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// Copyright (C) 2023 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use std::sync::{Arc, Mutex};
use crate::*;
/// A simple sharable helper that can be used as a [BufferSubscription] by a [BufferSubscriber] and
/// as a state tracker by a [BufferPublisher].
#[derive(Clone, Debug)]
pub struct SharedBufferSubscription(Arc<Mutex<BufferSubscriptionData>>);
#[derive(Debug, Default)]
struct BufferSubscriptionData {
requests: u64,
is_cancelled: bool,
}
impl SharedBufferSubscription {
/// Create a new [SharedBufferSubscription].
pub fn new() -> Self {
SharedBufferSubscription::default()
}
/// Clone this [SharedBufferSubscription] so it can be passed into
/// [BufferSubscriber::on_subscribe].
pub fn clone_for_subscriber(&self) -> Box<dyn BufferSubscription> {
Box::new(self.clone()) as Box<dyn BufferSubscription>
}
/// If possible (not cancelled and with requests pending), take
pub fn take_request(&self) -> bool {
let mut data = self.0.lock().unwrap();
if data.is_cancelled || data.requests == 0 {
false
} else {
data.requests -= 1;
true
}
}
/// Get the number of pending requests made by the [BufferSubscriber] via
/// [BufferSubscription::request].
pub fn pending_requests(&self) -> u64 {
self.0.lock().unwrap().requests
}
/// Get get whether the [BufferSubscriber] has called [BufferSubscription::cancel].
pub fn is_cancelled(&self) -> bool {
self.0.lock().unwrap().is_cancelled
}
}
impl Default for SharedBufferSubscription {
fn default() -> Self {
Self(Arc::new(Mutex::new(BufferSubscriptionData::default())))
}
}
impl BufferSubscription for SharedBufferSubscription {
fn request(&self, n: u64) {
let mut data = self.0.lock().unwrap();
if !data.is_cancelled {
data.requests = data.requests.saturating_add(n);
}
}
fn cancel(&self) {
let mut data = self.0.lock().unwrap();
data.is_cancelled = true;
}
}
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