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 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208
use xlru_cache::LruCache; use std::borrow::Borrow; use std::hash::Hash; pub struct ArcCache<K, V> where K: Eq + Hash, { recent_set: LruCache<K, V>, recent_evicted: LruCache<K, ()>, frequent_set: LruCache<K, V>, frequent_evicted: LruCache<K, ()>, capacity: usize, p: usize, inserted: u64, evicted: u64, removed: u64, } impl<K, V> ArcCache<K, V> where K: Eq + Hash, { pub fn new(capacity: usize) -> Result<ArcCache<K, V>, &'static str> { if capacity <= 0 { return Err("Cache length cannot be zero"); } let cache = ArcCache { recent_set: LruCache::new(capacity), recent_evicted: LruCache::new(capacity), frequent_set: LruCache::new(capacity), frequent_evicted: LruCache::new(capacity), capacity: capacity, p: 0, inserted: 0, evicted: 0, removed: 0, }; Ok(cache) } pub fn contains_key<Q: ?Sized>(&mut self, key: &Q) -> bool where K: Borrow<Q>, Q: Hash + Eq, { self.frequent_set.contains_key(key) || self.recent_set.contains_key(key) } pub fn insert(&mut self, key: K, value: V) -> bool { if self.frequent_set.contains_key(&key) { self.frequent_set.insert(key, value); return true; } if self.recent_set.contains_key(&key) { self.recent_set.remove(&key); self.frequent_set.insert(key, value); return true; } if self.frequent_evicted.contains_key(&key) { let recent_evicted_len = self.recent_evicted.len(); let frequent_evicted_len = self.frequent_evicted.len(); let delta = if recent_evicted_len > frequent_evicted_len { recent_evicted_len / frequent_evicted_len } else { 1 }; if delta < self.p { self.p -= delta; } else { self.p = 0 } if self.recent_set.len() + self.frequent_set.len() >= self.capacity { self.replace(true); } self.frequent_evicted.remove(&key); self.frequent_set.insert(key, value); return true; } if self.recent_evicted.contains_key(&key) { let recent_evicted_len = self.recent_evicted.len(); let frequent_evicted_len = self.frequent_evicted.len(); let delta = if frequent_evicted_len > recent_evicted_len { frequent_evicted_len / recent_evicted_len } else { 1 }; if delta <= self.capacity - self.p { self.p += delta; } else { self.p = self.capacity; } if self.recent_set.len() + self.frequent_set.len() >= self.capacity { self.replace(false); } self.recent_evicted.remove(&key); self.frequent_set.insert(key, value); return true; } if self.recent_set.len() + self.frequent_set.len() >= self.capacity { self.replace(false); } if self.recent_evicted.len() > self.capacity - self.p { self.recent_evicted.remove_lru(); self.evicted += 1; } if self.frequent_evicted.len() > self.p { self.frequent_evicted.remove_lru(); self.evicted += 1; } self.recent_set.insert(key, value); self.inserted += 1; false } pub fn peek_mut(&mut self, key: &K) -> Option<&mut V> where K: Clone + Hash + Eq, { if let Some(entry) = self.frequent_set.peek_mut(key) { Some(entry) } else { self.recent_set.peek_mut(key) } } pub fn get_mut(&mut self, key: &K) -> Option<&mut V> where K: Clone + Hash + Eq, { if let Some(value) = self.recent_set.remove(&key) { self.frequent_set.insert((*key).clone(), value); } self.frequent_set.get_mut(key) } pub fn remove(&mut self, key: &K) -> Option<V> { let removed_frequent = self.frequent_set.remove(&key); let removed_recent = self.recent_set.remove(&key); self.frequent_evicted.remove(&key); self.recent_evicted.remove(&key); match removed_frequent.or(removed_recent) { Some(value) => { self.removed += 1; Some(value) }, None => None } } fn replace(&mut self, frequent_evicted_contains_key: bool) { let recent_set_len = self.recent_set.len(); if recent_set_len > 0 && (recent_set_len > self.p || (recent_set_len == self.p && frequent_evicted_contains_key)) { if let Some((old_key, _)) = self.recent_set.remove_lru() { self.recent_evicted.insert(old_key, ()); } } else { if let Some((old_key, _)) = self.frequent_set.remove_lru() { self.frequent_evicted.insert(old_key, ()); } } } pub fn len(&self) -> usize { self.recent_set.len() + self.frequent_set.len() } pub fn frequent_len(&self) -> usize { self.frequent_set.len() } pub fn recent_len(&self) -> usize { self.recent_set.len() } pub fn inserted(&self) -> u64 { self.inserted } pub fn evicted(&self) -> u64 { self.evicted } pub fn removed(&self) -> u64 { self.removed } } #[test] fn test_arc() { let mut arc: ArcCache<&str, &str> = ArcCache::new(2).unwrap(); arc.insert("testkey", "testvalue"); assert!(arc.contains_key(&"testkey")); arc.insert("testkey2", "testvalue2"); assert!(arc.contains_key(&"testkey2")); arc.insert("testkey3", "testvalue3"); assert!(arc.contains_key(&"testkey3")); assert!(arc.contains_key(&"testkey2")); assert!(!arc.contains_key(&"testkey")); arc.insert("testkey", "testvalue"); assert!(arc.get_mut(&"testkey").is_some()); assert!(arc.get_mut(&"testkey-nx").is_none()); }