1 /*!
2 This module defines "naive" implementations of substring search.
3
4 These are sometimes useful to compare with "real" substring implementations.
5 The idea is that they are so simple that they are unlikely to be incorrect.
6 */
7
8 /// Naively search forwards for the given needle in the given haystack.
find(haystack: &[u8], needle: &[u8]) -> Option<usize>9 pub(crate) fn find(haystack: &[u8], needle: &[u8]) -> Option<usize> {
10 let end = haystack.len().checked_sub(needle.len()).map_or(0, |i| i + 1);
11 for i in 0..end {
12 if needle == &haystack[i..i + needle.len()] {
13 return Some(i);
14 }
15 }
16 None
17 }
18
19 /// Naively search in reverse for the given needle in the given haystack.
rfind(haystack: &[u8], needle: &[u8]) -> Option<usize>20 pub(crate) fn rfind(haystack: &[u8], needle: &[u8]) -> Option<usize> {
21 let end = haystack.len().checked_sub(needle.len()).map_or(0, |i| i + 1);
22 for i in (0..end).rev() {
23 if needle == &haystack[i..i + needle.len()] {
24 return Some(i);
25 }
26 }
27 None
28 }
29
30 #[cfg(test)]
31 mod tests {
32 use crate::tests::substring;
33
34 use super::*;
35
36 #[test]
forward()37 fn forward() {
38 substring::Runner::new().fwd(|h, n| Some(find(h, n))).run()
39 }
40
41 #[test]
reverse()42 fn reverse() {
43 substring::Runner::new().rev(|h, n| Some(rfind(h, n))).run()
44 }
45 }
46