splituapp.py

#!/usr/bin/env python

# split_app for Python2/3 by SuperR. @XDA
#
# For extracting img files from UPDATE.APP

# Based on the app_structure file in split_up_data.pl by McSpoon

from __future__ import print_function

from string import printable
from struct import unpack
import sys
from os import makedirs, name, sep, path


def extract(source, flist):
    byte_num = 4
    out_dir = 'output'
    img_files = []

    try:
        makedirs(out_dir)
    finally:
        ...

    with open(source, 'rb') as f:
        while True:
            i = f.read(byte_num)

            if not i:
                break
            elif i != b'\x55\xAA\x5A\xA5':
                continue

            header_size = list(unpack('<L', f.read(byte_num)))[0]
            f.seek(16, 1)
            file_size = list(unpack('<L', f.read(byte_num)))[0]
            f.seek(32, 1)

            try:
                filename = str(f.read(16).decode())
                filename = ''.join(f for f in filename if f in printable).lower()
            except Exception or BaseException:
                filename = ''

            f.seek(22, 1)
            crc_data = f.read(header_size - 98)

            if not flist or filename in flist:
                if filename in img_files:
                    filename = filename + '_2'

                print(f'Extracting {filename}.img ...')

                chunk = 10240

                try:
                    with open(out_dir + sep + filename + '.img', 'wb') as o:
                        while file_size > 0:
                            if chunk > file_size:
                                chunk = file_size

                            o.write(f.read(chunk))
                            file_size -= chunk
                except Exception as e:
                    print('ERROR: Failed to create ' + filename + '.img:%s\n' % e)
                    return

                img_files.append(filename)

                if name != 'nt':
                    if path.isfile('crc'):
                        print('Calculating crc value for ' + filename + '.img ...\n')

                        crc_val = []
                        if sys.version_info.major < 3:
                            for i in crc_data:
                                crc_val.append('%02X' % int(i))
                        else:
                            for i in crc_data:
                                crc_val.append('%02X' % i)

            else:
                f.seek(file_size, 1)

            x_bytes = byte_num - f.tell() % byte_num
            if x_bytes < byte_num:
                f.seek(x_bytes, 1)

    print('\nExtraction complete')