Remark storage (#10698)

* Remark storage

* Fixed benches

* Update frame/remark/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Fixed build

* Fixed build

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/frame/remark/src/lib.rs

@@ -0,0 +1,85 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2022 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Remark storage pallet. Indexes remarks and stores them off chain.
+
+// Ensure we're `no_std` when compiling for Wasm.
+#![cfg_attr(not(feature = "std"), no_std)]
+
+mod benchmarking;
+pub mod weights;
+
+#[cfg(test)]
+mod mock;
+#[cfg(test)]
+mod tests;
+
+use sp_std::prelude::*;
+
+// Re-export pallet items so that they can be accessed from the crate namespace.
+pub use pallet::*;
+pub use weights::WeightInfo;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use super::*;
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {
+		/// The overarching event type.
+		type Event: From<Event<Self>> + IsType<<Self as frame_system::Config>::Event>;
+		/// Weight information for extrinsics in this pallet.
+		type WeightInfo: WeightInfo;
+	}
+
+	#[pallet::error]
+	pub enum Error<T> {
+		/// Attempting to store empty data.
+		Empty,
+		/// Attempted to call `store` outside of block execution.
+		BadContext,
+	}
+
+	#[pallet::pallet]
+	#[pallet::without_storage_info]
+	pub struct Pallet<T>(_);
+
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		/// Index and store data off chain.
+		#[pallet::weight(T::WeightInfo::store(remark.len() as u32))]
+		pub fn store(origin: OriginFor<T>, remark: Vec<u8>) -> DispatchResultWithPostInfo {
+			ensure!(!remark.is_empty(), Error::<T>::Empty);
+			let sender = ensure_signed(origin)?;
+			let content_hash = sp_io::hashing::blake2_256(&remark);
+			let extrinsic_index = <frame_system::Pallet<T>>::extrinsic_index()
+				.ok_or_else(|| Error::<T>::BadContext)?;
+			sp_io::transaction_index::index(extrinsic_index, remark.len() as u32, content_hash);
+			Self::deposit_event(Event::Stored { sender, content_hash: content_hash.into() });
+			Ok(().into())
+		}
+	}
+
+	#[pallet::event]
+	#[pallet::generate_deposit(pub(super) fn deposit_event)]
+	pub enum Event<T: Config> {
+		/// Stored data off chain.
+		Stored { sender: T::AccountId, content_hash: sp_core::H256 },
+	}
+}