1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146

//! `Map` and `Then`.

use core::future::Future;
use core::pin::Pin;
use core::task::{Context, Poll};

use completion_core::{CompletionFuture, CompletionStream};
use futures_core::{ready, Stream};
use pin_project_lite::pin_project;

pin_project! {
    /// Stream for [`CompletionStreamExt::map`](crate::CompletionStreamExt::map).
    #[derive(Debug, Clone)]
    pub struct Map<S, F> {
        #[pin]
        stream: S,
        f: F,
    }
}

impl<S, F> Map<S, F> {
    pub(crate) fn new(stream: S, f: F) -> Self {
        Self { stream, f }
    }
}

impl<S, F, T> CompletionStream for Map<S, F>
where
    S: CompletionStream,
    F: FnMut(S::Item) -> T,
{
    type Item = T;

    unsafe fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let mut this = self.project();
        this.stream
            .as_mut()
            .poll_next(cx)
            .map(|value| value.map(this.f))
    }
    unsafe fn poll_cancel(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
        self.project().stream.poll_cancel(cx)
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.stream.size_hint()
    }
}

impl<S, F, T> Stream for Map<S, F>
where
    S: CompletionStream + Stream<Item = <S as CompletionStream>::Item>,
    F: FnMut(<S as CompletionStream>::Item) -> T,
{
    type Item = T;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        unsafe { CompletionStream::poll_next(self, cx) }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        CompletionStream::size_hint(&self.stream)
    }
}

pin_project! {
    /// Stream for [`CompletionStreamExt::then`](crate::CompletionStreamExt::then).
    #[derive(Debug, Clone)]
    pub struct Then<S, F, Fut> {
        #[pin]
        stream: S,
        #[pin]
        fut: Option<Fut>,
        f: F,
    }
}

impl<S, F, Fut> Then<S, F, Fut> {
    pub(crate) fn new(stream: S, f: F) -> Self {
        Self {
            stream,
            fut: None,
            f,
        }
    }
}

impl<S, F, Fut> CompletionStream for Then<S, F, Fut>
where
    S: CompletionStream,
    F: FnMut(S::Item) -> Fut,
    Fut: CompletionFuture,
{
    type Item = Fut::Output;

    unsafe fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let mut this = self.project();

        if this.fut.is_none() {
            match ready!(this.stream.poll_next(cx)) {
                Some(item) => {
                    this.fut.set(Some((this.f)(item)));
                }
                None => {
                    return Poll::Ready(None);
                }
            }
        }

        let val = ready!(this.fut.as_mut().as_pin_mut().unwrap().poll(cx));
        this.fut.set(None);
        Poll::Ready(Some(val))
    }

    unsafe fn poll_cancel(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
        let mut this = self.project();
        if let Some(fut) = this.fut.as_mut().as_pin_mut() {
            fut.poll_cancel(cx)
        } else {
            this.stream.poll_cancel(cx)
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let future_len = if self.fut.is_some() { 1 } else { 0 };
        let (stream_min, stream_max) = self.stream.size_hint();
        (
            stream_min.saturating_add(future_len),
            stream_max.and_then(|l| l.checked_add(future_len)),
        )
    }
}

impl<S, F, Fut> Stream for Then<S, F, Fut>
where
    S: CompletionStream + Stream<Item = <S as CompletionStream>::Item>,
    F: FnMut(<S as CompletionStream>::Item) -> Fut,
    Fut: CompletionFuture + Future<Output = <Fut as CompletionFuture>::Output>,
{
    type Item = <Fut as CompletionFuture>::Output;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        unsafe { CompletionStream::poll_next(self, cx) }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        CompletionStream::size_hint(self)
    }
}