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/// Container which can be given a Vector and returns its single elements on request
pub struct OptFifo<T> {
data: Option<Vec<T>>,
}
impl<T> OptFifo<T> {
/// Initializes an empty OptFifo.
pub fn new() -> Self {
Self { data: None }
}
/// A new value can only be set if OptFifo::get() returned None once.
pub fn set(&mut self, data: Vec<T>) {
assert!(self.data.is_none());
self.data = Some(data);
}
/// Returns some value or None if contained Vector is empty. In this case
/// the Vector gets removed and a new Vector can be set.
pub fn get(&mut self) -> Option<T> {
if let Some(ref mut data) = self.data {
if data.is_empty() {
self.data = None;
} else {
let element = data.remove(0);
return Some(element);
}
}
None
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_lifecycle() {
let mut fifo = OptFifo::new();
// Starts empty
assert_eq!(fifo.get(), None);
fifo.set(vec![2, 3]);
assert_eq!(fifo.get(), Some(2));
assert_eq!(fifo.get(), Some(3));
assert_eq!(fifo.get(), None);
// Make sure None is returned repeatedly
assert_eq!(fifo.get(), None);
}
#[test]
#[should_panic]
fn test_double_set() {
let mut fifo = OptFifo::<i32>::new();
fifo.set(Vec::new());
fifo.set(Vec::new());
}
}