sp_database/
lib.rs

1// This file is part of Substrate.
2
3// Copyright (C) Parity Technologies (UK) Ltd.
4// SPDX-License-Identifier: Apache-2.0
5
6// Licensed under the Apache License, Version 2.0 (the "License");
7// you may not use this file except in compliance with the License.
8// You may obtain a copy of the License at
9//
10// 	http://www.apache.org/licenses/LICENSE-2.0
11//
12// Unless required by applicable law or agreed to in writing, software
13// distributed under the License is distributed on an "AS IS" BASIS,
14// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15// See the License for the specific language governing permissions and
16// limitations under the License.
17
18//! The main database trait, allowing Substrate to store data persistently.
19
20pub mod error;
21mod kvdb;
22mod mem;
23
24pub use crate::kvdb::as_database;
25pub use mem::MemDb;
26
27/// An identifier for a column.
28pub type ColumnId = u32;
29
30/// An alteration to the database.
31#[derive(Clone)]
32pub enum Change<H> {
33	Set(ColumnId, Vec<u8>, Vec<u8>),
34	Remove(ColumnId, Vec<u8>),
35	Store(ColumnId, H, Vec<u8>),
36	Reference(ColumnId, H),
37	Release(ColumnId, H),
38}
39
40/// A series of changes to the database that can be committed atomically. They do not take effect
41/// until passed into `Database::commit`.
42#[derive(Default, Clone)]
43pub struct Transaction<H>(pub Vec<Change<H>>);
44
45impl<H> Transaction<H> {
46	/// Create a new transaction to be prepared and committed atomically.
47	pub fn new() -> Self {
48		Transaction(Vec::new())
49	}
50	/// Set the value of `key` in `col` to `value`, replacing anything that is there currently.
51	pub fn set(&mut self, col: ColumnId, key: &[u8], value: &[u8]) {
52		self.0.push(Change::Set(col, key.to_vec(), value.to_vec()))
53	}
54	/// Set the value of `key` in `col` to `value`, replacing anything that is there currently.
55	pub fn set_from_vec(&mut self, col: ColumnId, key: &[u8], value: Vec<u8>) {
56		self.0.push(Change::Set(col, key.to_vec(), value))
57	}
58	/// Remove the value of `key` in `col`.
59	pub fn remove(&mut self, col: ColumnId, key: &[u8]) {
60		self.0.push(Change::Remove(col, key.to_vec()))
61	}
62	/// Store the `preimage` of `hash` into the database, so that it may be looked up later with
63	/// `Database::get`. This may be called multiple times, but subsequent
64	/// calls will ignore `preimage` and simply increase the number of references on `hash`.
65	pub fn store(&mut self, col: ColumnId, hash: H, preimage: Vec<u8>) {
66		self.0.push(Change::Store(col, hash, preimage))
67	}
68	/// Increase the number of references for `hash` in the database.
69	pub fn reference(&mut self, col: ColumnId, hash: H) {
70		self.0.push(Change::Reference(col, hash))
71	}
72	/// Release the preimage of `hash` from the database. An equal number of these to the number of
73	/// corresponding `store`s must have been given before it is legal for `Database::get` to
74	/// be unable to provide the preimage.
75	pub fn release(&mut self, col: ColumnId, hash: H) {
76		self.0.push(Change::Release(col, hash))
77	}
78}
79
80pub trait Database<H: Clone + AsRef<[u8]>>: Send + Sync {
81	/// Commit the `transaction` to the database atomically. Any further calls to `get` or `lookup`
82	/// will reflect the new state.
83	fn commit(&self, transaction: Transaction<H>) -> error::Result<()>;
84
85	/// Retrieve the value previously stored against `key` or `None` if
86	/// `key` is not currently in the database.
87	fn get(&self, col: ColumnId, key: &[u8]) -> Option<Vec<u8>>;
88
89	/// Check if the value exists in the database without retrieving it.
90	fn contains(&self, col: ColumnId, key: &[u8]) -> bool {
91		self.get(col, key).is_some()
92	}
93
94	/// Check value size in the database possibly without retrieving it.
95	fn value_size(&self, col: ColumnId, key: &[u8]) -> Option<usize> {
96		self.get(col, key).map(|v| v.len())
97	}
98
99	/// Call `f` with the value previously stored against `key`.
100	///
101	/// This may be faster than `get` since it doesn't allocate.
102	/// Use `with_get` helper function if you need `f` to return a value from `f`
103	fn with_get(&self, col: ColumnId, key: &[u8], f: &mut dyn FnMut(&[u8])) {
104		if let Some(v) = self.get(col, key) {
105			f(&v)
106		}
107	}
108
109	/// Check if database supports internal ref counting for state data.
110	///
111	/// For backwards compatibility returns `false` by default.
112	fn supports_ref_counting(&self) -> bool {
113		false
114	}
115
116	/// Remove a possible path-prefix from the key.
117	///
118	/// Not all database implementations use a prefix for keys, so this function may be a noop.
119	fn sanitize_key(&self, _key: &mut Vec<u8>) {}
120}
121
122impl<H> std::fmt::Debug for dyn Database<H> {
123	fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
124		write!(f, "Database")
125	}
126}
127
128/// Call `f` with the value previously stored against `key` and return the result, or `None` if
129/// `key` is not currently in the database.
130///
131/// This may be faster than `get` since it doesn't allocate.
132pub fn with_get<R, H: Clone + AsRef<[u8]>>(
133	db: &dyn Database<H>,
134	col: ColumnId,
135	key: &[u8],
136	mut f: impl FnMut(&[u8]) -> R,
137) -> Option<R> {
138	let mut result: Option<R> = None;
139	let mut adapter = |k: &_| {
140		result = Some(f(k));
141	};
142	db.with_get(col, key, &mut adapter);
143	result
144}
sp_database/lib.rs

sp_database/
lib.rs
