example_erc20_gas/
main.rs

1//! Example of a custom handler for ERC20 gas calculation.
2//!
3//! Gas is going to be deducted from ERC20 token.
4
5#![cfg_attr(not(test), warn(unused_crate_dependencies))]
6
7use alloy_provider::{network::Ethereum, DynProvider, Provider, ProviderBuilder};
8use alloy_sol_types::SolValue;
9use anyhow::Result;
10use exec::transact_erc20evm_commit;
11use revm::{
12    context_interface::{
13        result::{InvalidHeader, InvalidTransaction},
14        ContextTr, JournalTr,
15    },
16    database::{AlloyDB, BlockId, CacheDB},
17    database_interface::WrapDatabaseAsync,
18    primitives::{
19        address, hardfork::SpecId, keccak256, Address, StorageValue, TxKind, KECCAK_EMPTY, U256,
20    },
21    state::AccountInfo,
22    Context, Database, MainBuilder, MainContext,
23};
24
25/// Execution utilities for ERC20 gas payment transactions
26pub mod exec;
27/// Custom handler implementation for ERC20 gas payment
28pub mod handler;
29
30type AlloyCacheDB = CacheDB<WrapDatabaseAsync<AlloyDB<Ethereum, DynProvider>>>;
31
32// Constants
33/// USDC token address on Ethereum mainnet
34pub const TOKEN: Address = address!("a0b86991c6218b36c1d19d4a2e9eb0ce3606eb48");
35/// Treasury address that receives ERC20 gas payments
36pub const TREASURY: Address = address!("0000000000000000000000000000000000000001");
37
38#[tokio::main]
39async fn main() -> Result<()> {
40    // Initialize the Alloy provider and database
41    let rpc_url = "https://mainnet.infura.io/v3/c60b0bb42f8a4c6481ecd229eddaca27";
42    let provider = ProviderBuilder::new().connect(rpc_url).await?.erased();
43
44    let alloy_db = WrapDatabaseAsync::new(AlloyDB::new(provider, BlockId::latest())).unwrap();
45    let mut cache_db = CacheDB::new(alloy_db);
46
47    // Random empty account: From
48    let account = address!("18B06aaF27d44B756FCF16Ca20C1f183EB49111f");
49    // Random empty account: To
50    let account_to = address!("21a4B6F62E51e59274b6Be1705c7c68781B87C77");
51
52    // USDC has 6 decimals
53    let hundred_tokens = U256::from(100_000_000_000_000_000u128);
54
55    let balance_slot = erc_address_storage(account);
56    println!("Balance slot: {balance_slot}");
57    cache_db
58        .insert_account_storage(TOKEN, balance_slot, hundred_tokens * StorageValue::from(2))
59        .unwrap();
60    cache_db.insert_account_info(
61        account,
62        AccountInfo {
63            nonce: 0,
64            balance: hundred_tokens * U256::from(2),
65            code_hash: KECCAK_EMPTY,
66            code: None,
67        },
68    );
69
70    let balance_before = balance_of(account, &mut cache_db).unwrap();
71    println!("Balance before: {balance_before}");
72
73    // Transfer 100 tokens from account to account_to
74    // Magic happens here with custom handlers
75    transfer(account, account_to, hundred_tokens, &mut cache_db)?;
76
77    let balance_after = balance_of(account, &mut cache_db)?;
78    println!("Balance after: {balance_after}");
79
80    Ok(())
81}
82
83/// Helpers
84pub fn token_operation<CTX, ERROR>(
85    context: &mut CTX,
86    sender: Address,
87    recipient: Address,
88    amount: U256,
89) -> Result<(), ERROR>
90where
91    CTX: ContextTr,
92    ERROR: From<InvalidTransaction> + From<InvalidHeader> + From<<CTX::Db as Database>::Error>,
93{
94    let sender_balance_slot = erc_address_storage(sender);
95    let sender_balance = context
96        .journal_mut()
97        .sload(TOKEN, sender_balance_slot)?
98        .data;
99
100    if sender_balance < amount {
101        return Err(ERROR::from(
102            InvalidTransaction::MaxFeePerBlobGasNotSupported,
103        ));
104    }
105    // Subtract the amount from the sender's balance
106    let sender_new_balance = sender_balance.saturating_sub(amount);
107    context
108        .journal_mut()
109        .sstore(TOKEN, sender_balance_slot, sender_new_balance)?;
110
111    // Add the amount to the recipient's balance
112    let recipient_balance_slot = erc_address_storage(recipient);
113    let recipient_balance = context
114        .journal_mut()
115        .sload(TOKEN, recipient_balance_slot)?
116        .data;
117
118    let recipient_new_balance = recipient_balance.saturating_add(amount);
119    context
120        .journal_mut()
121        .sstore(TOKEN, recipient_balance_slot, recipient_new_balance)?;
122
123    Ok(())
124}
125
126fn balance_of(address: Address, alloy_db: &mut AlloyCacheDB) -> Result<StorageValue> {
127    let slot = erc_address_storage(address);
128    alloy_db.storage(TOKEN, slot).map_err(From::from)
129}
130
131fn transfer(from: Address, to: Address, amount: U256, cache_db: &mut AlloyCacheDB) -> Result<()> {
132    let mut ctx = Context::mainnet()
133        .with_db(cache_db)
134        .modify_cfg_chained(|cfg| {
135            cfg.spec = SpecId::CANCUN;
136        })
137        .modify_tx_chained(|tx| {
138            tx.caller = from;
139            tx.kind = TxKind::Call(to);
140            tx.value = amount;
141            tx.gas_price = 2;
142        })
143        .modify_block_chained(|b| {
144            b.basefee = 1;
145        })
146        .build_mainnet();
147
148    transact_erc20evm_commit(&mut ctx).unwrap();
149
150    Ok(())
151}
152
153/// Calculates the storage slot for an ERC20 balance mapping.
154/// This implements the standard Solidity mapping storage layout where
155/// slot = keccak256(abi.encode(address, slot_number))
156pub fn erc_address_storage(address: Address) -> U256 {
157    keccak256((address, U256::from(4)).abi_encode()).into()
158}
example_erc20_gas/main.rs

example_erc20_gas/
main.rs
