from __future__ import annotations

import hashlib
from typing import BinaryIO


def hashfile(afile: BinaryIO, blocksize: int = 65536) -> str:
    """Hash the contents of an open file handle with SHA256"""
    hasher = hashlib.sha256()
    buf = afile.read(blocksize)
    while len(buf) > 0:
        hasher.update(buf)
        buf = afile.read(blocksize)
    return hasher.hexdigest()