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bit32

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bit32

This library is a back-ported feature from Lua 5.2 which provides functions to perform bitwise operations.

number bit32.arshift ( number x, number disp )

Returns the number x shifted disp bits to the right. The number disp may be any representable integer. Negative displacements shift to the left.

This shift operation is what is called arithmetic shift. Vacant bits on the left are filled with copies of the higher bit of x; vacant bits on the right are filled with zeros. In particular, displacements with absolute values higher than 31 result in zero or 0xFFFFFFFF (all original bits are shifted out).
number bit32.band ( Tuple numbers )

Returns the bitwise and of its operands.
number bit32.bnot ( number x )

Returns the bitwise negation of x. For any integer x, the following identity holds:

assert(bit32.bnot(x) == (-1 - x) % 2^32)
number bit32.bor ( Tuple numbers )

Returns the bitwise or of its operands.
boolean bit32.btest ( Tuple numbers )

Returns a boolean signalling whether the bitwise and of its operands is different from zero.
number bit32.bxor ( Tuple numbers )

Returns the bitwise exclusive or of its operands.
number bit32.extract ( number n, number field, number width = 1 )

Returns the unsigned number formed by the bits field to field + width - 1 from n. Bits are numbered from 0 (least significant) to 31 (most significant). All accessed bits must be in the range [0, 31]. The default for width is 1.
number bit32.replace ( number n, number v, number field, number width = 1 )

Returns a copy of n with the bits field to field + width - 1 replaced by the value v. See bit32.extract for details about field and width.
number bit32.lrotate ( number x, number disp )

Returns the number x rotated disp bits to the left. The number disp may be any representable integer. For any valid displacement, the following identity holds:

assert(bit32.lrotate(x, disp) == bit32.lrotate(x, disp % 32))

In particular, negative displacements rotate to the right.
number bit32.lshift ( number x, number disp )

Returns the number x shifted disp bits to the left. The number disp may be any representable integer. Negative displacements shift to the right. In any direction, vacant bits are filled with zeros. In particular, displacements with absolute values higher than 31 result in zero (all bits are shifted out).

For positive displacements, the following equality holds:

assert(bit32.lshift(b, disp) == (b * 2^disp) % 2^32)
number bit32.rrotate ( number x, number disp )

Returns the number x rotated disp bits to the right. The number disp may be any representable integer.

For any valid displacement, the following identity holds:

assert(bit32.rrotate(x, disp) == bit32.rrotate(x , disp % 32))

In particular, negative displacements rotate to the left.
number bit32.rshift ( number x, number disp )

Returns the number x shifted disp bits to the right. The number disp may be any representable integer. Negative displacements shift to the left. In any direction, vacant bits are filled with zeros. In particular, displacements with absolute values higher than 31 result in zero (all bits are shifted out).

For positive displacements, the following equality holds:

assert(bit32.rshift(b, disp) == math.floor(b % 2^32 / 2^disp))

This shift operation is what is called logical shift.