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//! Queue that plays sounds one after the other.
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, Mutex};
use std::time::Duration;
use crate::source::{Empty, Source, Zero};
use crate::Sample;
#[cfg(feature = "crossbeam-channel")]
use crossbeam_channel::{unbounded as channel, Receiver, Sender};
#[cfg(not(feature = "crossbeam-channel"))]
use std::sync::mpsc::{channel, Receiver, Sender};
/// Builds a new queue. It consists of an input and an output.
///
/// The input can be used to add sounds to the end of the queue, while the output implements
/// `Source` and plays the sounds.
///
/// The parameter indicates how the queue should behave if the queue becomes empty:
///
/// - If you pass `true`, then the queue is infinite and will play a silence instead until you add
/// a new sound.
/// - If you pass `false`, then the queue will report that it has finished playing.
///
pub fn queue<S>(keep_alive_if_empty: bool) -> (Arc<SourcesQueueInput<S>>, SourcesQueueOutput<S>)
where
S: Sample + Send + 'static,
{
let input = Arc::new(SourcesQueueInput {
next_sounds: Mutex::new(Vec::new()),
keep_alive_if_empty: AtomicBool::new(keep_alive_if_empty),
});
let output = SourcesQueueOutput {
current: Box::new(Empty::<S>::new()) as Box<_>,
signal_after_end: None,
input: input.clone(),
};
(input, output)
}
// TODO: consider reimplementing this with `from_factory`
/// The input of the queue.
pub struct SourcesQueueInput<S> {
next_sounds: Mutex<Vec<(Box<dyn Source<Item = S> + Send>, Option<Sender<()>>)>>,
// See constructor.
keep_alive_if_empty: AtomicBool,
}
impl<S> SourcesQueueInput<S>
where
S: Sample + Send + 'static,
{
/// Adds a new source to the end of the queue.
#[inline]
pub fn append<T>(&self, source: T)
where
T: Source<Item = S> + Send + 'static,
{
self.next_sounds
.lock()
.unwrap()
.push((Box::new(source) as Box<_>, None));
}
/// Adds a new source to the end of the queue.
///
/// The `Receiver` will be signalled when the sound has finished playing.
///
/// Enable the feature flag `crossbeam-channel` in rodio to use a `crossbeam_channel::Receiver` instead.
#[inline]
pub fn append_with_signal<T>(&self, source: T) -> Receiver<()>
where
T: Source<Item = S> + Send + 'static,
{
let (tx, rx) = channel();
self.next_sounds
.lock()
.unwrap()
.push((Box::new(source) as Box<_>, Some(tx)));
rx
}
/// Sets whether the queue stays alive if there's no more sound to play.
///
/// See also the constructor.
pub fn set_keep_alive_if_empty(&self, keep_alive_if_empty: bool) {
self.keep_alive_if_empty
.store(keep_alive_if_empty, Ordering::Release);
}
/// Removes all the sounds from the queue. Returns the number of sounds cleared.
pub fn clear(&self) -> usize {
let mut sounds = self.next_sounds.lock().unwrap();
let len = sounds.len();
sounds.clear();
len
}
}
/// The output of the queue. Implements `Source`.
pub struct SourcesQueueOutput<S> {
// The current iterator that produces samples.
current: Box<dyn Source<Item = S> + Send>,
// Signal this sender before picking from `next`.
signal_after_end: Option<Sender<()>>,
// The next sounds.
input: Arc<SourcesQueueInput<S>>,
}
const THRESHOLD: usize = 512;
impl<S> Source for SourcesQueueOutput<S>
where
S: Sample + Send + 'static,
{
#[inline]
fn current_frame_len(&self) -> Option<usize> {
// This function is non-trivial because the boundary between two sounds in the queue should
// be a frame boundary as well.
//
// The current sound is free to return `None` for `current_frame_len()`, in which case
// we *should* return the number of samples remaining the current sound.
// This can be estimated with `size_hint()`.
//
// If the `size_hint` is `None` as well, we are in the worst case scenario. To handle this
// situation we force a frame to have a maximum number of samples indicate by this
// constant.
// Try the current `current_frame_len`.
if let Some(val) = self.current.current_frame_len() {
if val != 0 {
return Some(val);
} else if self.input.keep_alive_if_empty.load(Ordering::Acquire)
&& self.input.next_sounds.lock().unwrap().is_empty()
{
// The next source will be a filler silence which will have the length of `THRESHOLD`
return Some(THRESHOLD);
}
}
// Try the size hint.
let (lower_bound, _) = self.current.size_hint();
// The iterator default implementation just returns 0.
// That's a problematic value, so skip it.
if lower_bound > 0 {
return Some(lower_bound);
}
// Otherwise we use the constant value.
Some(THRESHOLD)
}
#[inline]
fn channels(&self) -> u16 {
self.current.channels()
}
#[inline]
fn sample_rate(&self) -> u32 {
self.current.sample_rate()
}
#[inline]
fn total_duration(&self) -> Option<Duration> {
None
}
}
impl<S> Iterator for SourcesQueueOutput<S>
where
S: Sample + Send + 'static,
{
type Item = S;
#[inline]
fn next(&mut self) -> Option<S> {
loop {
// Basic situation that will happen most of the time.
if let Some(sample) = self.current.next() {
return Some(sample);
}
// Since `self.current` has finished, we need to pick the next sound.
// In order to avoid inlining this expensive operation, the code is in another function.
if self.go_next().is_err() {
return None;
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(self.current.size_hint().0, None)
}
}
impl<S> SourcesQueueOutput<S>
where
S: Sample + Send + 'static,
{
// Called when `current` is empty and we must jump to the next element.
// Returns `Ok` if the sound should continue playing, or an error if it should stop.
//
// This method is separate so that it is not inlined.
fn go_next(&mut self) -> Result<(), ()> {
if let Some(signal_after_end) = self.signal_after_end.take() {
let _ = signal_after_end.send(());
}
let (next, signal_after_end) = {
let mut next = self.input.next_sounds.lock().unwrap();
if next.len() == 0 {
let silence = Box::new(Zero::<S>::new_samples(1, 44100, THRESHOLD)) as Box<_>;
if self.input.keep_alive_if_empty.load(Ordering::Acquire) {
// Play a short silence in order to avoid spinlocking.
(silence, None)
} else {
return Err(());
}
} else {
next.remove(0)
}
};
self.current = next;
self.signal_after_end = signal_after_end;
Ok(())
}
}
#[cfg(test)]
mod tests {
use crate::buffer::SamplesBuffer;
use crate::queue;
use crate::source::Source;
#[test]
#[ignore] // FIXME: samples rate and channel not updated immediately after transition
fn basic() {
let (tx, mut rx) = queue::queue(false);
tx.append(SamplesBuffer::new(1, 48000, vec![10i16, -10, 10, -10]));
tx.append(SamplesBuffer::new(2, 96000, vec![5i16, 5, 5, 5]));
assert_eq!(rx.channels(), 1);
assert_eq!(rx.sample_rate(), 48000);
assert_eq!(rx.next(), Some(10));
assert_eq!(rx.next(), Some(-10));
assert_eq!(rx.next(), Some(10));
assert_eq!(rx.next(), Some(-10));
assert_eq!(rx.channels(), 2);
assert_eq!(rx.sample_rate(), 96000);
assert_eq!(rx.next(), Some(5));
assert_eq!(rx.next(), Some(5));
assert_eq!(rx.next(), Some(5));
assert_eq!(rx.next(), Some(5));
assert_eq!(rx.next(), None);
}
#[test]
fn immediate_end() {
let (_, mut rx) = queue::queue::<i16>(false);
assert_eq!(rx.next(), None);
}
#[test]
fn keep_alive() {
let (tx, mut rx) = queue::queue(true);
tx.append(SamplesBuffer::new(1, 48000, vec![10i16, -10, 10, -10]));
assert_eq!(rx.next(), Some(10));
assert_eq!(rx.next(), Some(-10));
assert_eq!(rx.next(), Some(10));
assert_eq!(rx.next(), Some(-10));
for _ in 0..100000 {
assert_eq!(rx.next(), Some(0));
}
}
#[test]
#[ignore] // TODO: not yet implemented
fn no_delay_when_added() {
let (tx, mut rx) = queue::queue(true);
for _ in 0..500 {
assert_eq!(rx.next(), Some(0));
}
tx.append(SamplesBuffer::new(1, 48000, vec![10i16, -10, 10, -10]));
assert_eq!(rx.next(), Some(10));
assert_eq!(rx.next(), Some(-10));
assert_eq!(rx.next(), Some(10));
assert_eq!(rx.next(), Some(-10));
}
}