###############################################################################
# RLE encoder
###############################################################################
# Takes any binary file and converts to RLE sequenced (ended with length 0)
# Input:  FF FF FF FF FF FF FF FF FF 0A FF FF FF
# Output: 09 FF 01 0A 03 FF 00
###############################################################################
import os
import sys
import math

input = sys.argv[1]

if len(sys.argv) == 1:
  print("Usage:\n $ python3 ./rle.py <BIN_FILENAME>\n\nOutput .rle format.")
  sys.exit()

def compress(data):
  output = []
  i = 1
  total = 0
  char = data[0]
  count = 1

  while i <= len(data):
    if i == len(data):
      output.append(bytes([count]))
      output.append(bytes([char]))
      total += count
      break
    if char == data[i]:
      count += 1
      if count == 255:
        total += count
        output.append(bytes([count]))
        output.append(bytes([char]))
        count = 0
      i += 1
      continue 
    else:
      total += count
      output.append(bytes([count]))
      output.append(bytes([char]))
      count = 1
      char = data[i] 
      i += 1
      continue 
    
  print(total, "bytes compresed to", len(output))
  return output

def read_file_bytes(file):
  with open(file, 'rb') as f:
    return f.read()

def read_file(input):
    inbytes = read_file_bytes(input)
    output = compress(inbytes)
    f = None 
    try: 
      f = open(input.split('.')[0]+".rle", "wb")
      for b in output:
        f.write(b)
      f.write(b'\x00')
    finally:
      f.close()

read_file(input)

print("File written successfully.")