precache.py 文件源码

def file_digest(self, file_path, digest_type=None):
        '''Creates a digest based on the digest_type argument.
        digest_type defaults to SHA256.'''
        valid_digests = ['md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512']
        block_size = 65536

        if not digest_type:
            digest_type = 'sha256'

        if digest_type in valid_digests:
            h = hashlib.new(digest_type)
            with open(file_path, 'rb') as f:
                for block in iter(lambda: f.read(block_size), b''):
                    h.update(block)
                return h.hexdigest()
        else:
            raise Exception('%s not a valid digest - choose from %s' %
                            (digest_type, valid_digests))