state, header, timeout, gp, &blockContext, vmConfig, precompiles, opts.Validation)
if err != nil {
callErr := callErrorFromError(err)
callResults[i] = callResult{Error: callErr, Status: hexutil.Uint64(types.ReceiptStatusFailed)}
continue
}
// If the result contains a revert reason, try to unpack it.
if len(result.Revert()) > 0 {
result.Err = newRevertError(result)
}
logs := vmConfig.Tracer.(*tracer).Logs()
callRes := callResult{ReturnValue: result.Return(), Logs: logs, GasUsed: hexutil.Uint64(result.UsedGas)}
if result.Failed() {
callRes.Status = hexutil.Uint64(types.ReceiptStatusFailed)
if errors.Is(result.Err, vm.ErrExecutionReverted) {
callRes.Error = &callError{Message: result.Err.Error(), Code: -32000}
} else {
callRes.Error = &callError{Message: result.Err.Error(), Code: -32015}
}
} else {
callRes.Status = hexutil.Uint64(types.ReceiptStatusSuccessful)
}
callResults[i] = callRes
gasUsed += result.UsedGas
state.Finalise(true)
}
var (
parentHash common.Hash
err error
)
parentHash, hashes, err = getHash(ctx, header.Number.Uint64()-1, base, headers, s.b, hashes)
if err != nil {
return nil, err
}
header.ParentHash = parentHash
header.Root = state.IntermediateRoot(true)
header.GasUsed = gasUsed
header.TxHash = types.DeriveSha(types.Transactions(txes), trie.NewStackTrie(nil))
results[bi] = mcBlockResultFromHeader(header, callResults)
repairLogs(results, header.Hash())
}
return results, nil
}
// getHash returns the hash for the block of the given number. Block can be
// part of the canonical chain, a simulated block or a phantom block.
// Note getHash assumes `n` is smaller than the last already simulated block
// and smaller than the last block to be simulated.
func getHash(ctx context.Context, n uint64, base *types.Header, headers []*types.Header, backend Backend, hashes []common.Hash) (common.Hash, []common.Hash, error) {
// getIndex returns the index of the hash in the hashes cache.
// The cache potentially includes 255 blocks prior to the base.
getIndex := func(n uint64) int {
first := base.Number.Uint64() - 255
return int(n - first)
}
index := getIndex(n)
if h := hashes[index]; h != (common.Hash{}) {
return h, hashes, nil
}
h, err := computeHash(ctx, n, base, headers, backend, hashes)
if err != nil {
return common.Hash{}, hashes, err
}
if h != (common.Hash{}) {
hashes[index] = h
}
return h, hashes, nil
}
func computeHash(ctx context.Context, n uint64, base *types.Header, headers []*types.Header, backend Backend, hashes []common.Hash) (common.Hash, error) {
if n == base.Number.Uint64() {
return base.Hash(), nil
} else if n < base.Number.Uint64() {
h, err := backend.HeaderByNumber(ctx, rpc.BlockNumber(n))
if err != nil {
return common.Hash{}, fmt.Errorf("failed to load block hash for number %d. Err: %v\n", n, err)
}
return h.Hash(), nil
}
h := base
for i, _ := range headers {
tmp := headers[i]
// BLOCKHASH will only allow numbers prior to current block
// so no need to check that condition.
if tmp.Number.Uint64() == n {
hash := tmp.Hash()
return hash, nil
} else if tmp.Number.Uint64() > n {
// Phantom block.
lastNonPhantomHash, _, err := getHash(ctx, h.Number.Uint64(), base, headers, backend, hashes)
if err != nil {
return common.Hash{}, err
}
// keccak(rlp(lastNonPhantomBlockHash, blockNumber))
hashData, err := rlp.EncodeToBytes([][]byte{lastNonPhantomHash.Bytes(), big.NewInt(int64(n)).Bytes()})
if err != nil {
return common.Hash{}, err
}
return crypto.Keccak256Hash(hashData), nil
}
h = tmp
}
return common.Hash{}, errors.New("requested block is in future")
}
// repairLogs updates the block hash in the logs present in a multicall
// result object. This is needed as during execution when logs are collected
// the block hash is not known.
func repairLogs(results []blockResult, blockHash common.Hash) {
for i := range results {
for j := range results[i].Calls {
for k := range results[i].Calls[j].Logs {
results[i].Calls[j].Logs[k].BlockHash = blockHash
}
}
}
}
func makeHeaders(ctx context.Context, config *params.ChainConfig, blocks []CallBatch, base *types.Header) ([]*types.Header, error) {
res := make([]*types.Header, len(blocks))
var (
prevNumber = base.Number.Uint64()
prevTimestamp = base.Time
header = base
)
for bi, block := range blocks {
overrides := new(BlockOverrides)
if block.BlockOverrides != nil {
overrides = block.BlockOverrides
}
// Sanitize block number and timestamp
if overrides.Number == nil {
n := new(big.Int).Add(big.NewInt(int64(prevNumber)), big.NewInt(1))
overrides.Number = (*hexutil.Big)(n)
} else if overrides.Number.ToInt().Uint64() <= prevNumber {
return nil, fmt.Errorf("block numbers must be in order")
}
prevNumber = overrides.Number.ToInt().Uint64()
if overrides.Time == nil {
t := prevTimestamp + 1
overrides.Time = (*hexutil.Uint64)(&t)
} else if time := (*uint64)(overrides.Time); *time <= prevTimestamp {
return nil, fmt.Errorf("timestamps must be in order")
}
prevTimestamp = uint64(*overrides.Time)
var baseFee *big.Int
if config.IsLondon(overrides.Number.ToInt()) {
baseFee = eip1559.CalcBaseFee(config, header)
}
header = &types.Header{
UncleHash: types.EmptyUncleHash,
Coinbase: base.Coinbase,
Difficulty: base.Difficulty,
GasLimit: base.GasLimit,
//MixDigest: header.MixDigest,
BaseFee: baseFee,
}
overrides.ApplyToHeader(header)
res[bi] = header
}
return res, nil
mc := &multicall{b: s.b, blockNrOrHash: *blockNrOrHash}
return mc.execute(ctx, opts)
}
// executeEstimate is a helper that executes the transaction under a given gas limit and returns

View file

@ -0,0 +1,348 @@
// Copyright 2023 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 ethapi
import (
"context"
"encoding/json"
"errors"
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"github.com/ethereum/go-ethereum/consensus/misc/eip1559"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/params"
"github.com/ethereum/go-ethereum/rlp"
"github.com/ethereum/go-ethereum/rpc"
"github.com/ethereum/go-ethereum/trie"
)
// CallBatch is a batch of calls to be simulated sequentially.
type CallBatch struct {
BlockOverrides *BlockOverrides
StateOverrides *StateOverride
Calls []TransactionArgs
}
type blockResult struct {
Number hexutil.Uint64 `json:"number"`
Hash common.Hash `json:"hash"`
Time hexutil.Uint64 `json:"timestamp"`
GasLimit hexutil.Uint64 `json:"gasLimit"`
GasUsed hexutil.Uint64 `json:"gasUsed"`
FeeRecipient common.Address `json:"feeRecipient"`
BaseFee *hexutil.Big `json:"baseFeePerGas"`
PrevRandao common.Hash `json:"prevRandao"`
Calls []callResult `json:"calls"`
}
func mcBlockResultFromHeader(header *types.Header, callResults []callResult) blockResult {
return blockResult{
Number: hexutil.Uint64(header.Number.Uint64()),
Hash: header.Hash(),
Time: hexutil.Uint64(header.Time),
GasLimit: hexutil.Uint64(header.GasLimit),
GasUsed: hexutil.Uint64(header.GasUsed),
FeeRecipient: header.Coinbase,
BaseFee: (*hexutil.Big)(header.BaseFee),
PrevRandao: header.MixDigest,
Calls: callResults,
}
}
type callResult struct {
ReturnValue hexutil.Bytes `json:"returnData"`
Logs []*types.Log `json:"logs"`
GasUsed hexutil.Uint64 `json:"gasUsed"`
Status hexutil.Uint64 `json:"status"`
Error *callError `json:"error,omitempty"`
}
func (r *callResult) MarshalJSON() ([]byte, error) {
type callResultAlias callResult
// Marshal logs to be an empty array instead of nil when empty
if r.Logs == nil {
r.Logs = []*types.Log{}
}
return json.Marshal((*callResultAlias)(r))
}
type multicallOpts struct {
BlockStateCalls []CallBatch
TraceTransfers bool
Validation bool
}
type multicall struct {
blockNrOrHash rpc.BlockNumberOrHash
b Backend
hashes []common.Hash
}
func (mc *multicall) execute(ctx context.Context, opts multicallOpts) ([]blockResult, error) {
state, base, err := mc.b.StateAndHeaderByNumberOrHash(ctx, mc.blockNrOrHash)
if state == nil || err != nil {
return nil, err
}
// Setup context so it may be cancelled before the calls completed
// or, in case of unmetered gas, setup a context with a timeout.
var (
cancel context.CancelFunc
timeout = mc.b.RPCEVMTimeout()
blocks = opts.BlockStateCalls
)
if timeout > 0 {
ctx, cancel = context.WithTimeout(ctx, timeout)
} else {
ctx, cancel = context.WithCancel(ctx)
}
// Make sure the context is cancelled when the call has completed
// this makes sure resources are cleaned up.
defer cancel()
headers, err := makeHeaders(mc.b.ChainConfig(), blocks, base)
if err != nil {
return nil, err
}
var (
results = make([]blockResult, len(blocks))
// Each tx and all the series of txes shouldn't consume more gas than cap
globalGasCap = mc.b.RPCGasCap()
gp = new(core.GasPool).AddGas(globalGasCap)
header = base
blockContext = core.NewEVMBlockContext(header, NewChainContext(ctx, mc.b), nil)
rules = mc.b.ChainConfig().Rules(blockContext.BlockNumber, blockContext.Random != nil, blockContext.Time)
precompiles = vm.ActivePrecompiledContracts(rules).Copy()
numHashes = headers[len(headers)-1].Number.Uint64() - base.Number.Uint64() + 256
)
// Cache for the block hashes.
mc.hashes = make([]common.Hash, numHashes)
for bi, block := range blocks {
header = headers[bi]
blockContext = core.NewEVMBlockContext(header, NewChainContext(ctx, mc.b), nil)
// Respond to BLOCKHASH requests.
blockContext.GetHash = func(n uint64) common.Hash {
h, err := mc.getBlockHash(ctx, n, base, headers)
if err != nil {
log.Warn(err.Error())
return common.Hash{}
}
return h
}
// State overrides are applied prior to execution of a block
if err := block.StateOverrides.Apply(state, precompiles); err != nil {
return nil, err
}
var (
gasUsed uint64
txes = make([]*types.Transaction, len(block.Calls))
callResults = make([]callResult, len(block.Calls))
)
for i, call := range block.Calls {
if call.Nonce == nil {
nonce := state.GetNonce(call.from())
call.Nonce = (*hexutil.Uint64)(&nonce)
}
// Let the call run wild unless explicitly specified.
if call.Gas == nil {
remaining := blockContext.GasLimit - gasUsed
call.Gas = (*hexutil.Uint64)(&remaining)
}
if call.GasPrice == nil && call.MaxFeePerGas == nil && call.MaxPriorityFeePerGas == nil {
call.MaxFeePerGas = (*hexutil.Big)(big.NewInt(0))
call.MaxPriorityFeePerGas = (*hexutil.Big)(big.NewInt(0))
}
// TODO: check chainID and against current header for london fees
if err := call.validateAll(); err != nil {
return nil, err
}
tx := call.ToTransaction(true)
txes[i] = tx
// TODO: repair log block hashes post execution.
vmConfig := &vm.Config{
NoBaseFee: true,
// Block hash will be repaired after execution.
Tracer: newTracer(opts.TraceTransfers, blockContext.BlockNumber.Uint64(), common.Hash{}, tx.Hash(), uint(i)),
}
result, err := applyMessage(ctx, mc.b, call, state, header, timeout, gp, &blockContext, vmConfig, precompiles, opts.Validation)
if err != nil {
callErr := callErrorFromError(err)
callResults[i] = callResult{Error: callErr, Status: hexutil.Uint64(types.ReceiptStatusFailed)}
continue
}
// If the result contains a revert reason, try to unpack it.
if len(result.Revert()) > 0 {
result.Err = newRevertError(result)
}
logs := vmConfig.Tracer.(*tracer).Logs()
callRes := callResult{ReturnValue: result.Return(), Logs: logs, GasUsed: hexutil.Uint64(result.UsedGas)}
if result.Failed() {
callRes.Status = hexutil.Uint64(types.ReceiptStatusFailed)
if errors.Is(result.Err, vm.ErrExecutionReverted) {
callRes.Error = &callError{Message: result.Err.Error(), Code: -32000}
} else {
callRes.Error = &callError{Message: result.Err.Error(), Code: -32015}
}
} else {
callRes.Status = hexutil.Uint64(types.ReceiptStatusSuccessful)
}
callResults[i] = callRes
gasUsed += result.UsedGas
state.Finalise(true)
}
var (
parentHash common.Hash
err error
)
parentHash, err = mc.getBlockHash(ctx, header.Number.Uint64()-1, base, headers)
if err != nil {
return nil, err
}
header.ParentHash = parentHash
header.Root = state.IntermediateRoot(true)
header.GasUsed = gasUsed
header.TxHash = types.DeriveSha(types.Transactions(txes), trie.NewStackTrie(nil))
results[bi] = mcBlockResultFromHeader(header, callResults)
repairLogs(results, header.Hash())
}
return results, nil
}
// getBlockHash returns the hash for the block of the given number. Block can be
// part of the canonical chain, a simulated block or a phantom block.
// Note getBlockHash assumes `n` is smaller than the last already simulated block
// and smaller than the last block to be simulated.
func (mc *multicall) getBlockHash(ctx context.Context, n uint64, base *types.Header, headers []*types.Header) (common.Hash, error) {
// getIndex returns the index of the hash in the hashes cache.
// The cache potentially includes 255 blocks prior to the base.
getIndex := func(n uint64) int {
first := base.Number.Uint64() - 255
return int(n - first)
}
index := getIndex(n)
if h := mc.hashes[index]; h != (common.Hash{}) {
return h, nil
}
h, err := mc.computeBlockHash(ctx, n, base, headers)
if err != nil {
return common.Hash{}, err
}
if h != (common.Hash{}) {
mc.hashes[index] = h
}
return h, nil
}
func (mc *multicall) computeBlockHash(ctx context.Context, n uint64, base *types.Header, headers []*types.Header) (common.Hash, error) {
if n == base.Number.Uint64() {
return base.Hash(), nil
} else if n < base.Number.Uint64() {
h, err := mc.b.HeaderByNumber(ctx, rpc.BlockNumber(n))
if err != nil {
return common.Hash{}, fmt.Errorf("failed to load block hash for number %d. Err: %v\n", n, err)
}
return h.Hash(), nil
}
h := base
for i, _ := range headers {
tmp := headers[i]
// BLOCKHASH will only allow numbers prior to current block
// so no need to check that condition.
if tmp.Number.Uint64() == n {
hash := tmp.Hash()
return hash, nil
} else if tmp.Number.Uint64() > n {
// Phantom block.
lastNonPhantomHash, err := mc.getBlockHash(ctx, h.Number.Uint64(), base, headers)
if err != nil {
return common.Hash{}, err
}
// keccak(rlp(lastNonPhantomBlockHash, blockNumber))
hashData, err := rlp.EncodeToBytes([][]byte{lastNonPhantomHash.Bytes(), big.NewInt(int64(n)).Bytes()})
if err != nil {
return common.Hash{}, err
}
return crypto.Keccak256Hash(hashData), nil
}
h = tmp
}
return common.Hash{}, errors.New("requested block is in future")
}
// repairLogs updates the block hash in the logs present in a multicall
// result object. This is needed as during execution when logs are collected
// the block hash is not known.
func repairLogs(results []blockResult, blockHash common.Hash) {
for i := range results {
for j := range results[i].Calls {
for k := range results[i].Calls[j].Logs {
results[i].Calls[j].Logs[k].BlockHash = blockHash
}
}
}
}
func makeHeaders(config *params.ChainConfig, blocks []CallBatch, base *types.Header) ([]*types.Header, error) {
res := make([]*types.Header, len(blocks))
var (
prevNumber = base.Number.Uint64()
prevTimestamp = base.Time
header = base
)
for bi, block := range blocks {
overrides := new(BlockOverrides)
if block.BlockOverrides != nil {
overrides = block.BlockOverrides
}
// Sanitize block number and timestamp
if overrides.Number == nil {
n := new(big.Int).Add(big.NewInt(int64(prevNumber)), big.NewInt(1))
overrides.Number = (*hexutil.Big)(n)
} else if overrides.Number.ToInt().Uint64() <= prevNumber {
return nil, fmt.Errorf("block numbers must be in order")
}
prevNumber = overrides.Number.ToInt().Uint64()
if overrides.Time == nil {
t := prevTimestamp + 1
overrides.Time = (*hexutil.Uint64)(&t)
} else if time := (*uint64)(overrides.Time); *time <= prevTimestamp {
return nil, fmt.Errorf("timestamps must be in order")
}
prevTimestamp = uint64(*overrides.Time)
var baseFee *big.Int
if config.IsLondon(overrides.Number.ToInt()) {
baseFee = eip1559.CalcBaseFee(config, header)
}
header = &types.Header{
UncleHash: types.EmptyUncleHash,
Coinbase: base.Coinbase,
Difficulty: base.Difficulty,
GasLimit: base.GasLimit,
//MixDigest: header.MixDigest,
BaseFee: baseFee,
}
overrides.ApplyToHeader(header)
res[bi] = header
}
return res, nil
}