use std::cell::RefCell;
use std::fmt::{self, Write};
use std::str;
use time::{self, Duration};
pub struct Now(());
pub fn now() -> Now {
Now(())
}
struct LastRenderedNow {
bytes: [u8; 128],
amt: usize,
next_update: time::Timespec,
}
thread_local!(static LAST: RefCell<LastRenderedNow> = RefCell::new(LastRenderedNow {
bytes: [0; 128],
amt: 0,
next_update: time::Timespec::new(0, 0),
}));
impl fmt::Display for Now {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
LAST.with(|cache| {
let mut cache = cache.borrow_mut();
let now = time::get_time();
if now > cache.next_update {
cache.update(now);
}
f.write_str(cache.buffer())
})
}
}
impl LastRenderedNow {
fn buffer(&self) -> &str {
str::from_utf8(&self.bytes[..self.amt]).unwrap()
}
fn update(&mut self, now: time::Timespec) {
self.amt = 0;
write!(LocalBuffer(self), "{}", time::at(now).rfc822()).unwrap();
self.next_update = now + Duration::seconds(1);
self.next_update.nsec = 0;
}
}
struct LocalBuffer<'a>(&'a mut LastRenderedNow);
impl<'a> fmt::Write for LocalBuffer<'a> {
fn write_str(&mut self, s: &str) -> fmt::Result {
let start = self.0.amt;
let end = start + s.len();
self.0.bytes[start..end].copy_from_slice(s.as_bytes());
self.0.amt += s.len();
Ok(())
}
}