Search for the last occurrence of a byte in a slice.
This returns the index corresponding to the last occurrence of
None if one is not found.
While this is operationally the same as something like
haystack.iter().rposition(|&b| b == needle),
memrchr will use a highly
optimized routine that can be up to an order of magnitude faster in some
This shows how to find the last position of a byte in a byte string.
use memchr::memrchr; let haystack = b"the quick brown fox"; assert_eq!(memrchr(b'o', haystack), Some(17));