foundry_evm_networks/celo/
transfer.rs

1//! Celo precompile implementation for token transfers.
2//!
3//! This module implements the Celo transfer precompile that enables native token transfers from an
4//! EVM contract. The precompile is part of Celo's token duality system, allowing transfer of
5//! native tokens via ERC20.
6//!
7//! For more details, see: <https://specs.celo.org/token_duality.html#the-transfer-precompile>
8//!
9//! The transfer precompile is deployed at address 0xfd and accepts 96 bytes of input:
10//! - from address (32 bytes, left-padded)
11//! - to address (32 bytes, left-padded)
12//! - value (32 bytes, big-endian U256)
13
14use std::borrow::Cow;
15
16use alloy_evm::precompiles::{DynPrecompile, PrecompileInput};
17use alloy_primitives::{Address, U256, address};
18use revm::precompile::{PrecompileError, PrecompileId, PrecompileOutput, PrecompileResult};
19
20/// Address of the Celo transfer precompile.
21pub const CELO_TRANSFER_ADDRESS: Address = address!("0x00000000000000000000000000000000000000fd");
22
23/// ID for the [Celo transfer precompile](CELO_TRANSFER_ADDRESS).
24pub static PRECOMPILE_ID_CELO_TRANSFER: PrecompileId =
25    PrecompileId::Custom(Cow::Borrowed("celo transfer"));
26
27/// Gas cost for Celo transfer precompile.
28const CELO_TRANSFER_GAS_COST: u64 = 9000;
29
30/// Returns the Celo native transfer.
31pub fn precompile() -> DynPrecompile {
32    DynPrecompile::new_stateful(PRECOMPILE_ID_CELO_TRANSFER.clone(), celo_transfer_precompile)
33}
34
35/// Celo transfer precompile implementation.
36///
37/// Uses load_account to modify balances directly, making it compatible with PrecompilesMap.
38pub fn celo_transfer_precompile(input: PrecompileInput<'_>) -> PrecompileResult {
39    // Check minimum gas requirement
40    if input.gas < CELO_TRANSFER_GAS_COST {
41        return Err(PrecompileError::OutOfGas);
42    }
43
44    // Validate input length (must be exactly 96 bytes: 32 + 32 + 32)
45    if input.data.len() != 96 {
46        return Err(PrecompileError::Other(format!(
47            "Invalid input length for Celo transfer precompile: expected 96 bytes, got {}",
48            input.data.len()
49        )));
50    }
51
52    // Parse input: from (bytes 12-32), to (bytes 44-64), value (bytes 64-96)
53    let from_bytes = &input.data[12..32];
54    let to_bytes = &input.data[44..64];
55    let value_bytes = &input.data[64..96];
56
57    let from_address = Address::from_slice(from_bytes);
58    let to_address = Address::from_slice(to_bytes);
59    let value = U256::from_be_slice(value_bytes);
60
61    // Perform the transfer using load_account to modify balances directly
62    let mut internals = input.internals;
63
64    // Load and check the from account balance first
65    {
66        let from_account = match internals.load_account(from_address) {
67            Ok(account) => account,
68            Err(e) => {
69                return Err(PrecompileError::Other(format!("Failed to load from account: {e:?}")));
70            }
71        };
72
73        // Check if from account has sufficient balance
74        if from_account.data.info.balance < value {
75            return Err(PrecompileError::Other("Insufficient balance".into()));
76        }
77
78        // Deduct balance from the from account
79        from_account.data.info.balance -= value;
80    }
81
82    // Load and update the to account
83    {
84        let to_account = match internals.load_account(to_address) {
85            Ok(account) => account,
86            Err(e) => {
87                return Err(PrecompileError::Other(format!("Failed to load to account: {e:?}")));
88            }
89        };
90
91        // Check for overflow in to account
92        if to_account.data.info.balance.checked_add(value).is_none() {
93            return Err(PrecompileError::Other("Balance overflow in to account".into()));
94        }
95
96        // Add balance to the to account
97        to_account.data.info.balance += value;
98    }
99
100    // No output data for successful transfer
101    Ok(PrecompileOutput::new(CELO_TRANSFER_GAS_COST, alloy_primitives::Bytes::new()))
102}
foundry_evm_networks/celo/transfer.rs

foundry_evm_networks/celo/
transfer.rs
