rosu_mods/
util.rs

1use std::borrow::Cow;
2
3/// Provide an iterator over substrings of the given length on the given
4/// source string
5pub(crate) fn cut(mut source: &str, n: usize) -> impl Iterator<Item = &str> {
6    std::iter::from_fn(move || {
7        if source.is_empty() {
8            None
9        } else {
10            let end_idx = source
11                .char_indices()
12                .nth(n - 1)
13                .map_or_else(|| source.len(), |(idx, c)| idx + c.len_utf8());
14
15            let (sub_str, rest) = source.split_at(end_idx);
16            source = rest;
17
18            Some(sub_str)
19        }
20    })
21}
22
23/// Put a `&str` into ASCII uppercase.
24///
25/// Doesn't allocate if it already is uppercase.
26pub(crate) fn to_uppercase(s: &str) -> Cow<'_, str> {
27    match s.as_bytes().iter().position(u8::is_ascii_lowercase) {
28        Some(pos) => {
29            let mut output = s.to_owned();
30
31            // SAFETY: Index is certain to be contained
32            unsafe { output.get_unchecked_mut(pos..) }.make_ascii_uppercase();
33
34            Cow::Owned(output)
35        }
36        None => Cow::Borrowed(s),
37    }
38}
39
40/// Splits the first `N` characters off
41pub(crate) fn split_prefix<const N: usize>(s: &str) -> (&str, &str) {
42    let end_idx = s
43        .char_indices()
44        .nth(N - 1)
45        .map_or_else(|| s.len(), |(idx, c)| idx + c.len_utf8());
46
47    s.split_at(end_idx)
48}
49
50#[cfg(test)]
51mod tests {
52    #[test]
53    fn cut() {
54        let mut iter = super::cut("hDHrdTv2n", 2);
55
56        assert_eq!(iter.next(), Some("hD"));
57        assert_eq!(iter.next(), Some("Hr"));
58        assert_eq!(iter.next(), Some("dT"));
59        assert_eq!(iter.next(), Some("v2"));
60        assert_eq!(iter.next(), Some("n"));
61        assert_eq!(iter.next(), None);
62    }
63
64    #[test]
65    fn to_uppercase() {
66        let upper = super::to_uppercase("MANAmE JeF");
67        assert_eq!(upper.as_ref(), "MANAME JEF");
68
69        let upper = super::to_uppercase("mAn4me jäf");
70        assert_eq!(upper.as_ref(), "MAN4ME JäF");
71    }
72
73    #[test]
74    fn split_prefix() {
75        assert_eq!(super::split_prefix::<1>("abc"), ("a", "bc"));
76        assert_eq!(super::split_prefix::<4>("abc"), ("abc", ""));
77    }
78}
rosu_mods/util.rs

rosu_mods/
util.rs
