rust-utils: add util to find a slice in another slice
Differential Revision: https://phab.mercurial-scm.org/D7863
--- a/rust/hg-core/src/utils.rs Tue Jan 14 16:00:57 2020 +0100
+++ b/rust/hg-core/src/utils.rs Tue Jan 14 18:00:05 2020 +0100
@@ -10,6 +10,26 @@
pub mod files;
pub mod hg_path;
+/// Useful until rust/issues/56345 is stable
+///
+/// # Examples
+///
+/// ```
+/// use crate::hg::utils::find_slice_in_slice;
+///
+/// let haystack = b"This is the haystack".to_vec();
+/// assert_eq!(find_slice_in_slice(&haystack, b"the"), Some(8));
+/// assert_eq!(find_slice_in_slice(&haystack, b"not here"), None);
+/// ```
+pub fn find_slice_in_slice<T>(slice: &[T], needle: &[T]) -> Option<usize>
+where
+ for<'a> &'a [T]: PartialEq,
+{
+ slice
+ .windows(needle.len())
+ .position(|window| window == needle)
+}
+
/// Replaces the `from` slice with the `to` slice inside the `buf` slice.
///
/// # Examples