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Auto merge of #121428 - okaneco:ipaddr_parse, r=cuviper
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net: Don't use checked arithmetic when parsing numbers with known max digits

Add a branch to `Parser::read_number` that determines whether checked or regular arithmetic is used.

- If `max_digits.is_some()`, then we know we are parsing a `u8` or `u16` because `read_number` is only called with `Some(3)` or `Some(4)`. Both types fit within a `u32` without risk of overflow. Thus, we can use plain arithmetic to avoid extra instructions from `checked_mul` and `checked_add`.

Add benches for `IpAddr`, `Ipv4Addr`, `Ipv6Addr`, `SocketAddr`, `SocketAddrV4`, and `SocketAddrV6` parsing
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bors committed Mar 5, 2024
2 parents c7beecf + 69637c9 commit 96561a8
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Showing 4 changed files with 131 additions and 21 deletions.
1 change: 1 addition & 0 deletions library/core/benches/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ mod char;
mod fmt;
mod hash;
mod iter;
mod net;
mod num;
mod ops;
mod pattern;
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78 changes: 78 additions & 0 deletions library/core/benches/net/addr_parser.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,78 @@
use core::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
use core::str::FromStr;

use test::{black_box, Bencher};

const IPV4_STR: &str = "192.168.0.1";
const IPV4_STR_PORT: &str = "192.168.0.1:8080";

const IPV6_STR_FULL: &str = "2001:db8:0:0:0:0:c0a8:1";
const IPV6_STR_COMPRESS: &str = "2001:db8::c0a8:1";
const IPV6_STR_V4: &str = "2001:db8::192.168.0.1";
const IPV6_STR_PORT: &str = "[2001:db8::c0a8:1]:8080";
const IPV6_STR_PORT_SCOPE_ID: &str = "[2001:db8::c0a8:1%1337]:8080";

#[bench]
fn bench_parse_ipv4(b: &mut Bencher) {
b.iter(|| Ipv4Addr::from_str(black_box(IPV4_STR)));
}

#[bench]
fn bench_parse_ipv6_full(b: &mut Bencher) {
b.iter(|| Ipv6Addr::from_str(black_box(IPV6_STR_FULL)));
}

#[bench]
fn bench_parse_ipv6_compress(b: &mut Bencher) {
b.iter(|| Ipv6Addr::from_str(black_box(IPV6_STR_COMPRESS)));
}

#[bench]
fn bench_parse_ipv6_v4(b: &mut Bencher) {
b.iter(|| Ipv6Addr::from_str(black_box(IPV6_STR_V4)));
}

#[bench]
fn bench_parse_ipaddr_v4(b: &mut Bencher) {
b.iter(|| IpAddr::from_str(black_box(IPV4_STR)));
}

#[bench]
fn bench_parse_ipaddr_v6_full(b: &mut Bencher) {
b.iter(|| IpAddr::from_str(black_box(IPV6_STR_FULL)));
}

#[bench]
fn bench_parse_ipaddr_v6_compress(b: &mut Bencher) {
b.iter(|| IpAddr::from_str(black_box(IPV6_STR_COMPRESS)));
}

#[bench]
fn bench_parse_ipaddr_v6_v4(b: &mut Bencher) {
b.iter(|| IpAddr::from_str(black_box(IPV6_STR_V4)));
}

#[bench]
fn bench_parse_socket_v4(b: &mut Bencher) {
b.iter(|| SocketAddrV4::from_str(black_box(IPV4_STR_PORT)));
}

#[bench]
fn bench_parse_socket_v6(b: &mut Bencher) {
b.iter(|| SocketAddrV6::from_str(black_box(IPV6_STR_PORT)));
}

#[bench]
fn bench_parse_socket_v6_scope_id(b: &mut Bencher) {
b.iter(|| SocketAddrV6::from_str(black_box(IPV6_STR_PORT_SCOPE_ID)));
}

#[bench]
fn bench_parse_socketaddr_v4(b: &mut Bencher) {
b.iter(|| SocketAddr::from_str(black_box(IPV4_STR_PORT)));
}

#[bench]
fn bench_parse_socketaddr_v6(b: &mut Bencher) {
b.iter(|| SocketAddr::from_str(black_box(IPV6_STR_PORT)));
}
1 change: 1 addition & 0 deletions library/core/benches/net/mod.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
mod addr_parser;
72 changes: 51 additions & 21 deletions library/core/src/net/parser.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
//! This module is "publicly exported" through the `FromStr` implementations
//! below.

use crate::convert::TryInto;
use crate::convert::{TryFrom, TryInto};
use crate::error::Error;
use crate::fmt;
use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
Expand Down Expand Up @@ -104,36 +104,66 @@ impl<'a> Parser<'a> {
// Read a number off the front of the input in the given radix, stopping
// at the first non-digit character or eof. Fails if the number has more
// digits than max_digits or if there is no number.
fn read_number<T: ReadNumberHelper>(
//
// INVARIANT: `max_digits` must be less than the number of digits that `u32`
// can represent.
fn read_number<T: ReadNumberHelper + TryFrom<u32>>(
&mut self,
radix: u32,
max_digits: Option<usize>,
allow_zero_prefix: bool,
) -> Option<T> {
self.read_atomically(move |p| {
let mut result = T::ZERO;
let mut digit_count = 0;
let has_leading_zero = p.peek_char() == Some('0');

while let Some(digit) = p.read_atomically(|p| p.read_char()?.to_digit(radix)) {
result = result.checked_mul(radix)?;
result = result.checked_add(digit)?;
digit_count += 1;
if let Some(max_digits) = max_digits {
// If max_digits.is_some(), then we are parsing a `u8` or `u16` and
// don't need to use checked arithmetic since it fits within a `u32`.
if let Some(max_digits) = max_digits {
// u32::MAX = 4_294_967_295u32, which is 10 digits long.
// `max_digits` must be less than 10 to not overflow a `u32`.
debug_assert!(max_digits < 10);

self.read_atomically(move |p| {
let mut result = 0_u32;
let mut digit_count = 0;
let has_leading_zero = p.peek_char() == Some('0');

while let Some(digit) = p.read_atomically(|p| p.read_char()?.to_digit(radix)) {
result *= radix;
result += digit;
digit_count += 1;

if digit_count > max_digits {
return None;
}
}
}

if digit_count == 0 {
None
} else if !allow_zero_prefix && has_leading_zero && digit_count > 1 {
None
} else {
Some(result)
}
})
if digit_count == 0 {
None
} else if !allow_zero_prefix && has_leading_zero && digit_count > 1 {
None
} else {
result.try_into().ok()
}
})
} else {
self.read_atomically(move |p| {
let mut result = T::ZERO;
let mut digit_count = 0;
let has_leading_zero = p.peek_char() == Some('0');

while let Some(digit) = p.read_atomically(|p| p.read_char()?.to_digit(radix)) {
result = result.checked_mul(radix)?;
result = result.checked_add(digit)?;
digit_count += 1;
}

if digit_count == 0 {
None
} else if !allow_zero_prefix && has_leading_zero && digit_count > 1 {
None
} else {
Some(result)
}
})
}
}

/// Read an IPv4 address.
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