der/
arrayvec.rs

1//! Array-backed append-only vector type.
2// TODO(tarcieri): use `core` impl of `ArrayVec`
3// See: https://github.com/rust-lang/rfcs/pull/2990
4
5use crate::{ErrorKind, Result};
6
7/// Array-backed append-only vector type.
8#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
9pub(crate) struct ArrayVec<T, const N: usize> {
10    /// Elements of the set.
11    elements: [Option<T>; N],
12
13    /// Last populated element.
14    length: usize,
15}
16
17impl<T, const N: usize> ArrayVec<T, N> {
18    /// Create a new [`ArrayVec`].
19    pub fn new() -> Self {
20        Self {
21            elements: [(); N].map(|_| None),
22            length: 0,
23        }
24    }
25
26    /// Push an item into this [`ArrayVec`].
27    pub fn push(&mut self, item: T) -> Result<()> {
28        match self.length.checked_add(1) {
29            Some(n) if n <= N => {
30                self.elements[self.length] = Some(item);
31                self.length = n;
32                Ok(())
33            }
34            _ => Err(ErrorKind::Overlength.into()),
35        }
36    }
37
38    /// Get an element from this [`ArrayVec`].
39    pub fn get(&self, index: usize) -> Option<&T> {
40        match self.elements.get(index) {
41            Some(Some(ref item)) => Some(item),
42            _ => None,
43        }
44    }
45
46    /// Iterate over the elements in this [`ArrayVec`].
47    pub fn iter(&self) -> Iter<'_, T> {
48        Iter::new(&self.elements)
49    }
50
51    /// Is this [`ArrayVec`] empty?
52    pub fn is_empty(&self) -> bool {
53        self.length == 0
54    }
55
56    /// Get the number of elements in this [`ArrayVec`].
57    pub fn len(&self) -> usize {
58        self.length
59    }
60
61    /// Get the last item from this [`ArrayVec`].
62    pub fn last(&self) -> Option<&T> {
63        self.length.checked_sub(1).and_then(|n| self.get(n))
64    }
65
66    /// Extract the inner array.
67    pub fn into_array(self) -> [Option<T>; N] {
68        self.elements
69    }
70}
71
72impl<T, const N: usize> AsRef<[Option<T>]> for ArrayVec<T, N> {
73    fn as_ref(&self) -> &[Option<T>] {
74        &self.elements[..self.length]
75    }
76}
77
78impl<T, const N: usize> AsMut<[Option<T>]> for ArrayVec<T, N> {
79    fn as_mut(&mut self) -> &mut [Option<T>] {
80        &mut self.elements[..self.length]
81    }
82}
83
84impl<T, const N: usize> Default for ArrayVec<T, N> {
85    fn default() -> Self {
86        Self::new()
87    }
88}
89
90/// Iterator over the elements of an [`ArrayVec`].
91#[derive(Clone, Debug)]
92pub struct Iter<'a, T> {
93    /// Decoder which iterates over the elements of the message.
94    elements: &'a [Option<T>],
95
96    /// Position within the iterator.
97    position: usize,
98}
99
100impl<'a, T> Iter<'a, T> {
101    pub(crate) fn new(elements: &'a [Option<T>]) -> Self {
102        Self {
103            elements,
104            position: 0,
105        }
106    }
107}
108
109impl<'a, T> Iterator for Iter<'a, T> {
110    type Item = &'a T;
111
112    fn next(&mut self) -> Option<&'a T> {
113        match self.elements.get(self.position) {
114            Some(Some(res)) => {
115                self.position = self.position.checked_add(1)?;
116                Some(res)
117            }
118            _ => None,
119        }
120    }
121
122    fn size_hint(&self) -> (usize, Option<usize>) {
123        let len = self.elements.len().saturating_sub(self.position);
124        (len, Some(len))
125    }
126}
127
128impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
129
130#[cfg(test)]
131mod tests {
132    use super::ArrayVec;
133    use crate::ErrorKind;
134
135    #[test]
136    fn add() {
137        let mut vec = ArrayVec::<u8, 3>::new();
138        vec.push(1).unwrap();
139        vec.push(2).unwrap();
140        vec.push(3).unwrap();
141
142        assert_eq!(vec.push(4).err().unwrap(), ErrorKind::Overlength.into());
143        assert_eq!(vec.len(), 3);
144    }
145}
der/arrayvec.rs

der/
arrayvec.rs
