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// Copyright 2018 MaidSafe.net limited.
//
// This SAFE Network Software is licensed to you under The General Public License (GPL), version 3.
// Unless required by applicable law or agreed to in writing, the SAFE Network Software distributed
// under the GPL Licence is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. Please review the Licences for the specific language governing
// permissions and limitations relating to use of the SAFE Network Software.
use std::sync::mpsc::{RecvError, TryRecvError};
/// Trait to fake a channel.
pub trait EventStream {
/// Item produced by this stream.
type Item;
/// Read the next available event from the stream, blocking until one becomes available.
fn next_ev(&mut self) -> Result<Self::Item, RecvError>;
/// Try to read the next available event from the stream without blocking.
///
/// Implementations should return an error if there are no items available, OR
/// a real error occurs.
fn try_next_ev(&mut self) -> Result<Self::Item, TryRecvError>;
/// Process events, storing them on the internal buffer.
///
/// After calling poll, any events produced will be accessible via `next_ev` and `try_next_ev`.
fn poll(&mut self) -> bool;
}
/// Trait for state machines and other event producers who produce multiple events at once.
pub trait EventStepper {
type Item;
/// Produce multiple events and store them internally, or return a `RecvError` if
/// something goes wrong.
fn produce_events(&mut self) -> Result<(), RecvError>;
// Produce multiple events in a non-blocking fashion.
fn try_produce_events(&mut self) -> Result<(), TryRecvError>;
/// Pop an item from this type's internal buffer.
fn pop_item(&mut self) -> Option<Self::Item>;
}
/// Blanket implementation of `EventStream` for types implementing `EventStepper`.
impl<S> EventStream for S
where
S: EventStepper,
{
type Item = <S as EventStepper>::Item;
fn next_ev(&mut self) -> Result<Self::Item, RecvError> {
// We loop blocking on `produce_events` until an event is produced.
loop {
if let Some(cached_ev) = self.pop_item() {
return Ok(cached_ev);
}
match self.produce_events() {
Ok(()) => {}
Err(RecvError) => return Err(RecvError),
}
}
}
fn try_next_ev(&mut self) -> Result<Self::Item, TryRecvError> {
if let Some(cached_ev) = self.pop_item() {
return Ok(cached_ev);
}
match self.try_produce_events() {
Ok(()) => self.pop_item().ok_or(TryRecvError::Empty),
Err(err) => Err(err),
}
}
fn poll(&mut self) -> bool {
let mut result = false;
while Ok(()) == self.try_produce_events() {
result = true;
}
result
}
}