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::TxEnv,
13    database::{AlloyDB, BlockId, CacheDB},
14    database_interface::WrapDatabaseAsync,
15    primitives::{address, hardfork::SpecId, keccak256, Address, StorageValue, TxKind, U256},
16    state::AccountInfo,
17    Context, Database, MainBuilder, MainContext,
18};
19
20/// Execution utilities for ERC20 gas payment transactions
21pub mod exec;
22/// Custom handler implementation for ERC20 gas payment
23pub mod handler;
24
25type AlloyCacheDB = CacheDB<WrapDatabaseAsync<AlloyDB<Ethereum, DynProvider>>>;
26
27// Constants
28/// USDC token address on Ethereum mainnet
29pub const TOKEN: Address = address!("a0b86991c6218b36c1d19d4a2e9eb0ce3606eb48");
30/// Treasury address that receives ERC20 gas payments
31pub const TREASURY: Address = address!("0000000000000000000000000000000000000001");
32
33#[tokio::main]
34async fn main() -> Result<()> {
35    // Initialize the Alloy provider and database
36    let rpc_url = "https://mainnet.infura.io/v3/c60b0bb42f8a4c6481ecd229eddaca27";
37    let provider = ProviderBuilder::new().connect(rpc_url).await?.erased();
38
39    let alloy_db = WrapDatabaseAsync::new(AlloyDB::new(provider, BlockId::latest())).unwrap();
40    let mut cache_db = CacheDB::new(alloy_db);
41
42    // Random empty account: From
43    let account = address!("18B06aaF27d44B756FCF16Ca20C1f183EB49111f");
44    // Random empty account: To
45    let account_to = address!("21a4B6F62E51e59274b6Be1705c7c68781B87C77");
46
47    // USDC has 6 decimals
48    let hundred_tokens = U256::from(100_000_000_000_000_000u128);
49
50    let balance_slot = erc_address_storage(account);
51    println!("Balance slot: {balance_slot}");
52    cache_db
53        .insert_account_storage(TOKEN, balance_slot, hundred_tokens * StorageValue::from(2))
54        .unwrap();
55    cache_db.insert_account_info(
56        account,
57        AccountInfo {
58            balance: hundred_tokens * U256::from(2),
59            ..Default::default()
60        },
61    );
62
63    let balance_before = balance_of(account, &mut cache_db).unwrap();
64    println!("Balance before: {balance_before}");
65
66    // Transfer 100 tokens from account to account_to
67    // Magic happens here with custom handlers
68    transfer(account, account_to, hundred_tokens, &mut cache_db)?;
69
70    let balance_after = balance_of(account, &mut cache_db)?;
71    println!("Balance after: {balance_after}");
72
73    Ok(())
74}
75
76fn balance_of(address: Address, alloy_db: &mut AlloyCacheDB) -> Result<StorageValue> {
77    let slot = erc_address_storage(address);
78    alloy_db.storage(TOKEN, slot).map_err(From::from)
79}
80
81fn transfer(from: Address, to: Address, amount: U256, cache_db: &mut AlloyCacheDB) -> Result<()> {
82    let mut ctx = Context::mainnet()
83        .with_db(cache_db)
84        .modify_cfg_chained(|cfg| {
85            cfg.spec = SpecId::CANCUN;
86        })
87        .with_tx(
88            TxEnv::builder()
89                .caller(from)
90                .kind(TxKind::Call(to))
91                .value(amount)
92                .gas_price(2)
93                .build()
94                .unwrap(),
95        )
96        .modify_block_chained(|b| {
97            b.basefee = 1;
98        })
99        .build_mainnet();
100
101    transact_erc20evm_commit(&mut ctx).unwrap();
102
103    Ok(())
104}
105
106/// Calculates the storage slot for an ERC20 balance mapping.
107/// This implements the standard Solidity mapping storage layout where
108/// slot = keccak256(abi.encode(address, slot_number))
109pub fn erc_address_storage(address: Address) -> U256 {
110    keccak256((address, U256::from(4)).abi_encode()).into()
111}
example_erc20_gas/main.rs

example_erc20_gas/
main.rs
