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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>)>;
}