bdd2e1a3ad
This is actually one of the biggest impacts to benchmark performances at this point. Caching the rendering of the Date header improves "hello world" benchmarks by around 10%.
59 lines
1.4 KiB
Rust
59 lines
1.4 KiB
Rust
use std::cell::RefCell;
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use std::fmt::{self, Write};
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use std::str;
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use time::{self, Duration};
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// "Sun, 06 Nov 1994 08:49:37 GMT".len()
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pub const DATE_VALUE_LENGTH: usize = 29;
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pub fn extend(dst: &mut Vec<u8>) {
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CACHED.with(|cache| {
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let mut cache = cache.borrow_mut();
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let now = time::get_time();
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if now > cache.next_update {
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cache.update(now);
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}
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dst.extend_from_slice(cache.buffer());
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})
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}
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struct CachedDate {
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bytes: [u8; DATE_VALUE_LENGTH],
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pos: usize,
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next_update: time::Timespec,
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}
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thread_local!(static CACHED: RefCell<CachedDate> = RefCell::new(CachedDate {
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bytes: [0; DATE_VALUE_LENGTH],
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pos: 0,
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next_update: time::Timespec::new(0, 0),
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}));
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impl CachedDate {
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fn buffer(&self) -> &[u8] {
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&self.bytes[..]
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}
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fn update(&mut self, now: time::Timespec) {
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self.pos = 0;
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write!(self, "{}", time::at_utc(now).rfc822()).unwrap();
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assert!(self.pos == DATE_VALUE_LENGTH);
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self.next_update = now + Duration::seconds(1);
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self.next_update.nsec = 0;
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}
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}
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impl fmt::Write for CachedDate {
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fn write_str(&mut self, s: &str) -> fmt::Result {
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let len = s.len();
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self.bytes[self.pos..self.pos + len].copy_from_slice(s.as_bytes());
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self.pos += len;
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Ok(())
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}
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}
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#[test]
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fn test_date_len() {
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assert_eq!(DATE_VALUE_LENGTH, "Sun, 06 Nov 1994 08:49:37 GMT".len());
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} |