#!/usr/bin/env python3
"""Parse and verify DA14585 firmware image header (Dialog SUOTA/multi-image format).

Image header layout (64 bytes):
  +0x00  u8[2]  magic      0x70 0x51 ('pQ' LE word 0x5170) = IMAGE_VALID
  +0x02  u8[2]  signature  version/application id (here 0xAA 0x01)
  +0x04  u32    code_size  size of code region (= file_size - 64)
  +0x08  u32    crc32      CRC over code region
  +0x0C  52B    reserved   0xFF
"""
import struct, sys, zlib, binascii

IMG = "/mnt/documents/Works/Eink/qianbian/app/firmware-PP_da14585_4.2_CH.img"

def crc32_mpeg(data, init=0xFFFFFFFF, xorout=0, poly=0x04C11DB7):
    crc = init
    for b in data:
        crc ^= b << 24
        for _ in range(8):
            crc = ((crc << 1) ^ poly) & 0xFFFFFFFF if (crc & 0x80000000) else (crc << 1) & 0xFFFFFFFF
    return crc ^ xorout

def main():
    data = open(IMG, "rb").read()
    print(f"file size: {len(data)} (0x{len(data):x})")
    magic = data[0:2]
    sig = data[2:4]
    code_size, crc_hdr = struct.unpack_from("<II", data, 4)
    reserved = data[12:64]
    print(f"magic      : {magic.hex()} ({magic!r})")
    print(f"signature  : {sig.hex()}")
    print(f"code_size  : {code_size} (0x{code_size:x})  file-64 = {len(data)-64}")
    print(f"header CRC : 0x{crc_hdr:08x}")
    print(f"reserved   : all 0xff = {all(b==0xff for b in reserved)}")
    print(f"size match : {code_size == len(data)-64}")

    code = data[64:64+code_size]
    # try CRC variants
    c_zlib   = zlib.crc32(code) & 0xFFFFFFFF                       # CRC-32 (reflected, init/xor FF)
    c_bzip2  = crc32_mpeg(code, 0xFFFFFFFF, 0xFFFFFFFF)            # CRC-32/BZIP2
    c_mpeg   = crc32_mpeg(code, 0xFFFFFFFF, 0)                     # CRC-32/MPEG-2
    c_posix  = crc32_mpeg(code, 0, 0xFFFFFFFF)                     # CRC-32/POSIX (cksum-ish)
    c_jam    = zlib.crc32(code, 0xFFFFFFFF) ^ 0 ^ 0xFFFFFFFF       # jamcrc style check
    print(f"CRC32 zlib    : 0x{c_zlib:08x}  match={c_zlib==crc_hdr}")
    print(f"CRC32 bzip2   : 0x{c_bzip2:08x}  match={c_bzip2==crc_hdr}")
    print(f"CRC32 mpeg2   : 0x{c_mpeg:08x}  match={c_mpeg==crc_hdr}")
    print(f"CRC32 posix   : 0x{c_posix:08x}  match={c_posix==crc_hdr}")
    # also try crc over code with initial vector table included (whole thing)
    c_zlib_all = zlib.crc32(data[0:64+code_size]) & 0xFFFFFFFF
    print(f"CRC32 zlib(all incl hdr): 0x{c_zlib_all:08x}")

if __name__ == "__main__":
    main()