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fix: use u128 for calc_blob_gasprice #764

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merged 2 commits into from
Oct 2, 2023
Merged

fix: use u128 for calc_blob_gasprice #764

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4a1159c
fix: use u128 for fake_exponential and calc_blob_gasprice
Rjected Oct 2, 2023
9ce9ee5
add comment for calc_blob_gasprice test
Rjected Oct 2, 2023
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4 changes: 2 additions & 2 deletions crates/primitives/src/env.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ pub struct BlockEnv {
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct BlobExcessGasAndPrice {
pub excess_blob_gas: u64,
pub blob_gasprice: u64,
pub blob_gasprice: u128,
}

impl BlobExcessGasAndPrice {
Expand Down Expand Up @@ -106,7 +106,7 @@ impl BlockEnv {
///
/// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
#[inline]
pub fn get_blob_gasprice(&self) -> Option<u64> {
pub fn get_blob_gasprice(&self) -> Option<u128> {
self.blob_excess_gas_and_price
.as_ref()
.map(|a| a.blob_gasprice)
Expand Down
25 changes: 20 additions & 5 deletions crates/primitives/src/utilities.rs
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Expand Up @@ -45,7 +45,7 @@ pub fn calc_excess_blob_gas(parent_excess_blob_gas: u64, parent_blob_gas_used: u
///
/// See also [the EIP-4844 helpers](https://eips.ethereum.org/EIPS/eip-4844#helpers).
#[inline]
pub fn calc_blob_gasprice(excess_blob_gas: u64) -> u64 {
pub fn calc_blob_gasprice(excess_blob_gas: u64) -> u128 {
fake_exponential(
MIN_BLOB_GASPRICE,
excess_blob_gas,
Expand All @@ -63,7 +63,7 @@ pub fn calc_blob_gasprice(excess_blob_gas: u64) -> u64 {
///
/// Panics if `denominator` is zero.
#[inline]
pub fn fake_exponential(factor: u64, numerator: u64, denominator: u64) -> u64 {
pub fn fake_exponential(factor: u64, numerator: u64, denominator: u64) -> u128 {
assert_ne!(denominator, 0, "attempt to divide by zero");
let factor = factor as u128;
let numerator = numerator as u128;
Expand All @@ -79,7 +79,7 @@ pub fn fake_exponential(factor: u64, numerator: u64, denominator: u64) -> u64 {
numerator_accum = (numerator_accum * numerator) / (denominator * i);
i += 1;
}
(output / denominator) as u64
output / denominator
}

/// Serde functions to serde as [bytes::Bytes] hex string
Expand Down Expand Up @@ -173,7 +173,22 @@ mod tests {
// https://github.com/ethereum/go-ethereum/blob/28857080d732857030eda80c69b9ba2c8926f221/consensus/misc/eip4844/eip4844_test.go#L60
#[test]
fn test_calc_blob_fee() {
for &(excess, expected) in &[(0, 1), (2314057, 1), (2314058, 2), (10 * 1024 * 1024, 23)] {
let blob_fee_vectors = &[
(0, 1),
(2314057, 1),
(2314058, 2),
(10 * 1024 * 1024, 23),
// calc_blob_gasprice approximates `e ** (excess_blob_gas / BLOB_GASPRICE_UPDATE_FRACTION)` using Taylor expansion
//
// to roughly find where boundaries will be hit:
// 2 ** bits = e ** (excess_blob_gas / BLOB_GASPRICE_UPDATE_FRACTION)
// excess_blob_gas = ln(2 ** bits) * BLOB_GASPRICE_UPDATE_FRACTION
(148099578, 18446739238971471609), // output is just below the overflow
(148099579, 18446744762204311910), // output is just after the overflow
(161087488, 902580055246494526580),
];

for &(excess, expected) in blob_fee_vectors {
let actual = calc_blob_gasprice(excess);
assert_eq!(actual, expected, "test: {excess}");
}
Expand All @@ -183,7 +198,7 @@ mod tests {
#[test]
fn fake_exp() {
for t @ &(factor, numerator, denominator, expected) in &[
(1u64, 0u64, 1u64, 1u64),
(1u64, 0u64, 1u64, 1u128),
(38493, 0, 1000, 38493),
(0, 1234, 2345, 0),
(1, 2, 1, 6), // approximate 7.389
Expand Down