Created
May 3, 2019 20:50
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pub struct SelectIterator<'i, I> { | |
iters: Vec<&'i mut dyn Iterator<Item=I>> | |
} | |
pub fn select<'i, I>(iters: Vec<&'i mut dyn Iterator<Item=I>>) | |
-> SelectIterator<'i, I> | |
{ | |
SelectIterator { iters } | |
} | |
impl<'i, I> Iterator for SelectIterator<'i, I> { | |
type Item = I; | |
fn next(&mut self) -> Option<Self::Item> { | |
for iter in self.iters.iter_mut() { | |
let n = iter.next(); | |
if n.is_some() { | |
return n | |
} | |
} | |
None | |
} | |
} | |
#[cfg(test)] | |
mod test { | |
use super::*; | |
#[test] | |
fn basic_select() { | |
let v1 = vec![1i32, 2]; | |
let mut iter1 = v1.iter(); | |
let v2 = vec![-1i32, -2, -3]; | |
let mut iter2 = v2.iter(); | |
let mut select_iter = select(vec![ | |
&mut iter1, &mut iter2]); | |
assert_eq!(Some(&1), select_iter.next()); | |
assert_eq!(Some(&2), select_iter.next()); | |
assert_eq!(Some(&-1), select_iter.next()); | |
assert_eq!(Some(&-2), select_iter.next()); | |
assert_eq!(Some(&-3), select_iter.next()); | |
assert_eq!(None, select_iter.next()); | |
} | |
#[test] | |
fn with_mappings() { | |
let left = vec!["a", "b", "c"]; | |
let mut left_merge = left.iter().map(|s| Merged::Left(s.to_string())); | |
let right = vec![1i32, 2, 3]; | |
let mut right_merge = right.iter().map(|i| Merged::Right(*i)); | |
let mut select_iter: SelectIterator<Merged> = select(vec![ | |
&mut left_merge, &mut right_merge | |
]); | |
assert_eq!(Some(Merged::Left("a".into())), select_iter.next()); | |
assert_eq!(Some(Merged::Left("b".into())), select_iter.next()); | |
assert_eq!(Some(Merged::Left("c".into())), select_iter.next()); | |
assert_eq!(Some(Merged::Right(1)), select_iter.next()); | |
assert_eq!(Some(Merged::Right(2)), select_iter.next()); | |
assert_eq!(Some(Merged::Right(3)), select_iter.next()); | |
assert_eq!(None, select_iter.next()); | |
} | |
#[derive(Debug, PartialEq)] | |
enum Merged { | |
Left(String), | |
Right(i32) | |
} | |
#[test] | |
fn from_channels_try_iter() { | |
use std::sync::mpsc::*; | |
let (tx1, rx1) = channel(); | |
let (tx2, rx2) = channel(); | |
let mut iter1 = rx1.try_iter(); | |
let mut iter2 = rx2.try_iter(); | |
let mut select_iter = select(vec![ | |
&mut iter1, &mut iter2 | |
]); | |
tx2.send(1u32).unwrap(); | |
assert_eq!(Some(1u32), select_iter.next()); | |
tx1.send(10u32).unwrap(); | |
tx2.send(2u32).unwrap(); | |
tx1.send(20u32).unwrap(); | |
assert_eq!(Some(10u32), select_iter.next()); | |
assert_eq!(Some(20u32), select_iter.next()); | |
assert_eq!(Some(2u32), select_iter.next()); | |
assert_eq!(None, select_iter.next()); | |
} | |
#[test] | |
fn from_channels_blocking_iter() { | |
use std::sync::mpsc::*; | |
use std::thread; | |
let (tx1, rx1) = channel(); | |
let (tx2, rx2) = channel(); | |
let (signal_tx, signal_rx) = channel(); | |
let _ = thread::spawn(move ||{ | |
let mut iter1 = rx1.iter(); | |
let mut iter2 = rx2.iter(); | |
let mut select_iter = select(vec![ | |
&mut iter1, &mut iter2 | |
]); | |
assert_eq!(Some(1u32), select_iter.next()); | |
assert_eq!(Some(10u32), select_iter.next()); | |
assert_eq!(Some(20u32), select_iter.next()); | |
assert_eq!(Some(2u32), select_iter.next()); | |
assert_eq!(None, select_iter.next()); | |
signal_tx.send(true).unwrap(); | |
}); | |
tx2.send(1u32).unwrap(); | |
tx1.send(10u32).unwrap(); | |
tx2.send(2u32).unwrap(); | |
tx1.send(20u32).unwrap(); | |
// should block until we get the signal | |
assert!(signal_rx.recv().unwrap()); | |
} | |
} |
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