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/* * Copyright 2018 Intel Corporation * * 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. * ------------------------------------------------------------------------------ */ //! Traits for reading and writing from databases. //! //! Transact operates on key-value entries at the database level, where both keys and values are //! opaque bytes. //! //! # Readers and Writers //! //! Both the DatabsaeReader and DatabaseWriter traits imply that the underlying database //! implementation maintains transactional consistency throughout their lifetimes. For example, //! while a cursor on a DatabaseReader is in use, any changes to the underlying data should not //! alter the iteration of the reader. //! //! Changes to the underlying database are rendered via the DatabaseWriter's commit method. pub mod btree; pub mod error; pub mod lmdb; #[cfg(feature = "redis-db")] pub mod redis; #[cfg(feature = "sqlite-db")] pub mod sqlite; pub use crate::database::error::DatabaseError; pub type DatabaseCursor<'a> = Box<dyn DatabaseReaderCursor<Item = (Vec<u8>, Vec<u8>)> + 'a>; pub trait Database: Sync + Send { fn get_reader<'a>(&'a self) -> Result<Box<dyn DatabaseReader + 'a>, DatabaseError>; fn get_writer<'a>(&'a self) -> Result<Box<dyn DatabaseWriter + 'a>, DatabaseError>; fn clone_box(&self) -> Box<dyn Database>; } impl Clone for Box<dyn Database> { fn clone(&self) -> Box<dyn Database> { self.clone_box() } } /// A DatabaseReader provides read access to a database instance. pub trait DatabaseReader { /// Returns the bytes stored at the given key, if found. fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>, DatabaseError>; /// Returns the bytes stored at the given key on a specified index, if found. fn index_get(&self, index: &str, key: &[u8]) -> Result<Option<Vec<u8>>, DatabaseError>; /// Returns a cursor against the main database. The cursor iterates over /// the entries in the natural key order. fn cursor(&self) -> Result<DatabaseCursor, DatabaseError>; /// Returns a cursor against the given index. The cursor iterates over /// the entries in the index's natural key order. fn index_cursor(&self, index: &str) -> Result<DatabaseCursor, DatabaseError>; /// Returns the number of entries in the main database. fn count(&self) -> Result<usize, DatabaseError>; /// Returns the number of entries in the given index. fn index_count(&self, index: &str) -> Result<usize, DatabaseError>; } /// A DatabaseReader provides read access to a database instance. pub trait DatabaseWriter: DatabaseReader { /// Writes the given key/value pair. If the key/value pair already exists, /// it will return a DatabaseError::DuplicateEntry. fn put(&mut self, key: &[u8], value: &[u8]) -> Result<(), DatabaseError>; /// Writes the given key/value pair. If the key/value pair already exists, /// it overwrites the old value fn overwrite(&mut self, key: &[u8], value: &[u8]) -> Result<(), DatabaseError>; /// Deletes the given key/value pair. If the key does exist, it returns an error, fn delete(&mut self, key: &[u8]) -> Result<(), DatabaseError>; /// Writes the given key/value pair at index. fn index_put(&mut self, index: &str, key: &[u8], value: &[u8]) -> Result<(), DatabaseError>; /// Deletes the given key/value pair at index. fn index_delete(&mut self, index: &str, key: &[u8]) -> Result<(), DatabaseError>; // Commit changes to database fn commit(self: Box<Self>) -> Result<(), DatabaseError>; // Use writer as reader fn as_reader(&self) -> &dyn DatabaseReader; } pub trait DatabaseReaderCursor: Iterator { fn seek_first(&mut self) -> Option<(Vec<u8>, Vec<u8>)>; fn seek_last(&mut self) -> Option<(Vec<u8>, Vec<u8>)>; }