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use std::cell::RefCell;
use std::fmt::{self, Write};
use std::str;
use std::time::{Duration, SystemTime};
#[cfg(feature = "http2")]
use http::header::HeaderValue;
use httpdate::HttpDate;
// "Sun, 06 Nov 1994 08:49:37 GMT".len()
pub(crate) const DATE_VALUE_LENGTH: usize = 29;
#[cfg(feature = "http1")]
pub(crate) fn extend(dst: &mut Vec<u8>) {
CACHED.with(|cache| {
dst.extend_from_slice(cache.borrow().buffer());
})
}
#[cfg(feature = "http1")]
pub(crate) fn update() {
CACHED.with(|cache| {
cache.borrow_mut().check();
})
}
#[cfg(feature = "http2")]
pub(crate) fn update_and_header_value() -> HeaderValue {
CACHED.with(|cache| {
let mut cache = cache.borrow_mut();
cache.check();
HeaderValue::from_bytes(cache.buffer()).expect("Date format should be valid HeaderValue")
})
}
struct CachedDate {
bytes: [u8; DATE_VALUE_LENGTH],
pos: usize,
next_update: SystemTime,
}
thread_local!(static CACHED: RefCell<CachedDate> = RefCell::new(CachedDate::new()));
impl CachedDate {
fn new() -> Self {
let mut cache = CachedDate {
bytes: [0; DATE_VALUE_LENGTH],
pos: 0,
next_update: SystemTime::now(),
};
cache.update(cache.next_update);
cache
}
fn buffer(&self) -> &[u8] {
&self.bytes[..]
}
fn check(&mut self) {
let now = SystemTime::now();
if now > self.next_update {
self.update(now);
}
}
fn update(&mut self, now: SystemTime) {
self.render(now);
self.next_update = now + Duration::new(1, 0);
}
fn render(&mut self, now: SystemTime) {
self.pos = 0;
let _ = write!(self, "{}", HttpDate::from(now));
debug_assert!(self.pos == DATE_VALUE_LENGTH);
}
}
impl fmt::Write for CachedDate {
fn write_str(&mut self, s: &str) -> fmt::Result {
let len = s.len();
self.bytes[self.pos..self.pos + len].copy_from_slice(s.as_bytes());
self.pos += len;
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
#[cfg(feature = "nightly")]
use test::Bencher;
#[test]
fn test_date_len() {
assert_eq!(DATE_VALUE_LENGTH, "Sun, 06 Nov 1994 08:49:37 GMT".len());
}
#[cfg(feature = "nightly")]
#[bench]
fn bench_date_check(b: &mut Bencher) {
let mut date = CachedDate::new();
// cache the first update
date.check();
b.iter(|| {
date.check();
});
}
#[cfg(feature = "nightly")]
#[bench]
fn bench_date_render(b: &mut Bencher) {
let mut date = CachedDate::new();
let now = SystemTime::now();
date.render(now);
b.bytes = date.buffer().len() as u64;
b.iter(|| {
date.render(now);
test::black_box(&date);
});
}
}