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"""Asset data encoding and decoding utilities."""
from mypy_extensions import TypedDict
import eth_abi
from zero_ex.dev_utils import abi_utils
from zero_ex.dev_utils.type_assertions import assert_is_string
ERC20_ASSET_DATA_BYTE_LENGTH = 36
SELECTOR_LENGTH = 10
class ERC20AssetData(TypedDict):
"""Object interface to ERC20 asset data."""
asset_proxy_id: str
token_address: str
def encode_erc20_asset_data(token_address: str) -> str:
"""Encode an ERC20 token address into an asset data string.
:param token_address: the ERC20 token's contract address.
:rtype: hex encoded asset data string, usable in the makerAssetData or
takerAssetData fields in a 0x order.
>>> encode_erc20_asset_data('0x1dc4c1cefef38a777b15aa20260a54e584b16c48')
'0xf47261b00000000000000000000000001dc4c1cefef38a777b15aa20260a54e584b16c48'
"""
assert_is_string(token_address, "token_address")
return (
"0x"
+ abi_utils.simple_encode("ERC20Token(address)", token_address).hex()
)
def decode_erc20_asset_data(asset_data: str) -> ERC20AssetData:
# docstring considered all one line by pylint: disable=line-too-long
"""Decode an ERC20 assetData hex string.
:param asset_data: String produced by prior call to encode_erc20_asset_data()
>>> decode_erc20_asset_data("0xf47261b00000000000000000000000001dc4c1cefef38a777b15aa20260a54e584b16c48")
{'asset_proxy_id': '0xf47261b0', 'token_address': '0x1dc4c1cefef38a777b15aa20260a54e584b16c48'}
""" # noqa: E501 (line too long)
assert_is_string(asset_data, "asset_data")
if len(asset_data) < ERC20_ASSET_DATA_BYTE_LENGTH:
raise ValueError(
"Could not decode ERC20 Proxy Data. Expected length of encoded"
+ f" data to be at least {str(ERC20_ASSET_DATA_BYTE_LENGTH)}."
+ f" Got {str(len(asset_data))}."
)
asset_proxy_id: str = asset_data[0:10]
if asset_proxy_id != abi_utils.method_id("ERC20Token", ["address"]):
raise ValueError(
"Could not decode ERC20 Proxy Data. Expected Asset Proxy Id to be"
+ f" ERC20 ({abi_utils.method_id('ERC20Token', ['address'])})"
+ f" but got {asset_proxy_id}."
)
# workaround for https://github.com/PyCQA/pylint/issues/1498
# pylint: disable=unsubscriptable-object
token_address = eth_abi.decode_abi(
["address"], bytes.fromhex(asset_data[SELECTOR_LENGTH:])
)[0]
return {"asset_proxy_id": asset_proxy_id, "token_address": token_address}
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