90 lines
2.9 KiB
Rust
90 lines
2.9 KiB
Rust
// Copyright 2016 Mozilla
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
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// this file except in compliance with the License. You may obtain a copy of the
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// License at http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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#![allow(dead_code)]
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use std::collections::BTreeMap;
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/// Witness assertions and retractions, folding (assertion, retraction) pairs into alterations.
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/// Assumes that no assertion or retraction will be witnessed more than once.
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///
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/// This keeps track of when we see a :db/add, a :db/retract, or both :db/add and :db/retract in
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/// some order.
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#[derive(Clone, Debug, Eq, Hash, Ord, PartialOrd, PartialEq)]
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pub struct AddRetractAlterSet<K, V> {
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pub asserted: BTreeMap<K, V>,
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pub retracted: BTreeMap<K, V>,
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pub altered: BTreeMap<K, (V, V)>,
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}
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impl<K, V> Default for AddRetractAlterSet<K, V>
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where
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K: Ord,
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{
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fn default() -> AddRetractAlterSet<K, V> {
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AddRetractAlterSet {
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asserted: BTreeMap::default(),
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retracted: BTreeMap::default(),
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altered: BTreeMap::default(),
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}
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}
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}
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impl<K, V> AddRetractAlterSet<K, V>
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where
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K: Ord,
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{
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pub fn witness(&mut self, key: K, value: V, added: bool) {
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if added {
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if let Some(retracted_value) = self.retracted.remove(&key) {
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self.altered.insert(key, (retracted_value, value));
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} else {
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self.asserted.insert(key, value);
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}
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} else if let Some(asserted_value) = self.asserted.remove(&key) {
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self.altered.insert(key, (value, asserted_value));
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} else {
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self.retracted.insert(key, value);
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test() {
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let mut set: AddRetractAlterSet<i64, char> = AddRetractAlterSet::default();
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// Assertion.
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set.witness(1, 'a', true);
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// Retraction.
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set.witness(2, 'b', false);
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// Alteration.
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set.witness(3, 'c', true);
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set.witness(3, 'd', false);
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// Alteration, witnessed in the with the retraction before the assertion.
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set.witness(4, 'e', false);
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set.witness(4, 'f', true);
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let mut asserted = BTreeMap::default();
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asserted.insert(1, 'a');
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let mut retracted = BTreeMap::default();
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retracted.insert(2, 'b');
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let mut altered = BTreeMap::default();
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altered.insert(3, ('d', 'c'));
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altered.insert(4, ('e', 'f'));
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assert_eq!(set.asserted, asserted);
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assert_eq!(set.retracted, retracted);
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assert_eq!(set.altered, altered);
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}
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}
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