lua 脚本按位与运算

-数字转二进制
function ToSecond(num)
	local str = ""
	local tmp = num
	while (tmp > 0) do
		if (tmp % 2 == 1) then
			str = str .. "1"
		else
			str = str .. "0"
		end
		
		tmp = math.modf(tmp / 2)
	end
	str = string.reverse(str)
	return str
end

--先补齐两个数字的二进制位数
function makeSameLength(num1, num2)
	local str1 = ToSecond(num1) 
	local str2 = ToSecond(num2)
	
	local len1 = string.len(str1)
	local len2 = string.len(str2)
	print("len1 = " .. len1)
	print("len2 = " .. len2)
	
	local len = 0
	local x = 0
	
	if (len1 > len2) then
		x = len1 - len2
		for i = 1, x do
			str2 = "0" .. str2
		end
		len = len1
		print("len = "..len)
	elseif (len2 > len1) then
		x = len2 - len1
		for i = 1, x do
			str1 = "0" .. str1
		end
		len = len2
	end
	len = len1
	return str1, str2, len
end

--按位与
function BitAnd(num1, num2)
	local str1, str2, len = makeSameLength(num1, num2)
	local rtmp = ""
	
	for i = 1, len do
		local st1 = tonumber(string.sub(str1, i, i))
		local st2 = tonumber(string.sub(str2, i, i))
		if(st1 == 0) then
			rtmp = rtmp .. "0"	
		else
			if (st2 ~= 0) then
				rtmp = rtmp .. "1"
			else
				rtmp = rtmp .. "0"
			end
		end
	end
	rtmp = tostring(rtmp)
	return rtmp
end