From 5a11b814d4cd84d43f7b96a81f3e1595187c26a1 Mon Sep 17 00:00:00 2001 From: Markus Reiter Date: Tue, 16 Aug 2022 14:42:00 +0200 Subject: [PATCH 1/4] Add `IpDisplayBuffer` helper struct. --- library/std/src/net/ip.rs | 79 ++++++++++++++++++++++++--------------- 1 file changed, 48 insertions(+), 31 deletions(-) diff --git a/library/std/src/net/ip.rs b/library/std/src/net/ip.rs index 41ca9ba842588..f4fba7f73869f 100644 --- a/library/std/src/net/ip.rs +++ b/library/std/src/net/ip.rs @@ -3,12 +3,44 @@ mod tests; use crate::cmp::Ordering; -use crate::fmt::{self, Write as FmtWrite}; -use crate::io::Write as IoWrite; +use crate::fmt::{self, Write}; use crate::mem::transmute; +use crate::str; use crate::sys::net::netc as c; use crate::sys_common::{FromInner, IntoInner}; +/// Used for slow path in `Display` implementations when alignment is required. +struct IpDisplayBuffer { + buf: [u8; SIZE], + len: usize, +} + +impl IpDisplayBuffer { + #[inline(always)] + pub const fn new(_ip: &[u8; SIZE]) -> Self { + Self { buf: [0; SIZE], len: 0 } + } + + #[inline(always)] + pub fn as_str(&self) -> &str { + // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation + // which writes a valid UTF-8 string to `buf` and correctly sets `len`. + unsafe { str::from_utf8_unchecked(&self.buf[..self.len]) } + } +} + +impl fmt::Write for IpDisplayBuffer { + fn write_str(&mut self, s: &str) -> fmt::Result { + if let Some(buf) = self.buf.get_mut(self.len..(self.len + s.len())) { + buf.copy_from_slice(s.as_bytes()); + self.len += s.len(); + Ok(()) + } else { + Err(fmt::Error) + } + } +} + /// An IP address, either IPv4 or IPv6. /// /// This enum can contain either an [`Ipv4Addr`] or an [`Ipv6Addr`], see their @@ -991,21 +1023,17 @@ impl From for IpAddr { impl fmt::Display for Ipv4Addr { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { let octets = self.octets(); - // Fast Path: if there's no alignment stuff, write directly to the buffer + + // If there are no alignment requirements, write the IP address directly to `f`. + // Otherwise, write it to a local buffer and then use `f.pad`. 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(); + let mut buf = IpDisplayBuffer::new(b"255.255.255.255"); + // Buffer is long enough for the longest possible IPv4 address, so this should never fail. + write!(buf, "{}.{}.{}.{}", octets[0], octets[1], octets[2], octets[3]).unwrap(); - // 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) + fmt.pad(buf.as_str()) } } } @@ -1708,8 +1736,8 @@ impl Ipv6Addr { #[stable(feature = "rust1", since = "1.0.0")] impl fmt::Display for Ipv6Addr { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - // If there are no alignment requirements, write out the IP address to - // f. Otherwise, write it to a local buffer, then use f.pad. + // If there are no alignment requirements, write the IP address directly to `f`. + // Otherwise, write it to a local buffer and then use `f.pad`. if f.precision().is_none() && f.width().is_none() { let segments = self.segments(); @@ -1780,22 +1808,11 @@ impl fmt::Display for Ipv6Addr { } } } else { - // Slow path: write the address to a local buffer, then use f.pad. - // Defined recursively by using the fast path to write to the - // buffer. - - // This is the largest possible size of an IPv6 address - const IPV6_BUF_LEN: usize = (4 * 8) + 7; - let mut buf = [0u8; IPV6_BUF_LEN]; - let mut buf_slice = &mut buf[..]; - - // Note: This call to write should never fail, so unwrap is okay. - write!(buf_slice, "{}", self).unwrap(); - let len = IPV6_BUF_LEN - buf_slice.len(); - - // This is safe because we know exactly what can be in this buffer - let buf = unsafe { crate::str::from_utf8_unchecked(&buf[..len]) }; - f.pad(buf) + let mut buf = IpDisplayBuffer::new(b"ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"); + // Buffer is long enough for the longest possible IPv6 address, so this should never fail. + write!(buf, "{}", self).unwrap(); + + f.pad(buf.as_str()) } } } From 033e9d66ffa918b2cd78649c5b8cba372f58f9e4 Mon Sep 17 00:00:00 2001 From: Markus Reiter Date: Tue, 16 Aug 2022 17:48:55 +0200 Subject: [PATCH 2/4] Move `IpDisplayBuffer` into submodule. --- library/std/src/net/ip.rs | 34 ++---------------------- library/std/src/net/ip/display_buffer.rs | 34 ++++++++++++++++++++++++ 2 files changed, 36 insertions(+), 32 deletions(-) create mode 100644 library/std/src/net/ip/display_buffer.rs diff --git a/library/std/src/net/ip.rs b/library/std/src/net/ip.rs index f4fba7f73869f..198dcff12b95c 100644 --- a/library/std/src/net/ip.rs +++ b/library/std/src/net/ip.rs @@ -5,41 +5,11 @@ mod tests; use crate::cmp::Ordering; use crate::fmt::{self, Write}; use crate::mem::transmute; -use crate::str; use crate::sys::net::netc as c; use crate::sys_common::{FromInner, IntoInner}; -/// Used for slow path in `Display` implementations when alignment is required. -struct IpDisplayBuffer { - buf: [u8; SIZE], - len: usize, -} - -impl IpDisplayBuffer { - #[inline(always)] - pub const fn new(_ip: &[u8; SIZE]) -> Self { - Self { buf: [0; SIZE], len: 0 } - } - - #[inline(always)] - pub fn as_str(&self) -> &str { - // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation - // which writes a valid UTF-8 string to `buf` and correctly sets `len`. - unsafe { str::from_utf8_unchecked(&self.buf[..self.len]) } - } -} - -impl fmt::Write for IpDisplayBuffer { - fn write_str(&mut self, s: &str) -> fmt::Result { - if let Some(buf) = self.buf.get_mut(self.len..(self.len + s.len())) { - buf.copy_from_slice(s.as_bytes()); - self.len += s.len(); - Ok(()) - } else { - Err(fmt::Error) - } - } -} +mod display_buffer; +use display_buffer::IpDisplayBuffer; /// An IP address, either IPv4 or IPv6. /// diff --git a/library/std/src/net/ip/display_buffer.rs b/library/std/src/net/ip/display_buffer.rs new file mode 100644 index 0000000000000..06acfa5e21522 --- /dev/null +++ b/library/std/src/net/ip/display_buffer.rs @@ -0,0 +1,34 @@ +use crate::fmt; +use crate::str; + +/// Used for slow path in `Display` implementations when alignment is required. +pub struct IpDisplayBuffer { + buf: [u8; SIZE], + len: usize, +} + +impl IpDisplayBuffer { + #[inline(always)] + pub const fn new(_ip: &[u8; SIZE]) -> Self { + Self { buf: [0; SIZE], len: 0 } + } + + #[inline(always)] + pub fn as_str(&self) -> &str { + // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation + // which writes a valid UTF-8 string to `buf` and correctly sets `len`. + unsafe { str::from_utf8_unchecked(&self.buf[..self.len]) } + } +} + +impl fmt::Write for IpDisplayBuffer { + fn write_str(&mut self, s: &str) -> fmt::Result { + if let Some(buf) = self.buf.get_mut(self.len..(self.len + s.len())) { + buf.copy_from_slice(s.as_bytes()); + self.len += s.len(); + Ok(()) + } else { + Err(fmt::Error) + } + } +} From 31540f5e15d5785a61d96869b373f7ed4d4a3654 Mon Sep 17 00:00:00 2001 From: Markus Reiter Date: Tue, 16 Aug 2022 18:12:06 +0200 Subject: [PATCH 3/4] Use `MaybeUninit` for `IpDisplayBuffer`. --- library/std/src/lib.rs | 2 ++ library/std/src/net/ip/display_buffer.rs | 18 ++++++++++++------ 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs index 475a1d9fd9920..a8d6645794ae5 100644 --- a/library/std/src/lib.rs +++ b/library/std/src/lib.rs @@ -294,6 +294,8 @@ #![feature(std_internals)] #![feature(str_internals)] #![feature(strict_provenance)] +#![feature(maybe_uninit_uninit_array)] +#![feature(const_maybe_uninit_uninit_array)] // // Library features (alloc): #![feature(alloc_layout_extra)] diff --git a/library/std/src/net/ip/display_buffer.rs b/library/std/src/net/ip/display_buffer.rs index 06acfa5e21522..65f11b8ae93f5 100644 --- a/library/std/src/net/ip/display_buffer.rs +++ b/library/std/src/net/ip/display_buffer.rs @@ -1,31 +1,37 @@ use crate::fmt; +use crate::mem::MaybeUninit; use crate::str; /// Used for slow path in `Display` implementations when alignment is required. pub struct IpDisplayBuffer { - buf: [u8; SIZE], + buf: [MaybeUninit; SIZE], len: usize, } impl IpDisplayBuffer { #[inline(always)] pub const fn new(_ip: &[u8; SIZE]) -> Self { - Self { buf: [0; SIZE], len: 0 } + Self { buf: MaybeUninit::uninit_array::(), len: 0 } } #[inline(always)] pub fn as_str(&self) -> &str { // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation // which writes a valid UTF-8 string to `buf` and correctly sets `len`. - unsafe { str::from_utf8_unchecked(&self.buf[..self.len]) } + unsafe { + let s = MaybeUninit::slice_assume_init_ref(&self.buf[..self.len]); + str::from_utf8_unchecked(s) + } } } impl fmt::Write for IpDisplayBuffer { fn write_str(&mut self, s: &str) -> fmt::Result { - if let Some(buf) = self.buf.get_mut(self.len..(self.len + s.len())) { - buf.copy_from_slice(s.as_bytes()); - self.len += s.len(); + let bytes = s.as_bytes(); + + if let Some(buf) = self.buf.get_mut(self.len..(self.len + bytes.len())) { + MaybeUninit::write_slice(buf, bytes); + self.len += bytes.len(); Ok(()) } else { Err(fmt::Error) From 44d62425b9e08c1eebd329766b5e4dd7f8bc3216 Mon Sep 17 00:00:00 2001 From: Markus Reiter Date: Tue, 16 Aug 2022 19:32:00 +0200 Subject: [PATCH 4/4] Simplify `IpDisplayBuffer` API. --- library/std/src/net/ip.rs | 8 ++++++-- library/std/src/net/ip/display_buffer.rs | 8 ++++---- 2 files changed, 10 insertions(+), 6 deletions(-) diff --git a/library/std/src/net/ip.rs b/library/std/src/net/ip.rs index 198dcff12b95c..189754a161e71 100644 --- a/library/std/src/net/ip.rs +++ b/library/std/src/net/ip.rs @@ -999,7 +999,9 @@ impl fmt::Display for Ipv4Addr { if fmt.precision().is_none() && fmt.width().is_none() { write!(fmt, "{}.{}.{}.{}", octets[0], octets[1], octets[2], octets[3]) } else { - let mut buf = IpDisplayBuffer::new(b"255.255.255.255"); + const LONGEST_IPV4_ADDR: &str = "255.255.255.255"; + + let mut buf = IpDisplayBuffer::<{ LONGEST_IPV4_ADDR.len() }>::new(); // Buffer is long enough for the longest possible IPv4 address, so this should never fail. write!(buf, "{}.{}.{}.{}", octets[0], octets[1], octets[2], octets[3]).unwrap(); @@ -1778,7 +1780,9 @@ impl fmt::Display for Ipv6Addr { } } } else { - let mut buf = IpDisplayBuffer::new(b"ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"); + const LONGEST_IPV6_ADDR: &str = "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"; + + let mut buf = IpDisplayBuffer::<{ LONGEST_IPV6_ADDR.len() }>::new(); // Buffer is long enough for the longest possible IPv6 address, so this should never fail. write!(buf, "{}", self).unwrap(); diff --git a/library/std/src/net/ip/display_buffer.rs b/library/std/src/net/ip/display_buffer.rs index 65f11b8ae93f5..bd852d5da8ec5 100644 --- a/library/std/src/net/ip/display_buffer.rs +++ b/library/std/src/net/ip/display_buffer.rs @@ -9,12 +9,12 @@ pub struct IpDisplayBuffer { } impl IpDisplayBuffer { - #[inline(always)] - pub const fn new(_ip: &[u8; SIZE]) -> Self { - Self { buf: MaybeUninit::uninit_array::(), len: 0 } + #[inline] + pub const fn new() -> Self { + Self { buf: MaybeUninit::uninit_array(), len: 0 } } - #[inline(always)] + #[inline] pub fn as_str(&self) -> &str { // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation // which writes a valid UTF-8 string to `buf` and correctly sets `len`.