local mtpt = {}

local eformat = "c20c4>I4>I4"

local function aop(td,n,mn,...)
 local rts = td.seek(-math.huge)
 td.seek(n)
 local rv = {td[mn](...)}
 td.seek(-math.huge)
 td.seek(rts)
 return table.unpack(rv)
end

function mtpt.parse(s)
 local rt = {}
 for i = 1, s:len(), 32 do
  local n, t, start, length = string.unpack(eformat, s, i)
  n = n:gsub("\0", "")
  if n ~= "" then
   rt[#rt+1] = {n,t,start,length}
  end
 end
 return rt
end
function mtpt.generate(pt)
 local ps = ""
 for k,v in ipairs(pt) do
  ps = ps .. string.pack(eformat, table.unpack(v))
 end
 return ps
end

function mtpt.getPartitions(drive)
 local rv
 if drive.type == "tape_drive" then
  local ts = drive.getSize()
  local lso = (math.floor(ts / 512) - 1) * 512
  rv = mtpt.parse(aop(drive, lso, "read", ts - lso))
 else
  rv = mtpt.parse(drive.readSector(drive.getCapacity() / drive.getSectorSize()))
 end
 return rv[1][2] == "mtpt" and rv
end
function mtpt.setPartitions(drive, pt, name)
 name = name or ""
 if pt[1][2] ~= "mtpt" then table.insert(pt, 1, {name, "mtpt", 0, 0}) end
 local ns = mtpt.generate(pt)
 if drive.type == "tape_drive" then
  local ts = drive.getSize()
  local lso = (math.floor(ts / 512) - 1) * 512
  return aop(drive, lso, "write", ns .. ("\0"):rep(ts - lso - #ns))
 end
 return drive.writeSector(drive.getCapacity() / drive.getSectorSize(), ns .. ("\0"):rep(drive.getSectorSize() - #ns))
end

return mtpt