uniswap-universal-router-decoder 1.2.1

Decode & Encode transactions sent to the Uniswap Universal Router

Uniswap Universal Router Decoder & Encoder

Many thanks to everyone who has ☕️ offered some coffees! ☕️ or ⭐ starred this project! ⭐
It is greatly appreciated! :)

---

Project Information

Code Quality

---

Release Notes

v1.2.1

• Add support for web3 v7
• Add support for Python 3.12 & 3.13

v1.2.0

• Add compute_gas_fees(): utility function to compute gas fees
• Add build_transaction() method: It's now possible to build the full transaction i/o just the input data.
• Add fetch_permit2_allowance(): Easy way to check the current Permit2 allowed amount, expiration and nonce.
• Make verifying contract (Permit2) configurable (Thanks to @speedssr and @freereaper)
• Replace deprecated eth_account.encode_structured_data() with eth_account.messages.encode_typed_data()

v1.1.0

• Add support for the TRANSFER function
• Add support for decoding the "revert on fail" flag and prepare for encoding on UR functions that support it.
• Add support for encoding the execute() function without deadline

---

Overview and Points of Attention

The object of this library is to decode & encode the transaction input sent to the Uniswap universal router (UR) (address 0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD on Ethereum Mainnet). It is based on, and is intended to be used with web3.py
The target audience is Python developers who are familiar with the Ethereum blockchain concepts and web3.py, and how DEXes work.

⚠ This library has not been audited, so use at your own risk !

⚠ Before using this library, ensure you are familiar with general blockchain concepts and web3.py in particular.

⚠ This project is a work in progress so not all commands are decoded yet. Below the list of the already implemented ones.

Command Id	Function Name	Decode	Encode
0x00	V3_SWAP_EXACT_IN	✅	✅
0x01	V3_SWAP_EXACT_OUT	✅	✅
0x02 - 0x03		❌	❌
0x04	SWEEP	✅	✅
0x05	TRANSFER	✅	✅
0x06	PAY_PORTION	✅	✅
0x07	placeholder	N/A	N/A
0x08	V2_SWAP_EXACT_IN	✅	✅
0x09	V2_SWAP_EXACT_OUT	✅	✅
0x0a	PERMIT2_PERMIT	✅	✅
0x0b	WRAP_ETH	✅	✅
0x0c	UNWRAP_WETH	✅	✅
0x0d	PERMIT2_TRANSFER_FROM_BATCH	❌	❌
0x0e - 0x0f	placeholders	N/A	N/A
0x10 - 0x1d		❌	❌
0x1e - 0x3f	placeholders	N/A	N/A

---

Installation

A good practice is to use Python virtual environments, here is a tutorial.

The library can be pip installed from pypi.org as usual:

# update pip to latest version if needed
pip install -U pip

# install the decoder from pypi.org
pip install uniswap-universal-router-decoder

---

Usage

The library exposes a class, RouterCodec with several public methods that can be used to decode or encode UR data.

How to decode a transaction input

To decode a transaction input, use the decode.function_input() method as follows:

from uniswap_universal_router_decoder import RouterCodec

trx_input = "0x3593564c000000000000000000 ... 90095b5c4e9f5845bba"  # the trx input to decode
codec = RouterCodec()
decoded_trx_input = codec.decode.function_input(trx_input)

Example of decoded input returned by decode.function_input():

(
    <Function execute(bytes,bytes[],uint256)>,  # the UR function that executes all commands
    {
        'commands': b'\x0b\x00',  # the list of commands sent to the UR
        'inputs': [  # the inputs used for each command
            (
                <Function WRAP_ETH(address,uint256)>,  # the function corresponding to the first command
                {                                      # and its parameters
                    'recipient': '0x0000000000000000000000000000000000000002',  # code indicating the recipient of this command is the router
                    'amountMin': 4500000000000000000  # the amount in WEI to wrap
                },
                {
                    'revert_on_fail': True  # flag indicating if the transaction must revert when this command fails
                },
            ),
            (
                <Function V3_SWAP_EXACT_IN(address,uint256,uint256,bytes,bool)>,  # the function corresponding to the second command
                {                                                                 # and its parameters
                    'recipient': '0x0000000000000000000000000000000000000001',  # code indicating the sender will receive the output of this command
                    'amountIn': 4500000000000000000,  # the exact amount sent
                    'amountOutMin': 6291988002,  # the min amount expected of the bought token for the swap to be executed 
                    'path': b"\xc0*\xaa9\xb2#\xfe\x8d\n\x0e\\O'\xea\xd9\x08<ul\xc2"  # the V3 path (tokens + pool fees)
                           b'\x00\x01\xf4\xa0\xb8i\x91\xc6!\x8b6\xc1\xd1\x9dJ.'  # can be decoded with the method decode.v3_path()
                           b'\x9e\xb0\xce6\x06\xebH',
                    'payerIsSender': False  # a bool indicating if the input tokens come from the sender or are already in the UR
                },
                {
                    'revert_on_fail': True  # flag indicating if the transaction must revert when this command fails
                },
            )
        ],
        'deadline': 1678441619  # The deadline after which the transaction is not valid any more.
    }
)

How to decode a transaction

It's also possible to decode the whole transaction, given its hash and providing the codec has been built with either a valid Web3 instance or the link to a rpc endpoint:

# Using a web3 instance
from web3 import Web3
from uniswap_universal_router_decoder import RouterCodec
w3 = Web3(...)  # your web3 instance
codec = RouterCodec(w3=w3)

# Using a rpc endpoint
from web3 import Web3
from uniswap_universal_router_decoder import RouterCodec
rpc_link = "https://..."  # your rpc endpoint
codec = RouterCodec(rpc_endpoint=rpc_link)

And then the decoder will get the transaction from the blockchain and decode it, along with its input data:

trx_hash = "0x52e63b7 ... 11b979dd9"
decoded_transaction = codec.decode.transaction(trx_hash)

How to decode an Uniswap V3 swap path

The RouterCodec class exposes also the method decode.v3_path() which can be used to decode a given Uniswap V3 path.

from uniswap_universal_router_decoder import RouterCodec

uniswap_v3_path = b"\xc0*\xaa9\xb2#\xfe\x8d\n\x0e ... \xd7\x89"  # bytes or str hex
fn_name = "V3_SWAP_EXACT_IN"  # Or V3_SWAP_EXACT_OUT
codec = RouterCodec()
decoded_path = codec.decode.v3_path(fn_name, uniswap_v3_path)

The result is a tuple, starting with the "in-token" and ending with the "out-token", with the pool fees between each pair.

How to encode

The Universal Router allows the chaining of several functions in the same transaction. This codec supports it (at least for supported functions) and exposes public methods that can be chained.

The chaining starts with the encode.chain() method and ends with the build() one which returns the full encoded data to be included in the transaction. Below some examples of encoded data for one function and one example for 2 functions.

Default values for deadlines and expirations can be computed with the static methods get_default_deadline() and get_default_expiration() respectively.

from uniswap_universal_router_decoder import RouterCodec

default_deadline = RouterCodec.get_default_deadline()
default_expiration = RouterCodec.get_default_expiration()

These 2 functions accept a custom duration in seconds as argument.

How to encode a call to the function WRAP_ETH

This function can be used to convert eth to weth using the UR.

from uniswap_universal_router_decoder import FunctionRecipient, RouterCodec

codec = RouterCodec()
encoded_data = codec.encode.chain().wrap_eth(FunctionRecipient.SENDER, amount_in_wei).build(1676825611)  # to convert amount_in_wei eth to weth, and send them to the transaction sender.

# then in your transaction dict:
transaction["data"] = encoded_data

# you can now sign and send the transaction to the UR

How to encode a call to the function V2_SWAP_EXACT_IN

This function can be used to swap tokens on a V2 pool. Correct allowances must have been set before sending such transaction.

from uniswap_universal_router_decoder import FunctionRecipient, RouterCodec

codec = RouterCodec()
encoded_data = codec.encode.chain().v2_swap_exact_in(
        FunctionRecipient.SENDER,  # the output tokens are sent to the transaction sender
        amount_in,  # in Wei
        min_amount_out,  # in Wei
        [
            in_token_address,  # checksum address of the token sent to the UR 
            out_token_address,  # checksum address of the received token
        ],
    ).build(timestamp)  # unix timestamp after which the trx will not be valid any more

# then in your transaction dict:
transaction["data"] = encoded_data

# you can now sign and send the transaction to the UR

For more details, see this tutorial

How to encode a call to the function V2_SWAP_EXACT_OUT

This function can be used to swap tokens on a V2 pool. Correct allowances must have been set before sending such transaction.

from uniswap_universal_router_decoder import FunctionRecipient, RouterCodec

codec = RouterCodec()
encoded_data = codec.encode.chain().v2_swap_exact_out(
        FunctionRecipient.SENDER,
        amount_out,  # in Wei
        max_amount_in,  # in Wei
        [
            in_token_address,
            out_token_address,
        ],
    ).build(timestamp)  # unix timestamp after which the trx will not be valid any more

# then in your transaction dict:
transaction["data"] = encoded_data
# you can now sign and send the transaction to the UR

How to encode a call to the function V3_SWAP_EXACT_IN

This function can be used to swap tokens on a V3 pool. Correct allowances must have been set before using sending such transaction.

from uniswap_universal_router_decoder import FunctionRecipient, RouterCodec

codec = RouterCodec()
encoded_data = codec.encode.chain().v3_swap_exact_in(
        FunctionRecipient.SENDER,
        amount_in,  # in Wei
        min_amount_out,  # in Wei
        [
            in_token_address,
            pool_fee,
            out_token_address,
        ],
    ).build(timestamp)  # unix timestamp after which the trx will not be valid any more

# then in your transaction dict:
transaction["data"] = encoded_data

# you can now sign and send the transaction to the UR

How to encode a call to the function V3_SWAP_EXACT_OUT

This function can be used to swap tokens on a V3 pool. Correct allowances must have been set before sending such transaction.

from uniswap_universal_router_decoder import FunctionRecipient, RouterCodec

codec = RouterCodec()
encoded_data = codec.encode.chain().v3_swap_exact_out(
        FunctionRecipient.SENDER,
        amount_out,  # in Wei
        max_amount_in,  # in Wei
        [
            in_token_address,
            pool_fee,
            out_token_address,
        ],
    ).build(timestamp)  # unix timestamp after which the trx will not be valid any more

# then in your transaction dict:
transaction["data"] = encoded_data
# you can now sign and send the transaction to the UR

How to encode a call to the function PERMIT2_PERMIT

This function is used to give an allowance to the universal router thanks to the Permit2 contract (0x000000000022D473030F116dDEE9F6B43aC78BA3). It is also necessary to approve the Permit2 contract using the token approve function. See this tutorial

from uniswap_universal_router_decoder import RouterCodec

codec = RouterCodec()
data, signable_message = codec.create_permit2_signable_message(
    token_address,
    amount,  # max = 2**160 - 1
    expiration,
    nonce,  # Permit2 nonce, see below how to get it
    spender,  # The UR checksum address
    deadline,
    1,  # chain id
)

# Then you need to sign the message:
signed_message = acc.sign_message(signable_message)  # where acc is your LocalAccount

# And now you can encode the data:
encoded_data = codec.encode.chain().permit2_permit(data, signed_message).build(deadline)

# Then in your transaction dict:
transaction["data"] = encoded_data

# you can now sign and send the transaction to the UR

After that, you can swap tokens using the Uniswap universal router.

How to get the current permit2 allowance, expiration and nonce

You can get the nonce you need to build the permit2 signable message like this:

amount, expiration, nonce = codec.fetch_permit2_allowance(acc.address, token_address)  # where acc is your LocalAccount

How to chain a call to PERMIT2_PERMIT and V2_SWAP_EXACT_IN in the same transaction

Don't forget to give a token allowance to the Permit2 contract as well.

from uniswap_universal_router_decoder import FunctionRecipient, RouterCodec

codec = RouterCodec()

# Permit signature
data, signable_message = codec.create_permit2_signable_message(
    token_address,
    amount,  # max = 2**160 - 1
    expiration,
    nonce,  # Permit2 nonce
    spender,  # The UR checksum address
    deadline,
    1,  # chain id
)

# Then you need to sign the message:
signed_message = acc.sign_message(signable_message)  # where acc is your LocalAccount

# Permit + v2 swap encoding
path = [token_in_address, token_out_address]
encoded_data = (
    codec
        .encode
        .chain()
        .permit2_permit(data, signed_message)
        .v2_swap_exact_in(FunctionRecipient.SENDER, Wei(10**18), Wei(0), path)
        .build(deadline)
)

# Then in your transaction dict:
transaction["data"] = encoded_data

# you can now sign and send the transaction to the UR

Other chainable functions

(See integration tests for full examples)

PAY_PORTION

Example where a recipient is paid 1% of the USDC amount:

.pay_portion(FunctionRecipient.CUSTOM, usdc_address, 100, recipient_address)

SWEEP

Example where the sender gets back all remaining USDC:

.sweep(FunctionRecipient.SENDER, usdc_address, 0)

TRANSFER

Example where an USDC amount is sent to a recipient:

.transfer(FunctionRecipient.CUSTOM, usdc_address, usdc_amount, recipient_address)

How to build directly a transaction

The SDK provides a handy method to build very easily the full transaction in addition to the input data. It can compute most of the transaction parameters (if the codec has been instantiated with a valid w3 or rpc url) or you can provide them.

Example where a swap is encoded and a transaction is built automatically:

from uniswap_universal_router_decoder import FunctionRecipient, RouterCodec

codec = RouterCodec()
trx_params = (
    codec.encode.chain().v2_swap_exact_in(
        FunctionRecipient.SENDER,  # the output tokens are sent to the transaction sender
        amount_in,  # in Wei
        min_amount_out,  # in Wei
        [
            in_token_address,  # checksum address of the token sent to the UR 
            out_token_address,  # checksum address of the received token
        ],
    ).build_transaction(
        sender_address,  # 'from'
        deadline=timestamp,  # the swap deadline
    )
)

And that's it! You can now sign and send this transaction. A few other important parameters:

• value: the quantity of ETH in wei you send to the Universal Router (for ex when you wrap them before a swap)
• trx_speed: an enum which influences the transaction rank in the block. Values are:
  • TransactionSpeed.SLOW
  • TransactionSpeed.AVERAGE
  • TransactionSpeed.FAST (default)
  • TransactionSpeed.FASTER
• max_fee_per_gas_limit: if the computed max_fee_per_gas is greater than max_fee_per_gas_limit a ValueError will be raised to allow you to stay in control. Default is 100 gwei.

How to use the trx_speed parameter:

from uniswap_universal_router_decoder import TransactionSpeed

.build_transaction(sender_address, trx_speed=TransactionSpeed.FASTER)

Utility functions

How to compute the gas fees

The SDK provides a handy method to compute the current "priority fee" and "max fee per gas":

from uniswap_universal_router_decoder.utils import compute_gas_fees
priority_fee, max_fee_per_gas = compute_gas_fees(w3)  # w3 is a valid Web3 instance

Tutorials and Recipes:

See the SDK Wiki.

News and Q&A:

See the Discussions and 𝕏