alloy_eips/eip1559/helpers.rs
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use crate::eip1559::BaseFeeParams;
/// Calculate the base fee for the next block based on the EIP-1559 specification.
///
/// This function calculates the base fee for the next block according to the rules defined in the
/// EIP-1559. EIP-1559 introduces a new transaction pricing mechanism that includes a
/// fixed-per-block network fee that is burned and dynamically adjusts block sizes to handles
/// transient congestion.
///
/// For each block, the base fee per gas is determined by the gas used in the parent block and the
/// target gas (the block gas limit divided by the elasticity multiplier). The algorithm increases
/// the base fee when blocks are congested and decreases it when they are under the target gas
/// usage. The base fee per gas is always burned.
///
/// Parameters:
/// - `gas_used`: The gas used in the current block.
/// - `gas_limit`: The gas limit of the current block.
/// - `base_fee`: The current base fee per gas.
/// - `base_fee_params`: Base fee parameters such as elasticity multiplier and max change
/// denominator.
///
/// Returns:
/// The calculated base fee for the next block as a `u64`.
///
/// For more information, refer to the [EIP-1559 spec](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-1559.md).
pub fn calc_next_block_base_fee(
gas_used: u64,
gas_limit: u64,
base_fee: u64,
base_fee_params: BaseFeeParams,
) -> u64 {
// Calculate the target gas by dividing the gas limit by the elasticity multiplier.
let gas_target = gas_limit / base_fee_params.elasticity_multiplier as u64;
match gas_used.cmp(&gas_target) {
// If the gas used in the current block is equal to the gas target, the base fee remains the
// same (no increase).
core::cmp::Ordering::Equal => base_fee,
// If the gas used in the current block is greater than the gas target, calculate a new
// increased base fee.
core::cmp::Ordering::Greater => {
// Calculate the increase in base fee based on the formula defined by EIP-1559.
base_fee
+ (core::cmp::max(
// Ensure a minimum increase of 1.
1,
base_fee as u128 * (gas_used - gas_target) as u128
/ (gas_target as u128 * base_fee_params.max_change_denominator),
) as u64)
}
// If the gas used in the current block is less than the gas target, calculate a new
// decreased base fee.
core::cmp::Ordering::Less => {
// Calculate the decrease in base fee based on the formula defined by EIP-1559.
base_fee.saturating_sub(
(base_fee as u128 * (gas_target - gas_used) as u128
/ (gas_target as u128 * base_fee_params.max_change_denominator))
as u64,
)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::eip1559::constants::{MIN_PROTOCOL_BASE_FEE, MIN_PROTOCOL_BASE_FEE_U256};
#[test]
fn min_protocol_sanity() {
assert_eq!(MIN_PROTOCOL_BASE_FEE_U256.to::<u64>(), MIN_PROTOCOL_BASE_FEE);
}
#[test]
fn calculate_base_fee_success() {
let base_fee = [
1000000000, 1000000000, 1000000000, 1072671875, 1059263476, 1049238967, 1049238967, 0,
1, 2,
];
let gas_used = [
10000000, 10000000, 10000000, 9000000, 10001000, 0, 10000000, 10000000, 10000000,
10000000,
];
let gas_limit = [
10000000, 12000000, 14000000, 10000000, 14000000, 2000000, 18000000, 18000000,
18000000, 18000000,
];
let next_base_fee = [
1125000000, 1083333333, 1053571428, 1179939062, 1116028649, 918084097, 1063811730, 1,
2, 3,
];
for i in 0..base_fee.len() {
assert_eq!(
next_base_fee[i],
calc_next_block_base_fee(
gas_used[i],
gas_limit[i],
base_fee[i],
BaseFeeParams::ethereum(),
)
);
}
}
#[test]
fn calculate_optimism_sepolia_base_fee_success() {
let base_fee = [
1000000000, 1000000000, 1000000000, 1072671875, 1059263476, 1049238967, 1049238967, 0,
1, 2,
];
let gas_used = [
10000000, 10000000, 10000000, 9000000, 10001000, 0, 10000000, 10000000, 10000000,
10000000,
];
let gas_limit = [
10000000, 12000000, 14000000, 10000000, 14000000, 2000000, 18000000, 18000000,
18000000, 18000000,
];
let next_base_fee = [
1100000048, 1080000000, 1065714297, 1167067046, 1128881311, 1028254188, 1098203452, 1,
2, 3,
];
for i in 0..base_fee.len() {
assert_eq!(
next_base_fee[i],
calc_next_block_base_fee(
gas_used[i],
gas_limit[i],
base_fee[i],
BaseFeeParams::optimism_sepolia(),
)
);
}
}
#[test]
fn calculate_optimism_base_fee_success() {
let base_fee = [
1000000000, 1000000000, 1000000000, 1072671875, 1059263476, 1049238967, 1049238967, 0,
1, 2,
];
let gas_used = [
10000000, 10000000, 10000000, 9000000, 10001000, 0, 10000000, 10000000, 10000000,
10000000,
];
let gas_limit = [
10000000, 12000000, 14000000, 10000000, 14000000, 2000000, 18000000, 18000000,
18000000, 18000000,
];
let next_base_fee = [
1100000048, 1080000000, 1065714297, 1167067046, 1128881311, 1028254188, 1098203452, 1,
2, 3,
];
for i in 0..base_fee.len() {
assert_eq!(
next_base_fee[i],
calc_next_block_base_fee(
gas_used[i],
gas_limit[i],
base_fee[i],
BaseFeeParams::optimism(),
)
);
}
}
#[test]
fn calculate_optimism_canyon_base_fee_success() {
let base_fee = [
1000000000, 1000000000, 1000000000, 1072671875, 1059263476, 1049238967, 1049238967, 0,
1, 2,
];
let gas_used = [
10000000, 10000000, 10000000, 9000000, 10001000, 0, 10000000, 10000000, 10000000,
10000000,
];
let gas_limit = [
10000000, 12000000, 14000000, 10000000, 14000000, 2000000, 18000000, 18000000,
18000000, 18000000,
];
let next_base_fee = [
1020000009, 1016000000, 1013142859, 1091550909, 1073187043, 1045042012, 1059031864, 1,
2, 3,
];
for i in 0..base_fee.len() {
assert_eq!(
next_base_fee[i],
calc_next_block_base_fee(
gas_used[i],
gas_limit[i],
base_fee[i],
BaseFeeParams::optimism_canyon(),
)
);
}
}
#[test]
fn calculate_base_sepolia_base_fee_success() {
let base_fee = [
1000000000, 1000000000, 1000000000, 1072671875, 1059263476, 1049238967, 1049238967, 0,
1, 2,
];
let gas_used = [
10000000, 10000000, 10000000, 9000000, 10001000, 0, 10000000, 10000000, 10000000,
10000000,
];
let gas_limit = [
10000000, 12000000, 14000000, 10000000, 14000000, 2000000, 18000000, 18000000,
18000000, 18000000,
];
let next_base_fee = [
1180000000, 1146666666, 1122857142, 1244299375, 1189416692, 1028254188, 1144836295, 1,
2, 3,
];
for i in 0..base_fee.len() {
assert_eq!(
next_base_fee[i],
calc_next_block_base_fee(
gas_used[i],
gas_limit[i],
base_fee[i],
BaseFeeParams::base_sepolia(),
)
);
}
}
}