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| 1 | +use std::mem; |
| 2 | + |
| 3 | +/// A small map backed by an unsorted vector. |
| 4 | +/// |
| 5 | +/// Maintains key uniqueness at cost of O(n) lookup/insert/remove. Maintains insertion order |
| 6 | +/// (`insert` calls that overwrite an existing value don't change order). |
| 7 | +#[derive(Clone, Default)] |
| 8 | +pub struct VecMap<K, V>(Vec<(K, V)>); |
| 9 | + |
| 10 | +impl<K: Eq, V> VecMap<K, V> { |
| 11 | + pub fn new() -> Self { |
| 12 | + VecMap(Vec::new()) |
| 13 | + } |
| 14 | + |
| 15 | + pub fn is_empty(&self) -> bool { |
| 16 | + self.0.is_empty() |
| 17 | + } |
| 18 | + |
| 19 | + pub fn clear(&mut self) { |
| 20 | + self.0.clear(); |
| 21 | + } |
| 22 | + |
| 23 | + fn find(&self, key: &K) -> Option<usize> { |
| 24 | + for (i, (k, _)) in self.0.iter().enumerate() { |
| 25 | + if k == key { |
| 26 | + return Some(i); |
| 27 | + } |
| 28 | + } |
| 29 | + None |
| 30 | + } |
| 31 | + |
| 32 | + pub fn contains(&self, key: &K) -> bool { |
| 33 | + self.find(key).is_some() |
| 34 | + } |
| 35 | + |
| 36 | + pub fn get(&self, key: &K) -> Option<&V> { |
| 37 | + match self.find(key) { |
| 38 | + Some(i) => Some(&self.0[i].1), |
| 39 | + None => None, |
| 40 | + } |
| 41 | + } |
| 42 | + |
| 43 | + pub fn get_mut(&mut self, key: &K) -> Option<&mut V> { |
| 44 | + match self.find(key) { |
| 45 | + Some(i) => Some(&mut self.0[i].1), |
| 46 | + None => None, |
| 47 | + } |
| 48 | + } |
| 49 | + |
| 50 | + pub fn insert(&mut self, key: K, value: V) -> Option<V> { |
| 51 | + if let Some(old) = self.get_mut(&key) { |
| 52 | + return Some(mem::replace(old, value)); |
| 53 | + } |
| 54 | + self.0.push((key, value)); |
| 55 | + None |
| 56 | + } |
| 57 | + |
| 58 | + pub fn remove(&mut self, key: &K) -> Option<V> { |
| 59 | + match self.find(key) { |
| 60 | + Some(i) => Some(self.0.remove(i).1), |
| 61 | + None => None, |
| 62 | + } |
| 63 | + } |
| 64 | + |
| 65 | + pub fn values(&self) -> impl Iterator<Item = &V> { |
| 66 | + self.0.iter().map(|kv| &kv.1) |
| 67 | + } |
| 68 | +} |
| 69 | + |
| 70 | +#[cfg(test)] |
| 71 | +mod tests { |
| 72 | + use super::*; |
| 73 | + |
| 74 | + #[test] |
| 75 | + fn empty() { |
| 76 | + let m: VecMap<char, u32> = VecMap::new(); |
| 77 | + assert!(m.is_empty()); |
| 78 | + assert!(!m.contains(&'a')); |
| 79 | + assert!(m.values().next().is_none()); |
| 80 | + } |
| 81 | + |
| 82 | + #[test] |
| 83 | + fn insert_update_get() { |
| 84 | + let mut m: VecMap<char, u32> = VecMap::new(); |
| 85 | + assert!(m.insert('a', 1).is_none()); |
| 86 | + assert!(m.insert('b', 2).is_none()); |
| 87 | + assert_eq!(m.get(&'a'), Some(&1)); |
| 88 | + assert_eq!(m.get(&'b'), Some(&2)); |
| 89 | + *m.get_mut(&'a').unwrap() += 10; |
| 90 | + assert_eq!(m.get(&'a'), Some(&11)); |
| 91 | + assert_eq!(m.get(&'b'), Some(&2)); |
| 92 | + } |
| 93 | + |
| 94 | + #[test] |
| 95 | + fn insert_overwrite() { |
| 96 | + let mut m = VecMap::new(); |
| 97 | + assert_eq!(m.insert('a', 1), None); |
| 98 | + assert_eq!(m.insert('b', 2), None); |
| 99 | + assert_eq!(m.insert('a', 3), Some(1)); |
| 100 | + assert_eq!(m.insert('a', 4), Some(3)); |
| 101 | + assert_eq!(m.get(&'a').copied(), Some(4)); |
| 102 | + assert_eq!(m.get(&'b').copied(), Some(2)); |
| 103 | + assert_eq!(m.insert('b', 5), Some(2)); |
| 104 | + assert_eq!(m.get(&'a').copied(), Some(4)); |
| 105 | + assert_eq!(m.get(&'b').copied(), Some(5)); |
| 106 | + } |
| 107 | + |
| 108 | + #[test] |
| 109 | + fn insert_remove() { |
| 110 | + let mut m: VecMap<char, u32> = VecMap::new(); |
| 111 | + assert_eq!(m.remove(&'a'), None); |
| 112 | + m.insert('a', 1); |
| 113 | + m.insert('b', 2); |
| 114 | + assert_eq!(m.remove(&'a'), Some(1)); |
| 115 | + assert_eq!(m.remove(&'a'), None); |
| 116 | + assert_eq!(m.remove(&'b'), Some(2)); |
| 117 | + assert!(m.is_empty()); |
| 118 | + } |
| 119 | + |
| 120 | + #[test] |
| 121 | + fn insertion_order() { |
| 122 | + let mut m: VecMap<char, u32> = VecMap::new(); |
| 123 | + let values = |m: &VecMap<char, u32>| -> Vec<u32> { m.values().copied().collect() }; |
| 124 | + m.insert('b', 2); |
| 125 | + m.insert('a', 1); |
| 126 | + m.insert('c', 3); |
| 127 | + assert_eq!(values(&m), vec![2, 1, 3]); |
| 128 | + m.insert('a', 11); |
| 129 | + m.remove(&'b'); |
| 130 | + assert_eq!(values(&m), vec![11, 3]); |
| 131 | + m.insert('b', 2); |
| 132 | + assert_eq!(values(&m), vec![11, 3, 2]); |
| 133 | + } |
| 134 | + |
| 135 | + #[test] |
| 136 | + fn containment_equivalences() { |
| 137 | + let mut m = VecMap::new(); |
| 138 | + for i in 0u8..=255 { |
| 139 | + if i % 10 < 3 { |
| 140 | + m.insert(i, i); |
| 141 | + } |
| 142 | + } |
| 143 | + for i in 0u8..=255 { |
| 144 | + if m.contains(&i) { |
| 145 | + assert_eq!(m.get(&i).copied(), Some(i)); |
| 146 | + assert_eq!(m.get_mut(&i).copied(), Some(i)); |
| 147 | + assert_eq!(m.insert(i, i), Some(i)); |
| 148 | + assert_eq!(m.remove(&i), Some(i)); |
| 149 | + } else { |
| 150 | + assert!(m.get(&i).is_none()); |
| 151 | + assert!(m.get_mut(&i).is_none()); |
| 152 | + assert!(m.remove(&i).is_none()); |
| 153 | + assert!(m.insert(i, i).is_none()); |
| 154 | + } |
| 155 | + } |
| 156 | + } |
| 157 | + |
| 158 | + #[test] |
| 159 | + fn clear() { |
| 160 | + let mut m = VecMap::new(); |
| 161 | + m.clear(); |
| 162 | + assert!(m.is_empty()); |
| 163 | + m.insert('a', 1); |
| 164 | + m.insert('b', 2); |
| 165 | + assert!(!m.is_empty()); |
| 166 | + m.clear(); |
| 167 | + assert!(m.is_empty()); |
| 168 | + m.insert('c', 3); |
| 169 | + assert!(!m.is_empty()); |
| 170 | + } |
| 171 | +} |
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