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pub mod eip1559 {
use num_bigint::BigUint;
use num_traits::One;
use std::cmp::{self, Ordering};
const BASEFEE_MAX_CHANGE_DENOMINATOR: u64 = 8;
pub fn compute_base_fee(
parent_base_fee: &BigUint,
parent_gas_used: &BigUint,
parent_target_gas_used: &BigUint,
) -> BigUint {
match parent_gas_used.cmp(&parent_target_gas_used) {
Ordering::Equal => parent_base_fee.clone(),
Ordering::Greater => {
compute_base_fee_increase(parent_base_fee, parent_gas_used, parent_target_gas_used)
}
Ordering::Less => {
compute_base_fee_decrease(parent_base_fee, parent_gas_used, parent_target_gas_used)
}
}
}
fn compute_base_fee_increase(
parent_base_fee: &BigUint,
parent_gas_used: &BigUint,
parent_target_gas_used: &BigUint,
) -> BigUint {
let gas_delta = parent_gas_used - parent_target_gas_used;
let fee_delta = cmp::max(
(parent_base_fee * gas_delta) / parent_target_gas_used / BASEFEE_MAX_CHANGE_DENOMINATOR,
One::one(),
);
parent_base_fee + fee_delta
}
fn compute_base_fee_decrease(
parent_base_fee: &BigUint,
parent_gas_used: &BigUint,
parent_target_gas_used: &BigUint,
) -> BigUint {
let gas_delta = parent_target_gas_used - parent_gas_used;
let fee_delta =
(parent_base_fee * gas_delta) / parent_target_gas_used / BASEFEE_MAX_CHANGE_DENOMINATOR;
parent_base_fee - fee_delta
}
}
#[cfg(test)]
mod tests {
use super::*;
use num_bigint::BigUint;
use serde::{Deserialize, Serialize};
use std::{cmp::Ordering, fs, path::PathBuf};
#[test]
fn assert_basefee_computation_works() {
let mut d = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
d.push("resources/test/eip1559/basefee/reference-test.json");
let path = d.as_path().to_str().unwrap();
let data = fs::read_to_string(path);
let data = match data {
Ok(c) => c,
Err(error) => panic!("Problem opening the file: {:?}", error),
};
let test_cases = json_to_testcase(&data);
for case in &test_cases {
let parent_base_fee = BigUint::from(case.parent_base_fee);
let parent_gas_used = BigUint::from(case.parent_gas_used);
let parent_target_gas_used = BigUint::from(case.parent_target_gas_used);
let base_fee = eip1559::compute_base_fee(
&parent_base_fee,
&parent_gas_used,
&parent_target_gas_used,
);
assert_eq!(
true,
base_fee.cmp(&BigUint::from(case.expected_base_fee)) == Ordering::Equal
);
}
}
pub fn json_to_testcase(data: &str) -> Vec<TestCase> {
let t = serde_json::from_str(data);
match t {
Ok(c) => c,
Err(error) => panic!("Problem opening the file: {:?}", error),
}
}
#[derive(Debug, Serialize, Deserialize)]
pub struct TestCase {
#[serde(rename = "parentBaseFee")]
pub parent_base_fee: u64,
#[serde(rename = "parentGasUsed")]
pub parent_gas_used: u64,
#[serde(rename = "parentTargetGasUsed")]
pub parent_target_gas_used: u64,
#[serde(rename = "expectedBaseFee")]
pub expected_base_fee: u64,
}
}