Function bytes_to_read

invoke/terminals.py:227–248

Query stream ``input_`` to see how many bytes may be readable. .. note:: If we are unable to tell (e.g. if ``input_`` isn't a true file descriptor or isn't a valid TTY) we fall back to suggesting reading 1 byte only. :param input: Input stream object (file-like

(input_: IO)

def bytes_to_read(input_: IO) -> int:
    """
    Query stream ``input_`` to see how many bytes may be readable.

    .. note::
        If we are unable to tell (e.g. if ``input_`` isn't a true file
        descriptor or isn't a valid TTY) we fall back to suggesting reading 1
        byte only.

    :param input: Input stream object (file-like).

    :returns: `int` number of bytes to read.

    .. versionadded:: 1.0
    """
    # NOTE: we have to check both possibilities here; situations exist where
    # it's not a tty but has a fileno, or vice versa; neither is typically
    # going to work re: ioctl().
    if not WINDOWS and isatty(input_) and has_fileno(input_):
        fionread = fcntl.ioctl(input_, termios.FIONREAD, b"  ")
        return int(struct.unpack("h", fionread)[0])
    return 1