ethereum.forks.bpo5.state_trackerethereum.forks.amsterdam.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_and_trie_changes().

.. 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.

account_reads and storage_reads accumulate across all transactions for BAL generation.

42
@final
43
@dataclass
class BlockState:

pre_state

54
    pre_state: PreState

account_reads

55
    account_reads: Set[Address] = field(default_factory=set)

account_writes

56
    account_writes: Dict[Address, Optional[Account]] = field(
57
        default_factory=dict
58
    )

storage_reads

59
    storage_reads: Set[Tuple[Address, Bytes32]] = field(default_factory=set)

storage_writes

60
    storage_writes: Dict[Address, Dict[Bytes32, U256]] = field(
61
        default_factory=dict
62
    )

code_writes

63
    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.

storage_reads and account_reads are shared references that survive rollback (reads from failed calls still appear in the Block Access List).

66
@final
67
@dataclass
class TransactionState:

parent

79
    parent: BlockState

account_reads

80
    account_reads: Set[Address] = field(default_factory=set)

account_writes

81
    account_writes: Dict[Address, Optional[Account]] = field(
82
        default_factory=dict
83
    )

storage_reads

84
    storage_reads: Set[Tuple[Address, Bytes32]] = field(default_factory=set)

storage_writes

85
    storage_writes: Dict[Address, Dict[Bytes32, U256]] = field(
86
        default_factory=dict
87
    )

code_writes

88
    code_writes: Dict[Hash32, Bytes] = field(default_factory=dict)

created_accounts

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    created_accounts: Set[Address] = field(default_factory=set)

transient_storage

90
    transient_storage: Dict[Tuple[Address, Bytes32], U256] = field(
91
        default_factory=dict
92
    )

get_pre_state_account_optional

Get the Account object at an address that existed before the current transaction, or None (rather than EMPTY_ACCOUNT) if there was no account at the address at that point.

Use get_pre_state_account() if the difference between a non-existent account and EMPTY_ACCOUNT isn't important.

Parameters

tx_state : The transaction state. address : Address to look up.

Returns

account : Optional[Account] Account at address before the current transaction.

def get_pre_state_account_optional(​tx_state: TransactionState, ​​address: Address​) -> Optional[Account]:
98
    <snip>
122
    tx_state.account_reads.add(address)
123
    if address in tx_state.parent.account_writes:
124
        return tx_state.parent.account_writes[address]
125
    return tx_state.parent.pre_state.get_account_optional(address)

get_pre_state_account

Get the Account object at an address that existed before the current transaction, or EMPTY_ACCOUNT) if there was no account at the address at that point.

Use get_pre_state_account_optional() if the difference between a non-existent account and EMPTY_ACCOUNT is material.

Parameters

tx_state : The transaction state. address : Address to look up.

Returns

account : Account Account at address before the current transaction.

def get_pre_state_account(​tx_state: TransactionState, ​​address: Address​) -> Account:
131
    <snip>  # noqa: E501
155
    account = get_pre_state_account_optional(tx_state, address)
156
    if account is None:
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        return EMPTY_ACCOUNT
158
    else:
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        return account

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]:
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    <snip>
182
    tx_state.account_reads.add(address)
183
    if address in tx_state.account_writes:
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        return tx_state.account_writes[address]
103
    if address in tx_state.parent.account_writes:
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        return tx_state.parent.account_writes[address]
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    return tx_state.parent.pre_state.get_account_optional(address)
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    return get_pre_state_account_optional(tx_state, 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:
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    <snip>
209
    account = get_account_optional(tx_state, address)
210
    if account is None:
211
        return EMPTY_ACCOUNT
212
    else:
213
        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:
217
    <snip>
235
    if code_hash == EMPTY_CODE_HASH:
236
        return b""
237
    if code_hash in tx_state.code_writes:
238
        return tx_state.code_writes[code_hash]
239
    if code_hash in tx_state.parent.code_writes:
240
        return tx_state.parent.code_writes[code_hash]
241
    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:
247
    <snip>
266
    tx_state.storage_reads.add((address, key))
267
    if address in tx_state.storage_writes:
268
        if key in tx_state.storage_writes[address]:
269
            return tx_state.storage_writes[address][key]
270
    if address in tx_state.parent.storage_writes:
271
        if key in tx_state.parent.storage_writes[address]:
272
            return tx_state.parent.storage_writes[address][key]
273
    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:
279
    <snip>
295
    if address in tx_state.created_accounts:
296
        return U256(0)
297
    if address in tx_state.parent.storage_writes:
298
        if key in tx_state.parent.storage_writes[address]:
299
            return tx_state.parent.storage_writes[address][key]
300
    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:
306
    <snip>
325
    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:
329
    <snip>
345
    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:
349
    <snip>
352
    account = get_account(tx_state, address)
353
    if account.nonce != Uint(0) or account.code_hash != EMPTY_CODE_HASH:
354
        return False
355
356
    if account_has_storage(tx_state, address):
357
        return False
358
359
    return True

account_has_storage

Check if an account has storage.

Parameters

tx_state : The transaction state. address : Address of the account that needs to be checked.

Returns

has_storage : bool True if the account has storage, False otherwise.

def account_has_storage(​tx_state: TransactionState, ​​address: Address​) -> bool:
363
    <snip>
379
    if tx_state.storage_writes.get(address):
380
        return True
381
    if tx_state.parent.storage_writes.get(address):
382
        return True
383
    return tx_state.parent.pre_state.account_has_storage(address)

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:
389
    <snip>
407
    account = get_account_optional(tx_state, address)
408
    return (
409
        account is not None
410
        and account.nonce == Uint(0)
411
        and account.code_hash == EMPTY_CODE_HASH
412
        and account.balance == 0
413
    )

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:
417
    <snip>
433
    account = get_account_optional(tx_state, address)
434
    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:
442
    <snip>
457
    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:
466
    <snip>
481
    assert get_account_optional(tx_state, address) is not None
482
    if address not in tx_state.storage_writes:
483
        tx_state.storage_writes[address] = {}
484
    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 Invoked by SELFDESTRUCTmodify_state (and the coinbase fee-credit path) to opcode. It is expected that SELFDESTRUCT will be disabled in aclean up an account that has become empty (zero nonce, empty future hardfork and this function will be removed. Only supports same transaction destruction.code, and zero balance) so it does not appear in the post-state.

Parameters

tx_state : The transaction state. address : Address of account to destroy.

def destroy_account(​tx_state: TransactionState, ​​address: Address​) -> None:
488
    <snip>
503
    destroy_storage(tx_state, address)
504
    set_account(tx_state, address, None)

clear_account_preserving_balance

Clear an account's nonce, code, and storage while preserving its balance.

Parameters

tx_state : The transaction state. address : Address of the account to modify.

def clear_account_preserving_balance(​tx_state: TransactionState, ​​address: Address​) -> None:
510
    <snip>
522
523
    def clear_account(account: Account) -> None:
524
        account.nonce = Uint(0)
525
        account.code_hash = EMPTY_CODE_HASH
526
527
    destroy_storage(tx_state, address)
528
    modify_state(tx_state, address, clear_account)

destroy_storage

Completely remove the storage at address.

Only supports same transaction destruction.Convert storage writes to reads before deleting so that accesses from created-then-destroyed accounts appear in the Block Access List. 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:
532
    <snip>
547
    if address in tx_state.storage_writes:
442
        del tx_state.storage_writes[address]
548
        for key in tx_state.storage_writes[address]:
549
            tx_state.storage_reads.add((address, key))
550
        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:
554
    <snip>
572
    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.

def set_transient_storage(​tx_state: TransactionState, ​​address: Address, ​​key: Bytes32, ​​value: U256​) -> None:
581
    <snip>
596
    if value == U256(0):
597
        tx_state.transient_storage.pop((address, key), None)
598
    else:
599
        tx_state.transient_storage[(address, key)] = value

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:
607
    <snip>
612
    set_account(tx_state, address, modify(get_account(tx_state, address), f))
613
    if account_exists_and_is_empty(tx_state, address):
614
        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:
623
    <snip>
638
639
    def reduce_sender_balance(sender: Account) -> None:
640
        if sender.balance < amount:
641
            raise AssertionError
642
        sender.balance -= amount
643
644
    def increase_recipient_balance(recipient: Account) -> None:
645
        recipient.balance += amount
646
647
    modify_state(tx_state, sender_address, reduce_sender_balance)
648
    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:
654
    <snip>
667
668
    def increase_balance(account: Account) -> None:
669
        account.balance += amount
670
671
    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:
677
    <snip>
690
691
    def set_balance(account: Account) -> None:
692
        account.balance = amount
693
694
    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:
698
    <snip>
709
710
    def increase_nonce(sender: Account) -> None:
711
        sender.nonce += Uint(1)
712
713
    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:
719
    <snip>
732
    code_hash = keccak256(code)
733
    if code_hash != EMPTY_CODE_HASH:
734
        tx_state.code_writes[code_hash] = code
735
736
    def write_code_hash(sender: Account) -> None:
737
        sender.code_hash = code_hash
738
739
    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 andDeep-copy writes and transient storage. The parent reference, created_accounts are shared (not rolled back)., storage_reads, and account_reads 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:
746
    <snip>
764
    return TransactionState(
765
        parent=tx_state.parent,
766
        account_writes=dict(tx_state.account_writes),
767
        storage_writes={
768
            addr: dict(slots)
769
            for addr, slots in tx_state.storage_writes.items()
770
        },
771
        code_writes=dict(tx_state.code_writes),
772
        created_accounts=tx_state.created_accounts,
773
        transient_storage=dict(tx_state.transient_storage),
774
        storage_reads=tx_state.storage_reads,
775
        account_reads=tx_state.account_reads,
776
    )

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:
782
    <snip>
793
    tx_state.account_writes = snapshot.account_writes
794
    tx_state.storage_writes = snapshot.storage_writes
795
    tx_state.code_writes = snapshot.code_writes
796
    tx_state.transient_storage = snapshot.transient_storage

incorporate_tx_into_block

Merge transaction writes into the block state and clear for reuse.

Update the BAL builder incrementally by diffing this transaction's writes against the block's cumulative state. Merge reads and touches into block-level sets.

Parameters

tx_state : The transaction state to commit. builder : The BAL builder for incremental updates.

def incorporate_tx_into_block(​tx_state: TransactionState, ​​builder: "BlockAccessListBuilder"​) -> None:
806
    <snip>
821
    from .block_access_lists import update_builder_from_tx
822
823
    block = tx_state.parent
824
703
    for address, account in tx_state.account_writes.items():
825
    # Update BAL builder before merging writes into block state
826
    update_builder_from_tx(builder, tx_state)
827
828
    # Merge reads and touches into block-level sets
829
    block.storage_reads.update(tx_state.storage_reads)
830
    block.account_reads.update(tx_state.account_reads)
831
832
    # Merge cumulative writes
833
    for address, account in tx_state.account_writes.items():
834
        block.account_writes[address] = account
835
836
    for address, slots in tx_state.storage_writes.items():
837
        if address not in block.storage_writes:
838
            block.storage_writes[address] = {}
839
        block.storage_writes[address].update(slots)
840
841
    block.code_writes.update(tx_state.code_writes)
842
843
    tx_state.account_writes.clear()
844
    tx_state.storage_writes.clear()
845
    tx_state.code_writes.clear()
846
    tx_state.created_accounts.clear()
717
    tx_state.transient_storage.clear()
847
    tx_state.transient_storage.clear()
848
    tx_state.storage_reads = set()
849
    tx_state.account_reads = set()

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.

def extract_block_diff(​block_state: BlockState​) -> BlockDiff:
853
    <snip>
867
    return BlockDiff(
868
        account_changes=block_state.account_writes,
869
        storage_changes=block_state.storage_writes,
870
        code_changes=block_state.code_writes,
871
    )