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use super::*;
use fnv::FnvHashMap;
use libp2p_core::PeerId;
use std::{vec, collections::hash_map::Entry, num::NonZeroUsize};
pub struct FixedPeersIter {
parallelism: NonZeroUsize,
peers: FnvHashMap<PeerId, PeerState>,
iter: vec::IntoIter<PeerId>,
state: State,
}
#[derive(Debug, PartialEq, Eq)]
enum State {
Waiting { num_waiting: usize },
Finished
}
#[derive(Copy, Clone, PartialEq, Eq)]
enum PeerState {
Waiting,
Failed,
Succeeded,
}
impl FixedPeersIter {
pub fn new<I>(peers: I, parallelism: NonZeroUsize) -> Self
where
I: IntoIterator<Item = PeerId>
{
let peers = peers.into_iter().collect::<Vec<_>>();
Self {
parallelism,
peers: FnvHashMap::default(),
iter: peers.into_iter(),
state: State::Waiting { num_waiting: 0 },
}
}
pub fn on_success(&mut self, peer: &PeerId) -> bool {
if let State::Waiting { num_waiting } = &mut self.state {
if let Some(state @ PeerState::Waiting) = self.peers.get_mut(peer) {
*state = PeerState::Succeeded;
*num_waiting -= 1;
return true
}
}
false
}
pub fn on_failure(&mut self, peer: &PeerId) -> bool {
if let State::Waiting { num_waiting } = &mut self.state {
if let Some(state @ PeerState::Waiting) = self.peers.get_mut(peer) {
*state = PeerState::Failed;
*num_waiting -= 1;
return true
}
}
false
}
pub fn is_waiting(&self, peer: &PeerId) -> bool {
self.peers.get(peer) == Some(&PeerState::Waiting)
}
pub fn finish(&mut self) {
if let State::Waiting { .. } = self.state {
self.state = State::Finished
}
}
pub fn is_finished(&self) -> bool {
self.state == State::Finished
}
pub fn next(&mut self) -> PeersIterState<'_> {
match &mut self.state {
State::Finished => return PeersIterState::Finished,
State::Waiting { num_waiting } => {
if *num_waiting >= self.parallelism.get() {
return PeersIterState::WaitingAtCapacity
}
loop {
match self.iter.next() {
None => if *num_waiting == 0 {
self.state = State::Finished;
return PeersIterState::Finished
} else {
return PeersIterState::Waiting(None)
}
Some(p) => match self.peers.entry(p.clone()) {
Entry::Occupied(_) => {}
Entry::Vacant(e) => {
*num_waiting += 1;
e.insert(PeerState::Waiting);
return PeersIterState::Waiting(Some(Cow::Owned(p)))
}
}
}
}
}
}
}
pub fn into_result(self) -> impl Iterator<Item = PeerId> {
self.peers.into_iter()
.filter_map(|(p, s)|
if let PeerState::Succeeded = s {
Some(p)
} else {
None
})
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn decrease_num_waiting_on_failure() {
let mut iter = FixedPeersIter::new(
vec![PeerId::random(), PeerId::random()],
NonZeroUsize::new(1).unwrap(),
);
match iter.next() {
PeersIterState::Waiting(Some(peer)) => {
let peer = peer.into_owned();
iter.on_failure(&peer);
},
_ => panic!("Expected iterator to yield peer."),
}
match iter.next() {
PeersIterState::Waiting(Some(_)) => {},
PeersIterState::WaitingAtCapacity => panic!(
"Expected iterator to return another peer given that the \
previous `on_failure` call should have allowed another peer \
to be queried.",
),
_ => panic!("Expected iterator to yield peer."),
}
}
}