New database trait (#5549)

* Introduce trait

* The trait

* Generic

* Basic impls.

* Remove unneeded bounds

* Minor changes

* Switch over to the new DB trait

* Integrated parity-db and added CLI for db selection

* Default impl.

* Fix logs.

* Started integrating subdb

* Apply suggestions from code review

Co-Authored-By: Cecile Tonglet <cecile@parity.io>

* Apply suggestions from code review

Co-Authored-By: Nikolay Volf <nikvolf@gmail.com>

* Enable subdb

* Bump parity-db

* Fixed CLI macro

* Fixed browser build

* Fixed features

* Sort out features

* Use parity-db from crates.io

* Typo

Co-authored-by: arkpar <arkady.paronyan@gmail.com>
Co-authored-by: Cecile Tonglet <cecile@parity.io>
Co-authored-by: Nikolay Volf <nikvolf@gmail.com>

substrate/client/db/src/subdb.rs

@@ -0,0 +1,87 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate 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.
+
+// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+/// A `Database` adapter for subdb.
+
+use sp_database::{self, ColumnId};
+use parking_lot::RwLock;
+use blake2_rfc::blake2b::blake2b;
+use codec::Encode;
+use subdb::{Database, KeyType};
+
+/// A database hidden behind an RwLock, so that it implements Send + Sync.
+///
+/// Construct by creating a `Database` and then using `.into()`.
+pub struct DbAdapter<H: KeyType>(RwLock<Database<H>>);
+
+/// Wrap RocksDb database into a trait object that implements `sp_database::Database`
+pub fn open<H: KeyType + 'static>(
+	path: &std::path::Path,
+	_num_columns: u32,
+) -> Result<std::sync::Arc<dyn sp_database::Database<H>>, subdb::Error> {
+	let db = subdb::Options::from_path(path.into()).open()?;
+	Ok(std::sync::Arc::new(DbAdapter(RwLock::new(db))))
+}
+
+impl<H: KeyType> sp_database::Database<H> for DbAdapter<H> {
+	fn get(&self, col: ColumnId, key: &[u8]) -> Option<Vec<u8>> {
+		let mut hash = H::default();
+		(col, key).using_encoded(|d|
+			hash.as_mut().copy_from_slice(blake2b(32, &[], d).as_bytes())
+		);
+		self.0.read().get(&hash)
+	}
+
+	fn with_get(&self, col: ColumnId, key: &[u8], f: &mut dyn FnMut(&[u8])) {
+		let mut hash = H::default();
+		(col, key).using_encoded(|d|
+			hash.as_mut().copy_from_slice(blake2b(32, &[], d).as_bytes())
+		);
+		let _ = self.0.read().get_ref(&hash).map(|d| f(d.as_ref()));
+	}
+
+	fn set(&self, col: ColumnId, key: &[u8], value: &[u8]) {
+		let mut hash = H::default();
+		(col, key).using_encoded(|d|
+			hash.as_mut().copy_from_slice(blake2b(32, &[], d).as_bytes())
+		);
+		self.0.write().insert(&value, &hash);
+	}
+
+	fn remove(&self, col: ColumnId, key: &[u8]) {
+		let mut hash = H::default();
+		(col, key).using_encoded(|d|
+			hash.as_mut().copy_from_slice(blake2b(32, &[], d).as_bytes())
+		);
+		let _ = self.0.write().remove(&hash);
+	}
+
+	fn lookup(&self, hash: &H) -> Option<Vec<u8>> {
+		self.0.read().get(hash)
+	}
+
+	fn with_lookup(&self, hash: &H, f: &mut dyn FnMut(&[u8])) {
+		let _ = self.0.read().get_ref(hash).map(|d| f(d.as_ref()));
+	}
+
+	fn store(&self, hash: &H, preimage: &[u8]) {
+		self.0.write().insert(preimage, hash);
+	}
+
+	fn release(&self, hash: &H) {
+		let _ = self.0.write().remove(hash);
+	}
+}