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

use core::pin::Pin;

use futures::future::Future;
use futures::ready;
use futures::sink::Sink;
use futures::task::{Context, Poll};
use wasm_bindgen::prelude::*;
use wasm_bindgen_futures::JsFuture;

use super::WritableStreamDefaultWriter;

/// A [`Sink`](Sink) for the [`into_sink`](super::WritableStream::into_sink) method.
///
/// This sink holds a writer, and therefore locks the [`WritableStream`](super::WritableStream).
/// When this sink is dropped, it also drops its writer which in turn
/// [releases its lock](https://streams.spec.whatwg.org/#release-a-lock).
#[derive(Debug)]
pub struct IntoSink<'writer> {
    writer: Option<WritableStreamDefaultWriter<'writer>>,
    ready_fut: Option<JsFuture>,
    write_fut: Option<JsFuture>,
    close_fut: Option<JsFuture>,
}

impl<'writer> IntoSink<'writer> {
    #[inline]
    pub(super) fn new(writer: WritableStreamDefaultWriter) -> IntoSink {
        IntoSink {
            writer: Some(writer),
            ready_fut: None,
            write_fut: None,
            close_fut: None,
        }
    }
}

impl<'writer> Sink<JsValue> for IntoSink<'writer> {
    type Error = JsValue;

    fn poll_ready(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        if self.ready_fut.is_none() {
            // No pending ready future, start reading the next chunk
            match self.writer.as_ref() {
                Some(writer) => {
                    // Create future for ready promise
                    let fut = JsFuture::from(writer.as_raw().ready());
                    self.as_mut().ready_fut = Some(fut);
                }
                None => {
                    // Writer was already dropped
                    // TODO Return error?
                    return Poll::Ready(Ok(()));
                }
            }
        }

        // Poll the ready future
        let js_result = ready!(Pin::new(self.as_mut().ready_fut.as_mut().unwrap_throw()).poll(cx));
        self.as_mut().ready_fut = None;

        // Ready future completed
        Poll::Ready(match js_result {
            Ok(js_value) => {
                debug_assert!(js_value.is_undefined());
                Ok(())
            }
            Err(js_value) => {
                // Error, drop writer
                self.as_mut().writer = None;
                Err(js_value)
            }
        })
    }

    fn start_send(mut self: Pin<&mut Self>, item: JsValue) -> Result<(), Self::Error> {
        match self.writer.as_ref() {
            Some(writer) => {
                let fut = JsFuture::from(writer.as_raw().write(item));
                // Set or replace the pending write future
                self.as_mut().write_fut = Some(fut);
                Ok(())
            }
            None => {
                // TODO Return error?
                Ok(())
            }
        }
    }

    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        // If we're not writing, then there's nothing to flush
        if self.write_fut.is_none() {
            return Poll::Ready(Ok(()));
        }

        // Poll the write future
        let js_result = ready!(Pin::new(self.as_mut().write_fut.as_mut().unwrap_throw()).poll(cx));
        self.as_mut().write_fut = None;

        // Write future completed
        Poll::Ready(match js_result {
            Ok(js_value) => {
                debug_assert!(js_value.is_undefined());
                Ok(())
            }
            Err(js_value) => {
                // Error, drop writer
                self.as_mut().writer = None;
                Err(js_value)
            }
        })
    }

    fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        if self.close_fut.is_none() {
            // No pending close future, start closing the stream
            match self.writer.as_ref() {
                Some(writer) => {
                    // Create future for close promise
                    let fut = JsFuture::from(writer.as_raw().close());
                    self.as_mut().close_fut = Some(fut);
                }
                None => {
                    // Writer was already dropped
                    // TODO Return error?
                    return Poll::Ready(Ok(()));
                }
            }
        }

        // Poll the close future
        let js_result = ready!(Pin::new(self.as_mut().close_fut.as_mut().unwrap_throw()).poll(cx));
        self.as_mut().close_fut = None;

        // Close future completed
        self.as_mut().writer = None;
        Poll::Ready(match js_result {
            Ok(js_value) => {
                debug_assert!(js_value.is_undefined());
                Ok(())
            }
            Err(js_value) => Err(js_value),
        })
    }
}