You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: util.rs
    path of file: ./repos/fish-shell/src
    
    the code of the file until where you have to start completion: //! Generic utilities library.

use crate::wchar::prelude::*;
use std::cmp::Ordering;
use std::time;

/// Compares two wide character strings with an (arguably) intuitive ordering. This function tries
/// to order strings in a way which is intuitive to humans with regards to sorting strings
/// containing numbers.
///
/// Most sorting functions would sort the strings 'file1.txt' 'file5.txt' and 'file12.txt' as:
///
/// file1.txt
/// file12.txt
/// file5.txt
///
/// This function regards any sequence of digits as a single entity when performing comparisons, so
/// the output is instead:
///
/// file1.txt
/// file5.txt
/// file12.txt
///
/// Which most people would find more intuitive.
///
/// This won't return the optimum results for numbers in bases higher than ten, such as hexadecimal,
/// but at least a stable sort order will result.
///
/// This function performs a two-tiered sort, where difference in case and in number of leading
/// zeroes in numbers only have effect if no other differences between strings are found. This way,
/// a 'file1' and 'File1' will not be considered identical, and hence their internal sort order is
/// not arbitrary, but the names 'file1', 'File2' and 'file3' will still be sorted in the
    
pub fn wcsfilecmp(a: &wstr, b: &wstr) -> Ordering {
    let mut retval = Ordering::Equal;
    let mut ai = 0;
    let mut bi = 0;
    while ai < a.len() && bi < b.len() {
        let ac = a.as_char_slice()[ai];
        let bc = b.as_char_slice()[bi];
        if ac.is_ascii_digit() && bc.is_ascii_digit() {
            let (ad, bd);
            (retval, ad, bd) = wcsfilecmp_leading_digits(&a[ai..], &b[bi..]);
            ai += ad;
            bi += bd;
            if retval != Ordering::Equal || ai == a.len() || bi == b.len() {
                break;
            }
            continue;
        }

        // Fast path: Skip towupper.
        if ac == bc {
            ai += 1;
            bi += 1;
            continue;
        }

        // Sort dashes after Z - see #5634
        let mut acl = if ac == '-' { '[' } else { ac };
        let mut bcl = if bc == '-' { '[' } else { bc };
        // TODO Compare the tail (enabled by Rust's Unicode support).
        acl = acl.to_uppercase().next().unwrap();
        bcl = bcl.to_uppercase().next().unwrap();

        match acl.cmp(&bcl) {
            Ordering::Equal => {
                ai += 1;
                bi += 1;
            }
            o => {
                retval = o;
                break;
            }
        }
    }

    if retval != Ordering::Equal {
        return retval; // we already know the strings aren't logically equal
    }

    if ai == a.len() {
        if bi == b.len() {
            // The strings are logically equal. They may or may not be the same length depending on
            // whether numbers were present but that doesn't matter. Disambiguate strings that
            // differ by letter case or length. We don't bother optimizing the case where the file
            // names are literally identical because that won't occur given how this function is
            // used. And even if it were to occur (due to being reused in some other context) it
            // would be so rare that it isn't worth optimizing for.
            a.cmp(b)
        } else {
            Ordering::Less // string a is a prefix of b and b is longer
        }
    } else {
        assert!(bi == b.len());
        Ordering::Greater // string b is a prefix of a and a is longer
    }
}