bass-foundry/plugins/crucible/core/src/player.rs

//! Audition of slices on the audio thread without allocating or freeing there.
use crossbeam_queue::ArrayQueue;
use std::sync::Arc;

pub type Clip = Arc<[f32]>;

/// Shared queues. The GUI sends clips and drains finished ones, so all frees happen there.
pub struct Queues {
    incoming: ArrayQueue<Option<Clip>>,
    finished: ArrayQueue<Clip>,
}
impl Default for Queues {
    fn default() -> Self {
        Self {
            incoming: ArrayQueue::new(4),
            finished: ArrayQueue::new(16),
        }
    }
}
impl Queues {
    /// Plays an interleaved stereo clip, replacing the current one.
    pub fn play(&self, clip: Clip) {
        self.drain();
        let _ = self.incoming.force_push(Some(clip));
    }
    pub fn stop(&self) {
        let _ = self.incoming.force_push(None);
    }
    /// Frees finished clips. Call regularly from the GUI thread.
    pub fn drain(&self) {
        while self.finished.pop().is_some() {}
    }
}

#[derive(Default)]
pub struct Player {
    clip: Option<Clip>,
    at: usize,
}
impl Player {
    fn retire(&mut self, queues: &Queues) {
        if let Some(old) = self.clip.take() {
            // The GUI drains this queue every frame; a full queue only happens with no editor.
            if let Err(old) = queues.finished.push(old) {
                std::mem::forget(old);
            }
        }
    }
    /// Call once per block.
    pub fn block(&mut self, queues: &Queues) {
        while let Some(next) = queues.incoming.pop() {
            self.retire(queues);
            self.clip = next;
            self.at = 0;
        }
    }
    #[inline]
    pub fn next(&mut self, queues: &Queues) -> [f32; 2] {
        let Some(clip) = &self.clip else {
            return [0.; 2];
        };
        if self.at + 1 >= clip.len() {
            self.retire(queues);
            return [0.; 2];
        }
        let out = [clip[self.at], clip[self.at + 1]];
        self.at += 2;
        out
    }
    pub fn playing(&self) -> bool {
        self.clip.is_some()
    }
}