lowlet 0.1.2

Low-latency IPC library using shared memory and lock-free structures
Documentation 
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use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;

use crate::buf::RingBuffer;
use crate::err::{Error, Result};

pub struct Receiver<T, const N: usize> {
    buf: Arc<RingBuffer<T, N>>,
    closed: Arc<AtomicBool>,
}

impl<T, const N: usize> Receiver<T, N> {
    #[allow(dead_code)]
    pub(crate) fn new(buf: Arc<RingBuffer<T, N>>) -> Self {
        Self {
            buf,
            closed: Arc::new(AtomicBool::new(false)),
        }
    }

    pub(crate) fn new_with_closed(buf: Arc<RingBuffer<T, N>>, closed: Arc<AtomicBool>) -> Self {
        Self { buf, closed }
    }

    #[allow(dead_code)]
    pub(crate) fn closed_flag(&self) -> Arc<AtomicBool> {
        self.closed.clone()
    }

    #[inline]
    pub fn recv(&self) -> Result<T> {
        if self.closed.load(Ordering::Acquire) && self.buf.is_empty() {
            return Err(Error::ChannelClosed);
        }
        self.buf.recv()
    }

    #[inline]
    pub fn try_recv(&self) -> Result<T> {
        self.recv()
    }

    pub fn recv_spin(&self) -> Result<T> {
        loop {
            if self.closed.load(Ordering::Acquire) && self.buf.is_empty() {
                return Err(Error::ChannelClosed);
            }
            if let Ok(v) = self.buf.recv() {
                return Ok(v);
            }
            std::hint::spin_loop();
        }
    }

    #[inline]
    pub fn is_empty(&self) -> bool {
        self.buf.is_empty()
    }

    #[inline]
    pub fn len(&self) -> usize {
        self.buf.len()
    }

    #[inline]
    pub fn capacity(&self) -> usize {
        N
    }

    #[inline]
    pub fn is_closed(&self) -> bool {
        self.closed.load(Ordering::Acquire)
    }

    pub fn close(&self) {
        self.closed.store(true, Ordering::Release);
    }

    pub fn recv_batch(&self, buf: &mut [T], max: usize) -> usize {
        let count = max.min(buf.len());
        let mut received = 0;

        for item in buf.iter_mut().take(count) {
            match self.buf.recv() {
                Ok(value) => {
                    *item = value;
                    received += 1;
                }
                Err(_) => break,
            }
        }

        received
    }

    pub fn recv_timeout(&self, timeout: std::time::Duration) -> Result<T> {
        let start = std::time::Instant::now();

        loop {
            if self.closed.load(Ordering::Acquire) && self.buf.is_empty() {
                return Err(Error::ChannelClosed);
            }
            match self.buf.recv() {
                Ok(value) => return Ok(value),
                Err(e) => {
                    if start.elapsed() >= timeout {
                        return Err(e);
                    }
                    std::hint::spin_loop();
                }
            }
        }
    }

    pub fn drain(&self) -> DrainIter<'_, T, N> {
        DrainIter { receiver: self }
    }
}

pub struct DrainIter<'a, T, const N: usize> {
    receiver: &'a Receiver<T, N>,
}

impl<T, const N: usize> Iterator for DrainIter<'_, T, N> {
    type Item = T;

    fn next(&mut self) -> Option<Self::Item> {
        self.receiver.buf.recv().ok()
    }
}

impl<T, const N: usize> Clone for Receiver<T, N> {
    fn clone(&self) -> Self {
        Self {
            buf: self.buf.clone(),
            closed: self.closed.clone(),
        }
    }
}

unsafe impl<T: Send, const N: usize> Send for Receiver<T, N> {}
unsafe impl<T: Send, const N: usize> Sync for Receiver<T, N> {}