| use std::fmt; |
| use std::pin::Pin; |
| |
| use crate::io::{self, BufRead, Read}; |
| use crate::task::{Context, Poll}; |
| |
| /// Creates a reader that contains no data. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { |
| /// # |
| /// use async_std::io; |
| /// use async_std::prelude::*; |
| /// |
| /// let mut buf = Vec::new(); |
| /// let mut reader = io::empty(); |
| /// reader.read_to_end(&mut buf).await?; |
| /// |
| /// assert!(buf.is_empty()); |
| /// # |
| /// # Ok(()) }) } |
| /// ``` |
| pub fn empty() -> Empty { |
| Empty { _private: () } |
| } |
| |
| /// A reader that contains no data. |
| /// |
| /// This reader is created by the [`empty`] function. See its |
| /// documentation for more. |
| /// |
| /// [`empty`]: fn.empty.html |
| pub struct Empty { |
| _private: (), |
| } |
| |
| impl fmt::Debug for Empty { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.pad("Empty { .. }") |
| } |
| } |
| |
| impl Read for Empty { |
| #[inline] |
| fn poll_read( |
| self: Pin<&mut Self>, |
| _: &mut Context<'_>, |
| _: &mut [u8], |
| ) -> Poll<io::Result<usize>> { |
| Poll::Ready(Ok(0)) |
| } |
| } |
| |
| impl BufRead for Empty { |
| #[inline] |
| fn poll_fill_buf<'a>( |
| self: Pin<&'a mut Self>, |
| _: &mut Context<'_>, |
| ) -> Poll<io::Result<&'a [u8]>> { |
| Poll::Ready(Ok(&[])) |
| } |
| |
| #[inline] |
| fn consume(self: Pin<&mut Self>, _: usize) {} |
| } |