Function find_subsequence

cranelift/codegen/meta/src/unique_table.rs:88–101

Try to find the subsequence `sub` in the `whole` sequence. Returns None if it's not been found, or Some(index) if it has been. Naive implementation until proven we need something better.

(sub: &[T], whole: &[T])

/// it's not been found, or Some(index) if it has been. Naive implementation
/// until proven we need something better.
fn find_subsequence<T: PartialEq>(sub: &[T], whole: &[T]) -> Option<usize> {
    assert!(!sub.is_empty());
    // We want i + sub.len() <= whole.len(), i.e. i < whole.len() + 1 - sub.len().
    if whole.len() < sub.len() {
        return None;
    }
    let max = whole.len() - sub.len();
    for i in 0..=max {
        if whole[i..i + sub.len()] == sub[..] {
            return Some(i);
        }
    }
    None
}

#[test]
fn test_find_subsequence() {