Module bit32
Bitwise Operations.
This library provides bitwise operations. It provides all its functions inside the table bit32
.
Unless otherwise stated, all functions accept numeric arguments in the range (2^51,+2^51);
each argument is normalized to the remainder of its division by 2^32
and truncated to an integer
(in some unspecified way), so that its final value falls in the range [0,2^32  1]
.
Similarly, all results are in the range [0,2^32  1]
. Note that bit32.bnot(0)
is 0xFFFFFFFF
,
which is different from 1
.
Type bit32
bit32.arshift(x, disp) 
Returns the number 
bit32.band(...) 
Returns the bitwise 
bit32.bnot(x) 
Returns the bitwise negation of 
bit32.bor(...) 
Returns the bitwise 
bit32.btest() 
Returns a boolean signaling whether the bitwise 
bit32.bxor(...) 
Returns the bitwise exclusive 
bit32.extract(n, field, width) 
Returns the unsigned number formed by the bits 
bit32.lrotate(x, disp) 
Returns the number 
bit32.lshift(x, disp) 
Returns the number 
bit32.replace(n, v, field, width) 
Returns a copy of 
bit32.rrotate(x, disp) 
Returns the number 
bit32.rshift(x, disp) 
Returns the number 
Type bit32
Field(s)
 bit32.arshift(x, disp)

Returns the number
x
shifteddisp
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 or0xFFFFFFFF
(all original bits are shifted out).Parameters

#number x
: value to shift 
#number disp
: the number of shift, may an positive or negative integer
Return value
#number: shifted number

 bit32.band(...)

Returns the bitwise
and
of its operands.Parameter

#number ...
: operands
Return value
#number: bitwise
and
of operands 
 bit32.bnot(x)

Returns the bitwise negation of
x
.For any integer
x
, the following identity holds:assert(bit32.bnot(x) == (1  x) % 2^32)
Parameter

#number x
: Number to proceed
Return value
#number: bitwise negation

 bit32.bor(...)

Returns the bitwise
or
of its operands.Parameter

#number ...
: operands
Return value
#number: bitwise
or
of operands 
 bit32.btest()

Returns a boolean signaling whether the bitwise
and
of its operands is different from zero.Return value
#boolean: true if the bitwise
and
of its operands is different from zero
 bit32.bxor(...)

Returns the bitwise exclusive
or
of its operands.Parameter

#number ...
: operands
Return value
#number: bitwise exclusive
or
of its operands. 
 bit32.extract(n, field, width)

Returns the unsigned number formed by the bits
field
tofield + width  1
fromn
.Bits are numbered from
0
(least significant) to31
(most significant). All accessed bits must be in the range[0, 31]
.The default for
width
is1
.Parameters

#number n
: input number 
#number field
: bit field to apply 
#number width
: the number of bit to take in account (optional, 1 by default)
Return value
#number: extracted number

 bit32.lrotate(x, disp)

Returns the number
x
rotateddisp
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.
Parameters

#number x
: original number 
#number disp
: number of rotate
Return value
#number: rotated number

 bit32.lshift(x, disp)

Returns the number
x
shifteddisp
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 than31
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)
Parameters

#number x
: original number 
#number disp
: the number of shift
Return value
#number: shifted number

 bit32.replace(n, v, field, width)

Returns a copy of
n
with the bitsfield
tofield + width  1
replaced by the valuev
.See
bit32.extract
for details about field and width.Parameters

#number n
: the number to copy 
#number v
: the value v 
#number field
: bits field to apply 
#number width
: the number of bit to take in account (optional, 1 by default)
Return value
#number: replaced number

 bit32.rrotate(x, disp)

Returns the number
x
rotateddisp
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.
Parameters

#number x
: original number 
#number disp
: number of bits to rotate
Return value
#number: rotated number

 bit32.rshift(x, disp)

Returns the number
x
shifteddisp
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 than31
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.
Parameters

#number x
: original number 
#number disp
: the number of shift
Return value
#number: shifted number
