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use std::marker::Send;
use std::sync::atomic::AtomicPtr;

/// Size of the buffer used for the underlying circular buffer.
const BUFFER_SIZE: usize = 16;

/// A cell which is syncronized across threads.
///
/// When a reader requests the data held by this cell, the most recently
/// written data will be given to the reader.
pub struct SyncCell<T: Copy> {
    current: usize,

    last_update: AtomicPtr<T>,
    buffer: [T; BUFFER_SIZE]
}

impl<T: Copy> SyncCell<T> {
    /// Updates the data in the cell.
    pub fn update(&mut self, data: T) {
        self.current = (self.current + 1) % BUFFER_SIZE;
        self.buffer[self.current] = data;

        unsafe {
            self.last_update = self.buffer.as_mut_ptr().add(self.current).into();
        }
    }

    /// Reads the most recently available data from the cell.
    pub fn read(&mut self) -> T {
        unsafe { **self.last_update.get_mut() }
    }
}