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Message-ID: <20250115194229.04cd1068.gary@garyguo.net>
Date: Wed, 15 Jan 2025 19:42:29 +0000
From: Gary Guo <gary@...yguo.net>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Björn Roy Baron
<bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, Alice
Ryhl <aliceryhl@...gle.com>, Masahiro Yamada <masahiroy@...nel.org>, Nathan
Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, Luis
Chamberlain <mcgrof@...nel.org>, Trevor Gross <tmgross@...ch.edu>, Adam
Bratschi-Kaye <ark.email@...il.com>, rust-for-linux@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org, Petr Pavlu
<petr.pavlu@...e.com>, Sami Tolvanen <samitolvanen@...gle.com>, Daniel
Gomez <da.gomez@...sung.com>, Simona Vetter <simona.vetter@...ll.ch>, Greg
KH <gregkh@...uxfoundation.org>, linux-modules@...r.kernel.org
Subject: Re: [PATCH v4 3/4] rust: str: add radix prefixed integer parsing
functions
On Thu, 09 Jan 2025 11:54:58 +0100
Andreas Hindborg <a.hindborg@...nel.org> wrote:
> Add the trait `ParseInt` for parsing string representations of integers
> where the string representations are optionally prefixed by a radix
> specifier. Implement the trait for the primitive integer types.
>
> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> ---
> rust/kernel/str.rs | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 118 insertions(+)
>
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index 9c446ff1ad7adba7ca09a5ae9df00fd369a32899..14da40213f9eafa07a104eba3129efe07c8343f3 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -914,3 +914,121 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> macro_rules! fmt {
> ($($f:tt)*) => ( core::format_args!($($f)*) )
> }
> +
> +pub mod parse_int {
> + //! Integer parsing functions for parsing signed and unsigned integers
> + //! potentially prefixed with `0x`, `0o`, or `0b`.
> +
> + use crate::alloc::flags;
> + use crate::prelude::*;
> + use crate::str::BStr;
> +
> + /// Trait that allows parsing a [`&BStr`] to an integer with a radix.
> + ///
> + /// [`&BStr`]: kernel::str::BStr
> + // This is required because the `from_str_radix` function on the primitive
> + // integer types is not part of any trait.
> + pub trait FromStrRadix: Sized {
> + /// Parse `src` to `Self` using radix `radix`.
> + fn from_str_radix(src: &BStr, radix: u32) -> Result<Self, crate::error::Error>;
> + }
> +
> + /// Extract the radix from an integer literal optionally prefixed with
> + /// one of `0x`, `0X`, `0o`, `0O`, `0b`, `0B`, `0`.
> + fn strip_radix(src: &BStr) -> (u32, &BStr) {
> + if let Some(n) = src.strip_prefix(b_str!("0x")) {
> + (16, n)
> + } else if let Some(n) = src.strip_prefix(b_str!("0X")) {
> + (16, n)
> + } else if let Some(n) = src.strip_prefix(b_str!("0o")) {
> + (8, n)
> + } else if let Some(n) = src.strip_prefix(b_str!("0O")) {
> + (8, n)
> + } else if let Some(n) = src.strip_prefix(b_str!("0b")) {
> + (2, n)
> + } else if let Some(n) = src.strip_prefix(b_str!("0B")) {
> + (2, n)
> + } else if let Some(n) = src.strip_prefix(b_str!("0")) {
> + (8, n)
> + } else {
> + (10, src)
> + }
This can be done better with a match:
match src.deref() {
[b'0', b'x' | b'X', ..] => (16, &src[2..]),
[b'0', b'o' | b'O', ..] => (8, &src[2..]),
[b'0', b'b' | b'B', ..] => (2, &src[2..]),
[b'0', ..] => (8, &src[1..]),
_ => (10, src),
}
> + }
> +
> + /// Trait for parsing string representations of integers.
> + ///
> + /// Strings beginning with `0x`, `0o`, or `0b` are parsed as hex, octal, or
> + /// binary respectively. Strings beginning with `0` otherwise are parsed as
> + /// octal. Anything else is parsed as decimal. A leading `+` or `-` is also
> + /// permitted. Any string parsed by [`kstrtol()`] or [`kstrtoul()`] will be
> + /// successfully parsed.
> + ///
> + /// [`kstrtol()`]: https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.kstrtol
> + /// [`kstrtoul()`]: https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.kstrtoul
> + ///
> + /// # Example
> + /// ```
> + /// use kernel::str::parse_int::ParseInt;
> + /// use kernel::b_str;
> + ///
> + /// assert_eq!(Ok(0xa2u8), u8::from_str(b_str!("0xa2")));
> + /// assert_eq!(Ok(-0xa2i32), i32::from_str(b_str!("-0xa2")));
> + ///
> + /// assert_eq!(Ok(-0o57i8), i8::from_str(b_str!("-0o57")));
> + /// assert_eq!(Ok(0o57i8), i8::from_str(b_str!("057")));
> + ///
> + /// assert_eq!(Ok(0b1001i16), i16::from_str(b_str!("0b1001")));
> + /// assert_eq!(Ok(-0b1001i16), i16::from_str(b_str!("-0b1001")));
> + ///
> + /// assert_eq!(Ok(127), i8::from_str(b_str!("127")));
> + /// assert!(i8::from_str(b_str!("128")).is_err());
> + /// assert_eq!(Ok(-128), i8::from_str(b_str!("-128")));
> + /// assert!(i8::from_str(b_str!("-129")).is_err());
> + /// assert_eq!(Ok(255), u8::from_str(b_str!("255")));
> + /// assert!(u8::from_str(b_str!("256")).is_err());
> + /// ```
> + pub trait ParseInt: FromStrRadix {
> + /// Parse a string according to the description in [`Self`].
> + fn from_str(src: &BStr) -> Result<Self> {
> + match src.iter().next() {
> + None => Err(EINVAL),
> + Some(sign @ b'-') | Some(sign @ b'+') => {
> + let (radix, digits) = strip_radix(BStr::from_bytes(&src[1..]));
> + let mut n_digits: KVec<u8> =
> + KVec::with_capacity(digits.len() + 1, flags::GFP_KERNEL)?;
I don't think we should allocate for parsing. This can trivially be a
non-allocating. Just check that the next byte is an ASCII digit (reject
if so, in case people give multiple signs), and then from_str_radix and
return as is or use `checked_neg`.
> + n_digits.push(*sign, flags::GFP_KERNEL)?;
> + n_digits.extend_from_slice(digits, flags::GFP_KERNEL)?;
> + Self::from_str_radix(BStr::from_bytes(&n_digits), radix).map_err(|_| EINVAL)
> + }
> + Some(_) => {
> + let (radix, digits) = strip_radix(src);
> + Self::from_str_radix(digits, radix).map_err(|_| EINVAL)
> + }
> + }
> + }
> + }
> +
> + macro_rules! impl_parse_int {
> + ($ty:ty) => {
> + impl FromStrRadix for $ty {
> + fn from_str_radix(src: &BStr, radix: u32) -> Result<Self, crate::error::Error> {
> + <$ty>::from_str_radix(core::str::from_utf8(src).map_err(|_| EINVAL)?, radix)
> + .map_err(|_| EINVAL)
> + }
> + }
> +
> + impl ParseInt for $ty {}
> + };
> + }
> +
> + impl_parse_int!(i8);
> + impl_parse_int!(u8);
> + impl_parse_int!(i16);
> + impl_parse_int!(u16);
> + impl_parse_int!(i32);
> + impl_parse_int!(u32);
> + impl_parse_int!(i64);
> + impl_parse_int!(u64);
> + impl_parse_int!(isize);
> + impl_parse_int!(usize);
> +}
>
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