local partition = {}

local entryPattern = "(" .. ("."):rep(20) .. ")(....)(....)(....)"

local function cint(n,l)
 local t={}
 for i = 0, 7 do
  t[i+1] = (n >> (i * 8)) & 0xFF
 end
 return string.reverse(string.char(table.unpack(t)):sub(1,l))
end
local function toint(s)
 local n = 0
 local i = 1
 for p in s:gmatch(".") do
  n = n << 8
  n = n | string.byte(p)
  i=i+1
 end
 return n
end

function partition.parse(sector)
 local pt = {}
 for name,ptype,sstart,slen in sector:gmatch(entryPattern) do
  local pte = {}
  pte.name = name:gsub("\0","")
  if pte.name:len() > 0 then
   pte.type = ptype
   pte.start = toint(sstart)
   pte.len = toint(slen)
   pte.last = pte.start + toint(slen)
   pt[#pt+1] = pte
  end
 end
 return pt
end
function partition.generate(pt)
 local ps = ""
 for k,v in pairs(pt) do
  if not v.len then
   v.len = v.last - v.start
  end
--  ps = ps .. ("\0"):rep(math.max(20-v.name:len(),0)) .. v.name:sub(1,20) .. v.type:sub(1,4) .. cint(v.start,4) .. cint(v.len,4)
  ps = ps .. (("\0"):rep(20) .. v.name):sub(-20) .. v.type:sub(1,4) .. cint(v.start,4) .. cint(v.len,4)
 end
 return ps..("\0"):rep(512-ps:len())
end

return partition