cumulus_primitives_timestamp/
lib.rs

1// Copyright (C) Parity Technologies (UK) Ltd.
2// This file is part of Cumulus.
3// SPDX-License-Identifier: Apache-2.0
4
5// Licensed under the Apache License, Version 2.0 (the "License");
6// you may not use this file except in compliance with the License.
7// You may obtain a copy of the License at
8//
9// 	http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing, software
12// distributed under the License is distributed on an "AS IS" BASIS,
13// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14// See the License for the specific language governing permissions and
15// limitations under the License.
16
17//! Cumulus timestamp related primitives.
18//!
19//! Provides a [`InherentDataProvider`] that should be used in the validation phase of the
20//! parachain. It will be used to create the inherent data and that will be used to check the
21//! inherents inside the parachain block (in this case the timestamp inherent). As we don't have
22//! access to any clock from the runtime the timestamp is always passed as an inherent into the
23//! runtime. To check this inherent when validating the block, we will use the relay chain slot. As
24//! the relay chain slot is derived from a timestamp, we can easily convert it back to a timestamp
25//! by multiplying it with the slot duration. By comparing the relay chain slot derived timestamp
26//! with the timestamp we can ensure that the parachain timestamp is reasonable.
27
28#![cfg_attr(not(feature = "std"), no_std)]
29
30use core::time::Duration;
31use cumulus_primitives_core::relay_chain::Slot;
32use sp_inherents::{Error, InherentData};
33
34pub use sp_timestamp::{InherentType, INHERENT_IDENTIFIER};
35
36/// The inherent data provider for the timestamp.
37///
38/// This should be used in the runtime when checking the inherents in the validation phase of the
39/// parachain.
40pub struct InherentDataProvider {
41	relay_chain_slot: Slot,
42	relay_chain_slot_duration: Duration,
43}
44
45impl InherentDataProvider {
46	/// Create `Self` from the given relay chain slot and slot duration.
47	pub fn from_relay_chain_slot_and_duration(
48		relay_chain_slot: Slot,
49		relay_chain_slot_duration: Duration,
50	) -> Self {
51		Self { relay_chain_slot, relay_chain_slot_duration }
52	}
53
54	/// Create the inherent data.
55	pub fn create_inherent_data(&self) -> Result<InherentData, Error> {
56		let mut inherent_data = InherentData::new();
57		self.provide_inherent_data(&mut inherent_data).map(|_| inherent_data)
58	}
59
60	/// Provide the inherent data into the given `inherent_data`.
61	pub fn provide_inherent_data(&self, inherent_data: &mut InherentData) -> Result<(), Error> {
62		// As the parachain starts building at around `relay_chain_slot + 1` we use that slot to
63		// calculate the timestamp.
64		let data: InherentType = ((*self.relay_chain_slot + 1) *
65			self.relay_chain_slot_duration.as_millis() as u64)
66			.into();
67
68		inherent_data.put_data(INHERENT_IDENTIFIER, &data)
69	}
70}
cumulus_primitives_timestamp/lib.rs

cumulus_primitives_timestamp/
lib.rs
