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// This file is part of Gear.
// Copyright (C) 2022-2024 Gear Technologies Inc.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
// This program 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.
// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
//! Gas reservation structures.
use crate::{
ids::{prelude::*, MessageId, ReservationId},
message::IncomingDispatch,
};
use alloc::{collections::BTreeMap, format};
use gear_core_errors::ReservationError;
use scale_info::{
scale::{Decode, Encode},
TypeInfo,
};
/// An unchangeable wrapper over u64 value, which is required
/// to be used as a "view-only" reservations nonce in a message
/// execution context.
///
/// ### Note:
/// By contract, It must be instantiated only once, when message execution
/// context is created. Also the latter is required to be instantiated only
/// once, when incoming dispatch is created.
#[derive(
Clone, Copy, Default, Debug, Eq, Hash, Ord, PartialEq, PartialOrd, Decode, Encode, TypeInfo,
)]
pub struct ReservationNonce(u64);
impl From<&InnerNonce> for ReservationNonce {
fn from(nonce: &InnerNonce) -> Self {
ReservationNonce(nonce.0)
}
}
/// A changeable wrapper over u64 value, which is required
/// to be used as an "active" reservations nonce in a gas reserver.
#[derive(Debug, Clone, Encode, Decode, PartialEq, Eq)]
struct InnerNonce(u64);
impl InnerNonce {
/// Fetches current state of the nonce and
/// updates its state by incrementing it.
fn fetch_inc(&mut self) -> u64 {
let current = self.0;
self.0 = self.0.saturating_add(1);
current
}
}
impl From<ReservationNonce> for InnerNonce {
fn from(frozen_nonce: ReservationNonce) -> Self {
InnerNonce(frozen_nonce.0)
}
}
/// Gas reserver.
///
/// Controls gas reservations states.
#[derive(Debug, Clone, Encode, Decode, PartialEq, Eq)]
pub struct GasReserver {
/// Message id within which reservations are created
/// by the current instance of [`GasReserver`].
message_id: MessageId,
/// Nonce used to generate [`ReservationId`]s.
///
/// It's really important that if gas reserver is created
/// several times with the same `message_id`, value of this
/// field is re-used. This property is guaranteed by instantiating
/// gas reserver from the [`IncomingDispatch`].
nonce: InnerNonce,
/// Gas reservations states.
states: GasReservationStates,
/// Maximum allowed reservations to be stored in `states`.
///
/// This field is used not only to control `states` during
/// one execution, but also during several execution using
/// gas reserver for the actor. To reach that `states` must
/// be set with reservation from previous executions of the
/// actor.
max_reservations: u64,
}
impl GasReserver {
/// Creates a new gas reserver.
///
/// `map`, which is a [`BTreeMap`] of [`GasReservationSlot`]s,
/// will be converted to the [`BTreeMap`] of [`GasReservationState`]s.
pub fn new(
incoming_dispatch: &IncomingDispatch,
map: GasReservationMap,
max_reservations: u64,
) -> Self {
let message_id = incoming_dispatch.id();
let nonce = incoming_dispatch
.context()
.as_ref()
.map(|c| c.reservation_nonce())
.unwrap_or_default()
.into();
Self {
message_id,
nonce,
states: {
let mut states = BTreeMap::new();
states.extend(map.into_iter().map(|(id, slot)| (id, slot.into())));
states
},
max_reservations,
}
}
/// Returns bool defining if gas reserver is empty.
pub fn is_empty(&self) -> bool {
self.states.is_empty()
}
/// Checks that the number of existing and newly created reservations
/// in the `states` is less than `max_reservations`. Removed reservations,
/// which are stored with the [`GasReservationState::Removed`] state in the
/// `states`, aren't excluded from the check.
fn check_execution_limit(&self) -> Result<(), ReservationError> {
// operation might very expensive in the future
// so we will store 2 numerics to optimize it maybe
let current_reservations = self
.states
.values()
.map(|state| {
matches!(
state,
GasReservationState::Exists { .. } | GasReservationState::Created { .. }
) as u64
})
.sum::<u64>();
if current_reservations > self.max_reservations {
Err(ReservationError::ReservationsLimitReached)
} else {
Ok(())
}
}
/// Returns amount of gas in reservation, if exists.
pub fn limit_of(&self, reservation_id: &ReservationId) -> Option<u64> {
self.states.get(reservation_id).and_then(|v| match v {
GasReservationState::Exists { amount, .. }
| GasReservationState::Created { amount, .. } => Some(*amount),
_ => None,
})
}
/// Reserves gas.
///
/// Creates a new reservation and returns its id.
///
/// Returns an error if maximum limit of reservations is reached.
pub fn reserve(
&mut self,
amount: u64,
duration: u32,
) -> Result<ReservationId, ReservationError> {
self.check_execution_limit()?;
let id = ReservationId::generate(self.message_id, self.nonce.fetch_inc());
let maybe_reservation = self.states.insert(
id,
GasReservationState::Created {
amount,
duration,
used: false,
},
);
if maybe_reservation.is_some() {
let err_msg = format!(
"GasReserver::reserve: created a duplicate reservation. \
Message id - {message_id}, nonce - {nonce}",
message_id = self.message_id,
nonce = self.nonce.0
);
log::error!("{err_msg}");
unreachable!("{err_msg}");
}
Ok(id)
}
/// Unreserves gas reserved within `id` reservation.
///
/// Return error if:
/// 1. Reservation doesn't exist.
/// 2. Reservation was "unreserved", so in [`GasReservationState::Removed`] state.
/// 3. Reservation was marked used.
pub fn unreserve(
&mut self,
id: ReservationId,
) -> Result<(u64, Option<UnreservedReimbursement>), ReservationError> {
// Docs error case #1.
let state = self
.states
.get(&id)
.ok_or(ReservationError::InvalidReservationId)?;
if matches!(
state,
// Docs error case #2.
GasReservationState::Removed { .. } |
// Docs error case #3.
GasReservationState::Exists { used: true, .. } |
GasReservationState::Created { used: true, .. }
) {
return Err(ReservationError::InvalidReservationId);
}
let state = self.states.remove(&id).unwrap();
Ok(match state {
GasReservationState::Exists { amount, finish, .. } => {
self.states
.insert(id, GasReservationState::Removed { expiration: finish });
(amount, None)
}
GasReservationState::Created {
amount, duration, ..
} => (amount, Some(UnreservedReimbursement(duration))),
GasReservationState::Removed { .. } => {
let err_msg =
"GasReserver::unreserve: `Removed` variant is unreachable, checked above";
log::error!("{err_msg}");
unreachable!("{err_msg}")
}
})
}
/// Marks reservation as used.
///
/// This allows to avoid double usage of the reservation
/// for sending a new message from execution of `message_id`
/// of current gas reserver.
pub fn mark_used(&mut self, id: ReservationId) -> Result<(), ReservationError> {
let used = self.check_not_used(id)?;
*used = true;
Ok(())
}
/// Check if reservation is not used.
///
/// If reservation does not exist returns `InvalidReservationId` error.
pub fn check_not_used(&mut self, id: ReservationId) -> Result<&mut bool, ReservationError> {
if let Some(
GasReservationState::Created { used, .. } | GasReservationState::Exists { used, .. },
) = self.states.get_mut(&id)
{
if *used {
Err(ReservationError::InvalidReservationId)
} else {
Ok(used)
}
} else {
Err(ReservationError::InvalidReservationId)
}
}
/// Returns gas reservations current nonce.
pub fn nonce(&self) -> ReservationNonce {
(&self.nonce).into()
}
/// Gets gas reservations states.
pub fn states(&self) -> &GasReservationStates {
&self.states
}
/// Converts current gas reserver into gas reservation map.
pub fn into_map<F>(
self,
current_block_height: u32,
duration_into_expiration: F,
) -> GasReservationMap
where
F: Fn(u32) -> u32,
{
self.states
.into_iter()
.flat_map(|(id, state)| match state {
GasReservationState::Exists {
amount,
start,
finish,
..
} => Some((
id,
GasReservationSlot {
amount,
start,
finish,
},
)),
GasReservationState::Created {
amount, duration, ..
} => {
let expiration = duration_into_expiration(duration);
Some((
id,
GasReservationSlot {
amount,
start: current_block_height,
finish: expiration,
},
))
}
GasReservationState::Removed { .. } => None,
})
.collect()
}
}
/// Safety token returned when unreserved gas can be returned back to the gas counter.
///
/// Wraps duration for the newly created reservation.
#[derive(Debug, PartialEq, Eq)]
pub struct UnreservedReimbursement(u32);
impl UnreservedReimbursement {
/// Returns duration for the newly created unreserved reservation.
pub fn duration(&self) -> u32 {
self.0
}
}
/// Gas reservations states.
pub type GasReservationStates = BTreeMap<ReservationId, GasReservationState>;
/// Gas reservation state.
///
/// Used to control whether reservation was created, removed or nothing happened.
#[derive(Debug, Clone, Copy, Eq, PartialEq, Encode, Decode)]
pub enum GasReservationState {
/// Reservation exists.
Exists {
/// Amount of reserved gas.
amount: u64,
/// Block number when reservation is created.
start: u32,
/// Block number when reservation will expire.
finish: u32,
/// Flag signalizing whether reservation is used.
used: bool,
},
/// Reservation will be created.
Created {
/// Amount of reserved gas.
amount: u64,
/// How many blocks reservation will live.
duration: u32,
/// Flag signalizing whether reservation is used.
used: bool,
},
/// Reservation will be removed.
Removed {
/// Block number when reservation will expire.
expiration: u32,
},
}
impl From<GasReservationSlot> for GasReservationState {
fn from(slot: GasReservationSlot) -> Self {
Self::Exists {
amount: slot.amount,
start: slot.start,
finish: slot.finish,
used: false,
}
}
}
/// Gas reservations map.
///
/// Used across execution and is stored to storage.
pub type GasReservationMap = BTreeMap<ReservationId, GasReservationSlot>;
/// Gas reservation slot.
#[derive(Debug, Clone, Eq, PartialEq, Encode, Decode, TypeInfo)]
pub struct GasReservationSlot {
/// Amount of reserved gas.
pub amount: u64,
/// Block number when reservation is created.
pub start: u32,
/// Block number when reservation will expire.
pub finish: u32,
}
#[cfg(test)]
mod tests {
use super::*;
const MAX_RESERVATIONS: u64 = 256;
fn new_reserver() -> GasReserver {
let d = IncomingDispatch::default();
GasReserver::new(&d, Default::default(), MAX_RESERVATIONS)
}
#[test]
fn max_reservations_limit_works() {
let mut reserver = new_reserver();
for n in 0..(MAX_RESERVATIONS * 10) {
let res = reserver.reserve(100, 10);
if n > MAX_RESERVATIONS {
assert_eq!(res, Err(ReservationError::ReservationsLimitReached));
} else {
assert!(res.is_ok());
}
}
}
#[test]
fn mark_used_for_unreserved_fails() {
let mut reserver = new_reserver();
let id = reserver.reserve(1, 1).unwrap();
reserver.unreserve(id).unwrap();
assert_eq!(
reserver.mark_used(id),
Err(ReservationError::InvalidReservationId)
);
}
#[test]
fn mark_used_twice_fails() {
let mut reserver = new_reserver();
let id = reserver.reserve(1, 1).unwrap();
reserver.mark_used(id).unwrap();
assert_eq!(
reserver.mark_used(id),
Err(ReservationError::InvalidReservationId)
);
// not found
assert_eq!(
reserver.mark_used(ReservationId::default()),
Err(ReservationError::InvalidReservationId)
);
}
#[test]
fn remove_reservation_twice_fails() {
let mut reserver = new_reserver();
let id = reserver.reserve(1, 1).unwrap();
reserver.unreserve(id).unwrap();
assert_eq!(
reserver.unreserve(id),
Err(ReservationError::InvalidReservationId)
);
}
#[test]
fn remove_non_existing_reservation_fails() {
let id = ReservationId::from([0xff; 32]);
let mut map = GasReservationMap::new();
map.insert(
id,
GasReservationSlot {
amount: 1,
start: 1,
finish: 100,
},
);
let mut reserver = GasReserver::new(&Default::default(), map, 256);
reserver.unreserve(id).unwrap();
assert_eq!(
reserver.unreserve(id),
Err(ReservationError::InvalidReservationId)
);
}
#[test]
fn fresh_reserve_unreserve() {
let mut reserver = new_reserver();
let id = reserver.reserve(10_000, 5).unwrap();
reserver.mark_used(id).unwrap();
assert_eq!(
reserver.unreserve(id),
Err(ReservationError::InvalidReservationId)
);
}
#[test]
fn existing_reserve_unreserve() {
let id = ReservationId::from([0xff; 32]);
let mut map = GasReservationMap::new();
map.insert(
id,
GasReservationSlot {
amount: 1,
start: 1,
finish: 100,
},
);
let mut reserver = GasReserver::new(&Default::default(), map, 256);
reserver.mark_used(id).unwrap();
assert_eq!(
reserver.unreserve(id),
Err(ReservationError::InvalidReservationId)
);
}
#[test]
fn unreserving_unreserved() {
let id = ReservationId::from([0xff; 32]);
let slot = GasReservationSlot {
amount: 1,
start: 2,
finish: 3,
};
let mut map = GasReservationMap::new();
map.insert(id, slot.clone());
let mut reserver = GasReserver::new(&Default::default(), map, 256);
let (amount, _) = reserver.unreserve(id).expect("Shouldn't fail");
assert_eq!(amount, slot.amount);
assert!(reserver.unreserve(id).is_err());
assert_eq!(
reserver.states().get(&id).cloned(),
Some(GasReservationState::Removed {
expiration: slot.finish
})
);
}
}