LookupDistCode

const LookupDistCode = packed struct(u5) {
    code: ShortDistCode,

    const base_table = table: {
        var bases: [30]u15 = undefined;
        for (0.., &bases) |c, *b| {
            b.* = ShortDistCode.fromInt(c).base();
        }
        break :table bases;
    };

    pub fn fromVal(v: u15) LookupDistCode {
        return .{ .code = .fromVal(v) };
    }

    /// `@ctz(return) >= extraBits()`
    pub fn base(c: LookupDistCode) u15 {
        return base_table[c.toInt()];
    }

    pub fn extraBits(c: LookupDistCode) u4 {
        return c.code.extraBits();
    }

    pub fn toInt(c: LookupDistCode) u5 {
        return @bitCast(c);
    }

    pub fn fromInt(x: u5) LookupDistCode {
        return @bitCast(x);
    }
}