string_search.nct

//! Shared allocation-free byte search for UTF-8 string modules.
//!
//! Matching operates on bytes, but every successful match of a non-empty,
//! well-formed UTF-8 needle begins at a UTF-8 boundary in the haystack.

/// Returns the first byte offset of `needle` at or after `start`.
pub(nocter) func find_from_bytes(
    text: &str,
    needle: &str,
    start: usize,
): usize? {
    if start > text.len() { return none }
    if needle.len() == 0 { return start }
    var candidate: usize = start
    while candidate + needle.len() <= text.len() {
        var matched: usize = 0
        var equal: bool = true
        while matched < needle.len() {
            let actual: u8 = text[candidate + matched]
            let expected: u8 = needle[matched]
            if actual != expected {
                equal = false
            }
            matched = matched + 1
        }
        if equal { return candidate }
        candidate = candidate + 1
    }
    return none
}