bit32forluajit.lua

local bit32 = {}
local bit = require("bit")

for Index, Function in next, bit do
	bit32[Index] = Function
end

bit32.rrotate = bit.ror
bit32.lrotate = bit.rol

local TwoPower = setmetatable({}, {
	__index = function(self, Index)
		local Value = 2 ^ Index
		self[Index] = Value
		return Value
	end;
})

local bit32_band = bit.band
local bit32_bnot = bit.bnot
local bit32_rshift = bit.rshift
local bit32_lshift = bit.lshift

--[[**
	Returns the unsigned number formed by the bits field to field + width - 1 from n. Bits are numbered from 0 (least significant) to 31 (most significant). All accessed bits must be in the range [0, 31]. The default for width is 1.
	@param [t:integer] n The bits.
	@param [t:integer] field
	@param [t:optional<t:integer>] width The bit width. Defaults to one.
	@returns [t:integer]
**--]]
function bit32.extract(n, field, width)
	width = width or 1
	if field < 0 or field > 31 or width < 0 or field + width > 32 then error("trying to access non-existent bits", 2) end
	return bit32_band(bit32_rshift(n, field), TwoPower[width] - 1)
end

--[[**
	Returns a copy of n with the bits field to field + width - 1 replaced by the value v. Bits are numbered from 0 (least significant) to 31 (most significant). All accessed bits must be in the range [0, 31]. The default for width is 1.
	@param [t:integer] n The bits.
	@param [t:integer] v
	@param [t:integer] field
	@param [t:optional<t:integer>] width The bit width. Defaults to one.
	@returns [t:integer]
**--]]
function bit32.replace(n, v, field, width)
	width = width or 1
	if field < 0 or field > 31 or width < 0 or field + width > 32 then error("trying to access non-existent bits", 2) end
	local mask1 = TwoPower[width] - 1
	v = bit32_band(v, mask1)
	return bit32_band(n, bit32_bnot(bit32_lshift(mask1, field))) + bit32_lshift(v, field)
end

--[[**
	Returns a boolean signaling whether the bitwise and of its operands is different from.
	@param [t:integer] x
	@param [t:integer] y
	@returns [t:boolean]
**--]]
function bit32.btest(x, y)
	return bit32_band(x, y) ~= 0
end

return bit32