notedeck

One damus client to rule them all
git clone git://jb55.com/notedeck
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timecache.rs (1036B)

      1 use std::rc::Rc;
      2 use std::time::{Duration, Instant};
      3 
      4 #[derive(Clone)]
      5 pub struct TimeCached<T> {
      6     last_update: Instant,
      7     expires_in: Duration,
      8     value: Option<T>,
      9     refresh: Rc<dyn Fn() -> T + 'static>,
     10 }
     11 
     12 impl<T> TimeCached<T> {
     13     pub fn new(expires_in: Duration, refresh: impl Fn() -> T + 'static) -> Self {
     14         TimeCached {
     15             last_update: Instant::now(),
     16             expires_in,
     17             value: None,
     18             refresh: Rc::new(refresh),
     19         }
     20     }
     21 
     22     pub fn needs_update(&self) -> bool {
     23         self.value.is_none() || self.last_update.elapsed() > self.expires_in
     24     }
     25 
     26     pub fn update(&mut self) {
     27         self.last_update = Instant::now();
     28         self.value = Some((self.refresh)());
     29     }
     30 
     31     pub fn get(&self) -> Option<&T> {
     32         self.value.as_ref()
     33     }
     34 
     35     pub fn get_mut(&mut self) -> &T {
     36         if self.needs_update() {
     37             self.update();
     38         }
     39         self.value.as_ref().unwrap() // This unwrap is safe because we just set the value if it was None.
     40     }
     41 }