async_codec_util/decoder/
and_then.rs

1use async_codec::{AsyncDecode, PollDec};
2use async_codec::PollDec::{Done, Progress, Pending, Errored};
3use futures_core::task::Context;
4use futures_io::AsyncRead;
5
6enum State<S, T, F> {
7    First(S, F),
8    Second(T),
9}
10
11/// Run a decoder and use the produced item to construct the next decoder to run.
12pub struct AndThen<S, T, F>(State<S, T, F>);
13
14impl<S, T, F> AndThen<S, T, F> {
15    /// Run a decoder and use the produced item to construct the next decoder to run.
16    pub fn new(first: S, f: F) -> AndThen<S, T, F> {
17        AndThen(State::First(first, f))
18    }
19}
20
21impl<S, T, F> AsyncDecode for AndThen<S, T, F>
22    where S: AsyncDecode,
23          T: AsyncDecode<Error = S::Error>,
24          F: FnOnce(S::Item) -> T
25{
26    type Item = T::Item;
27    type Error = T::Error;
28
29    fn poll_decode<R: AsyncRead>(mut self,
30                                 cx: &mut Context,
31                                 reader: &mut R)
32                                 -> PollDec<Self::Item, Self, Self::Error> {
33        match self.0 {
34            State::First(first, f) => {
35                match first.poll_decode(cx, reader) {
36                    Done(item, read) => {
37                        self.0 = State::Second(f(item));
38                        Progress(self, read)
39                    }
40                    Progress(first, read) => {
41                        self.0 = State::First(first, f);
42                        Progress(self, read)
43                    }
44                    Pending(first) => {
45                        self.0 = State::First(first, f);
46                        Pending(self)
47                    }
48                    Errored(err) => Errored(err),
49                }
50            }
51            State::Second(second) => {
52                match second.poll_decode(cx, reader) {
53                    Done(item, read) => Done(item, read),
54                    Progress(second, read) => {
55                        self.0 = State::Second(second);
56                        Progress(self, read)
57                    }
58                    Pending(second) => {
59                        self.0 = State::Second(second);
60                        Pending(self)
61                    }
62                    Errored(err) => Errored(err),
63                }
64            }
65        }
66    }
67}
async_codec_util/decoder/and_then.rs

async_codec_util/decoder/
and_then.rs
