请求协助：解析BSC原始十六进制交易数据计算代币兑换价格

我正在开发一款工具，需要从Binance Smart Chain（BSC）获取最新Swap交易数据，目标是把日志输出的原始十六进制数据转换为实际的代币兑换价格。

提供的Swap日志示例（PERRY/WBNB交易对） #

{
    'address': '0x560a3375c67c8ad4c13018c87633e6066477151f',
    'topics': [
        '0x19b47279256b2a23a1665c810c8d55a1758940ee09377d4f8d26497a3577dc83',
        '0x00000000000000000000000013f4ea83d0bd40e75c8222255bc855a974568dd4',
        '0x00000000000000000000000068f9dd546d6dadf72862fda46910e5d9bed93321'
    ],
    'data': '0xffffffffffffffffffffffffffffffffffffffffffffbc79ad35ea205f38ecd30000000000000000000000000000000000000000000000001bac1c6f72210000000000000000000000000000000000000000000000a3f94aae886f87faa0174e000000000000000000000000000000000000000000000f0a82803a369f4c9774fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe2bf500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000016ab4dc5620000',
    'blockNumber': '0x2c7f78c',
    'transactionHash': '0x468655b34618fef300638a2cf72e4668f7f7851bcbd69543b52081743dc55f43',
    'transactionIndex': '0x2',
    'blockHash': '0xff7781a757058ada921f5f12696825c8b772ee071dc67bef97b74273f78b3004',
    'logIndex': '0x9',
    'removed': False
}

我尝试的代码（无法得到正确价格） #

from web3 import Web3
data = "0x00000000000000000000000000000000000000000000cd27cac5635ee2dc3373ffffffffffffffffffffffffffffffffffffffffffffffffcc666e6a579a81c40000000000000000000000000000000000000000007f5079c6974c18eb15de37000000000000000000000000000000000000000000000ee6581d2f59caeb088afffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe182f0000000000000000000000000000000000000000000000a81036b2e7516aca810000000000000000000000000000000000000000000000000000000000000000"
decoded_data = Web3.to_bytes(hexstr=data)
chunks = [decoded_data[i:i+32] for i in range(0, len(decoded_data), 32)]
values = [int.from_bytes(chunk, byteorder="big", signed=True) for chunk in chunks]
for i, value in enumerate(values):
    print(f"Slot {i}: {value}")
amount_in = abs(values[2]) / 1e18
amount_out = abs(values[3]) / 1e18
swap_price = amount_out / amount_in

解决方案：用ABI解码Swap事件 #

你的问题出在手动分割数据并错误处理有符号整数上。BSC上的Swap交易大多基于Uniswap V2协议，其Swap事件有固定的ABI，直接用Web3的ABI解码工具才能准确提取数据。

步骤1：使用Uniswap V2 Swap事件ABI #

[
    {
        "anonymous": false,
        "inputs": [
            {"indexed": true, "internalType": "address", "name": "sender", "type": "address"},
            {"indexed": false, "internalType": "uint256", "name": "amount0In", "type": "uint256"},
            {"indexed": false, "internalType": "uint256", "name": "amount1In", "type": "uint256"},
            {"indexed": false, "internalType": "uint256", "name": "amount0Out", "type": "uint256"},
            {"indexed": false, "internalType": "uint256", "name": "amount1Out", "type": "uint256"},
            {"indexed": true, "internalType": "address", "name": "to", "type": "address"}
        ],
        "name": "Swap",
        "type": "event"
    }
]

步骤2：正确的解码代码 #

from web3 import Web3

# Swap事件ABI
swap_abi = [
    {
        "anonymous": False,
        "inputs": [
            {"indexed": True, "internalType": "address", "name": "sender", "type": "address"},
            {"indexed": False, "internalType": "uint256", "name": "amount0In", "type": "uint256"},
            {"indexed": False, "internalType": "uint256", "name": "amount1In", "type": "uint256"},
            {"indexed": False, "internalType": "uint256", "name": "amount0Out", "type": "uint256"},
            {"indexed": False, "internalType": "uint256", "name": "amount1Out", "type": "uint256"},
            {"indexed": True, "internalType": "address", "name": "to", "type": "address"}
        ],
        "name": "Swap",
        "type": "event"
    }
]

# 你的Swap日志数据
log = {
    'address': '0x560a3375c67c8ad4c13018c87633e6066477151f',
    'topics': ['0x19b47279256b2a23a1665c810c8d55a1758940ee09377d4f8d26497a3577dc83', '0x00000000000000000000000013f4ea83d0bd40e75c8222255bc855a974568dd4', '0x00000000000000000000000068f9dd546d6dadf72862fda46910e5d9bed93321'],
    'data': '0xffffffffffffffffffffffffffffffffffffffffffffbc79ad35ea205f38ecd30000000000000000000000000000000000000000000000001bac1c6f72210000000000000000000000000000000000000000000000a3f94aae886f87faa0174e000000000000000000000000000000000000000000000f0a82803a369f4c9774fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe2bf500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000016ab4dc5620000',
    'blockNumber': '0x2c7f78c',
    'transactionHash': '0x468655b34618fef300638a2cf72e4668f7f7851bcbd69543b52081743dc55f43',
    'transactionIndex': '0x2',
    'blockHash': '0xff7781a757058ada921f5f12696825c8b772ee071dc67bef97b74273f78b3004',
    'logIndex': '0x9',
    'removed': False
}

# 初始化Web3实例（无需连接节点即可解码）
w3 = Web3()

# 解码日志数据
decoded_swap = w3.eth.abi.decode_log(swap_abi[0]['inputs'], log['data'], log['topics'])

# 提取金额参数
amount0_in = decoded_swap['amount0In']
amount1_in = decoded_swap['amount1In']
amount0_out = decoded_swap['amount0Out']
amount1_out = decoded_swap['amount1Out']

# 假设交易对中token0是PERRY，token1是WBNB，两者小数位数均为18
perry_decimals = 18
wbnb_decimals = 18

# 判断交易方向并计算价格
if amount0_in > 0 and amount1_out > 0:
    # PERRY兑换WBNB：1 PERRY = X WBNB
    perry_amount = amount0_in / (10 ** perry_decimals)
    wbnb_amount = amount1_out / (10 ** wbnb_decimals)
    price = wbnb_amount / perry_amount
    print(f"1 PERRY = {price:.8f} WBNB")
elif amount1_in > 0 and amount0_out > 0:
    # WBNB兑换PERRY：1 WBNB = X PERRY
    wbnb_amount = amount1_in / (10 ** wbnb_decimals)
    perry_amount = amount0_out / (10 ** perry_decimals)
    price = perry_amount / wbnb_amount
    print(f"1 WBNB = {price:.8f} PERRY")
else:
    print("无效的Swap交易数据")

关键说明 #

1. ABI解码更可靠：手动分割十六进制数据容易出错，ABI定义了事件的参数类型和顺序，解码结果准确。
2. 无符号整数处理：Swap事件的金额都是uint256（无符号整数），不需要用signed=True解析，避免负数错误。
3. 代币小数位数：不同代币的小数位数可能不同，需要提前确认（比如WBNB是18位，PERRY需查询合约确认）。

内容的提问来源于stack exchange，提问作者luminusresearch