Data

    const Data = packed struct(u16) {
        len: Len,
        /// Low bits of the alignment.
        ///
        /// For non-extended headers, this is the entire alignment. The location of the previous
        /// header is directly before this allocation since footers in `Bucket` are gauraunteed to
        /// have at least 8-byte alignment.
        alignment: u2,
        /// Used only for bucket allocations.
        prev_extended: bool,

        const Len = enum(u13) {
            _,

            /// This footer is trailed (before the traces) by `Extended`.
            /// The high bits of the alignment are encoded as the offset from `extended_start`.
            ///
            /// This may be set even if `Extended` is not strictly necesary
            /// as a result of resizes and remaps.
            const extended_start: u13 = math.maxInt(u13) - ((@bitSizeOf(usize) - 1) >> 2);
        };
    }