import hashlib
import base64


def verify_sha512(filename, inithash):
    """
    Compare the original hash value with the current.

    :param filename: Signed file to check.
    :type filename: str

    :param inithash: Original SHA512 hash, as bytestring.
    :type inithash: bytes
    """
    sha512 = hashlib.sha512()
    with open(filename, 'rb') as file:
        while True:
            data = file.read(16 * 1024 * 1024)
            if not data:
                break
            sha512.update(data)
    rawdigest = sha512.digest()  # must be bytestring, not hexadecimalized str
    b64h = base64.b64encode(rawdigest, altchars=b"-_")  # replace some chars
    b64h = b64h.strip(b"==")  # remove padding
    return b64h == inithash