Lua BitOp is a C extension module for Lua 5.1/5.2 which adds bitwise operations on numbers.
Lua BitOp is Copyright © 2008-2012 Mike Pall. Lua BitOp is free software, released under the MIT license (same license as the Lua core).
Lua BitOp is compatible with the built-in bitwise operations in LuaJIT 2.0 and is used on platforms where Defold runs without LuaJIT.
For clarity the examples assume the definition of a helper function printx().
This prints its argument as an unsigned 32 bit hexadecimal number on all platforms:
function printx(x) print("0x"..bit.tohex(x)) end
bitwise arithmetic right-shift
Returns the bitwise arithmetic right-shift of its first argument by the number of bits given by the second argument. Arithmetic right-shift treats the most-significant bit as a sign bit and replicates it. Only the lower 5 bits of the shift count are used (reduces to the range [0..31]).
x -
number number
n -
number number of bits
y -
number bitwise arithmetic right-shifted number
print(bit.arshift(256, 8)) --> 1 print(bit.arshift(-256, 8)) --> -1 printx(bit.arshift(0x87654321, 12)) --> 0xfff87654
bitwise and
Returns the bitwise and of all of its arguments. Note that more than two arguments are allowed.
x1 -
number number
[x2...] -
number number(s)
y -
number bitwise and of the provided arguments
printx(bit.band(0x12345678, 0xff)) --> 0x00000078
bitwise not
Returns the bitwise not of its argument.
x -
number number
y -
number bitwise not of number x
print(bit.bnot(0)) --> -1 printx(bit.bnot(0)) --> 0xffffffff print(bit.bnot(-1)) --> 0 print(bit.bnot(0xffffffff)) --> 0 printx(bit.bnot(0x12345678)) --> 0xedcba987
bitwise or
Returns the bitwise or of all of its arguments. Note that more than two arguments are allowed.
x1 -
number number
[x2...] -
number number(s)
y -
number bitwise or of the provided arguments
print(bit.bor(1, 2, 4, 8)) --> 15
bitwise swap
Swaps the bytes of its argument and returns it. This can be used to convert little-endian 32 bit numbers to big-endian 32 bit numbers or vice versa.
x -
number number
y -
number bitwise swapped number
printx(bit.bswap(0x12345678)) --> 0x78563412 printx(bit.bswap(0x78563412)) --> 0x12345678
bitwise xor
Returns the bitwise xor of all of its arguments. Note that more than two arguments are allowed.
x1 -
number number
[x2...] -
number number(s)
y -
number bitwise xor of the provided arguments
printx(bit.bxor(0xa5a5f0f0, 0xaa55ff00)) --> 0x0ff00ff0
bitwise logical left-shift
Returns the bitwise logical left-shift of its first argument by the number of bits given by the second argument. Logical shifts treat the first argument as an unsigned number and shift in 0-bits. Only the lower 5 bits of the shift count are used (reduces to the range [0..31]).
x -
number number
n -
number number of bits
y -
number bitwise logical left-shifted number
print(bit.lshift(1, 0)) --> 1 print(bit.lshift(1, 8)) --> 256 print(bit.lshift(1, 40)) --> 256 printx(bit.lshift(0x87654321, 12)) --> 0x54321000
bitwise left rotation
Returns the bitwise left rotation of its first argument by the number of bits given by the second argument. Bits shifted out on one side are shifted back in on the other side. Only the lower 5 bits of the rotate count are used (reduces to the range [0..31]).
x -
number number
n -
number number of bits
y -
number bitwise left-rotated number
printx(bit.rol(0x12345678, 12)) --> 0x45678123
bitwise right rotation
Returns the bitwise right rotation of its first argument by the number of bits given by the second argument. Bits shifted out on one side are shifted back in on the other side. Only the lower 5 bits of the rotate count are used (reduces to the range [0..31]).
x -
number number
n -
number number of bits
y -
number bitwise right-rotated number
printx(bit.ror(0x12345678, 12)) --> 0x67812345
bitwise logical right-shift
Returns the bitwise logical right-shift of its first argument by the number of bits given by the second argument. Logical shifts treat the first argument as an unsigned number and shift in 0-bits. Only the lower 5 bits of the shift count are used (reduces to the range [0..31]).
x -
number number
n -
number number of bits
y -
number bitwise logical right-shifted number
print(bit.rshift(256, 8)) --> 1 print(bit.rshift(-256, 8)) --> 16777215 printx(bit.rshift(0x87654321, 12)) --> 0x00087654
normalize number to the numeric range for bit operations
Normalizes a number to the numeric range for bit operations and returns it. This function is usually not needed since all bit operations already normalize all of their input arguments.
x -
number number to normalize
y -
number normalized number
print(0xffffffff) --> 4294967295 (*) print(bit.tobit(0xffffffff)) --> -1 printx(bit.tobit(0xffffffff)) --> 0xffffffff print(bit.tobit(0xffffffff + 1)) --> 0 print(bit.tobit(2^40 + 1234)) --> 1234
(*) See the treatment of hex literals for an explanation why the printed numbers in the first two lines differ (if your Lua installation uses a double number type).
convert number to a hex string
Converts its first argument to a hex string. The number of hex digits is given by the absolute value of the optional second argument. Positive numbers between 1 and 8 generate lowercase hex digits. Negative numbers generate uppercase hex digits. Only the least-significant 4*|n| bits are used. The default is to generate 8 lowercase hex digits.
x -
number number to convert
n -
number number of hex digits to return
s -
string hexadecimal string
print(bit.tohex(1)) --> 00000001 print(bit.tohex(-1)) --> ffffffff print(bit.tohex(0xffffffff)) --> ffffffff print(bit.tohex(-1, -8)) --> FFFFFFFF print(bit.tohex(0x21, 4)) --> 0021 print(bit.tohex(0x87654321, 4)) --> 4321