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// This file is part of Substrate.
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// Copyright (C) Parity Technologies (UK) Ltd.
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// SPDX-License-Identifier: Apache-2.0
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// 	http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/// A wrapper around `kvdb::Database` that implements `sp_database::Database` trait
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use ::kvdb::{DBTransaction, KeyValueDB};
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use crate::{error, Change, ColumnId, Database, Transaction};
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struct DbAdapter<D: KeyValueDB + 'static>(D);
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fn handle_err<T>(result: std::io::Result<T>) -> T {
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	match result {
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		Ok(r) => r,
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		Err(e) => {
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			panic!("Critical database error: {:?}", e);
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		},
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	}
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}
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/// Wrap RocksDb database into a trait object that implements `sp_database::Database`
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pub fn as_database<D, H>(db: D) -> std::sync::Arc<dyn Database<H>>
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where
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	D: KeyValueDB + 'static,
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	H: Clone + AsRef<[u8]>,
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{
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	std::sync::Arc::new(DbAdapter(db))
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}
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impl<D: KeyValueDB> DbAdapter<D> {
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	// Returns counter key and counter value if it exists.
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	fn read_counter(&self, col: ColumnId, key: &[u8]) -> error::Result<(Vec<u8>, Option<u32>)> {
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		// Add a key suffix for the counter
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		let mut counter_key = key.to_vec();
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		counter_key.push(0);
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		Ok(match self.0.get(col, &counter_key).map_err(|e| error::DatabaseError(Box::new(e)))? {
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			Some(data) => {
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				let mut counter_data = [0; 4];
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				if data.len() != 4 {
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					return Err(error::DatabaseError(Box::new(std::io::Error::new(
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						std::io::ErrorKind::Other,
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						format!("Unexpected counter len {}", data.len()),
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					))))
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				}
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				counter_data.copy_from_slice(&data);
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				let counter = u32::from_le_bytes(counter_data);
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				(counter_key, Some(counter))
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			},
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			None => (counter_key, None),
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		})
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	}
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}
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impl<D: KeyValueDB, H: Clone + AsRef<[u8]>> Database<H> for DbAdapter<D> {
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	fn commit(&self, transaction: Transaction<H>) -> error::Result<()> {
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		let mut tx = DBTransaction::new();
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		for change in transaction.0.into_iter() {
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			match change {
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				Change::Set(col, key, value) => tx.put_vec(col, &key, value),
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				Change::Remove(col, key) => tx.delete(col, &key),
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				Change::Store(col, key, value) => match self.read_counter(col, key.as_ref())? {
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					(counter_key, Some(mut counter)) => {
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						counter += 1;
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						tx.put(col, &counter_key, &counter.to_le_bytes());
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					},
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					(counter_key, None) => {
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						let d = 1u32.to_le_bytes();
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						tx.put(col, &counter_key, &d);
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						tx.put_vec(col, key.as_ref(), value);
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					},
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				},
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				Change::Reference(col, key) => {
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					if let (counter_key, Some(mut counter)) =
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						self.read_counter(col, key.as_ref())?
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					{
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						counter += 1;
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						tx.put(col, &counter_key, &counter.to_le_bytes());
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					}
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				},
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				Change::Release(col, key) => {
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					if let (counter_key, Some(mut counter)) =
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						self.read_counter(col, key.as_ref())?
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					{
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						counter -= 1;
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						if counter == 0 {
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							tx.delete(col, &counter_key);
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							tx.delete(col, key.as_ref());
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						} else {
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							tx.put(col, &counter_key, &counter.to_le_bytes());
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						}
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					}
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				},
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			}
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		}
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		self.0.write(tx).map_err(|e| error::DatabaseError(Box::new(e)))
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	}
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	fn get(&self, col: ColumnId, key: &[u8]) -> Option<Vec<u8>> {
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		handle_err(self.0.get(col, key))
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	}
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	fn contains(&self, col: ColumnId, key: &[u8]) -> bool {
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		handle_err(self.0.has_key(col, key))
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	}
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}