bit.lua

if jit then
	return require 'bit'
end

local bit = {}

local loadstring = loadstring or load
local format = string.format

function bit.tobit(x)
	x = (x - x % 1) % 2 ^ 32
	if x >= 2 ^ 31 then
		return x - 2 ^ 32
	end
	return x
end

function bit.tohex(x, n)
	if n == 0 then
		return ''
	end
	n = n or 8
	
	local upper = false
	if n < 0 then
		n = -n
		upper = true
	end
	
	x = x % 2 ^ 32
	
	local str
	if upper then
		str = format('%08X', x)
	else
		str = format('%08x', x)
	end
	
	return ('0'):rep(n - 8) .. str:sub(-n)
end

function bit.bnot(x)
	x = (-(x - x % 1) - 1) % 2 ^ 32
	if x >= 2 ^ 31 then
		return x - 2 ^ 32
	end
	return x
end

local logicTemplate = [[
	return function(a, ...)
		a = a % 2 ^ 32
		local result
		for i = 1, select('#', ...) do
			result = 0
			local b = select(i, ...) % 2 ^ 32
			{body}
			a = result
		end
		if result >= 2 ^ 31 then
			result = result - 2 ^ 32
		end
		return result
	end
]]

do
	local cycle = [[
		if a >= {c} then
			if b >= {c} then
				b = b - {c}
			end
			result = result + {c}
			a = a - {c}
		elseif b >= {c} then
			result = result + {c}
			b = b - {c}
		end
	]]
	
	local t = {}
	for i = 31, 0, -1 do
		table.insert(t, (cycle:gsub('{c}', 2 ^ i)))
	end
	
	local src = logicTemplate:gsub('{body}', table.concat(t))
	bit.bor = assert(loadstring(src))()
end

do
	local cycle = [[
		if a >= {c} then
			if b >= {c} then
				result = result + {c}
				b = b - {c}
			end
			a = a - {c}
		elseif b >= {c} then
			b = b - {c}
		end
	]]
	
	local t = {}
	for i = 31, 0, -1 do
		table.insert(t, (cycle:gsub('{c}', 2 ^ i)))
	end
	
	local src = logicTemplate:gsub('{body}', table.concat(t))
	bit.band = assert(loadstring(src))()
end

do
	local cycle = [[
		if a >= {c} then
			if b >= {c} then
				b = b - {c}
			else
				result = result + {c}
			end
			a = a - {c}
		elseif b >= {c} then
			result = result + {c}
			b = b - {c}
		end
	]]
	
	local t = {}
	for i = 31, 0, -1 do
		table.insert(t, (cycle:gsub('{c}', 2 ^ i)))
	end
	
	local src = logicTemplate:gsub('{body}', table.concat(t))
	bit.bxor = assert(loadstring(src))()
end

function bit.lshift(x, n)
	n = (n - n % 1) % 2 ^ 5
	x = (x - x % 1) % 2 ^ (32 - n) * 2 ^ n
	if x >= 2 ^ 31 then
		x = x - 2 ^ 32
	end
	return x
end

function bit.rshift(x, n)
	n = (n - n % 1) % 2 ^ 5
	x = x % 2 ^ 32
	x = x / 2 ^ n
	x = x - x % 1
	if x >= 2 ^ 31 then
		x = x - 2 ^ 32
	end
	return x
end

function bit.arshift(x, n)
	n = (n - n % 1) % 2 ^ 5
	x = x % 2 ^ 32
	local result = x / 2 ^ n
	result = result - result % 1
	if x >= 2 ^ 31 then
		result = result + (2 ^ n - 1) * 2 ^ (32 - n)
	end
	if result >= 2 ^ 31 then
		result = result - 2 ^ 32
	end
	return result
end

function bit.rol(x, n)
	n = (n - n % 1) % 2 ^ 5
	x = (x - x % 1) % 2 ^ 32
	local low = x % 2 ^ (32 - n)
	x = (x - low) / 2 ^ (32 - n) + low * 2 ^ n
	if x >= 2 ^ 31 then
		x = x - 2 ^ 32
	end
	return x
end

function bit.ror(x, n)
	n = (n - n % 1) % 2 ^ 5
	x = (x - x % 1) % 2 ^ 32
	local low = x % 2 ^ n
	x = (x - low) / 2 ^ n + low * 2 ^ (32 - n)
	if x >= 2 ^ 31 then
		x = x - 2 ^ 32
	end
	return x
end

function bit.bswap(x)
	x = (x - x % 1) % 2 ^ 32
	
	local b1 = x % (2 ^ 8)
	local b2 = x % (2 ^ 16)
	local b3 = x % (2 ^ 24)
	
	x = b1 * 2 ^ 24 +
		(b2 - b1) * 2 ^ 8 +
		(b3 - b2) / 2 ^ 8 +
		(x - b3) / 2 ^ 24
	
	if x >= 2 ^ 31 then
		x = x - 2 ^ 32
	end
	return x
end

return bit