async_std/io/write/
write_fmt.rs

1use std::pin::Pin;
2use std::future::Future;
3
4use crate::io::{self, Write};
5use crate::task::{Context, Poll};
6
7#[doc(hidden)]
8#[allow(missing_debug_implementations)]
9#[must_use]
10pub struct WriteFmtFuture<'a, T: Unpin + ?Sized> {
11    pub(crate) writer: &'a mut T,
12    pub(crate) res: Option<io::Result<Vec<u8>>>,
13    pub(crate) buffer: Option<Vec<u8>>,
14    pub(crate) amt: usize,
15}
16
17impl<T: Write + Unpin + ?Sized> Future for WriteFmtFuture<'_, T> {
18    type Output = io::Result<()>;
19
20    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
21        // Process the internal Result the first time we run.
22        if self.buffer.is_none() {
23            match self.res.take().unwrap() {
24                Err(err) => return Poll::Ready(Err(err)),
25                Ok(buffer) => self.buffer = Some(buffer),
26            };
27        }
28
29        // Get the types from the future.
30        let Self {
31            writer,
32            amt,
33            buffer,
34            ..
35        } = &mut *self;
36        let buffer = buffer.as_mut().unwrap();
37
38        // Copy the data from the buffer into the writer until it's done.
39        loop {
40            if *amt == buffer.len() {
41                futures_core::ready!(Pin::new(&mut **writer).poll_flush(cx))?;
42                return Poll::Ready(Ok(()));
43            }
44            let i = futures_core::ready!(Pin::new(&mut **writer).poll_write(cx, &buffer[*amt..]))?;
45            if i == 0 {
46                return Poll::Ready(Err(io::ErrorKind::WriteZero.into()));
47            }
48            *amt += i;
49        }
50    }
51}
async_std/io/write/write_fmt.rs

async_std/io/write/
write_fmt.rs
