forked from cerc-io/plugeth
core/types: fix immutability guarantees in Block (#27844)
This change rearranges the accessor methods in block.go and fixes some minor issues with the copy-on-write logic of block data. Fixed issues: - Block.WithWithdrawals did not create a shallow copy of the block. - Block.WithBody copied the header unnecessarily, and did not preserve withdrawals. However, the bugs did not affect any code in go-ethereum because blocks are *always* created using NewBlockWithHeader().WithBody().WithWithdrawals()
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Felix Lange
GitHub
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6e934f40f9
commit
df544350bc
@ -170,7 +170,23 @@ type Body struct {
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Withdrawals []*Withdrawal `rlp:"optional"`
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}
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// Block represents an entire block in the Ethereum blockchain.
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// Block represents an Ethereum block.
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//
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// Note the Block type tries to be 'immutable', and contains certain caches that rely
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// on that. The rules around block immutability are as follows:
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//
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// - We copy all data when the block is constructed. This makes references held inside
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// the block independent of whatever value was passed in.
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//
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// - We copy all header data on access. This is because any change to the header would mess
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// up the cached hash and size values in the block. Calling code is expected to take
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// advantage of this to avoid over-allocating!
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//
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// - When new body data is attached to the block, a shallow copy of the block is returned.
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// This ensures block modifications are race-free.
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//
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// - We do not copy body data on access because it does not affect the caches, and also
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// because it would be too expensive.
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type Block struct {
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header *Header
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uncles []*Header
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@ -195,9 +211,8 @@ type extblock struct {
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Withdrawals []*Withdrawal `rlp:"optional"`
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}
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// NewBlock creates a new block. The input data is copied,
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// changes to header and to the field values will not affect the
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// block.
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// NewBlock creates a new block. The input data is copied, changes to header and to the
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// field values will not affect the block.
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//
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// The values of TxHash, UncleHash, ReceiptHash and Bloom in header
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// are ignored and set to values derived from the given txs, uncles
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@ -234,13 +249,11 @@ func NewBlock(header *Header, txs []*Transaction, uncles []*Header, receipts []*
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return b
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}
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// NewBlockWithWithdrawals creates a new block with withdrawals. The input data
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// is copied, changes to header and to the field values will not
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// affect the block.
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// NewBlockWithWithdrawals creates a new block with withdrawals. The input data is copied,
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// changes to header and to the field values will not affect the block.
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//
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// The values of TxHash, UncleHash, ReceiptHash and Bloom in header
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// are ignored and set to values derived from the given txs, uncles
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// and receipts.
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// The values of TxHash, UncleHash, ReceiptHash and Bloom in header are ignored and set to
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// values derived from the given txs, uncles and receipts.
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func NewBlockWithWithdrawals(header *Header, txs []*Transaction, uncles []*Header, receipts []*Receipt, withdrawals []*Withdrawal, hasher TrieHasher) *Block {
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b := NewBlock(header, txs, uncles, receipts, hasher)
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@ -256,15 +269,7 @@ func NewBlockWithWithdrawals(header *Header, txs []*Transaction, uncles []*Heade
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return b.WithWithdrawals(withdrawals)
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}
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// NewBlockWithHeader creates a block with the given header data. The
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// header data is copied, changes to header and to the field values
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// will not affect the block.
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func NewBlockWithHeader(header *Header) *Block {
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return &Block{header: CopyHeader(header)}
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}
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// CopyHeader creates a deep copy of a block header to prevent side effects from
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// modifying a header variable.
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// CopyHeader creates a deep copy of a block header.
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func CopyHeader(h *Header) *Header {
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cpy := *h
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if cpy.Difficulty = new(big.Int); h.Difficulty != nil {
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@ -295,7 +300,7 @@ func CopyHeader(h *Header) *Header {
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return &cpy
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}
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// DecodeRLP decodes the Ethereum
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// DecodeRLP decodes a block from RLP.
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func (b *Block) DecodeRLP(s *rlp.Stream) error {
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var eb extblock
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_, size, _ := s.Kind()
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@ -307,9 +312,9 @@ func (b *Block) DecodeRLP(s *rlp.Stream) error {
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return nil
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}
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// EncodeRLP serializes b into the Ethereum RLP block format.
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// EncodeRLP serializes a block as RLP.
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func (b *Block) EncodeRLP(w io.Writer) error {
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return rlp.Encode(w, extblock{
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return rlp.Encode(w, &extblock{
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Header: b.header,
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Txs: b.transactions,
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Uncles: b.uncles,
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@ -317,10 +322,18 @@ func (b *Block) EncodeRLP(w io.Writer) error {
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})
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}
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// TODO: copies
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// Body returns the non-header content of the block.
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// Note the returned data is not an independent copy.
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func (b *Block) Body() *Body {
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return &Body{b.transactions, b.uncles, b.withdrawals}
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}
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// Accessors for body data. These do not return a copy because the content
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// of the body slices does not affect the cached hash/size in block.
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func (b *Block) Uncles() []*Header { return b.uncles }
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func (b *Block) Transactions() Transactions { return b.transactions }
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func (b *Block) Withdrawals() Withdrawals { return b.withdrawals }
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func (b *Block) Transaction(hash common.Hash) *Transaction {
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for _, transaction := range b.transactions {
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@ -331,6 +344,13 @@ func (b *Block) Transaction(hash common.Hash) *Transaction {
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return nil
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}
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// Header returns the block header (as a copy).
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func (b *Block) Header() *Header {
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return CopyHeader(b.header)
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}
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// Header value accessors. These do copy!
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func (b *Block) Number() *big.Int { return new(big.Int).Set(b.header.Number) }
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func (b *Block) GasLimit() uint64 { return b.header.GasLimit }
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func (b *Block) GasUsed() uint64 { return b.header.GasUsed }
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@ -356,10 +376,6 @@ func (b *Block) BaseFee() *big.Int {
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return new(big.Int).Set(b.header.BaseFee)
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}
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func (b *Block) Withdrawals() Withdrawals {
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return b.withdrawals
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}
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func (b *Block) ExcessBlobGas() *uint64 {
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var excessBlobGas *uint64
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if b.header.ExcessBlobGas != nil {
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@ -378,11 +394,6 @@ func (b *Block) BlobGasUsed() *uint64 {
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return blobGasUsed
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}
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func (b *Block) Header() *Header { return CopyHeader(b.header) }
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// Body returns the non-header content of the block.
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func (b *Block) Body() *Body { return &Body{b.transactions, b.uncles, b.withdrawals} }
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// Size returns the true RLP encoded storage size of the block, either by encoding
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// and returning it, or returning a previously cached value.
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func (b *Block) Size() uint64 {
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@ -415,25 +426,31 @@ func CalcUncleHash(uncles []*Header) common.Hash {
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return rlpHash(uncles)
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}
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// NewBlockWithHeader creates a block with the given header data. The
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// header data is copied, changes to header and to the field values
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// will not affect the block.
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func NewBlockWithHeader(header *Header) *Block {
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return &Block{header: CopyHeader(header)}
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}
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// WithSeal returns a new block with the data from b but the header replaced with
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// the sealed one.
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func (b *Block) WithSeal(header *Header) *Block {
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cpy := *header
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return &Block{
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header: &cpy,
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header: CopyHeader(header),
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transactions: b.transactions,
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uncles: b.uncles,
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withdrawals: b.withdrawals,
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}
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}
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// WithBody returns a new block with the given transaction and uncle contents.
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// WithBody returns a copy of the block with the given transaction and uncle contents.
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func (b *Block) WithBody(transactions []*Transaction, uncles []*Header) *Block {
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block := &Block{
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header: CopyHeader(b.header),
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header: b.header,
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transactions: make([]*Transaction, len(transactions)),
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uncles: make([]*Header, len(uncles)),
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withdrawals: b.withdrawals,
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}
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copy(block.transactions, transactions)
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for i := range uncles {
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@ -442,13 +459,18 @@ func (b *Block) WithBody(transactions []*Transaction, uncles []*Header) *Block {
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return block
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}
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// WithWithdrawals sets the withdrawal contents of a block, does not return a new block.
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// WithWithdrawals returns a copy of the block containing the given withdrawals.
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func (b *Block) WithWithdrawals(withdrawals []*Withdrawal) *Block {
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if withdrawals != nil {
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b.withdrawals = make([]*Withdrawal, len(withdrawals))
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copy(b.withdrawals, withdrawals)
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block := &Block{
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header: b.header,
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transactions: b.transactions,
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uncles: b.uncles,
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}
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return b
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if withdrawals != nil {
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block.withdrawals = make([]*Withdrawal, len(withdrawals))
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copy(block.withdrawals, withdrawals)
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}
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return block
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}
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// Hash returns the keccak256 hash of b's header.
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