ethereum.forks.cancun.state_trackerethereum.forks.prague.state_tracker
State Tracking for Block Execution.
Track state changes on top of a read-only PreState. At block end,
accumulated diffs feed into
PreState.compute_state_root().
.. contents:: Table of Contents :backlinks: none :local:
Introduction
Replace the mutable State class with lightweight state trackers that
record diffs. BlockState accumulates committed transaction
changes across a block. TransactionState tracks in-flight changes
within a single transaction and supports copy-on-write rollback.
BlockState ¶
Accumulate committed transaction-level changes across a block.
Read chain: block writes -> pre_state.
| 39 | @final |
|---|
| 40 | @dataclass |
|---|
class BlockState:
pre_state¶
| 48 | pre_state: PreState |
|---|
account_writes¶
| 49 | account_writes: Dict[Address, Optional[Account]] = field( |
|---|---|
| 50 | default_factory=dict |
| 51 | ) |
storage_writes¶
| 52 | storage_writes: Dict[Address, Dict[Bytes32, U256]] = field( |
|---|---|
| 53 | default_factory=dict |
| 54 | ) |
code_writes¶
| 55 | code_writes: Dict[Hash32, Bytes] = field(default_factory=dict) |
|---|
TransactionState ¶
Track in-flight state changes within a single transaction.
Read chain: tx writes -> block writes -> pre_state.
| 58 | @final |
|---|
| 59 | @dataclass |
|---|
class TransactionState:
parent¶
| 67 | parent: BlockState |
|---|
account_writes¶
| 68 | account_writes: Dict[Address, Optional[Account]] = field( |
|---|---|
| 69 | default_factory=dict |
| 70 | ) |
storage_writes¶
| 71 | storage_writes: Dict[Address, Dict[Bytes32, U256]] = field( |
|---|---|
| 72 | default_factory=dict |
| 73 | ) |
code_writes¶
| 74 | code_writes: Dict[Hash32, Bytes] = field(default_factory=dict) |
|---|
created_accounts¶
| 75 | created_accounts: Set[Address] = field(default_factory=set) |
|---|
transient_storage¶
| 76 | transient_storage: Dict[Tuple[Address, Bytes32], U256] = field( |
|---|---|
| 77 | default_factory=dict |
| 78 | ) |
get_account_optional ¶
Get the Account object at an address. Return None (rather than
EMPTY_ACCOUNT) if there is no account at the address.
Parameters
tx_state : The transaction state. address : Address to look up.
Returns
account : Optional[Account]
Account at address.
def get_account_optional(tx_state: TransactionState, address: Address) -> Optional[Account]:
| 84 | <snip> |
|---|---|
| 101 | if address in tx_state.account_writes: |
| 102 | return tx_state.account_writes[address] |
| 103 | if address in tx_state.parent.account_writes: |
| 104 | return tx_state.parent.account_writes[address] |
| 105 | return tx_state.parent.pre_state.get_account_optional(address) |
get_account ¶
Get the Account object at an address. Return EMPTY_ACCOUNT
if there is no account at the address.
Use get_account_optional() if you care about the difference
between a non-existent account and EMPTY_ACCOUNT.
Parameters
tx_state : The transaction state. address : Address to look up.
Returns
account : Account
Account at address.
def get_account(tx_state: TransactionState, address: Address) -> Account:
| 109 | <snip> |
|---|---|
| 129 | account = get_account_optional(tx_state, address) |
| 130 | if account is None: |
| 131 | return EMPTY_ACCOUNT |
| 132 | else: |
| 133 | return account |
get_code ¶
Get the bytecode for a given code hash.
Read chain: tx code_writes -> block code_writes -> pre_state.
Parameters
tx_state : The transaction state. code_hash : Hash of the code to look up.
Returns
code : Bytes
The bytecode.
def get_code(tx_state: TransactionState, code_hash: Hash32) -> Bytes:
| 137 | <snip> |
|---|---|
| 155 | if code_hash == EMPTY_CODE_HASH: |
| 156 | return b"" |
| 157 | if code_hash in tx_state.code_writes: |
| 158 | return tx_state.code_writes[code_hash] |
| 159 | if code_hash in tx_state.parent.code_writes: |
| 160 | return tx_state.parent.code_writes[code_hash] |
| 161 | return tx_state.parent.pre_state.get_code(code_hash) |
get_storage ¶
Get a value at a storage key on an account. Return U256(0) if
the storage key has not been set previously.
Parameters
tx_state : The transaction state. address : Address of the account. key : Key to look up.
Returns
value : U256
Value at the key.
def get_storage(tx_state: TransactionState, address: Address, key: Bytes32) -> U256:
| 167 | <snip> |
|---|---|
| 186 | if address in tx_state.storage_writes: |
| 187 | if key in tx_state.storage_writes[address]: |
| 188 | return tx_state.storage_writes[address][key] |
| 189 | if address in tx_state.parent.storage_writes: |
| 190 | if key in tx_state.parent.storage_writes[address]: |
| 191 | return tx_state.parent.storage_writes[address][key] |
| 192 | return tx_state.parent.pre_state.get_storage(address, key) |
get_storage_original ¶
Get the original value in a storage slot i.e. the value before the
current transaction began. Read from block-level writes, then
pre_state. Return U256(0) for accounts created in the current
transaction.
Parameters
tx_state : The transaction state. address : Address of the account to read the value from. key : Key of the storage slot.
def get_storage_original(tx_state: TransactionState, address: Address, key: Bytes32) -> U256:
| 198 | <snip> |
|---|---|
| 214 | if address in tx_state.created_accounts: |
| 215 | return U256(0) |
| 216 | if address in tx_state.parent.storage_writes: |
| 217 | if key in tx_state.parent.storage_writes[address]: |
| 218 | return tx_state.parent.storage_writes[address][key] |
| 219 | return tx_state.parent.pre_state.get_storage(address, key) |
get_transient_storage ¶
Get a value at a storage key on an account from transient storage.
Return U256(0) if the storage key has not been set previously.
Parameters
tx_state : The transaction state. address : Address of the account. key : Key to look up.
Returns
value : U256
Value at the key.
def get_transient_storage(tx_state: TransactionState, address: Address, key: Bytes32) -> U256:
| 225 | <snip> |
|---|---|
| 244 | return tx_state.transient_storage.get((address, key), U256(0)) |
account_exists ¶
Check if an account exists in the state trie.
Parameters
tx_state : The transaction state. address : Address of the account that needs to be checked.
Returns
account_exists : bool
True if account exists in the state trie, False otherwise.
def account_exists(tx_state: TransactionState, address: Address) -> bool:
| 248 | <snip> |
|---|---|
| 264 | return get_account_optional(tx_state, address) is not None |
account_deployable ¶
Check if an account's code can be written to.
def account_deployable(tx_state: TransactionState, address: Address) -> bool:
| 268 | <snip> |
|---|---|
| 271 | account = get_account(tx_state, address) |
| 272 | if account.nonce != Uint(0) or account.code_hash != EMPTY_CODE_HASH: |
| 273 | return False |
| 274 | |
| 275 | return True |
account_exists_and_is_empty ¶
Check if an account exists and has zero nonce, empty code and zero balance.
Parameters
tx_state : The transaction state. address : Address of the account that needs to be checked.
Returns
exists_and_is_empty : bool
True if an account exists and has zero nonce, empty code and
zero balance, False otherwise.
def account_exists_and_is_empty(tx_state: TransactionState, address: Address) -> bool:
| 281 | <snip> |
|---|---|
| 299 | account = get_account_optional(tx_state, address) |
| 300 | return ( |
| 301 | account is not None |
| 302 | and account.nonce == Uint(0) |
| 303 | and account.code_hash == EMPTY_CODE_HASH |
| 304 | and account.balance == 0 |
| 305 | ) |
is_account_alive ¶
Check whether an account is both in the state and non-empty.
Parameters
tx_state : The transaction state. address : Address of the account that needs to be checked.
Returns
is_alive : bool
True if the account is alive.
def is_account_alive(tx_state: TransactionState, address: Address) -> bool:
| 309 | <snip> |
|---|---|
| 325 | account = get_account_optional(tx_state, address) |
| 326 | return account is not None and account != EMPTY_ACCOUNT |
set_account ¶
Set the Account object at an address. Setting to None
deletes the account (but not its storage, see
destroy_account()).
Parameters
tx_state : The transaction state. address : Address to set. account : Account to set at address.
def set_account(tx_state: TransactionState, address: Address, account: Optional[Account]) -> None:
| 334 | <snip> |
|---|---|
| 349 | tx_state.account_writes[address] = account |
set_storage ¶
Set a value at a storage key on an account.
Parameters
tx_state : The transaction state. address : Address of the account. key : Key to set. value : Value to set at the key.
def set_storage(tx_state: TransactionState, address: Address, key: Bytes32, value: U256) -> None:
| 358 | <snip> |
|---|---|
| 373 | assert get_account_optional(tx_state, address) is not None |
| 374 | if address not in tx_state.storage_writes: |
| 375 | tx_state.storage_writes[address] = {} |
| 376 | tx_state.storage_writes[address][key] = value |
destroy_account ¶
Completely remove the account at address and all of its storage.
This function is made available exclusively for the SELFDESTRUCT
opcode. It is expected that SELFDESTRUCT will be disabled in a
future hardfork and this function will be removed. Only supports same
transaction destruction.
Parameters
tx_state : The transaction state. address : Address of account to destroy.
def destroy_account(tx_state: TransactionState, address: Address) -> None:
| 380 | <snip> |
|---|---|
| 396 | destroy_storage(tx_state, address) |
| 397 | set_account(tx_state, address, None) |
destroy_storage ¶
Completely remove the storage at address.
Only supports same transaction destruction.
Parameters
tx_state : The transaction state. address : Address of account whose storage is to be deleted.
def destroy_storage(tx_state: TransactionState, address: Address) -> None:
| 401 | <snip> |
|---|---|
| 414 | if address in tx_state.storage_writes: |
| 415 | del tx_state.storage_writes[address] |
mark_account_created ¶
Mark an account as having been created in the current transaction.
This information is used by get_storage_original() to handle an
obscure edgecase, and to respect the constraints added to
SELFDESTRUCT by EIP-6780.
The marker is not removed even if the account creation reverts.
Since the account cannot have had code prior to its creation and
can't call get_storage_original(), this is harmless.
Parameters
tx_state : The transaction state. address : Address of the account that has been created.
def mark_account_created(tx_state: TransactionState, address: Address) -> None:
| 419 | <snip> |
|---|---|
| 437 | tx_state.created_accounts.add(address) |
set_transient_storage ¶
Set a value at a storage key on an account in transient storage.
Parameters
tx_state : The transaction state. address : Address of the account. key : Key to set. value : Value to set at the key.
modify_state ¶
Modify an Account in the state. If, after modification, the
account exists and has zero nonce, empty code, and zero balance, it
is destroyed.
def modify_state(tx_state: TransactionState, address: Address, f: Callable[[Account], None]) -> None:
| 472 | <snip> |
|---|---|
| 477 | set_account(tx_state, address, modify(get_account(tx_state, address), f)) |
| 478 | if account_exists_and_is_empty(tx_state, address): |
| 479 | destroy_account(tx_state, address) |
move_ether ¶
Move funds between accounts.
Parameters
tx_state : The transaction state. sender_address : Address of the sender. recipient_address : Address of the recipient. amount : The amount to transfer.
def move_ether(tx_state: TransactionState, sender_address: Address, recipient_address: Address, amount: U256) -> None:
| 488 | <snip> |
|---|---|
| 503 | |
| 504 | def reduce_sender_balance(sender: Account) -> None: |
| 505 | if sender.balance < amount: |
| 506 | raise AssertionError |
| 507 | sender.balance -= amount |
| 508 | |
| 509 | def increase_recipient_balance(recipient: Account) -> None: |
| 510 | recipient.balance += amount |
| 511 | |
| 512 | modify_state(tx_state, sender_address, reduce_sender_balance) |
| 513 | modify_state(tx_state, recipient_address, increase_recipient_balance) |
create_ether ¶
Add newly created ether to an account.
Parameters
tx_state : The transaction state. address : Address of the account to which ether is added. amount : The amount of ether to be added to the account of interest.
def create_ether(tx_state: TransactionState, address: Address, amount: U256) -> None:
| 519 | <snip> |
|---|---|
| 532 | |
| 533 | def increase_balance(account: Account) -> None: |
| 534 | account.balance += amount |
| 535 | |
| 536 | modify_state(tx_state, address, increase_balance) |
set_account_balance ¶
Set the balance of an account.
Parameters
tx_state : The transaction state. address : Address of the account whose balance needs to be set. amount : The amount that needs to be set in the balance.
def set_account_balance(tx_state: TransactionState, address: Address, amount: U256) -> None:
| 542 | <snip> |
|---|---|
| 555 | |
| 556 | def set_balance(account: Account) -> None: |
| 557 | account.balance = amount |
| 558 | |
| 559 | modify_state(tx_state, address, set_balance) |
increment_nonce ¶
Increment the nonce of an account.
Parameters
tx_state : The transaction state. address : Address of the account whose nonce needs to be incremented.
def increment_nonce(tx_state: TransactionState, address: Address) -> None:
| 563 | <snip> |
|---|---|
| 574 | |
| 575 | def increase_nonce(sender: Account) -> None: |
| 576 | sender.nonce += Uint(1) |
| 577 | |
| 578 | modify_state(tx_state, address, increase_nonce) |
set_code ¶
Set Account code.
Parameters
tx_state : The transaction state. address : Address of the account whose code needs to be updated. code : The bytecode that needs to be set.
def set_code(tx_state: TransactionState, address: Address, code: Bytes) -> None:
| 584 | <snip> |
|---|---|
| 597 | code_hash = keccak256(code) |
| 598 | if code_hash != EMPTY_CODE_HASH: |
| 599 | tx_state.code_writes[code_hash] = code |
| 600 | |
| 601 | def write_code_hash(sender: Account) -> None: |
| 602 | sender.code_hash = code_hash |
| 603 | |
| 604 | modify_state(tx_state, address, write_code_hash) |
copy_tx_state ¶
Create a snapshot of the transaction state for rollback.
Deep-copy writes and transient storage. The parent reference and
created_accounts are shared (not rolled back).
Parameters
tx_state : The transaction state to snapshot.
Returns
snapshot : TransactionState
A copy of the transaction state.
def copy_tx_state(tx_state: TransactionState) -> TransactionState:
| 611 | <snip> |
|---|---|
| 628 | return TransactionState( |
| 629 | parent=tx_state.parent, |
| 630 | account_writes=dict(tx_state.account_writes), |
| 631 | storage_writes={ |
| 632 | addr: dict(slots) |
| 633 | for addr, slots in tx_state.storage_writes.items() |
| 634 | }, |
| 635 | code_writes=dict(tx_state.code_writes), |
| 636 | created_accounts=tx_state.created_accounts, |
| 637 | transient_storage=dict(tx_state.transient_storage), |
| 638 | ) |
restore_tx_state ¶
Restore transaction state from a snapshot (rollback on failure).
Parameters
tx_state : The transaction state to restore. snapshot : The snapshot to restore from.
def restore_tx_state(tx_state: TransactionState, snapshot: TransactionState) -> None:
| 644 | <snip> |
|---|---|
| 655 | tx_state.account_writes = snapshot.account_writes |
| 656 | tx_state.storage_writes = snapshot.storage_writes |
| 657 | tx_state.code_writes = snapshot.code_writes |
| 658 | tx_state.transient_storage = snapshot.transient_storage |
incorporate_tx_into_block ¶
Merge transaction writes into the block state and clear for reuse.
Parameters
tx_state : The transaction state to commit.
def incorporate_tx_into_block(tx_state: TransactionState) -> None:
| 665 | <snip> |
|---|---|
| 674 | block = tx_state.parent |
| 675 | |
| 676 | for address, account in tx_state.account_writes.items(): |
| 677 | block.account_writes[address] = account |
| 678 | |
| 679 | for address, slots in tx_state.storage_writes.items(): |
| 680 | if address not in block.storage_writes: |
| 681 | block.storage_writes[address] = {} |
| 682 | block.storage_writes[address].update(slots) |
| 683 | |
| 684 | block.code_writes.update(tx_state.code_writes) |
| 685 | |
| 686 | tx_state.account_writes.clear() |
| 687 | tx_state.storage_writes.clear() |
| 688 | tx_state.code_writes.clear() |
| 689 | tx_state.created_accounts.clear() |
| 690 | tx_state.transient_storage.clear() |
extract_block_diff ¶
Extract account, storage, and code diff from the block state.
Parameters
block_state : The block state.
Returns
diff : BlockDiff
Account, storage, and code changes accumulated during block execution.