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monero-serai: fee calculation parity with Monero's wallet2 (#301)
* monero-serai: fee calculation parity with Monero's wallet2 * Minor lint --------- Co-authored-by: Luke Parker <lukeparker5132@gmail.com>
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@@ -37,24 +37,41 @@ pub enum Bulletproofs {
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}
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impl Bulletproofs {
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pub(crate) fn fee_weight(plus: bool, outputs: usize) -> usize {
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let fields = if plus { 6 } else { 9 };
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fn bp_fields(plus: bool) -> usize {
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if plus {
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6
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} else {
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9
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}
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}
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// TODO: Shouldn't this use u32/u64?
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// https://github.com/monero-project/monero/blob/94e67bf96bbc010241f29ada6abc89f49a81759c/
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// src/cryptonote_basic/cryptonote_format_utils.cpp#L106-L124
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pub(crate) fn calculate_bp_clawback(plus: bool, n_outputs: usize) -> (usize, usize) {
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#[allow(non_snake_case)]
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let mut LR_len = usize::try_from(usize::BITS - (outputs - 1).leading_zeros()).unwrap();
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let padded_outputs = 1 << LR_len;
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let mut LR_len = 0;
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let mut n_padded_outputs = 1;
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while n_padded_outputs < n_outputs {
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LR_len += 1;
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n_padded_outputs = 1 << LR_len;
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}
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LR_len += LOG_N;
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let len = (fields + (2 * LR_len)) * 32;
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len +
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if padded_outputs <= 2 {
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0
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} else {
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let base = ((fields + (2 * (LOG_N + 1))) * 32) / 2;
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let size = (fields + (2 * LR_len)) * 32;
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((base * padded_outputs) - size) * 4 / 5
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}
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let mut bp_clawback = 0;
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if n_padded_outputs > 2 {
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let fields = Bulletproofs::bp_fields(plus);
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let base = ((fields + (2 * (LOG_N + 1))) * 32) / 2;
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let size = (fields + (2 * LR_len)) * 32;
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bp_clawback = ((base * n_padded_outputs) - size) * 4 / 5;
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}
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(bp_clawback, LR_len)
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}
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pub(crate) fn fee_weight(plus: bool, outputs: usize) -> usize {
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#[allow(non_snake_case)]
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let (bp_clawback, LR_len) = Bulletproofs::calculate_bp_clawback(plus, outputs);
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32 * (Bulletproofs::bp_fields(plus) + (2 * LR_len)) + 2 + bp_clawback
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}
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/// Prove the list of commitments are within [0 .. 2^64).
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@@ -124,8 +124,9 @@ pub struct RctBase {
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}
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impl RctBase {
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pub(crate) fn fee_weight(outputs: usize) -> usize {
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1 + 8 + (outputs * (8 + 32))
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pub(crate) fn fee_weight(outputs: usize, fee: u64) -> usize {
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// 1 byte for the RCT signature type
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1 + (outputs * (8 + 32)) + varint_len(fee)
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}
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pub fn write<W: Write>(&self, w: &mut W, rct_type: RctType) -> io::Result<()> {
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@@ -211,6 +212,7 @@ pub enum RctPrunable {
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impl RctPrunable {
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pub(crate) fn fee_weight(protocol: Protocol, inputs: usize, outputs: usize) -> usize {
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// 1 byte for number of BPs (technically a VarInt, yet there's always just zero or one)
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1 + Bulletproofs::fee_weight(protocol.bp_plus(), outputs) +
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(inputs * (Clsag::fee_weight(protocol.ring_len()) + 32))
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}
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@@ -377,8 +379,8 @@ impl RctSignatures {
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}
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}
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pub(crate) fn fee_weight(protocol: Protocol, inputs: usize, outputs: usize) -> usize {
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RctBase::fee_weight(outputs) + RctPrunable::fee_weight(protocol, inputs, outputs)
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pub(crate) fn fee_weight(protocol: Protocol, inputs: usize, outputs: usize, fee: u64) -> usize {
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RctBase::fee_weight(outputs, fee) + RctPrunable::fee_weight(protocol, inputs, outputs)
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}
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pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
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