From 7d8fb631a074dc31cde9a3da4a82acb9b027563f Mon Sep 17 00:00:00 2001
From: Nick Kolpinskiy <nick.kolpinskiy@yandex.ru>
Date: Thu, 21 May 2020 22:25:34 +0300
Subject: [PATCH] Use `itoa` in the content-length helper

---
 actix-http/Cargo.toml                |   1 +
 actix-http/benches/content-length.rs |  24 +++++++
 actix-http/src/helpers.rs            | 101 +++------------------------
 3 files changed, 33 insertions(+), 93 deletions(-)

diff --git a/actix-http/Cargo.toml b/actix-http/Cargo.toml
index 573fcf1e4..deb63197a 100644
--- a/actix-http/Cargo.toml
+++ b/actix-http/Cargo.toml
@@ -64,6 +64,7 @@ h2 = "0.2.1"
 http = "0.2.0"
 httparse = "1.3"
 indexmap = "1.3"
+itoa = "0.4"
 lazy_static = "1.4"
 language-tags = "0.2"
 log = "0.4"
diff --git a/actix-http/benches/content-length.rs b/actix-http/benches/content-length.rs
index b001b3931..18a55a33b 100644
--- a/actix-http/benches/content-length.rs
+++ b/actix-http/benches/content-length.rs
@@ -25,6 +25,13 @@ fn bench_write_content_length(c: &mut Criterion) {
                 _new::write_content_length(i, &mut b)
             })
         });
+
+        group.bench_with_input(BenchmarkId::new("itoa", i), i, |b, &i| {
+            b.iter(|| {
+                let mut b = BytesMut::with_capacity(35);
+                _itoa::write_content_length(i, &mut b)
+            })
+        });
     }
 
     group.finish();
@@ -33,6 +40,23 @@ fn bench_write_content_length(c: &mut Criterion) {
 criterion_group!(benches, bench_write_content_length);
 criterion_main!(benches);
 
+mod _itoa {
+    use bytes::{BufMut, BytesMut};
+
+    pub fn write_content_length(n: usize, bytes: &mut BytesMut) {
+        if n == 0 {
+            bytes.put_slice(b"\r\ncontent-length: 0\r\n");
+            return;
+        }
+
+        let mut buf = itoa::Buffer::new();
+
+        bytes.put_slice(b"\r\ncontent-length: ");
+        bytes.put_slice(buf.format(n).as_bytes());
+        bytes.put_slice(b"\r\n");
+    }
+}
+
 mod _new {
     use bytes::{BufMut, BytesMut};
 
diff --git a/actix-http/src/helpers.rs b/actix-http/src/helpers.rs
index 5ac6c9be5..bbf358b66 100644
--- a/actix-http/src/helpers.rs
+++ b/actix-http/src/helpers.rs
@@ -31,103 +31,18 @@ pub(crate) fn write_status_line(version: Version, n: u16, bytes: &mut BytesMut)
 
 /// NOTE: bytes object has to contain enough space
 pub fn write_content_length(n: u64, bytes: &mut BytesMut) {
+    if n == 0 {
+        bytes.put_slice(b"\r\ncontent-length: 0\r\n");
+        return;
+    }
+
+    let mut buf = itoa::Buffer::new();
+
     bytes.put_slice(b"\r\ncontent-length: ");
-
-    if n < 10 {
-        bytes.put_u8(DIGITS_START + (n as u8));
-    } else if n < 100 {
-        let n = n as u8;
-
-        let d10 = n / 10;
-        let d1 = n % 10;
-
-        bytes.put_u8(DIGITS_START + d10);
-        bytes.put_u8(DIGITS_START + d1);
-    } else if n < 1000 {
-        let n = n as u16;
-
-        let d100 = (n / 100) as u8;
-        let d10 = ((n / 10) % 10) as u8;
-        let d1 = (n % 10) as u8;
-
-        bytes.put_u8(DIGITS_START + d100);
-        bytes.put_u8(DIGITS_START + d10);
-        bytes.put_u8(DIGITS_START + d1);
-    } else if n < 10_000 {
-        let n = n as u16;
-
-        let d1000 = (n / 1000) as u8;
-        let d100 = ((n / 100) % 10) as u8;
-        let d10 = ((n / 10) % 10) as u8;
-        let d1 = (n % 10) as u8;
-
-        bytes.put_u8(DIGITS_START + d1000);
-        bytes.put_u8(DIGITS_START + d100);
-        bytes.put_u8(DIGITS_START + d10);
-        bytes.put_u8(DIGITS_START + d1);
-    } else if n < 100_000 {
-        let n = n as u32;
-
-        let d10000 = (n / 10000) as u8;
-        let d1000 = ((n / 1000) % 10) as u8;
-        let d100 = ((n / 100) % 10) as u8;
-        let d10 = ((n / 10) % 10) as u8;
-        let d1 = (n % 10) as u8;
-
-        bytes.put_u8(DIGITS_START + d10000);
-        bytes.put_u8(DIGITS_START + d1000);
-        bytes.put_u8(DIGITS_START + d100);
-        bytes.put_u8(DIGITS_START + d10);
-        bytes.put_u8(DIGITS_START + d1);
-    } else if n < 1_000_000 {
-        let n = n as u32;
-
-        let d100000 = (n / 100_000) as u8;
-        let d10000 = ((n / 10000) % 10) as u8;
-        let d1000 = ((n / 1000) % 10) as u8;
-        let d100 = ((n / 100) % 10) as u8;
-        let d10 = ((n / 10) % 10) as u8;
-        let d1 = (n % 10) as u8;
-
-        bytes.put_u8(DIGITS_START + d100000);
-        bytes.put_u8(DIGITS_START + d10000);
-        bytes.put_u8(DIGITS_START + d1000);
-        bytes.put_u8(DIGITS_START + d100);
-        bytes.put_u8(DIGITS_START + d10);
-        bytes.put_u8(DIGITS_START + d1);
-    } else {
-        write_u64(n, bytes);
-    }
-
+    bytes.put_slice(buf.format(n).as_bytes());
     bytes.put_slice(b"\r\n");
 }
 
-pub(crate) fn write_u64(n: u64, bytes: &mut BytesMut) {
-    let mut n = n;
-
-    // 20 chars is max length of a u64 (2^64)
-    // digits will be added to the buffer from lsd to msd
-    let mut buf = BytesMut::with_capacity(20);
-
-    while n > 9 {
-        // "pop" the least-significant digit
-        let lsd = (n % 10) as u8;
-
-        // remove the lsd from n
-        n /= 10;
-
-        buf.put_u8(DIGITS_START + lsd);
-    }
-
-    // put msd to result buffer
-    bytes.put_u8(DIGITS_START + (n as u8));
-
-    // put, in reverse (msd to lsd), remaining digits to buffer
-    for i in (0..buf.len()).rev() {
-        bytes.put_u8(buf[i]);
-    }
-}
-
 pub(crate) struct Writer<'a>(pub &'a mut BytesMut);
 
 impl<'a> io::Write for Writer<'a> {