new crate sc-light (#6235)

* sc-light

* remove unused deps

* fix line width

* move more fns to sc_light

substrate/client/light/src/backend.rs

@@ -0,0 +1,518 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2020 Parity Technologies (UK) Ltd.
+// 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/>.
+
+//! Light client backend. Only stores headers and justifications of blocks.
+//! Everything else is requested from full nodes on demand.
+
+use std::collections::HashMap;
+use std::sync::Arc;
+use parking_lot::RwLock;
+
+use codec::{Decode, Encode};
+
+use sp_core::ChangesTrieConfiguration;
+use sp_core::storage::{well_known_keys, ChildInfo};
+use sp_core::offchain::storage::InMemOffchainStorage;
+use sp_state_machine::{
+	Backend as StateBackend, TrieBackend, InMemoryBackend, ChangesTrieTransaction,
+	StorageCollection, ChildStorageCollection,
+};
+use sp_runtime::{generic::BlockId, Justification, Storage};
+use sp_runtime::traits::{Block as BlockT, NumberFor, Zero, Header, HashFor};
+use sp_blockchain::{Error as ClientError, Result as ClientResult};
+use sc_client_api::{
+	backend::{
+		AuxStore, Backend as ClientBackend, BlockImportOperation, RemoteBackend, NewBlockState,
+		PrunableStateChangesTrieStorage,
+	},
+	blockchain::{
+		HeaderBackend as BlockchainHeaderBackend, well_known_cache_keys,
+	},
+	light::Storage as BlockchainStorage,
+	in_mem::check_genesis_storage,
+	UsageInfo,
+};
+use super::blockchain::Blockchain;
+use hash_db::Hasher;
+
+const IN_MEMORY_EXPECT_PROOF: &str = "InMemory state backend has Void error type and always succeeds; qed";
+
+/// Light client backend.
+pub struct Backend<S, H: Hasher> {
+	blockchain: Arc<Blockchain<S>>,
+	genesis_state: RwLock<Option<InMemoryBackend<H>>>,
+	import_lock: RwLock<()>,
+}
+
+/// Light block (header and justification) import operation.
+pub struct ImportOperation<Block: BlockT, S> {
+	header: Option<Block::Header>,
+	cache: HashMap<well_known_cache_keys::Id, Vec<u8>>,
+	leaf_state: NewBlockState,
+	aux_ops: Vec<(Vec<u8>, Option<Vec<u8>>)>,
+	finalized_blocks: Vec<BlockId<Block>>,
+	set_head: Option<BlockId<Block>>,
+	storage_update: Option<InMemoryBackend<HashFor<Block>>>,
+	changes_trie_config_update: Option<Option<ChangesTrieConfiguration>>,
+	_phantom: std::marker::PhantomData<S>,
+}
+
+/// Either in-memory genesis state, or locally-unavailable state.
+pub enum GenesisOrUnavailableState<H: Hasher> {
+	/// Genesis state - storage values are stored in-memory.
+	Genesis(InMemoryBackend<H>),
+	/// We know that state exists, but all calls will fail with error, because it
+	/// isn't locally available.
+	Unavailable,
+}
+
+impl<S, H: Hasher> Backend<S, H> {
+	/// Create new light backend.
+	pub fn new(blockchain: Arc<Blockchain<S>>) -> Self {
+		Self {
+			blockchain,
+			genesis_state: RwLock::new(None),
+			import_lock: Default::default(),
+		}
+	}
+
+	/// Get shared blockchain reference.
+	pub fn blockchain(&self) -> &Arc<Blockchain<S>> {
+		&self.blockchain
+	}
+}
+
+impl<S: AuxStore, H: Hasher> AuxStore for Backend<S, H> {
+	fn insert_aux<
+		'a,
+		'b: 'a,
+		'c: 'a,
+		I: IntoIterator<Item=&'a(&'c [u8], &'c [u8])>,
+		D: IntoIterator<Item=&'a &'b [u8]>,
+	>(&self, insert: I, delete: D) -> ClientResult<()> {
+		self.blockchain.storage().insert_aux(insert, delete)
+	}
+
+	fn get_aux(&self, key: &[u8]) -> ClientResult<Option<Vec<u8>>> {
+		self.blockchain.storage().get_aux(key)
+	}
+}
+
+impl<S, Block> ClientBackend<Block> for Backend<S, HashFor<Block>>
+	where
+		Block: BlockT,
+		S: BlockchainStorage<Block>,
+		Block::Hash: Ord,
+{
+	type BlockImportOperation = ImportOperation<Block, S>;
+	type Blockchain = Blockchain<S>;
+	type State = GenesisOrUnavailableState<HashFor<Block>>;
+	type OffchainStorage = InMemOffchainStorage;
+
+	fn begin_operation(&self) -> ClientResult<Self::BlockImportOperation> {
+		Ok(ImportOperation {
+			header: None,
+			cache: Default::default(),
+			leaf_state: NewBlockState::Normal,
+			aux_ops: Vec::new(),
+			finalized_blocks: Vec::new(),
+			set_head: None,
+			storage_update: None,
+			changes_trie_config_update: None,
+			_phantom: Default::default(),
+		})
+	}
+
+	fn begin_state_operation(
+		&self,
+		_operation: &mut Self::BlockImportOperation,
+		_block: BlockId<Block>
+	) -> ClientResult<()> {
+		Ok(())
+	}
+
+	fn commit_operation(&self, mut operation: Self::BlockImportOperation) -> ClientResult<()> {
+		if !operation.finalized_blocks.is_empty() {
+			for block in operation.finalized_blocks {
+				self.blockchain.storage().finalize_header(block)?;
+			}
+		}
+
+		if let Some(header) = operation.header {
+			let is_genesis_import = header.number().is_zero();
+			if let Some(new_config) = operation.changes_trie_config_update {
+				operation.cache.insert(well_known_cache_keys::CHANGES_TRIE_CONFIG, new_config.encode());
+			}
+			self.blockchain.storage().import_header(
+				header,
+				operation.cache,
+				operation.leaf_state,
+				operation.aux_ops,
+			)?;
+
+			// when importing genesis block => remember its state
+			if is_genesis_import {
+				*self.genesis_state.write() = operation.storage_update.take();
+			}
+		} else {
+			for (key, maybe_val) in operation.aux_ops {
+				match maybe_val {
+					Some(val) => self.blockchain.storage().insert_aux(
+						&[(&key[..], &val[..])],
+						std::iter::empty(),
+					)?,
+					None => self.blockchain.storage().insert_aux(std::iter::empty(), &[&key[..]])?,
+				}
+			}
+		}
+
+		if let Some(set_head) = operation.set_head {
+			self.blockchain.storage().set_head(set_head)?;
+		}
+
+		Ok(())
+	}
+
+	fn finalize_block(
+		&self,
+		block: BlockId<Block>,
+		_justification: Option<Justification>,
+	) -> ClientResult<()> {
+		self.blockchain.storage().finalize_header(block)
+	}
+
+	fn blockchain(&self) -> &Blockchain<S> {
+		&self.blockchain
+	}
+
+	fn usage_info(&self) -> Option<UsageInfo> {
+		self.blockchain.storage().usage_info()
+	}
+
+	fn changes_trie_storage(&self) -> Option<&dyn PrunableStateChangesTrieStorage<Block>> {
+		None
+	}
+
+	fn offchain_storage(&self) -> Option<Self::OffchainStorage> {
+		None
+	}
+
+	fn state_at(&self, block: BlockId<Block>) -> ClientResult<Self::State> {
+		let block_number = self.blockchain.expect_block_number_from_id(&block)?;
+
+		// special case for genesis block
+		if block_number.is_zero() {
+			if let Some(genesis_state) = self.genesis_state.read().clone() {
+				return Ok(GenesisOrUnavailableState::Genesis(genesis_state));
+			}
+		}
+
+		// else return unavailable state. We do not return error here, because error
+		// would mean that we do not know this state at all. But we know that it exists
+		Ok(GenesisOrUnavailableState::Unavailable)
+	}
+
+	fn revert(
+		&self,
+		_n: NumberFor<Block>,
+		_revert_finalized: bool,
+	) -> ClientResult<NumberFor<Block>> {
+		Err(ClientError::NotAvailableOnLightClient)
+	}
+
+	fn get_import_lock(&self) -> &RwLock<()> {
+		&self.import_lock
+	}
+}
+
+impl<S, Block> RemoteBackend<Block> for Backend<S, HashFor<Block>>
+where
+	Block: BlockT,
+	S: BlockchainStorage<Block> + 'static,
+	Block::Hash: Ord,
+{
+	fn is_local_state_available(&self, block: &BlockId<Block>) -> bool {
+		self.genesis_state.read().is_some()
+			&& self.blockchain.expect_block_number_from_id(block)
+				.map(|num| num.is_zero())
+				.unwrap_or(false)
+	}
+
+	fn remote_blockchain(&self) -> Arc<dyn super::blockchain::RemoteBlockchain<Block>> {
+		self.blockchain.clone()
+	}
+}
+
+impl<S, Block> BlockImportOperation<Block> for ImportOperation<Block, S>
+	where
+		Block: BlockT,
+		S: BlockchainStorage<Block>,
+		Block::Hash: Ord,
+{
+	type State = GenesisOrUnavailableState<HashFor<Block>>;
+
+	fn state(&self) -> ClientResult<Option<&Self::State>> {
+		// None means 'locally-stateless' backend
+		Ok(None)
+	}
+
+	fn set_block_data(
+		&mut self,
+		header: Block::Header,
+		_body: Option<Vec<Block::Extrinsic>>,
+		_justification: Option<Justification>,
+		state: NewBlockState,
+	) -> ClientResult<()> {
+		self.leaf_state = state;
+		self.header = Some(header);
+		Ok(())
+	}
+
+	fn update_cache(&mut self, cache: HashMap<well_known_cache_keys::Id, Vec<u8>>) {
+		self.cache = cache;
+	}
+
+	fn update_db_storage(
+		&mut self,
+		_update: <Self::State as StateBackend<HashFor<Block>>>::Transaction,
+	) -> ClientResult<()> {
+		// we're not storing anything locally => ignore changes
+		Ok(())
+	}
+
+	fn update_changes_trie(
+		&mut self,
+		_update: ChangesTrieTransaction<HashFor<Block>, NumberFor<Block>>,
+	) -> ClientResult<()> {
+		// we're not storing anything locally => ignore changes
+		Ok(())
+	}
+
+	fn reset_storage(&mut self, input: Storage) -> ClientResult<Block::Hash> {
+		check_genesis_storage(&input)?;
+
+		// changes trie configuration
+		let changes_trie_config = input.top.iter()
+			.find(|(k, _)| &k[..] == well_known_keys::CHANGES_TRIE_CONFIG)
+			.map(|(_, v)| Decode::decode(&mut &v[..])
+				.expect("changes trie configuration is encoded properly at genesis"));
+		self.changes_trie_config_update = Some(changes_trie_config);
+
+		// this is only called when genesis block is imported => shouldn't be performance bottleneck
+		let mut storage: HashMap<Option<ChildInfo>, _> = HashMap::new();
+		storage.insert(None, input.top);
+
+		// create a list of children keys to re-compute roots for
+		let child_delta = input.children_default
+			.iter()
+			.map(|(_storage_key, storage_child)| (&storage_child.child_info, std::iter::empty()));
+
+		// make sure to persist the child storage
+		for (_child_key, storage_child) in input.children_default.clone() {
+			storage.insert(Some(storage_child.child_info), storage_child.data);
+		}
+
+		let storage_update = InMemoryBackend::from(storage);
+		let (storage_root, _) = storage_update.full_storage_root(std::iter::empty(), child_delta);
+		self.storage_update = Some(storage_update);
+
+		Ok(storage_root)
+	}
+
+	fn insert_aux<I>(&mut self, ops: I) -> ClientResult<()>
+		where I: IntoIterator<Item=(Vec<u8>, Option<Vec<u8>>)>
+	{
+		self.aux_ops.append(&mut ops.into_iter().collect());
+		Ok(())
+	}
+
+	fn update_storage(
+		&mut self,
+		_update: StorageCollection,
+		_child_update: ChildStorageCollection,
+	) -> ClientResult<()> {
+		// we're not storing anything locally => ignore changes
+		Ok(())
+	}
+
+	fn mark_finalized(
+		&mut self,
+		block: BlockId<Block>,
+		_justification: Option<Justification>,
+	) -> ClientResult<()> {
+		self.finalized_blocks.push(block);
+		Ok(())
+	}
+
+	fn mark_head(&mut self, block: BlockId<Block>) -> ClientResult<()> {
+		self.set_head = Some(block);
+		Ok(())
+	}
+}
+
+impl<H: Hasher> std::fmt::Debug for GenesisOrUnavailableState<H> {
+	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) => state.fmt(f),
+			GenesisOrUnavailableState::Unavailable => write!(f, "Unavailable"),
+		}
+	}
+}
+
+impl<H: Hasher> StateBackend<H> for GenesisOrUnavailableState<H>
+	where
+		H::Out: Ord + codec::Codec,
+{
+	type Error = ClientError;
+	type Transaction = <InMemoryBackend<H> as StateBackend<H>>::Transaction;
+	type TrieBackendStorage = <InMemoryBackend<H> as StateBackend<H>>::TrieBackendStorage;
+
+	fn storage(&self, key: &[u8]) -> ClientResult<Option<Vec<u8>>> {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) =>
+				Ok(state.storage(key).expect(IN_MEMORY_EXPECT_PROOF)),
+			GenesisOrUnavailableState::Unavailable => Err(ClientError::NotAvailableOnLightClient),
+		}
+	}
+
+	fn child_storage(
+		&self,
+		child_info: &ChildInfo,
+		key: &[u8],
+	) -> ClientResult<Option<Vec<u8>>> {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) =>
+				Ok(state.child_storage(child_info, key).expect(IN_MEMORY_EXPECT_PROOF)),
+			GenesisOrUnavailableState::Unavailable => Err(ClientError::NotAvailableOnLightClient),
+		}
+	}
+
+	fn next_storage_key(&self, key: &[u8]) -> Result<Option<Vec<u8>>, Self::Error> {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) =>
+				Ok(state.next_storage_key(key).expect(IN_MEMORY_EXPECT_PROOF)),
+			GenesisOrUnavailableState::Unavailable => Err(ClientError::NotAvailableOnLightClient),
+		}
+	}
+
+	fn next_child_storage_key(
+		&self,
+		child_info: &ChildInfo,
+		key: &[u8],
+	) -> Result<Option<Vec<u8>>, Self::Error> {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) => Ok(
+				state.next_child_storage_key(child_info, key)
+					.expect(IN_MEMORY_EXPECT_PROOF)
+			),
+			GenesisOrUnavailableState::Unavailable => Err(ClientError::NotAvailableOnLightClient),
+		}
+	}
+
+	fn for_keys_with_prefix<A: FnMut(&[u8])>(&self, prefix: &[u8], action: A) {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) => state.for_keys_with_prefix(prefix, action),
+			GenesisOrUnavailableState::Unavailable => (),
+		}
+	}
+
+	fn for_key_values_with_prefix<A: FnMut(&[u8], &[u8])>(&self, prefix: &[u8], action: A) {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) => state.for_key_values_with_prefix(prefix, action),
+			GenesisOrUnavailableState::Unavailable => (),
+		}
+	}
+
+	fn for_keys_in_child_storage<A: FnMut(&[u8])>(
+		&self,
+		child_info: &ChildInfo,
+		action: A,
+	) {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) =>
+				state.for_keys_in_child_storage(child_info, action),
+			GenesisOrUnavailableState::Unavailable => (),
+		}
+	}
+
+	fn for_child_keys_with_prefix<A: FnMut(&[u8])>(
+		&self,
+		child_info: &ChildInfo,
+		prefix: &[u8],
+		action: A,
+	) {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) =>
+				state.for_child_keys_with_prefix(child_info, prefix, action),
+			GenesisOrUnavailableState::Unavailable => (),
+		}
+	}
+
+	fn storage_root<'a>(
+		&self,
+		delta: impl Iterator<Item=(&'a [u8], Option<&'a [u8]>)>,
+	) -> (H::Out, Self::Transaction) where H::Out: Ord {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) =>
+				state.storage_root(delta),
+			GenesisOrUnavailableState::Unavailable => Default::default(),
+		}
+	}
+
+	fn child_storage_root<'a>(
+		&self,
+		child_info: &ChildInfo,
+		delta: impl Iterator<Item=(&'a [u8], Option<&'a [u8]>)>,
+	) -> (H::Out, bool, Self::Transaction) where H::Out: Ord {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) => {
+				let (root, is_equal, _) = state.child_storage_root(child_info, delta);
+				(root, is_equal, Default::default())
+			},
+			GenesisOrUnavailableState::Unavailable =>
+				(H::Out::default(), true, Default::default()),
+		}
+	}
+
+	fn pairs(&self) -> Vec<(Vec<u8>, Vec<u8>)> {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) => state.pairs(),
+			GenesisOrUnavailableState::Unavailable => Vec::new(),
+		}
+	}
+
+	fn keys(&self, prefix: &[u8]) -> Vec<Vec<u8>> {
+		match *self {
+			GenesisOrUnavailableState::Genesis(ref state) => state.keys(prefix),
+			GenesisOrUnavailableState::Unavailable => Vec::new(),
+		}
+	}
+
+	fn register_overlay_stats(&mut self, _stats: &sp_state_machine::StateMachineStats) { }
+
+	fn usage_info(&self) -> sp_state_machine::UsageInfo {
+		sp_state_machine::UsageInfo::empty()
+	}
+
+	fn as_trie_backend(&mut self) -> Option<&TrieBackend<Self::TrieBackendStorage, H>> {
+		match self {
+			GenesisOrUnavailableState::Genesis(ref mut state) => state.as_trie_backend(),
+			GenesisOrUnavailableState::Unavailable => None,
+		}
+	}
+}