def push_n(evm: Evm, num_bytes: int) -> None:
"""
Pushes a N-byte immediate onto the stack.
Parameters
----------
evm :
The current EVM frame.
num_bytes :
The number of immediate bytes to be read from the code and pushed to
the stack.
Raises
------
StackOverflowError
If `len(stack)` is equals `1024`.
OutOfGasError
If `evm.gas_left` is less than `3`.
"""
assert evm.pc + num_bytes < len(evm.code)
evm.gas_left = subtract_gas(evm.gas_left, GAS_VERY_LOW)
data_to_push = U256.from_be_bytes(evm.code[evm.pc + 1:evm.pc + num_bytes +
1])
push(evm.stack, data_to_push)
evm.pc += num_bytes
def signextend(evm: Evm) -> None:
"""
Sign extend operation. In other words, extend a signed number which
fits in N bytes to 32 bytes.
Parameters
----------
evm :
The current EVM frame.
Raises
------
StackUnderflowError
If `len(stack)` is less than `2`.
OutOfGasError
If `evm.gas_left` is less than `5`.
"""
evm.gas_left = subtract_gas(evm.gas_left, GAS_LOW)
# byte_num would be 0-indexed when inserted to the stack.
byte_num = pop(evm.stack)
value = pop(evm.stack)
if byte_num > 31:
# Can't extend any further
result = value
else:
# U256(0).to_be_bytes() gives b'' instead b'\x00'. # noqa: SC100
value_bytes = value.to_be_bytes() or b"\x00"
# Now among the obtained value bytes, consider only
# N `least significant bytes`, where N is `byte_num + 1`.
value_bytes = value_bytes[len(value_bytes) - 1 - byte_num:]
sign_bit = value_bytes[0] >> 7
if sign_bit == 0:
result = U256.from_be_bytes(value_bytes)
else:
num_bytes_prepend = 32 - (byte_num + 1)
result = U256.from_be_bytes(
bytearray([0xFF] * num_bytes_prepend) + value_bytes)
push(evm.stack, result)
def json_to_state(raw: Any) -> State:
state = {}
for (addr, acc_state) in raw.items():
account = Account(
nonce=hex2uint(acc_state.get("nonce", "0x0")),
balance=hex2uint(acc_state.get("balance", "0x0")),
code=hex2bytes(acc_state.get("code", "")),
storage={},
)
for (k, v) in acc_state.get("storage", {}).items():
account.storage[hex2bytes32(k)] = U256.from_be_bytes(
hex2bytes32(v)
)
state[hex2address(addr)] = account
return state
def test_u256_from_be_bytes_too_large() -> None:
with pytest.raises(ValueError):
U256.from_be_bytes(bytes([0xFF] * 33))
def test_u256_from_be_bytes_is_big_endian() -> None:
value = U256.from_be_bytes(bytes([0xAB, 0xCD]))
assert value == 0xABCD
def test_u256_from_be_bytes_one() -> None:
value = U256.from_be_bytes(bytes([1]))
assert value == 1
def test_u256_from_be_bytes_empty() -> None:
value = U256.from_be_bytes(b"")
assert value == 0
