perf: remove unnecessary allocation when writing http dates

Author: robjtede

.github/workflows/ci.yml

@@ -57,6 +57,8 @@ jobs:
       - name: workaround MSRV issues
         if: matrix.version.name == 'msrv'
         run: |
+          cargo update -p=ciborium --precise=0.2.1
+          cargo update -p=ciborium-ll --precise=0.2.1
           cargo update -p=clap --precise=4.3.24
           cargo update -p=clap_lex --precise=0.5.0
           cargo update -p=anstyle --precise=1.0.2

actix-http/Cargo.toml

@@ -113,6 +113,7 @@ actix-web = "4"
 
 async-stream = "0.3"
 criterion = { version = "0.5", features = ["html_reports"] }
+divan = "0.1.11"
 env_logger = "0.10"
 futures-util = { version = "0.3.17", default-features = false, features = ["alloc"] }
 memchr = "2.4"
@@ -140,3 +141,7 @@ required-features = ["http2", "rustls-0_21"]
 name = "response-body-compression"
 harness = false
 required-features = ["compress-brotli", "compress-gzip", "compress-zstd"]
+
+[[bench]]
+name = "date-formatting"
+harness = false

actix-http/benches/date-formatting.rs

@@ -0,0 +1,20 @@
+use std::time::SystemTime;
+
+use actix_http::header::HttpDate;
+use divan::{black_box, AllocProfiler, Bencher};
+
+#[global_allocator]
+static ALLOC: AllocProfiler = AllocProfiler::system();
+
+#[divan::bench]
+fn date_formatting(b: Bencher<'_, '_>) {
+    let now = SystemTime::now();
+
+    b.bench(|| {
+        black_box(HttpDate::from(black_box(now)).to_string());
+    })
+}
+
+fn main() {
+    divan::main();
+}

actix-http/src/date.rs

@@ -28,7 +28,7 @@ impl Date {
 
     fn update(&mut self) {
         self.pos = 0;
-        write!(self, "{}", httpdate::fmt_http_date(SystemTime::now())).unwrap();
+        write!(self, "{}", httpdate::HttpDate::from(SystemTime::now())).unwrap();
     }
 }
 

actix-http/src/header/shared/http_date.rs

@@ -24,8 +24,7 @@ impl FromStr for HttpDate {
 
 impl fmt::Display for HttpDate {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let date_str = httpdate::fmt_http_date(self.0);
-        f.write_str(&date_str)
+        httpdate::HttpDate::from(self.0).fmt(f)
     }
 }
 
@@ -37,7 +36,7 @@ impl TryIntoHeaderValue for HttpDate {
         let mut wrt = MutWriter(&mut buf);
 
         // unwrap: date output is known to be well formed and of known length
-        write!(wrt, "{}", httpdate::fmt_http_date(self.0)).unwrap();
+        write!(wrt, "{}", self).unwrap();
 
         HeaderValue::from_maybe_shared(buf.split().freeze())
     }