multipart_write/write/
fold_ret.rs

1use crate::{FusedMultipartWrite, MultipartWrite};
2
3use futures_core::ready;
4use std::fmt::{self, Debug, Formatter};
5use std::pin::Pin;
6use std::task::{Context, Poll};
7
8pin_project_lite::pin_project! {
9    /// `MultipartWrite` for [`fold_ret`](super::MultipartWriteExt::fold_ret).
10    #[must_use = "futures do nothing unless polled"]
11    pub struct FoldRet<Wr, F, T> {
12        #[pin]
13        writer: Wr,
14        acc: Option<T>,
15        f: F,
16    }
17}
18
19impl<Wr, F, T> FoldRet<Wr, F, T> {
20    pub(super) fn new(writer: Wr, id: T, f: F) -> Self {
21        Self {
22            writer,
23            acc: Some(id),
24            f,
25        }
26    }
27
28    /// Acquires a reference to the underlying writer.
29    pub fn get_ref(&self) -> &Wr {
30        &self.writer
31    }
32
33    /// Acquires a mutable reference to the underlying writer.
34    ///
35    /// It is inadvisable to directly write to the underlying writer.
36    pub fn get_mut(&mut self) -> &mut Wr {
37        &mut self.writer
38    }
39
40    /// Acquires a pinned mutable reference to the underlying writer.
41    ///
42    /// It is inadvisable to directly write to the underlying writer.
43    pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut Wr> {
44        self.project().writer
45    }
46}
47
48impl<Wr, F, T, Part> FusedMultipartWrite<Part> for FoldRet<Wr, F, T>
49where
50    Wr: FusedMultipartWrite<Part>,
51    F: FnMut(T, &Wr::Ret) -> T,
52{
53    fn is_terminated(&self) -> bool {
54        self.writer.is_terminated()
55    }
56}
57
58impl<Wr, F, T, Part> MultipartWrite<Part> for FoldRet<Wr, F, T>
59where
60    Wr: MultipartWrite<Part>,
61    F: FnMut(T, &Wr::Ret) -> T,
62{
63    type Ret = Wr::Ret;
64    type Output = (T, Wr::Output);
65    type Error = Wr::Error;
66
67    fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
68        self.project().writer.poll_ready(cx)
69    }
70
71    fn start_send(self: Pin<&mut Self>, part: Part) -> Result<Self::Ret, Self::Error> {
72        let mut this = self.project();
73        let ret = this.writer.as_mut().start_send(part)?;
74        let new_acc = this.acc.take().map(|acc| (this.f)(acc, &ret));
75        *this.acc = new_acc;
76        Ok(ret)
77    }
78
79    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
80        self.project().writer.poll_flush(cx)
81    }
82
83    fn poll_complete(
84        self: Pin<&mut Self>,
85        cx: &mut Context<'_>,
86    ) -> Poll<Result<Self::Output, Self::Error>> {
87        let mut this = self.project();
88        let output = ready!(this.writer.as_mut().poll_complete(cx))?;
89        let acc = this.acc.take().expect("polled FoldRet after completion");
90        Poll::Ready(Ok((acc, output)))
91    }
92}
93
94impl<Wr, F, T> Debug for FoldRet<Wr, F, T>
95where
96    Wr: Debug,
97    T: Debug,
98{
99    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
100        f.debug_struct("FoldRet")
101            .field("writer", &self.writer)
102            .field("acc", &self.acc)
103            .field("f", &"F")
104            .finish()
105    }
106}
multipart_write/write/fold_ret.rs

multipart_write/write/
fold_ret.rs
