quick and dirty tool to display the chunk structure of a .bpt file

puke_bpt.py

import io, struct, argparse

class Chunk:
    def __init__(self, id):
        self.id = id
        self.children = []

def process_chunk( input, size_encoding, parent_chunk, remaining_data, depth = 0 ):
    if None != parent_chunk.id and not parent_chunk.id in [ 'aBPT', 'aLII', 'aFRM', 'aLYR', 'aVEL', 'nPAL', 'nAMS', 'aANM', 'nFMS', 'nVLS', 'nLIS', 'nLRS' ]:
        input.seek( input.tell() + remaining_data )
        print( ' ' * depth + f'{parent_chunk.id} size={remaining_data}' )
        if remaining_data % 2 != 0: input.seek( input.tell() + 1 )
        return
    print( ' ' * depth + f'processing {parent_chunk.id}' )
    while 7 < remaining_data:
        id = input.read( 4 ).decode( 'ascii' )
        size = struct.unpack( size_encoding, input.read( 4 ))[0]
        chunk = Chunk( id )
        parent_chunk.children.append( chunk )
        process_chunk( input, size_encoding, chunk, size, depth + 1 )
        remaining_data -= size + 8

def parse_chunks_for_file( filename, size_encoding ):
    with open(filename,'rb') as f: raw_data = f.read()
    input = io.BytesIO( raw_data )
    root_chunk = Chunk( None )
    process_chunk( input, size_encoding, root_chunk, len( raw_data ) )
    return root_chunk

def main():
    parser = argparse.ArgumentParser( description='puke up some BPT file chunks' )
    parser.add_argument( 'filename', help='filename' )
    parser.add_argument( '-s', '--size', default='<I', help='size encoding (use <I)')
    args = parser.parse_args()
    file_chunks = parse_chunks_for_file( args.filename, args.size )

if __name__ == "__main__":
    main()