Faster Ipv4 serialization prototype

Author: saethlin

serde/src/ser/impls.rs

@@ -674,6 +674,40 @@ impl Serialize for net::IpAddr {
  }
 }
 
+#[inline]
+fn format_u8(mut v: u8, out: &mut [u8]) -> usize {
+ assert!(out.len() >= 3);
+ let mut written = 0;
+ let hundreds = v / 100;
+ v -= 100 * hundreds;
+ let tens = v / 10;
+ v -= 10 * tens;
+ let ones = v;
+ if hundreds > 0 {
+ out[written] = b'0' + hundreds;
+ written += 1;
+ }
+ if hundreds > 0 || tens > 0 {
+ out[written] = b'0' + tens;
+ written += 1;
+ }
+ out[written] = b'0' + ones;
+ written += 1;
+ written
+}
+
+#[cfg(test)]
+mod format_u8_tests {
+ #[test]
+ fn all() {
+ for i in 0..(u8::MAX as u16) {
+ let mut buf = [0u8; 3];
+ let written = super::format_u8(i as u8, &mut buf);
+ assert_eq!(i.to_string().as_bytes(), &buf[..written]);
+ }
+ }
+}
+
 #[cfg(feature = "std")]
 impl Serialize for net::Ipv4Addr {
  fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -683,7 +717,15 @@ impl Serialize for net::Ipv4Addr {
  if serializer.is_human_readable() {
  const MAX_LEN: usize = 15;
  debug_assert_eq!(MAX_LEN, "101.102.103.104".len());
- serialize_display_bounded_length!(self, MAX_LEN, serializer)
+ let mut buf = [0u8; MAX_LEN];
+ let mut written = 0;
+ written += format_u8(self.octets()[0], &mut buf);
+ for oct in &self.octets()[1..] {
+ buf[written] = b'.';
+ written += 1;
+ written += format_u8(*oct, &mut buf[written..]);
+ }
+ serializer.serialize_str(str::from_utf8(&buf[..written]).unwrap())
  } else {
  self.octets().serialize(serializer)
  }