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// Copyright 2019-2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
//! Auxillary struct/enums for polkadot runtime.
use sp_runtime::traits::{Convert, Saturating};
use sp_runtime::{Fixed64, Perbill};
use frame_support::traits::{OnUnbalanced, Imbalance, Currency, Get};
use crate::{MaximumBlockWeight, NegativeImbalance};
/// Logic for the author to get a portion of fees.
pub struct ToAuthor<R>(sp_std::marker::PhantomData<R>);
impl<R> OnUnbalanced<NegativeImbalance<R>> for ToAuthor<R>
where
R: balances::Trait + authorship::Trait,
<R as system::Trait>::AccountId: From<primitives::AccountId>,
<R as system::Trait>::AccountId: Into<primitives::AccountId>,
<R as system::Trait>::Event: From<balances::RawEvent<
<R as system::Trait>::AccountId,
<R as balances::Trait>::Balance,
balances::DefaultInstance>
>,
{
fn on_nonzero_unbalanced(amount: NegativeImbalance<R>) {
let numeric_amount = amount.peek();
let author = <authorship::Module<R>>::author();
<balances::Module<R>>::resolve_creating(&<authorship::Module<R>>::author(), amount);
<system::Module<R>>::deposit_event(balances::RawEvent::Deposit(author, numeric_amount));
}
}
/// Converter for currencies to votes.
pub struct CurrencyToVoteHandler<R>(sp_std::marker::PhantomData<R>);
impl<R> CurrencyToVoteHandler<R>
where
R: balances::Trait,
R::Balance: Into<u128>,
{
fn factor() -> u128 {
let issuance: u128 = <balances::Module<R>>::total_issuance().into();
(issuance / u64::max_value() as u128).max(1)
}
}
impl<R> Convert<u128, u64> for CurrencyToVoteHandler<R>
where
R: balances::Trait,
R::Balance: Into<u128>,
{
fn convert(x: u128) -> u64 { (x / Self::factor()) as u64 }
}
impl<R> Convert<u128, u128> for CurrencyToVoteHandler<R>
where
R: balances::Trait,
R::Balance: Into<u128>,
{
fn convert(x: u128) -> u128 { x * Self::factor() }
}
/// Update the given multiplier based on the following formula
///
/// diff = (target_weight - previous_block_weight)
/// v = 0.00004
/// next_weight = weight * (1 + (v . diff) + (v . diff)^2 / 2)
///
/// Where `target_weight` must be given as the `Get` implementation of the `T` generic type.
/// https://research.web3.foundation/en/latest/polkadot/Token%20Economics/#relay-chain-transaction-fees
pub struct TargetedFeeAdjustment<T, R>(sp_std::marker::PhantomData<(T, R)>);
impl<T: Get<Perbill>, R: system::Trait> Convert<Fixed64, Fixed64> for TargetedFeeAdjustment<T, R> {
fn convert(multiplier: Fixed64) -> Fixed64 {
let block_weight = <system::Module<R>>::all_extrinsics_weight();
let max_weight = MaximumBlockWeight::get();
let target_weight = (T::get() * max_weight) as u128;
let block_weight = block_weight as u128;
// determines if the first_term is positive
let positive = block_weight >= target_weight;
let diff_abs = block_weight.max(target_weight) - block_weight.min(target_weight);
// diff is within u32, safe.
let diff = Fixed64::from_rational(diff_abs as i64, max_weight as u64);
let diff_squared = diff.saturating_mul(diff);
// 0.00004 = 4/100_000 = 40_000/10^9
let v = Fixed64::from_rational(4, 100_000);
// 0.00004^2 = 16/10^10 ~= 2/10^9. Taking the future /2 into account, then it is just 1
// parts from a billionth.
let v_squared_2 = Fixed64::from_rational(1, 1_000_000_000);
let first_term = v.saturating_mul(diff);
// It is very unlikely that this will exist (in our poor perbill estimate) but we are giving
// it a shot.
let second_term = v_squared_2.saturating_mul(diff_squared);
if positive {
// Note: this is merely bounded by how big the multiplier and the inner value can go,
// not by any economical reasoning.
let excess = first_term.saturating_add(second_term);
multiplier.saturating_add(excess)
} else {
// Proof: first_term > second_term. Safe subtraction.
let negative = first_term - second_term;
multiplier.saturating_sub(negative)
// despite the fact that apply_to saturates weight (final fee cannot go below 0)
// it is crucially important to stop here and don't further reduce the weight fee
// multiplier. While at -1, it means that the network is so un-congested that all
// transactions have no weight fee. We stop here and only increase if the network
// became more busy.
.max(Fixed64::from_rational(-1, 1))
}
}
}
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