[PokeCC] Save/Load code

local function log2(colour)
  return math.log(colour) / math.log(2)
end

local function findLongest( t )
  local l = #t[1]
  for _,v in pairs( t ) do
    l = math.max( l, #v )
  end
  return l
end

local function buildByte( color, state )
  --# in the high nibble we have 3 extra bits that could be used to store other small data
  local high = bit.band( state == true and 1 or 0, 0xF )
  local low = bit.band( log2( color ), 0xF )
  return bit.bor( bit.blshift( high, 4 ), low )
end

local function unpackByte( byte )
  local high = bit.brshift( byte, 4)
  local low = bit.band( byte, 0xF )
  return { c = 2^low, s = high == 1 }
end

function save(filename, map)
  local file = fs.open(filename, "wb")
  file.write(#map) --# height
  file.write(findLongest(map)) --# width
  for _,row in pairs(map) do
    for _,col in pairs(row) do
      file.write(buildByte(col.c, col.s))
    end
  end
  file.close()
end

function load(filename)
  local map = {}
  local file = fs.open(filename, "rb")
  local width = file.read()
  local height = file.read()
  local row, col, bc = 0,0,0
  for byte in file.read do
    row, col = (bc % width) + 1, (bc % height) + 1
    map[row] = map[row] or {}
    map[row][col] = unpackByte(byte)
    bc = bc + 1
  end
  return map, file.close()
end