system.py 文件源码

def uuid_from_file(fn, block_size=1 << 20):
    """
    Returns an arbitrary sized unique ASCII string based on the file contents.
    (exact hashing method may change).
    """
    with open(fn, 'rb') as f:
        # first get the size
        import os
        f.seek(0, os.SEEK_END)
        size = f.tell()
        f.seek(0, os.SEEK_SET)
        del os
        # done!

        import hashlib
        sha1 = hashlib.new('sha512')
        while True:
            data = f.read(block_size)
            if not data:
                break
            sha1.update(data)
        # skip the '0x'
        return hex(size)[2:] + sha1.hexdigest()