misc.py 文件源码

def open_image_file(root, path, flag, mode=None):
        """Safely open files that ensures that the path we'are accessing resides
        within a specified image root.

        'root' is a directory that the path must reside in.
        """

        try:
                return os.fdopen(os.open(path, flag|os.O_NOFOLLOW, mode))
        except EnvironmentError as e:
                if e.errno != errno.ELOOP:
                        # Access to protected member; pylint: disable=W0212
                        raise api_errors._convert_error(e)
        # If it is a symbolic link, fall back to ar_open. ar_open interprets
        # 'path' as relative to 'root', that is, 'root' will be prepended to
        # 'path', so we need to call os.path.relpath here.
        from pkg.altroot import ar_open
        return os.fdopen(ar_open(root, os.path.relpath(path, root), flag, mode))