collect_once_hashmap/
btreemap.rs

1use std::cmp::Ord;
2use std::collections::BTreeMap;
3use std::fmt::Debug;
4use std::hash::Hash;
5use std::iter::FromIterator;
6use std::iter::IntoIterator;
7
8#[derive(Debug, thiserror::Error)]
9pub enum Error<K>
10    where K: Debug,
11{
12    #[error("duplicated key in iterator: {:?}", _0)]
13    DuplicatedKey(K),
14
15    #[error("unknown error")]
16    Unknown,
17}
18
19pub struct CollectOnceBTreeMap<K, V>
20    where K: Eq + Ord + Hash + Debug
21{
22    inner: std::result::Result<BTreeMap<K, V>, Error<K>>
23}
24
25impl<K, V> CollectOnceBTreeMap<K, V>
26    where K: Eq + Ord + Hash + Debug
27{
28    pub fn into_inner(self) -> std::result::Result<BTreeMap<K, V>, Error<K>> {
29        self.inner
30    }
31}
32
33impl<K, V> FromIterator<(K, V)> for CollectOnceBTreeMap<K, V>
34    where K: Eq + Ord + Hash + Debug
35{
36    fn from_iter<T>(iter: T) -> Self
37        where T: IntoIterator<Item = (K, V)>
38    {
39        let mut hm = BTreeMap::new();
40
41        for (element_key, element_value) in iter.into_iter() {
42            if hm.contains_key(&element_key) {
43                return CollectOnceBTreeMap {
44                    inner: Err(Error::DuplicatedKey(element_key))
45                }
46            } else {
47                hm.insert(element_key, element_value);
48            }
49        }
50
51        CollectOnceBTreeMap {
52            inner: Ok(hm)
53        }
54    }
55}
56
57
58#[cfg(test)]
59mod tests {
60    use super::CollectOnceBTreeMap;
61    use super::Error;
62
63    #[test]
64    fn test_empty() {
65        let hm = vec![]
66            .into_iter()
67            .collect::<CollectOnceBTreeMap<u8, u8>>()
68            .into_inner()
69            .unwrap();
70
71        assert_eq!(0, hm.keys().count());
72    }
73
74    #[test]
75    fn test_simple() {
76        let hm = vec![(1, 1)]
77            .into_iter()
78            .collect::<CollectOnceBTreeMap<u8, u8>>()
79            .into_inner()
80            .unwrap();
81
82        assert_eq!(1, hm.keys().count());
83        assert!(hm.contains_key(&1));
84        assert!(hm.keys().all(|k| *k == 1));
85        assert!(hm.values().all(|k| *k == 1));
86    }
87
88    #[test]
89    fn test_duplicate() {
90        let hm = vec![(1, 1), (1, 2)]
91            .into_iter()
92            .collect::<CollectOnceBTreeMap<u8, u8>>()
93            .into_inner();
94
95        assert!(hm.is_err());
96        assert!(std::matches!(hm, Err(Error::DuplicatedKey(1))));
97    }
98}
99
collect_once_hashmap/btreemap.rs

collect_once_hashmap/
btreemap.rs
