Function skiproot

crates/vm/src/stdlib/nt.rs:1398–1464

Implements _Py_skiproot logic for Windows paths Returns (drive_size, root_size) where: - drive_size: length of the drive/UNC portion - root_size: length of the root separator (0 or 1)

(path: &[u16])

    /// - drive_size: length of the drive/UNC portion
    /// - root_size: length of the root separator (0 or 1)
    fn skiproot(path: &[u16]) -> (usize, usize) {
        let len = path.len();
        if len == 0 {
            return (0, 0);
        }

        const SEP: u16 = b'\\' as u16;
        const ALTSEP: u16 = b'/' as u16;
        const COLON: u16 = b':' as u16;

        let is_sep = |c: u16| c == SEP || c == ALTSEP;
        let get = |i: usize| path.get(i).copied().unwrap_or(0);

        if is_sep(get(0)) {
            if is_sep(get(1)) {
                // UNC or device path: \\server\share or \\?\device
                // Check for \\?\UNC\server\share
                let idx = if len >= 8
                    && get(2) == b'?' as u16
                    && is_sep(get(3))
                    && (get(4) == b'U' as u16 || get(4) == b'u' as u16)
                    && (get(5) == b'N' as u16 || get(5) == b'n' as u16)
                    && (get(6) == b'C' as u16 || get(6) == b'c' as u16)
                    && is_sep(get(7))
                {
                    8
                } else {
                    2
                };

                // Find the end of server name
                let mut i = idx;
                while i < len && !is_sep(get(i)) {
                    i += 1;
                }

                if i >= len {
                    // No share part: \\server
                    return (i, 0);
                }

                // Skip separator and find end of share name
                i += 1;
                while i < len && !is_sep(get(i)) {
                    i += 1;
                }

                // drive = \\server\share, root = \ (if present)
                if i >= len { (i, 0) } else { (i, 1) }
            } else {
                // Relative path with root: \Windows
                (0, 1)
            }
        } else if len >= 2 && get(1) == COLON {
            // Drive letter path
            if len >= 3 && is_sep(get(2)) {
                // Absolute: X:\Windows
                (2, 1)