import zlib


def _adler32(fname):
    """Compute the adler32 checksum on a file.

    :param fname: File path to the file to checksum
    :type fname: str
    """
    with open(fname, 'rb') as f:
        checksum = 1
        while True:
            buf = f.read(1024*1024*8)
            if not buf:
                break
            checksum = zlib.adler32(buf, checksum)
            
    return checksum