Update BP fee_weight

Closes https://github.com/serai-dex/serai/issues/8.

coins/monero/src/ringct/bulletproofs/mod.rs

@@ -11,6 +11,7 @@ use crate::{Commitment, wallet::TransactionError, serialize::*};
 
 pub(crate) mod scalar_vector;
 pub(crate) mod core;
+use self::core::LOG_N;
 
 pub(crate) mod original;
 pub(crate) mod plus;
@@ -28,19 +29,23 @@ pub enum Bulletproofs {
 }
 
 impl Bulletproofs {
-  // TODO
-  pub(crate) fn fee_weight(outputs: usize) -> usize {
-    let proofs = 6 + usize::try_from(usize::BITS - (outputs - 1).leading_zeros()).unwrap();
-    let len = (9 + (2 * proofs)) * 32;
+  pub(crate) fn fee_weight(plus: bool, outputs: usize) -> usize {
+    let fields = if plus { 6 } else { 9 };
 
-    let mut clawback = 0;
-    let padded = 1 << (proofs - 6);
-    if padded > 2 {
-      const BP_BASE: usize = 368;
-      clawback = ((BP_BASE * padded) - len) * 4 / 5;
-    }
+    #[allow(non_snake_case)]
+    let mut LR_len = usize::try_from(usize::BITS - (outputs - 1).leading_zeros()).unwrap();
+    let padded_outputs = 1 << LR_len;
+    LR_len += LOG_N;
 
-    len + clawback
+    let len = (fields + (2 * LR_len)) * 32;
+    len +
+      if padded_outputs <= 2 {
+        0
+      } else {
+        let base = ((fields + (2 * (LOG_N + 1))) * 32) / 2;
+        let size = (fields + (2 * LR_len)) * 32;
+        ((base * padded_outputs) - size) * 4 / 5
+      }
   }
 
   pub fn prove<R: RngCore + CryptoRng>(

coins/monero/src/ringct/mod.rs

@@ -9,6 +9,7 @@ pub mod clsag;
 pub mod bulletproofs;
 
 use crate::{
+  Protocol,
   serialize::*,
   ringct::{clsag::Clsag, bulletproofs::Bulletproofs},
 };
@@ -86,8 +87,9 @@ impl RctPrunable {
     }
   }
 
-  pub(crate) fn fee_weight(ring_len: usize, inputs: usize, outputs: usize) -> usize {
-    1 + Bulletproofs::fee_weight(outputs) + (inputs * (Clsag::fee_weight(ring_len) + 32))
+  pub(crate) fn fee_weight(protocol: Protocol, inputs: usize, outputs: usize) -> usize {
+    1 + Bulletproofs::fee_weight(protocol.bp_plus(), outputs) +
+      (inputs * (Clsag::fee_weight(protocol.ring_len()) + 32))
   }
 
   pub fn serialize<W: std::io::Write>(&self, w: &mut W) -> std::io::Result<()> {
@@ -142,8 +144,8 @@ pub struct RctSignatures {
 }
 
 impl RctSignatures {
-  pub(crate) fn fee_weight(ring_len: usize, inputs: usize, outputs: usize) -> usize {
-    RctBase::fee_weight(outputs) + RctPrunable::fee_weight(ring_len, inputs, outputs)
+  pub(crate) fn fee_weight(protocol: Protocol, inputs: usize, outputs: usize) -> usize {
+    RctBase::fee_weight(outputs) + RctPrunable::fee_weight(protocol, inputs, outputs)
   }
 
   pub fn serialize<W: std::io::Write>(&self, w: &mut W) -> std::io::Result<()> {

coins/monero/src/rpc.rs

@@ -371,8 +371,7 @@ impl Rpc {
       )
       .await?;
 
-    // TODO: Support time based lock times. These shouldn't be needed, and it may be painful to
-    // get the median time for the given height, yet we do need to in order to be complete
+    // TODO: https://github.com/serai-dex/serai/issues/104
     outs
       .outs
       .iter()

coins/monero/src/transaction.rs

@@ -5,7 +5,7 @@ use zeroize::Zeroize;
 use curve25519_dalek::edwards::EdwardsPoint;
 
 use crate::{
-  hash,
+  Protocol, hash,
   serialize::*,
   ringct::{RctPrunable, RctSignatures},
 };
@@ -193,9 +193,14 @@ pub struct Transaction {
 }
 
 impl Transaction {
-  pub(crate) fn fee_weight(ring_len: usize, inputs: usize, outputs: usize, extra: usize) -> usize {
-    TransactionPrefix::fee_weight(ring_len, inputs, outputs, extra) +
-      RctSignatures::fee_weight(ring_len, inputs, outputs)
+  pub(crate) fn fee_weight(
+    protocol: Protocol,
+    inputs: usize,
+    outputs: usize,
+    extra: usize,
+  ) -> usize {
+    TransactionPrefix::fee_weight(protocol.ring_len(), inputs, outputs, extra) +
+      RctSignatures::fee_weight(protocol, inputs, outputs)
   }
 
   pub fn serialize<W: std::io::Write>(&self, w: &mut W) -> std::io::Result<()> {

coins/monero/src/wallet/send/mod.rs

@@ -212,12 +212,8 @@ impl SignableTransaction {
     let extra = Extra::fee_weight(outputs);
 
     // Calculate the fee.
-    let mut fee = fee_rate.calculate(Transaction::fee_weight(
-      protocol.ring_len(),
-      inputs.len(),
-      outputs,
-      extra,
-    ));
+    let mut fee =
+      fee_rate.calculate(Transaction::fee_weight(protocol, inputs.len(), outputs, extra));
 
     // Make sure we have enough funds
     let in_amount = inputs.iter().map(|input| input.commitment.amount).sum::<u64>();
@@ -229,12 +225,9 @@ impl SignableTransaction {
     // If we have yet to add a change output, do so if it's economically viable
     if (!change) && change_address.is_some() && (in_amount != out_amount) {
       // Check even with the new fee, there's remaining funds
-      let change_fee = fee_rate.calculate(Transaction::fee_weight(
-        protocol.ring_len(),
-        inputs.len(),
-        outputs + 1,
-        extra,
-      )) - fee;
+      let change_fee =
+        fee_rate.calculate(Transaction::fee_weight(protocol, inputs.len(), outputs + 1, extra)) -
+          fee;
       if (out_amount + change_fee) < in_amount {
         change = true;
         out_amount += change_fee;