# Demo entry 1469027

LuaBit

Submitted by anonymous on Mar 16, 2015 at 02:48
Language: Lua. Code size: 4.7 kB.

```--[[---------------
LuaBit v0.4
-------------------
a bitwise operation lib for lua.

http://luaforge.net/projects/bit/

How to use:
-------------------
bit.bnot(n) -- bitwise not (~n)
bit.band(m, n) -- bitwise and (m & n)
bit.bor(m, n) -- bitwise or (m | n)
bit.bxor(m, n) -- bitwise xor (m ^ n)
bit.brshift(n, bits) -- right shift (n >> bits)
bit.blshift(n, bits) -- left shift (n << bits)
bit.blogic_rshift(n, bits) -- logic right shift(zero fill >>>)

Please note that bit.brshift and bit.blshift only support number within
32 bits.

2 utility functions are provided too:
bit.tobits(n) -- convert n into a bit table(which is a 1/0 sequence)
-- high bits first
bit.tonumb(bit_tbl) -- convert a bit table into a number
-------------------

--]]---------------

do

------------------------
-- bit lib implementions

local function check_int(n)
-- checking not float
if(n - math.floor(n) > 0) then
error("trying to use bitwise operation on non-integer!")
end
end

local function to_bits(n)
check_int(n)
if(n < 0) then
-- negative
end
-- to bits table
local tbl = {}
local cnt = 1
while (n > 0) do
local last = math.mod(n,2)
if(last == 1) then
tbl[cnt] = 1
else
tbl[cnt] = 0
end
n = (n-last)/2
cnt = cnt + 1
end

return tbl
end

local function tbl_to_number(tbl)
local n = table.getn(tbl)

local rslt = 0
local power = 1
for i = 1, n do
rslt = rslt + tbl[i]*power
power = power*2
end

return rslt
end

local function expand(tbl_m, tbl_n)
local big = {}
local small = {}
if(table.getn(tbl_m) > table.getn(tbl_n)) then
big = tbl_m
small = tbl_n
else
big = tbl_n
small = tbl_m
end
-- expand small
for i = table.getn(small) + 1, table.getn(big) do
small[i] = 0
end

end

local function bit_or(m, n)
local tbl_m = to_bits(m)
local tbl_n = to_bits(n)
expand(tbl_m, tbl_n)

local tbl = {}
local rslt = math.max(table.getn(tbl_m), table.getn(tbl_n))
for i = 1, rslt do
if(tbl_m[i]== 0 and tbl_n[i] == 0) then
tbl[i] = 0
else
tbl[i] = 1
end
end

return tbl_to_number(tbl)
end

local function bit_and(m, n)
local tbl_m = to_bits(m)
local tbl_n = to_bits(n)
expand(tbl_m, tbl_n)

local tbl = {}
local rslt = math.max(table.getn(tbl_m), table.getn(tbl_n))
for i = 1, rslt do
if(tbl_m[i]== 0 or tbl_n[i] == 0) then
tbl[i] = 0
else
tbl[i] = 1
end
end

return tbl_to_number(tbl)
end

local function bit_not(n)

local tbl = to_bits(n)
local size = math.max(table.getn(tbl), 32)
for i = 1, size do
if(tbl[i] == 1) then
tbl[i] = 0
else
tbl[i] = 1
end
end
return tbl_to_number(tbl)
end

local function bit_xor(m, n)
local tbl_m = to_bits(m)
local tbl_n = to_bits(n)
expand(tbl_m, tbl_n)

local tbl = {}
local rslt = math.max(table.getn(tbl_m), table.getn(tbl_n))
for i = 1, rslt do
if(tbl_m[i] ~= tbl_n[i]) then
tbl[i] = 1
else
tbl[i] = 0
end
end

--table.foreach(tbl, print)

return tbl_to_number(tbl)
end

local function bit_rshift(n, bits)
check_int(n)

local high_bit = 0
if(n < 0) then
-- negative
n = bit_not(math.abs(n)) + 1
high_bit = 2147483648 -- 0x80000000
end

for i=1, bits do
n = n/2
n = bit_or(math.floor(n), high_bit)
end
return math.floor(n)
end

-- logic rightshift assures zero filling shift
local function bit_logic_rshift(n, bits)
check_int(n)
if(n < 0) then
-- negative
n = bit_not(math.abs(n)) + 1
end
for i=1, bits do
n = n/2
end
return math.floor(n)
end

local function bit_lshift(n, bits)
check_int(n)

if(n < 0) then
-- negative
n = bit_not(math.abs(n)) + 1
end

for i=1, bits do
n = n*2
end
return bit_and(n, 4294967295) -- 0xFFFFFFFF
end

local function bit_xor2(m, n)
local rhs = bit_or(bit_not(m), bit_not(n))
local lhs = bit_or(m, n)
local rslt = bit_and(lhs, rhs)
return rslt
end

--------------------
-- bit lib interface

bit = {
-- bit operations
bnot = bit_not,
band = bit_and,
bor  = bit_or,
bxor = bit_xor,
brshift = bit_rshift,
blshift = bit_lshift,
bxor2 = bit_xor2,
blogic_rshift = bit_logic_rshift,

-- utility func
tobits = to_bits,
tonumb = tbl_to_number,
}

end

--[[
for i = 1, 100 do
for j = 1, 100 do
if(bit.bxor(i, j) ~= bit.bxor2(i, j)) then
error("bit.xor failed.")
end
end
end
--]]
```

This snippet took 0.01 seconds to highlight.

Back to the Entry List or Home.