eth-event

Simple tools for Ethereum event decoding and topic generation.

Installation

You can install the latest release via pip:

$ pip install eth-brownie

Or clone the repository and use setuptools for the most up-to-date version:

$ python3 setup.py install

Usage

The package includes the following functions:

• get_event_topic(event_abi): Given an event ABI, returns the 32 byte encoded topic.

>>> from eth_event import get_event_topic
>>> get_event_topic({'name': 'Approval', 'anonymous': False, 'type': 'event', 'inputs': [{'name': 'owner', 'type': 'address', 'indexed': True}, {'name': 'spender', 'type': 'address', 'indexed': True}, {'name': 'value', 'type': 'uint256', 'indexed': False}]})
'0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925'

• get_topics(contract_abi): Given a contract ABI, returns a dictionary of {'event name': "encrypted topic"}.

>>> from eth_event import get_topics

>>> abi = [{'name': 'Approval', 'anonymous': False, 'type': 'event', 'inputs': [{'name': 'owner', 'type': 'address', 'indexed': True}, {'name': 'spender', 'type': 'address', 'indexed': True}, {'name': 'value', 'type': 'uint256', 'indexed': False}]}, {'name': 'Transfer', 'anonymous': False, 'type': 'event', 'inputs': [{'name': 'from', 'type': 'address', 'indexed': True}, {'name': 'to', 'type': 'address', 'indexed': True}, {'name': 'value', 'type': 'uint256', 'indexed': False}]}]

>>> get_topics(abi)
{'Transfer': '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef', 'Approval': '0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925'}

• get_event_abi(contract_abi): Given a contract ABI, returns a dictionary of {'encrypted topic': "ABI"}. Useful for stripping an ABI so that only event related data remains.

>>> from eth_event import get_event_abi
>>> get_event_abi(abi)
{'0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef': {'name': 'Transfer', 'inputs': [{'name': 'from', 'type': 'address', 'indexed': True}, {'name': 'to', 'type': 'address', 'indexed': True}, {'name': 'value', 'type': 'uint256', 'indexed': False}]}, '0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925': {'name': 'Approval', 'inputs': [{'name': 'owner', 'type': 'address', 'indexed': True}, {'name': 'spender', 'type': 'address', 'indexed': True}, {'name': 'value', 'type': 'uint256', 'indexed': False}]}}

• decode_event(event, abi): Given a single event from a transaction log and an ABI, returns the decoded event. The ABI may supplied in the normal contract format, or as a dictionary value generated by get_event_abi

>>> tx = token.transfer(account[1], 100, {'from': account[0]})
<Transaction object '0xd0b9f575747eafdce3ba6ee8d6c16146bfff35cb86bec0a1909ab04fa94fc024'>

>>> log = tx.logs[0]
>>> eth_event.decode_event(log, token.abi)
{'name': 'Transfer', 'data': [{'name': 'from', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a'}, {'name': 'to', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True}, {'name': 'tokens', 'type': 'uint256', 'value': 100, 'decoded': True}]}

>>> eth_event.decode_event(log, event_abi[log['topics'][0]])
{'name': 'Transfer', 'data': [{'name': 'from', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a'}, {'name': 'to', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True}, {'name': 'tokens', 'type': 'uint256', 'value': 100, 'decoded': True}]}

• decode_logs(logs, abi): Given an entire transaction log and an ABI, returns the decoded events. The ABI may supplied in the normal contract format, or as a dictionary value generated by get_event_abi

>>> tx = token.transfer(account[1], 100, {'from': account[0]})
<Transaction object '0x615a157e84715d5f960a38fe2a3ddb566c8393cfc71f15b06170a0eff74dfdde'>

>>> eth_event.decode_logs(tx.logs, token.abi)
[{'name': 'Transfer', 'data': [{'name': 'from', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a'}, {'name': 'to', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True}, {'name': 'tokens', 'type': 'uint256', 'value': 100, 'decoded': True}]}]

• decode_trace(trace, abi): Given the structLog from a debug_traceTransaction RPC call, returns a list of the decoded events. Useful for obtaining events when a transaction reverts.

>>> tx = token.transfer(account[1], 100, {'from': account[0]})
<Transaction object '0x71a7146996957b8a465a4e5dd41951d614254f8271fc9140b875c4fc55dde578'>

>>> trace = web3.provider.make_request("debug_traceTransaction", ['0x71a7146996957b8a465a4e5dd41951d614254f8271fc9140b875c4fc55dde578', {}])['result']['structLogs]
]
>>> eth_event.decode_trace(trace, token.abi)
[{'name': 'Transfer', 'data': [{'name': 'from', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a'}, {'name': 'to', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True}, {'name': 'tokens', 'type': 'uint256', 'value': 100, 'decoded': True}]}]

Limitations

• If an array is indexed in an event, the topic is generated as a sha3 hash and so cannot be decrypted. In this case, the unencrypted topcic is returned and decoded is set to False.

• Anonymous events cannot be decoded.

Tests

To run the test suite:

$ tox

Development

This project is still in development and should be considered an alpha. Comments, questions, criticisms and pull requests are welcomed.

License

This project is licensed under the MIT license.