A LuaJIT port of Johannes Baagøe's Alea

alea.lua

-- A Lua port of Johannes Baagøe's Alea

-- From http://baagoe.com/en/RandomMusings/javascript/
-- Johannes Baagøe <baagoe@baagoe.com>, 2010

-- Mirrored at:
-- https://github.com/nquinlan/better-random-numbers-for-javascript-mirror

local floor = math.floor

function Mash ()
  local n = 0xefc8249d

  local function mash (data)
    data = tostring(data)
    
    for i = 1, data:len() do
      n = n + data:byte(i)
      local h = 0.02519603282416938 * n
      n = floor(h)
      h = h - n
      h = h * n
      n = floor(h)
      h = h - n
      n = n + h * 0x100000000 -- 2^32
    end
    return floor(n) * 2.3283064365386963e-10 -- 2^-32
  end

  return mash
end

local function Alea (...)
  return (function (args)
    local s0 = 0
    local s1 = 0
    local s2 = 0
    local c = 1

    if #args == 0 then
      args = { os.time() }
    end
    local mash = Mash()
    s0 = mash(' ')
    s1 = mash(' ')
    s2 = mash(' ')

    for i = 1, #args do
      s0 = s0 - mash(args[i])
      if s0 < 0 then
        s0 = s0 + 1
      end
      s1 = s1 - mash(args[i])
      if s1 < 0 then
        s1 = s1 + 1
      end
      s2 = s2 - mash(args[i])
      if s2 < 0 then
        s2 = s2 + 1
      end
    end
    mash = nil

    local random = {}
    local function _random ()
      local t = 2091639 * s0 + c * 2.3283064365386963e-10 -- 2^-32
      s0 = s1
      s1 = s2
      c = floor(t)
      s2 = t - c
      return s2
    end
    function random.uint32 ()
      return random() * 0x100000000 -- 2^32
    end
    function random.fract53 ()
      return random() + floor(random() * 0x200000) * 1.1102230246251565e-16 -- 2^-53
    end
    random.version = 'Alea 0.9'
    random.args = args
    return setmetatable(random, { __call = _random })

  end)({ ... })
end

return Alea