Module: Numeric::NumericExtensions::ClassMethods

Defined in:
lib/ruckus/extensions/numeric.rb

Instance Method Summary collapse

Instance Method Details

#mask_for(m) ⇒ Object

Make a bitmask with m-many bits, as an Integer



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# File 'lib/ruckus/extensions/numeric.rb', line 30

def mask_for(m)
    # This is just table lookup for values less than 65

    @@mask ||= {
        1 => 0x1,
        2 => 0x3,
        3 => 0x7,
        4 => 0xf,
        5 => 0x1f,
        6 => 0x3f,
        7 => 0x7f,
        8 => 0xff,
        9 => 0x1ff,
        10 => 0x3ff,
        11 => 0x7ff,
        12 => 0xfff,
        13 => 0x1fff,
        14 => 0x3fff,
        15 => 0x7fff,
        16 => 0xffff,
        17 => 0x1ffff,
        18 => 0x3ffff,
        19 => 0x7ffff,
        20 => 0xfffff,
        21 => 0x1fffff,
        22 => 0x3fffff,
        23 => 0x7fffff,
        24 => 0xffffff,
        25 => 0x1ffffff,
        26 => 0x3ffffff,
        27 => 0x7ffffff,
        28 => 0xfffffff,
        29 => 0x1fffffff,
        30 => 0x3fffffff,
        31 => 0x7fffffff,
        32 => 0xffffffff,
        33 => 0x1ffffffff,
        34 => 0x3ffffffff,
        35 => 0x7ffffffff,
        36 => 0xfffffffff,
        37 => 0x1fffffffff,
        38 => 0x3fffffffff,
        39 => 0x7fffffffff,
        40 => 0xffffffffff,
        41 => 0x1ffffffffff,
        42 => 0x3ffffffffff,
        43 => 0x7ffffffffff,
        44 => 0xfffffffffff,
        45 => 0x1fffffffffff,
        46 => 0x3fffffffffff,
        47 => 0x7fffffffffff,
        48 => 0xffffffffffff,
        49 => 0x1ffffffffffff,
        50 => 0x3ffffffffffff,
        51 => 0x7ffffffffffff,
        52 => 0xfffffffffffff,
        53 => 0x1fffffffffffff,
        54 => 0x3fffffffffffff,
        55 => 0x7fffffffffffff,
        56 => 0xffffffffffffff,
        57 => 0x1ffffffffffffff,
        58 => 0x3ffffffffffffff,
        59 => 0x7ffffffffffffff,
        60 => 0xfffffffffffffff,
        61 => 0x1fffffffffffffff,
        62 => 0x3fffffffffffffff,
        63 => 0x7fffffffffffffff,
        64 => 0xffffffffffffffff
    }

    if (v = @@mask[m])
        return v
    end

    # Compute it for crazy values.

    r = 0
    0.upto(m-1) {|q| r |= (1 << q)}
    return r
end