Chunklist

chunklist.py

import argparse
import binascii
import hashlib
import struct
from pathlib import Path
from sys import exit

CHUNK_LENGTH = 4 + 32


def hexswap(i):
    return struct.unpack("<I", struct.pack(">I", i))[0]


def chunk(chunklist, file_path, verbose):
    chunklist = Path(chunklist).read_bytes() if isinstance(
        chunklist, str) else chunklist

    header = {
        "magic": chunklist[:4],
        "length": int.from_bytes(chunklist[4:8], "little"),
        "fileVersion": chunklist[8],
        "chunkMethod": chunklist[9],
        "sigMethod": chunklist[10],
        "chunkCount": int.from_bytes(chunklist[12:20], "little"),
        "chunkOffset": int.from_bytes(chunklist[20:28], "little"),
        "sigOffset": int.from_bytes(chunklist[28:36], "little")
    }

    all_chunks = chunklist[header["chunkOffset"]:header["chunkOffset"]+header["chunkCount"]*CHUNK_LENGTH]
    chunks = [{"length": int.from_bytes(all_chunks[i:i+4], "little"), "checksum": all_chunks[i+4:i+CHUNK_LENGTH]}
              for i in range(0, len(all_chunks), CHUNK_LENGTH)]

    with Path(file_path).open("rb") as f:
        for chunk in chunks:
            status = hashlib.sha256(f.read(chunk["length"])).digest()
            if not status == chunk["checksum"]:
                print(
                    f"Chunk {chunks.index(chunk) + 1} checksum status FAIL: chunk sum {binascii.hexlify(chunk['checksum']).decode()}, calculated sum {binascii.hexlify(status).decode()}")
                return False
            elif verbose:
                print(
                    f"Chunk {chunks.index(chunk) + 1} checksum status success")
    return True


parser = argparse.ArgumentParser(description='Verify download.')
parser.add_argument('chunklist', type=str,
                    help='path')
parser.add_argument('file',
                    help='file to verify')
parser.add_argument('-v', '--verbose', action='store_true',
                    help='enable verbose printing')

args = parser.parse_args()

if chunk(args.chunklist, args.file, args.verbose):
    print("No failures")
else:
    print("Fail")
    sys.exit(1)