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Add fast-path optimization for Ipv4Addr::fmt

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This commit is contained in:
Nathan West 2020-05-20 16:49:31 -04:00
parent 672b272077
commit dc3de7cb2a
1 changed files with 16 additions and 9 deletions
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25
src/libstd/net/ip.rs
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@ -856,16 +856,23 @@ impl From<Ipv6Addr> for IpAddr {
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for Ipv4Addr {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
const IPV4_BUF_LEN: usize = 15; // Long enough for the longest possible IPv4 address
let mut buf = [0u8; IPV4_BUF_LEN];
let mut buf_slice = &mut buf[..];
let octets = self.octets();
// Note: The call to write should never fail, hence the unwrap
write!(buf_slice, "{}.{}.{}.{}", octets[0], octets[1], octets[2], octets[3]).unwrap();
let len = IPV4_BUF_LEN - buf_slice.len();
// This unsafe is OK because we know what is being written to the buffer
let buf = unsafe { crate::str::from_utf8_unchecked(&buf[..len]) };
fmt.pad(buf)
// Fast Path: if there's no alignment stuff, write directly to the buffer
if fmt.precision().is_none() && fmt.width().is_none() {
write!(fmt, "{}.{}.{}.{}", octets[0], octets[1], octets[2], octets[3])
} else {
const IPV4_BUF_LEN: usize = 15; // Long enough for the longest possible IPv4 address
let mut buf = [0u8; IPV4_BUF_LEN];
let mut buf_slice = &mut buf[..];
// Note: The call to write should never fail, hence the unwrap
write!(buf_slice, "{}.{}.{}.{}", octets[0], octets[1], octets[2], octets[3]).unwrap();
let len = IPV4_BUF_LEN - buf_slice.len();
// This unsafe is OK because we know what is being written to the buffer
let buf = unsafe { crate::str::from_utf8_unchecked(&buf[..len]) };
fmt.pad(buf)
}
}
}