qed/
imp.rs

1// Return the first index, if any, where the given byte occurs.
2#[must_use]
3pub const fn find(slice: &[u8], elem: u8) -> Option<usize> {
4    let mut idx = 0;
5    loop {
6        if idx == slice.len() {
7            return None;
8        }
9        if slice[idx] == elem {
10            return Some(idx);
11        }
12        idx += 1;
13    }
14}
15
16// Return true if the slice contains a single NUL byte in the last position of
17// the slice.
18#[must_use]
19pub const fn is_cstr(slice: &[u8]) -> bool {
20    matches!(find(slice, 0), Some(nul_pos) if nul_pos + 1 == slice.len())
21}
22
23// Returns true if the slice contains any NUL bytes.
24#[must_use]
25pub const fn contains_nul(slice: &[u8]) -> bool {
26    matches!(find(slice, 0), Some(_))
27}
28
29#[cfg(test)]
30mod tests {
31    use super::{contains_nul, find, is_cstr};
32
33    #[test]
34    fn find_nul_byte() {
35        assert_eq!(find(b"", 0), None);
36        assert_eq!(find(b"abc", 0), None);
37        assert_eq!(find(b"abc\xFFxyz", 0), None);
38
39        assert_eq!(find(b"abc\0xyz", 0), Some(3));
40        assert_eq!(find(b"abc\0xyz\0", 0), Some(3));
41        assert_eq!(find(b"abc\xFF\0xyz", 0), Some(4));
42        assert_eq!(find(b"abc\xFF\0xyz\0", 0), Some(4));
43
44        assert_eq!(find(b"\0", 0), Some(0));
45        assert_eq!(find(b"abc\0", 0), Some(3));
46        assert_eq!(find(b"abc\xFFxyz\0", 0), Some(7));
47    }
48
49    #[test]
50    fn check_is_cstr() {
51        assert!(!is_cstr(b""));
52        assert!(!is_cstr(b"abc"));
53        assert!(!is_cstr(b"abc\xFFxyz"));
54
55        assert!(!is_cstr(b"abc\0xyz"));
56        assert!(!is_cstr(b"abc\0xyz\0"));
57        assert!(!is_cstr(b"abc\xFF\0xyz"));
58        assert!(!is_cstr(b"abc\xFF\0xyz\0"));
59
60        assert!(is_cstr(b"\0"));
61        assert!(is_cstr(b"abc\0"));
62        assert!(is_cstr(b"abc\xFFxyz\0"));
63    }
64
65    #[test]
66    fn check_contains_nul_byte() {
67        assert!(!contains_nul(b""));
68        assert!(!contains_nul(b"abc"));
69        assert!(!contains_nul(b"abc\xFFxyz"));
70
71        assert!(contains_nul(b"abc\0xyz"));
72        assert!(contains_nul(b"abc\0xyz\0"));
73        assert!(contains_nul(b"abc\xFF\0xyz"));
74        assert!(contains_nul(b"abc\xFF\0xyz\0"));
75
76        assert!(contains_nul(b"\0"));
77        assert!(contains_nul(b"abc\0"));
78        assert!(contains_nul(b"abc\xFFxyz\0"));
79    }
80}
qed/imp.rs

qed/
imp.rs
