1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
// Copyright 2018-2021 Parity Technologies (UK) Ltd.
//
// 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.
use crate::Key;
/// A key pointer.
///
/// This wraps a base key and provides an interface to mimic pointer arithmetic.
/// Mainly used to coordinate keys through static storage structures.
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct KeyPtr {
/// The underlying offset key.
key: Key,
/// The last shift performed.
last_shift: u64,
}
impl From<Key> for KeyPtr {
#[inline]
fn from(key: Key) -> Self {
Self { key, last_shift: 0 }
}
}
impl KeyPtr {
/// Advances the key pointer by the given amount and returns the old value.
#[inline]
pub fn advance_by(&mut self, new_shift: u64) -> &Key {
let old_shift = core::mem::replace(&mut self.last_shift, new_shift);
self.key += old_shift;
&self.key
}
/// Returns the underlying offset key.
pub fn key(&self) -> &Key {
&self.key
}
}