2017-02-21 11:13:02 +01:00
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// Copyright 2015-2017 Parity Technologies (UK) Ltd.
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// This file is part of Parity.
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// Parity is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Parity is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with Parity. If not, see <http://www.gnu.org/licenses/>.
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//! A minimal "state backend" trait: an abstraction over the sources of data
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//! a blockchain state may draw upon.
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//!
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//! Currently assumes a very specific DB + cache structure, but
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//! should become general over time to the point where not even a
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//! merkle trie is strictly necessary.
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use std::sync::Arc;
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use state::Account;
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2017-02-21 12:35:21 +01:00
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use util::{Address, AsHashDB, HashDB, H256};
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2017-02-21 11:13:02 +01:00
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/// State backend. See module docs for more details.
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2017-02-21 12:35:21 +01:00
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pub trait Backend: Send {
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2017-02-21 11:13:02 +01:00
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/// Treat the backend as a read-only hashdb.
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fn as_hashdb(&self) -> &HashDB;
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/// Treat the backend as a writeable hashdb.
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fn as_hashdb_mut(&mut self) -> &mut HashDB;
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/// Add an account entry to the cache.
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fn add_to_account_cache(&mut self, addr: Address, data: Option<Account>, modified: bool);
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/// Add a global code cache entry. This doesn't need to worry about canonicality because
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/// it simply maps hashes to raw code and will always be correct in the absence of
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/// hash collisions.
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fn cache_code(&self, hash: H256, code: Arc<Vec<u8>>);
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2017-02-21 12:35:21 +01:00
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/// Get basic copy of the cached account. Not required to include storage.
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2017-02-21 11:13:02 +01:00
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/// Returns 'None' if cache is disabled or if the account is not cached.
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fn get_cached_account(&self, addr: &Address) -> Option<Option<Account>>;
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/// Get value from a cached account.
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/// `None` is passed to the closure if the account entry cached
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/// is known not to exist.
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/// `None` is returned if the entry is not cached.
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fn get_cached<F, U>(&self, a: &Address, f: F) -> Option<U>
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where F: FnOnce(Option<&mut Account>) -> U;
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/// Get cached code based on hash.
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fn get_cached_code(&self, hash: &H256) -> Option<Arc<Vec<u8>>>;
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2017-02-21 12:35:21 +01:00
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/// Note that an account with the given address is non-null.
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fn note_non_null_account(&self, address: &Address);
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/// Check whether an account is known to be empty. Returns true if known to be
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/// empty, false otherwise.
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fn is_known_null(&self, address: &Address) -> bool;
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}
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/// A raw backend which simply wraps a hashdb and does no caching.
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct NoCache<T>(T);
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impl<T> NoCache<T> {
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/// Create a new `NoCache` backend.
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pub fn new(inner: T) -> Self { NoCache(inner) }
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/// Consume the backend, yielding the inner database.
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pub fn into_inner(self) -> T { self.0 }
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}
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impl<T: AsHashDB + Send> Backend for NoCache<T> {
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fn as_hashdb(&self) -> &HashDB { self.0.as_hashdb() }
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fn as_hashdb_mut(&mut self) -> &mut HashDB { self.0.as_hashdb_mut() }
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fn add_to_account_cache(&mut self, _addr: Address, _data: Option<Account>, _modified: bool) {}
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fn cache_code(&self, _hash: H256, _code: Arc<Vec<u8>>) {}
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fn get_cached_account(&self, _addr: &Address) -> Option<Option<Account>> { None }
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fn get_cached<F, U>(&self, _a: &Address, _f: F) -> Option<U>
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where F: FnOnce(Option<&mut Account>) -> U
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{
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None
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}
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fn get_cached_code(&self, _hash: &H256) -> Option<Arc<Vec<u8>>> { None }
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fn note_non_null_account(&self, _address: &Address) {}
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fn is_known_null(&self, _address: &Address) -> bool { false }
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2017-02-21 11:13:02 +01:00
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}
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