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// Copyright 2019-2025 PureStake Inc.
// This file is part of Moonbeam.
// Moonbeam 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.
// Moonbeam 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 Moonbeam. If not, see <http://www.gnu.org/licenses/>.
//! Module that provides types to extend xcm holding.
use core::marker::PhantomData;
use sp_core::{H160, U256};
use sp_std::collections::btree_map::BTreeMap;
use sp_std::vec::Vec;
use xcm::prelude::*;
use xcm_executor::traits::{FeeManager, FeeReason, XcmAssetTransfers};
environmental::environmental!(XCM_HOLDING_ERC20_ORIGINS: XcmHoldingErc20sOrigins);
#[cfg_attr(test, derive(PartialEq, Debug))]
pub(crate) enum DrainError {
AssetNotFound,
NotEnoughFounds,
SplitError,
}
/// Xcm holding erc20 origins extension.
/// This extension track down the origin of alls erc20 tokens in the xcm holding.
#[derive(Default)]
pub(crate) struct XcmHoldingErc20sOrigins {
map: BTreeMap<H160, Vec<(H160, U256)>>,
impl XcmHoldingErc20sOrigins {
/// Take and remove a given amounts of erc20 tokens from the XCM holding.
/// These tokens can come from one or more holders that we had tracked earlier in the XCM
/// execution, so we return an array of (holder, balance).
pub(crate) fn drain(
&mut self,
contract_address: H160,
amount: U256,
) -> Result<Vec<(H160, U256)>, DrainError> {
let tokens_to_transfer = self.drain_inner(&contract_address, amount)?;
self.map
.entry(contract_address)
.and_modify(|erc20_origins| {
*erc20_origins = erc20_origins.split_off(tokens_to_transfer.len());
});
Ok(tokens_to_transfer)
fn drain_inner(
&self,
contract_address: &H160,
mut amount: U256,
let mut tokens_to_transfer = Vec::new();
if let Some(erc20_origins) = self.map.get(contract_address) {
for (from, subamount) in erc20_origins {
if &amount > subamount {
tokens_to_transfer.push((*from, *subamount));
amount -= *subamount;
} else if &amount == subamount {
return Ok(tokens_to_transfer);
} else {
// Each insertion of tokens must be drain at once
return Err(DrainError::SplitError);
// If there were enough tokens, we had to return in the for loop
Err(DrainError::NotEnoughFounds)
Err(DrainError::AssetNotFound)
pub(crate) fn insert(&mut self, contract_address: H160, who: H160, amount: U256) {
.or_default()
.push((who, amount));
pub(crate) fn with<R, F>(f: F) -> Option<R>
where
F: FnOnce(&mut Self) -> R,
{
XCM_HOLDING_ERC20_ORIGINS::with(|erc20s_origins| f(erc20s_origins))
/// Xcm executor wrapper that inject xcm holding extension "XcmHoldingErc20sOrigins"
pub struct XcmExecutorWrapper<Config, InnerXcmExecutor>(PhantomData<(Config, InnerXcmExecutor)>);
impl<Config, InnerXcmExecutor> xcm::latest::ExecuteXcm<Config::RuntimeCall>
for XcmExecutorWrapper<Config, InnerXcmExecutor>
Config: xcm_executor::Config,
InnerXcmExecutor: xcm::latest::ExecuteXcm<Config::RuntimeCall>,
type Prepared = InnerXcmExecutor::Prepared;
fn prepare(
message: xcm::latest::Xcm<Config::RuntimeCall>,
) -> Result<Self::Prepared, xcm::latest::Xcm<Config::RuntimeCall>> {
InnerXcmExecutor::prepare(message)
fn execute(
origin: impl Into<xcm::latest::Location>,
pre: Self::Prepared,
hash: &mut xcm::latest::XcmHash,
weight_credit: xcm::latest::Weight,
) -> xcm::latest::Outcome {
let mut erc20s_origins = Default::default();
XCM_HOLDING_ERC20_ORIGINS::using(&mut erc20s_origins, || {
InnerXcmExecutor::execute(origin, pre, hash, weight_credit)
})
fn charge_fees(
location: impl Into<xcm::latest::Location>,
fees: xcm::latest::Assets,
) -> Result<(), xcm::latest::Error> {
InnerXcmExecutor::charge_fees(location, fees)
impl<Config, InnerXcmExecutor> XcmAssetTransfers for XcmExecutorWrapper<Config, InnerXcmExecutor>
type IsReserve = Config::IsReserve;
type IsTeleporter = Config::IsTeleporter;
type AssetTransactor = Config::AssetTransactor;
impl<Config, InnerXcmExecutor> FeeManager for XcmExecutorWrapper<Config, InnerXcmExecutor>
InnerXcmExecutor: FeeManager,
fn is_waived(origin: Option<&Location>, r: FeeReason) -> bool {
InnerXcmExecutor::is_waived(origin, r)
fn handle_fee(fee: Assets, context: Option<&XcmContext>, r: FeeReason) {
InnerXcmExecutor::handle_fee(fee, context, r)
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_xcm_holding_ext_erc20s_origins() {
const TOKEN1: H160 = H160([1; 20]);
const TOKEN2: H160 = H160([2; 20]);
const USER1: H160 = H160([3; 20]);
const USER2: H160 = H160([4; 20]);
// Simple case
let mut erc20s_origins_ = Default::default();
XCM_HOLDING_ERC20_ORIGINS::using(&mut erc20s_origins_, || {
XcmHoldingErc20sOrigins::with(|erc20s_origins| {
erc20s_origins.insert(TOKEN1, USER1, U256::from(100));
assert_eq!(
erc20s_origins.drain(TOKEN2, U256::from(1)),
);
erc20s_origins.drain(TOKEN1, U256::from(100)),
Ok(vec![(USER1, U256::from(100))])
// Complex case
erc20s_origins.insert(TOKEN1, USER2, U256::from(200));
erc20s_origins.drain(TOKEN1, U256::from(201)),
erc20s_origins.drain(TOKEN1, U256::from(199)),
Err(DrainError::SplitError)
erc20s_origins.drain(TOKEN1, U256::from(200)),
Ok(vec![(USER2, U256::from(200))])