openwrt/scripts/cfe-partition-tag.py

#!/usr/bin/env python3

"""
CFE Partition Tag

{
	u32 part_id;
	u32 part_size;
	u16 flags;
	char part_name[33];
	char part_version[21];
	u32 part_crc32;
}

"""

import argparse
import os
import struct
import binascii


PART_NAME_SIZE = 33
PART_VERSION_SIZE = 21


def auto_int(x):
	return int(x, 0)

def str_to_bytes_pad(string, size):
	str_bytes = string.encode()
	num_bytes = len(str_bytes)
	if (num_bytes >= size):
		str_bytes = str_bytes[:size - 1] + '\0'.encode()
	else:
		str_bytes += '\0'.encode() * (size - num_bytes)
	return str_bytes

def create_tag(args, in_bytes, size):
    # JAM CRC32 is bitwise not and unsigned
    crc = (~binascii.crc32(in_bytes) & 0xFFFFFFFF)

	tag = bytearray()
	tag += struct.pack('>I', args.part_id)
	tag += struct.pack('>I', size)
	tag += struct.pack('>H', args.part_flags)
	tag += str_to_bytes_pad(args.part_name, PART_NAME_SIZE)
	tag += str_to_bytes_pad(args.part_version, PART_VERSION_SIZE)
	tag += struct.pack('>I', crc)

	return tag

def create_output(args):
	in_st = os.stat(args.input_file)
	in_size = in_st.st_size

	in_f = open(args.input_file, 'r+b')
	in_bytes = in_f.read(in_size)
	in_f.close()

	tag = create_tag(args, in_bytes, in_size)

	out_f = open(args.output_file, 'w+b')
	out_f.write(tag)
	out_f.close()

def main():
	global args

	parser = argparse.ArgumentParser(description='')

	parser.add_argument('--flags',
		dest='part_flags',
		action='store',
		type=auto_int,
		help='Partition Flags')

	parser.add_argument('--id',
		dest='part_id',
		action='store',
		type=auto_int,
		help='Partition ID')

	parser.add_argument('--input-file',
		dest='input_file',
		action='store',
		type=str,
		help='Input file')

	parser.add_argument('--output-file',
		dest='output_file',
		action='store',
		type=str,
		help='Output file')

	parser.add_argument('--name',
		dest='part_name',
		action='store',
		type=str,
		help='Partition Name')

	parser.add_argument('--version',
		dest='part_version',
		action='store',
		type=str,
		help='Partition Version')

	args = parser.parse_args()

	if ((not args.part_flags) or
	    (not args.part_id) or
	    (not args.input_file) or
	    (not args.output_file) or
	    (not args.part_name) or
	    (not args.part_version)):
		parser.print_help()
	else:
		create_output(args)

main()