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
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188

use crate::op_prelude::*;
use std::collections::hash_map::RandomState;
use std::collections::HashSet;
use std::hash::{BuildHasher, Hash, Hasher};

pin_project! {
    /// Stream for the [`try_dedup`](super::ext::JTryStreamExt::try_dedup) method
    #[must_use = "streams do nothing unless polled"]
    pub struct TryDedupStream<S> {
        #[pin]
        src: S,
        size_hint: (usize, Option<usize>),
        known: HashSet<u64>,
        hasher: RandomState,
    }
}

impl<S> Stream for TryDedupStream<S>
where
    S: TryStream,
    S::Ok: Hash,
{
    type Item = Result<S::Ok, S::Error>;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let mut this = self.project();
        Poll::Ready(loop {
            match ready!(this.src.as_mut().try_poll_next(cx)) {
                Some(Ok(v)) => if this.known.insert(hash(&*this.hasher, &v)) {
                    break Some(Ok(v));
                }
                other => break other,
            }
        })
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.size_hint
    }
}

impl<S> FusedStream for TryDedupStream<S>
where
    S: TryStream + FusedStream,
    S::Ok: Hash,
{
    delegate_fused!(src);
}

#[cfg(feature = "sink")]
impl<S, Item, E> Sink<Item> for TryDedupStream<S>
where
    S: Sink<Item, Error=E> + TryStream,
    S::Ok: Hash
{
    delegate_sink!(src, E, Item);
}

impl<S> TryDedupStream<S>
where
    S: TryStream,
    S::Ok: Hash,
{
    //noinspection DuplicatedCode
    pub(crate) fn new(src: S) -> Self {
        let size_hint = src.size_hint();
        Self {
            src,
            size_hint,
            hasher: RandomState::default(),
            known: HashSet::default(),
        }
    }
}

pin_project! {
    /// Stream for the [`dedup`](super::ext::JStreamExt::dedup) method
    #[must_use = "streams do nothing unless polled"]
    pub struct DedupStream<S> {
        #[pin]
        src: S,
        size_hint: (usize, Option<usize>),
        known: HashSet<u64>,
        hasher: RandomState,
    }
}

impl<S> Stream for DedupStream<S>
where
    S: Stream,
    S::Item: Hash,
{
    type Item = S::Item;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let mut this = self.project();
        Poll::Ready(loop {
            if let Some(next) = ready!(this.src.as_mut().poll_next(cx)) {
                if this.known.insert(hash(&*this.hasher, &next)) {
                    break Some(next);
                }
            } else {
                break None;
            }
        })
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.size_hint
    }
}

impl<S> FusedStream for DedupStream<S>
where
    S: Stream + FusedStream,
    S::Item: Hash
{
    delegate_fused!(src);
}

#[cfg(feature = "sink")]
impl<S, Item> Sink<Item> for DedupStream<S>
where
    S: Sink<Item> + Stream,
    S::Item: Hash
{
    delegate_sink!(src, S::Error, Item);
}

impl<S> DedupStream<S>
where
    S: Stream,
{
    //noinspection DuplicatedCode
    pub(crate) fn new(src: S) -> Self {
        let size_hint = src.size_hint();
        Self {
            src,
            size_hint,
            hasher: RandomState::default(),
            known: HashSet::default(),
        }
    }
}

fn hash<H>(hasher: &RandomState, value: &H) -> u64
where
    H: Hash,
{
    let mut hasher = hasher.build_hasher();
    value.hash(&mut hasher);
    hasher.finish()
}

#[cfg(test)]
mod tests {
    use super::TryDedupStream;
    use futures::executor::block_on;
    use futures::TryStreamExt;

    #[test]
    fn test_dedup_simple() {
        let src: Vec<Result<&str, ()>> = vec![
            Ok("hello"),
            Ok("hello"),
            Ok("world!"),
            Ok("world!"),
            Ok("123 123!"),
            Ok("123 123!"),
        ];

        let mut raised = TryDedupStream::new(futures::stream::iter(src));
        assert_eq!(block_on(raised.try_next()), Ok(Some("hello")));
        assert_eq!(block_on(raised.try_next()), Ok(Some("world!")));
        assert_eq!(block_on(raised.try_next()), Ok(Some("123 123!")));
        assert_eq!(block_on(raised.try_next()), Ok(None));
    }

    #[test]
    fn test_dedup_err() {
        let src: Vec<Result<&str, ()>> =
            vec![Ok("hello"), Ok("hello"), Ok("abc z"), Err(()), Ok("abc")];
        let mut raised = TryDedupStream::new(futures::stream::iter(src));
        assert_eq!(block_on(raised.try_next()), Ok(Some("hello")));
        assert_eq!(block_on(raised.try_next()), Ok(Some("abc z")));
        assert_eq!(block_on(raised.try_next()), Err(()));
    }
}