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Co-authored-by: Tilmann Zäschke <tilmann.zaeschke@inf.ethz.ch>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,103 @@ | ||
| // Copyright 2024 ETH Zurich | ||
| // | ||
| // 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. | ||
|
|
||
| package org.scion.internal; | ||
|
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| import java.util.HashMap; | ||
| import java.util.TreeMap; | ||
|
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| /** | ||
| * A simple cache that min/max watermark. Once max watermark is reached, the cache removes entries | ||
| * until min watermark is reached. Least recently accessed entries are removed first. | ||
| * | ||
| * @param <K> The key | ||
| * @param <V> The value | ||
| */ | ||
| public class SimpleCache<K, V> { | ||
| private final TreeMap<Long, Entry> ageMap = new TreeMap<>(); | ||
| private final HashMap<K, Entry> lookupMap = new HashMap<>(); | ||
|
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| private int capacity; | ||
| private long opCount = 0; | ||
|
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| public SimpleCache(int capacity) { | ||
| if (capacity < 1) { | ||
| throw new IllegalArgumentException(); | ||
| } | ||
| this.capacity = capacity; | ||
| } | ||
|
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| public void put(K key, V value) { | ||
| Entry e = lookupMap.get(key); | ||
| if (e == null) { | ||
| e = new Entry(opCount++, key, value); | ||
| checkCapacity(1); | ||
| lookupMap.put(key, e); | ||
| } else { | ||
| ageMap.remove(e.age); | ||
| e.age = opCount++; | ||
| e.value = value; | ||
| } | ||
| ageMap.put(e.age, e); | ||
| } | ||
|
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| public V get(K key) { | ||
| Entry e = lookupMap.get(key); | ||
| if (e == null) { | ||
| return null; | ||
| } | ||
|
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| ageMap.remove(e.age); | ||
| e.age = opCount++; | ||
| ageMap.put(e.age, e); | ||
|
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| return e.value; | ||
| } | ||
|
|
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| public void clear() { | ||
| lookupMap.clear(); | ||
| ageMap.clear(); | ||
| } | ||
|
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| public void setCapacity(int capacity) { | ||
| if (capacity < 1) { | ||
| throw new IllegalArgumentException(); | ||
| } | ||
| this.capacity = capacity; | ||
| checkCapacity(0); | ||
| } | ||
|
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| public int getCapacity() { | ||
| return capacity; | ||
| } | ||
|
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| private void checkCapacity(int spare) { | ||
| while (lookupMap.size() + spare > capacity) { | ||
| Entry e = ageMap.pollFirstEntry().getValue(); | ||
| lookupMap.remove(e.key); | ||
| } | ||
| } | ||
|
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| private class Entry { | ||
| private long age; | ||
| private final K key; | ||
| private V value; | ||
|
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| public Entry(long l, K key, V value) { | ||
| this.age = l; | ||
| this.key = key; | ||
| this.value = value; | ||
| } | ||
| } | ||
| } |
117 changes: 117 additions & 0 deletions
117
src/test/java/org/scion/jpan/internal/SimpleCacheTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,117 @@ | ||
| // Copyright 2024 ETH Zurich | ||
| // | ||
| // 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. | ||
|
|
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| package org.scion.internal; | ||
|
|
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| import static org.junit.jupiter.api.Assertions.*; | ||
|
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| import java.util.ArrayList; | ||
| import java.util.List; | ||
| import org.junit.jupiter.api.Test; | ||
|
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| class SimpleCacheTest { | ||
|
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| private static class Pair { | ||
| int i; | ||
| String s; | ||
|
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| Pair(int i, String s) { | ||
| this.i = i; | ||
| this.s = s; | ||
| } | ||
| } | ||
|
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| @Test | ||
| void testInsertOnly() { | ||
| SimpleCache<Integer, Pair> cache = new SimpleCache<>(10); | ||
| List<Pair> list = new ArrayList<>(); | ||
|
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| for (int i = 0; i < 30; i++) { | ||
| Pair p = new Pair(i, Integer.toString(i)); | ||
| cache.put(i, p); | ||
| list.add(p); | ||
| } | ||
|
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| // Test latest 10 remain | ||
| for (int i = 0; i < list.size(); i++) { | ||
| if (i < 20) { | ||
| assertNull(cache.get(i)); | ||
| } else { | ||
| assertEquals(list.get(i), cache.get(i)); | ||
| } | ||
| } | ||
| } | ||
|
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| @Test | ||
| void testMultiGet() { | ||
| SimpleCache<Integer, Pair> cache = new SimpleCache<>(10); | ||
| List<Pair> list = new ArrayList<>(); | ||
|
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| for (int i = 0; i < 30; i++) { | ||
| Pair p = new Pair(i, Integer.toString(i)); | ||
| cache.put(i, p); | ||
| list.add(p); | ||
| // keep using the first 5 entries | ||
| assertNotNull(cache.get(i % 5)); | ||
| } | ||
|
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| // Test latest 5 remain and most used 5 remain | ||
| for (int i = 0; i < list.size(); i++) { | ||
| if (i >= 5 && i < 25) { | ||
| assertNull(cache.get(i)); | ||
| } else { | ||
| assertEquals(list.get(i), cache.get(i)); | ||
| } | ||
| } | ||
| } | ||
|
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| @Test | ||
| void testReduceCapacity() { | ||
| SimpleCache<Integer, Pair> cache = new SimpleCache<>(10); | ||
| List<Pair> list = new ArrayList<>(); | ||
|
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| for (int i = 0; i < 30; i++) { | ||
| Pair p = new Pair(i, Integer.toString(i)); | ||
| cache.put(i, p); | ||
| list.add(p); | ||
| // keep using the first 2 entries | ||
| assertNotNull(cache.get(i % 2)); | ||
| } | ||
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| cache.setCapacity(5); | ||
| assertEquals(5, cache.getCapacity()); | ||
|
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| // Test latest 3 remain and most used 2 remain | ||
| for (int i = 0; i < list.size(); i++) { | ||
| if (i >= 2 && i < 27) { | ||
| assertNull(cache.get(i)); | ||
| } else { | ||
| assertEquals(list.get(i), cache.get(i)); | ||
| } | ||
| } | ||
| } | ||
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| @Test | ||
| void testSetCapacity() { | ||
| SimpleCache<Integer, Pair> cache = new SimpleCache<>(42); | ||
| assertEquals(42, cache.getCapacity()); | ||
|
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| cache.setCapacity(100); | ||
| assertEquals(100, cache.getCapacity()); | ||
|
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| assertThrows(IllegalArgumentException.class, () -> cache.setCapacity(0)); | ||
|
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| assertThrows(IllegalArgumentException.class, () -> new SimpleCache<>(0)); | ||
| } | ||
| } |
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