Lua random number generator

#!/usr/bin/env lua

--Lua random # generator module
--Seeded using any string
--Requires Lua 5.2 (bit32 library)

local _M={}
_M.new = function(seed)
    seed = tostring(seed) .. "#*]"
    assert(#seed >= 4, "Seed too short")
    local seeds = {0xdeadbeef,0x67898765,0xfacecafe,#seed}
    for i = 1, #seed do
        local chr = string.byte(seed:sub(i))
        for s = 1, 4 do
            if s > 1 then
                for s2 = 1, s-1 do
                    seeds[s]=seeds[s] + seeds[s2]
                end
            end
            seeds[s] = bit32.lrotate((seeds[s]+chr), (seeds[s] + chr) % 8 + 5)
        end
    end
    local w,x,y,z = seeds[4],seeds[3],seeds[2],seeds[1]
    if(w+x+y+z == 0) then
        w,x,y,z = 0xdeadbeef,0xfacecafe,0x12345678,999
    end
    local fun = function(arg)
        local t = bit32.bxor(x, bit32.lshift(x,11))
        x,y,z = y,z,w
        w = bit32.bxor(w, bit32.rshift(w,19), t, bit32.rshift(t,8))
        if arg == "bin" then
            return w,x,y,z
        end
        local float = bit32.rshift(w,1) / 0x80000000 --31bit float
        if not arg then
            return float
        end
        return math.floor(float * arg) + 1
    end
    --fun()
    return fun
end
return _M