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.

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@dataclass
class BlockState:

pre_state

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    pre_state: PreState

account_reads

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

account_writes

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

storage_reads

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

storage_writes

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

code_writes

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    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).

65
@dataclass
class TransactionState:

parent

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    parent: BlockState

account_reads

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

account_writes

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

storage_reads

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

storage_writes

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

code_writes

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    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

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

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>
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    tx_state.account_reads.add(address)
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    if address in tx_state.account_writes:
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        return tx_state.account_writes[address]
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    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)

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>
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    account = get_account_optional(tx_state, address)
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    if account is None:
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        return EMPTY_ACCOUNT
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    else:
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        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:
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    <snip>
168
    if code_hash == EMPTY_CODE_HASH:
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        return b""
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    if code_hash in tx_state.code_writes:
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        return tx_state.code_writes[code_hash]
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    if code_hash in tx_state.parent.code_writes:
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        return tx_state.parent.code_writes[code_hash]
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    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:
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    <snip>
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    tx_state.storage_reads.add((address, key))
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    if address in tx_state.storage_writes:
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        if key in tx_state.storage_writes[address]:
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            return tx_state.storage_writes[address][key]
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    if address in tx_state.parent.storage_writes:
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        if key in tx_state.parent.storage_writes[address]:
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            return tx_state.parent.storage_writes[address][key]
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    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:
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    <snip>
228
    if address in tx_state.created_accounts:
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        return U256(0)
230
    if address in tx_state.parent.storage_writes:
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        if key in tx_state.parent.storage_writes[address]:
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            return tx_state.parent.storage_writes[address][key]
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    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:
239
    <snip>
258
    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:
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    <snip>
278
    return get_account_optional(tx_state, address) is not None

account_has_code_or_nonce

Check if an account has non-zero nonce or non-empty code.

Parameters

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

Returns

has_code_or_nonce : bool True if the account has non-zero nonce or non-empty code, False otherwise.

def account_has_code_or_nonce(​tx_state: TransactionState, ​​address: Address​) -> bool:
284
    <snip>
301
    account = get_account(tx_state, address)
302
    return account.nonce != Uint(0) or account.code_hash != EMPTY_CODE_HASH

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:
306
    <snip>
322
    if tx_state.storage_writes.get(address):
323
        return True
324
    if tx_state.parent.storage_writes.get(address):
325
        return True
326
    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:
332
    <snip>
350
    account = get_account_optional(tx_state, address)
351
    return (
352
        account is not None
353
        and account.nonce == Uint(0)
354
        and account.code_hash == EMPTY_CODE_HASH
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        and account.balance == 0
356
    )

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:
360
    <snip>
376
    account = get_account_optional(tx_state, address)
377
    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:
385
    <snip>
400
    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:
409
    <snip>
424
    assert get_account_optional(tx_state, address) is not None
425
    if address not in tx_state.storage_writes:
426
        tx_state.storage_writes[address] = {}
427
    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:
431
    <snip>
447
    destroy_storage(tx_state, address)
448
    set_account(tx_state, address, None)

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:
452
    <snip>
467
    if address in tx_state.storage_writes:
450
        del tx_state.storage_writes[address]
468
        for key in tx_state.storage_writes[address]:
469
            tx_state.storage_reads.add((address, key))
470
        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:
474
    <snip>
492
    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:
501
    <snip>
516
    if value == U256(0):
517
        tx_state.transient_storage.pop((address, key), None)
518
    else:
519
        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:
527
    <snip>
532
    set_account(tx_state, address, modify(get_account(tx_state, address), f))
533
    if account_exists_and_is_empty(tx_state, address):
534
        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:
543
    <snip>
558
559
    def reduce_sender_balance(sender: Account) -> None:
560
        if sender.balance < amount:
561
            raise AssertionError
562
        sender.balance -= amount
563
564
    def increase_recipient_balance(recipient: Account) -> None:
565
        recipient.balance += amount
566
567
    modify_state(tx_state, sender_address, reduce_sender_balance)
568
    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:
574
    <snip>
587
588
    def increase_balance(account: Account) -> None:
589
        account.balance += amount
590
591
    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:
597
    <snip>
610
611
    def set_balance(account: Account) -> None:
612
        account.balance = amount
613
614
    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:
618
    <snip>
629
630
    def increase_nonce(sender: Account) -> None:
631
        sender.nonce += Uint(1)
632
633
    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:
639
    <snip>
652
    code_hash = keccak256(code)
653
    if code_hash != EMPTY_CODE_HASH:
654
        tx_state.code_writes[code_hash] = code
655
656
    def write_code_hash(sender: Account) -> None:
657
        sender.code_hash = code_hash
658
659
    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:
666
    <snip>
684
    return TransactionState(
685
        parent=tx_state.parent,
686
        account_writes=dict(tx_state.account_writes),
687
        storage_writes={
688
            addr: dict(slots)
689
            for addr, slots in tx_state.storage_writes.items()
690
        },
691
        code_writes=dict(tx_state.code_writes),
692
        created_accounts=tx_state.created_accounts,
693
        transient_storage=dict(tx_state.transient_storage),
694
        storage_reads=tx_state.storage_reads,
695
        account_reads=tx_state.account_reads,
696
    )

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:
702
    <snip>
713
    tx_state.account_writes = snapshot.account_writes
714
    tx_state.storage_writes = snapshot.storage_writes
715
    tx_state.code_writes = snapshot.code_writes
716
    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:
726
    <snip>
741
    from .block_access_lists import update_builder_from_tx
742
743
    block = tx_state.parent
744
711
    for address, account in tx_state.account_writes.items():
745
    # Update BAL builder before merging writes into block state
746
    update_builder_from_tx(builder, tx_state)
747
748
    # Merge reads and touches into block-level sets
749
    block.storage_reads.update(tx_state.storage_reads)
750
    block.account_reads.update(tx_state.account_reads)
751
752
    # Merge cumulative writes
753
    for address, account in tx_state.account_writes.items():
754
        block.account_writes[address] = account
755
756
    for address, slots in tx_state.storage_writes.items():
757
        if address not in block.storage_writes:
758
            block.storage_writes[address] = {}
759
        block.storage_writes[address].update(slots)
760
761
    block.code_writes.update(tx_state.code_writes)
762
763
    tx_state.account_writes.clear()
764
    tx_state.storage_writes.clear()
765
    tx_state.code_writes.clear()
766
    tx_state.created_accounts.clear()
725
    tx_state.transient_storage.clear()
767
    tx_state.transient_storage.clear()
768
    tx_state.storage_reads = set()
769
    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:
773
    <snip>
787
    return BlockDiff(
788
        account_changes=block_state.account_writes,
789
        storage_changes=block_state.storage_writes,
790
        code_changes=block_state.code_writes,
791
    )