repline/
iter.rs

1//! Shmancy iterator adapters
2
3pub use chars::Chars;
4pub use flatten::Flatten;
5
6pub mod chars {
7    //! Converts an <code>[Iterator]<Item = [u8]></code> into an
8    //! <code>[Iterator]<Item = [Result]<[char], [BadUnicode]>></code>
9
10    /// Invalid unicode codepoint found when iterating over [Chars]
11    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
12    pub struct BadUnicode(pub u32);
13
14    impl std::error::Error for BadUnicode {}
15
16    impl std::fmt::Display for BadUnicode {
17        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
18            let Self(code) = self;
19            write!(f, "Bad unicode: {code}")
20        }
21    }
22
23    /// Converts an <code>[Iterator]<Item = [u8]></code> into an
24    /// <code>[Iterator]<Item = [char]></code>
25    #[derive(Clone, Debug)]
26    pub struct Chars<I: Iterator<Item = u8>>(pub I);
27
28    impl<I: Iterator<Item = u8>> Iterator for Chars<I> {
29        type Item = Result<char, BadUnicode>;
30
31        fn next(&mut self) -> Option<Self::Item> {
32            let Self(bytes) = self;
33            let start = bytes.next()? as u32;
34            let (mut out, count) = match start {
35                start if start & 0x80 == 0x00 => (start, 0), // ASCII valid range
36                start if start & 0xe0 == 0xc0 => (start & 0x1f, 1), // 1 continuation byte
37                start if start & 0xf0 == 0xe0 => (start & 0x0f, 2), // 2 continuation bytes
38                start if start & 0xf8 == 0xf0 => (start & 0x07, 3), // 3 continuation bytes
39                _ => return None,
40            };
41            for _ in 0..count {
42                let cont = bytes.next()? as u32;
43                if cont & 0xc0 != 0x80 {
44                    return None;
45                }
46                out = (out << 6) | (cont & 0x3f);
47            }
48            Some(char::from_u32(out).ok_or(BadUnicode(out)))
49        }
50    }
51}
52pub mod flatten {
53    //! Flattens an [Iterator] returning [`Result<T, E>`](Result) or [`Option<T>`](Option)
54    //! into a *non-[FusedIterator](std::iter::FusedIterator)* over `T`
55
56    /// Flattens an [Iterator] returning [`Result<T, E>`](Result) or [`Option<T>`](Option)
57    /// into a *non-[FusedIterator](std::iter::FusedIterator)* over `T`
58    #[derive(Clone, Debug)]
59    pub struct Flatten<T, I: Iterator<Item = T>>(pub I);
60
61    impl<T, E, I: Iterator<Item = Result<T, E>>> Iterator for Flatten<Result<T, E>, I> {
62        type Item = T;
63        fn next(&mut self) -> Option<Self::Item> {
64            self.0.next()?.ok()
65        }
66    }
67
68    impl<T, I: Iterator<Item = Option<T>>> Iterator for Flatten<Option<T>, I> {
69        type Item = T;
70        fn next(&mut self) -> Option<Self::Item> {
71            self.0.next()?
72        }
73    }
74}
repline/iter.rs

repline/
iter.rs
