def rsyncdelta(bufstream, remotesignatures, blocksize=4096):
    remote_weak, remote_strong = remotesignatures
    match = True
    matchblock = -1
    deltaqueue = collections.deque()

    while True:
        if match and bufstream is not None:
            window = collections.deque(bytes(bufstream.read(blocksize)))
            checksum, a, b = weakchecksum(window)

        try:
            matchblock = remote_weak.index(checksum, matchblock + 1)
            stronghash = hashlib.md5(bytes(window)).hexdigest()

            if remote_strong[matchblock] == stronghash:
                match = True
                deltaqueue.append(matchblock)

                if bufstream.closed:
                    break
                continue

        except ValueError:
            match = False
            try:
                if bufstream:
                    newbyte = ord(bufstream.read(1))
                    window.append(newbyte)
            except TypeError:
                newbyte = 0
                tailsize = bufstream.tell() % blocksize
                bufstream = None

            if bufstream is None and len(window) <= tailsize:
                deltaqueue.append(window)
                break

            oldbyte = window.popleft()
            checksum, a, b = rollingchecksum(oldbyte, newbyte, a, b, blocksize)
            #assert checksum == weakchecksum(window)[0]

            try:
                deltaqueue[-1].append(oldbyte)
            except (AttributeError, IndexError):
                deltaqueue.append([oldbyte])

    deltastructure = [blocksize]
    for element in deltaqueue:
        if isinstance(element, int):
            deltastructure.append(element)
        elif element:
            deltastructure.append(bytes(element))

    return deltastructure