-- bit operation
-- since axmol 2.1.3, this file will enable require('bit') for all Lua versions supported by axmol

function _vmversion()
    local major, minor = _VERSION:match("(%d+)%.(%d+)")
    return tonumber(major), tonumber(minor)
end

local major, minor = _vmversion()

if jit ~= nil then
    bit = require('bit')
elseif major >= 5 and minor >= 2 then
    if minor < 4 then
        bit = require('bit32')
    else
        -- note: Lua 5.4+ bit op is 64bit integer
        bit = {
            band = function(a, b)
                return a & b
            end,
            bor = function(a, b)
                return a | b
            end,
            bxor = function(a, b)
                return a ~ b
            end,
            bnot = function(a)
                return ~a
            end,
            lshift = function(a, n)
                return a << n
            end,
            rshift = function(a, n)
                return a >> n
            end
        }
    end
    package.loaded['bit'] = bit
else -- fallback to pure lua implementation, slowest
    bit.data32 = {}

    for i=1,32 do
        bit.data32[i]=2^(32-i)
    end

    function bit._b2d(arg)
        local nr=0
        for i=1,32 do
            if arg[i] ==1 then
                nr=nr+bit.data32[i]
            end
        end
        return  nr
    end

    function bit._d2b(arg)
        arg = arg >= 0 and arg or (0xFFFFFFFF + arg + 1)
        local tr={}
        for i=1,32 do
            if arg >= bit.data32[i] then
                tr[i]=1
                arg=arg-bit.data32[i]
            else
                tr[i]=0
            end
        end
        return   tr
    end

    function    bit._and(a,b)
        local op1=bit._d2b(a)
        local op2=bit._d2b(b)
        local r={}

        for i=1,32 do
            if op1[i]==1 and op2[i]==1  then
                r[i]=1
            else
                r[i]=0
            end
        end
        return  bit._b2d(r)

    end

    function    bit._rshift(a,n)
        local op1=bit._d2b(a)
        n = n <= 32 and n or 32
        n = n >= 0 and n or 0

        for i=32, n+1, -1 do
            op1[i] = op1[i-n]
        end
        for i=1, n do
            op1[i] = 0
        end

        return  bit._b2d(op1)
    end

    function bit._not(a)
        local op1=bit._d2b(a)
        local r={}

        for i=1,32 do
            if  op1[i]==1   then
                r[i]=0
            else
                r[i]=1
            end
        end
        return bit._b2d(r)
    end

    function bit._or(a,b)
        local op1=bit._d2b(a)
        local op2=bit._d2b(b)
        local r={}

        for i=1,32 do
            if op1[i]==1 or op2[i]==1  then
                r[i]=1
            else
                r[i]=0
            end
        end
        return bit._b2d(r)
    end

    bit.band   = bit.band or bit._and
    bit.rshift = bit.rshift or bit._rshift
    bit.bnot   = bit.bnot or bit._not
    package.loaded['bit'] = bit
end