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AJvYcCUhfDPN6AgVjS6V6P706Z6MDA4s816jeelwpoW05r5JfBuOnuWLvPT2FaUckZgEJC8bMrVBOrNbaQ==@kvack.org X-Gm-Message-State: AOJu0YxcOMWkKJm6EClzHGBa3j6jYSNPkAVro8c/Bg5vlUtbmbZRntVo dzmcR+8E7tMoeCejBhR90XsIhmrTMQgXWcRXtrqFj37dAQF/zqhYc9o+8sF1i4nAXchAyR/Hgxf bIdxqb0+WJORFQ3sfjDkJ1J32Q0l7ryrJn57NzPsBv2IPO0J56n9i X-Google-Smtp-Source: AGHT+IE6W9vQz1y68yO5qeHUn4/djJSdduZOAYLjB/UAITY2qd74Q9MXHNnrgxlzMmuajj/inFZcuqlopvdC7XxN3r8= X-Received: by 2002:adf:e6c8:0:b0:374:c3cd:73de with SMTP id ffacd0b85a97d-374c3cd74d5mr9938028f8f.35.1725445797876; Wed, 04 Sep 2024 03:29:57 -0700 (PDT) MIME-Version: 1.0 References: <20240816001216.26575-1-dakr@kernel.org> <20240816001216.26575-15-dakr@kernel.org> In-Reply-To: <20240816001216.26575-15-dakr@kernel.org> From: Alice Ryhl Date: Wed, 4 Sep 2024 12:29:44 +0200 Message-ID: Subject: Re: [PATCH v6 14/26] rust: alloc: implement `IntoIterator` for `Vec` To: Danilo Krummrich Cc: ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, akpm@linux-foundation.org, daniel.almeida@collabora.com, faith.ekstrand@collabora.com, boris.brezillon@collabora.com, lina@asahilina.net, mcanal@igalia.com, zhiw@nvidia.com, cjia@nvidia.com, jhubbard@nvidia.com, airlied@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C229EC0014 X-Stat-Signature: kyqhfym6ucu1nukwbiy3sz9c93f57gh9 X-Rspam-User: X-HE-Tag: 1725445799-460321 X-HE-Meta: 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 nLZLbRKF MfbfVs1dF7dQpp7ojv+ExHaFXac1wF8weaw0BJ9lW51GIp1fg4UN9o266ZDIdZh2ThDOPnhRz6WR5UjpJC9NI5mrqq6TeeyY2ktZUveSevTgDAWqKbjwrGjSx3teT0BiKJbHgJpjC9U0O3k6t9h4Se0K1rxbUHHRvZUjbhu2PO6LTlb1w0RifyAAxrL8qCbzBupkZFPT9z0xnSFNAFPY5nuXjBPEZKfEFQdrFfE6phJHiU1VT72XMTL6otA2GayUtgoIaUZO/BkTV30Jz9MQpbCsCrMPgbkFG8JehmMynVbqO7UL7EQpgekOpuHHDrwxiP4m5 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000015, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 16, 2024 at 2:13=E2=80=AFAM Danilo Krummrich = wrote: > > Implement `IntoIterator` for `Vec`, `Vec`'s `IntoIter` type, as well as > `Iterator` for `IntoIter`. > > `Vec::into_iter` disassembles the `Vec` into its raw parts; additionally, > `IntoIter` keeps track of a separate pointer, which is incremented > correspondingsly as the iterator advances, while the length, or the count > of elements, is decremented. > > This also means that `IntoIter` takes the ownership of the backing > buffer and is responsible to drop the remaining elements and free the > backing buffer, if it's dropped. > > Signed-off-by: Danilo Krummrich This looks ok to me. One nit below, though. Either way: Reviewed-by: Alice Ryhl > rust/kernel/alloc.rs | 1 + > rust/kernel/alloc/kvec.rs | 184 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 185 insertions(+) > > diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs > index e88c7e10ee9b..4ff4df4597a3 100644 > --- a/rust/kernel/alloc.rs > +++ b/rust/kernel/alloc.rs > @@ -19,6 +19,7 @@ > pub use self::kbox::KVBox; > pub use self::kbox::VBox; > > +pub use self::kvec::IntoIter; > pub use self::kvec::KVVec; > pub use self::kvec::KVec; > pub use self::kvec::VVec; > diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs > index 89afc0f25bd4..3b79f977b65e 100644 > --- a/rust/kernel/alloc/kvec.rs > +++ b/rust/kernel/alloc/kvec.rs > @@ -11,6 +11,7 @@ > ops::DerefMut, > ops::Index, > ops::IndexMut, > + ptr, > ptr::NonNull, > slice, > slice::SliceIndex, > @@ -627,3 +628,186 @@ fn eq(&self, other: &$rhs) -> bool { self[..] =3D= =3D other[..] } > __impl_slice_eq! { [A: Allocator] [T], Vec } > __impl_slice_eq! { [A: Allocator, const N: usize] Vec, [U; N] } > __impl_slice_eq! { [A: Allocator, const N: usize] Vec, &[U; N] } > + > +impl<'a, T, A> IntoIterator for &'a Vec > +where > + A: Allocator, > +{ > + type Item =3D &'a T; > + type IntoIter =3D slice::Iter<'a, T>; > + > + fn into_iter(self) -> Self::IntoIter { > + self.iter() > + } > +} > + > +impl<'a, T, A: Allocator> IntoIterator for &'a mut Vec > +where > + A: Allocator, > +{ > + type Item =3D &'a mut T; > + type IntoIter =3D slice::IterMut<'a, T>; > + > + fn into_iter(self) -> Self::IntoIter { > + self.iter_mut() > + } > +} > + > +/// An `Iterator` implementation for `Vec` that moves elements out = of a vector. > +/// > +/// This structure is created by the `Vec::into_iter` method on [`Vec`] = (provided by the > +/// [`IntoIterator`] trait). > +/// > +/// # Examples > +/// > +/// ``` > +/// let v =3D kernel::kvec![0, 1, 2]?; > +/// let iter =3D v.into_iter(); > +/// > +/// # Ok::<(), Error>(()) > +/// ``` > +pub struct IntoIter { > + ptr: *mut T, > + buf: NonNull, > + len: usize, > + cap: usize, > + _p: PhantomData, > +} > + > +impl IntoIter > +where > + A: Allocator, > +{ > + fn as_raw_mut_slice(&mut self) -> *mut [T] { > + ptr::slice_from_raw_parts_mut(self.ptr, self.len) > + } > +} > + > +impl Iterator for IntoIter > +where > + A: Allocator, > +{ > + type Item =3D T; > + > + /// # Examples > + /// > + /// ``` > + /// let v =3D kernel::kvec![1, 2, 3]?; > + /// let mut it =3D v.into_iter(); > + /// > + /// assert_eq!(it.next(), Some(1)); > + /// assert_eq!(it.next(), Some(2)); > + /// assert_eq!(it.next(), Some(3)); > + /// assert_eq!(it.next(), None); > + /// > + /// # Ok::<(), Error>(()) > + /// ``` > + fn next(&mut self) -> Option { > + if self.len =3D=3D 0 { > + return None; > + } > + > + let ptr =3D self.ptr; Nit: It would probably be slightly clearer to rename this variable to `curr= ent`. > + if !Vec::::is_zst() { > + // SAFETY: We can't overflow; `end` is guaranteed to mark th= e end of the buffer. > + unsafe { self.ptr =3D self.ptr.add(1) }; > + } else { > + // For ZST `ptr` has to stay where it is to remain aligned, = so we just reduce `self.len` > + // by 1. > + } > + self.len -=3D 1; > + > + // SAFETY: `ptr` is guaranteed to point at a valid element withi= n the buffer. > + Some(unsafe { ptr.read() }) > + } > + > + /// # Examples > + /// > + /// ``` > + /// let v: KVec =3D kernel::kvec![1, 2, 3]?; > + /// let mut iter =3D v.into_iter(); > + /// let size =3D iter.size_hint().0; > + /// > + /// iter.next(); > + /// assert_eq!(iter.size_hint().0, size - 1); > + /// > + /// iter.next(); > + /// assert_eq!(iter.size_hint().0, size - 2); > + /// > + /// iter.next(); > + /// assert_eq!(iter.size_hint().0, size - 3); > + /// > + /// # Ok::<(), Error>(()) > + /// ``` > + fn size_hint(&self) -> (usize, Option) { > + (self.len, Some(self.len)) > + } > +} > + > +impl Drop for IntoIter > +where > + A: Allocator, > +{ > + fn drop(&mut self) { > + // SAFETY: Drop the remaining vector's elements in place, before= we free the backing > + // memory. > + unsafe { ptr::drop_in_place(self.as_raw_mut_slice()) }; > + > + // If `cap =3D=3D 0` we never allocated any memory in the first = place. > + if self.cap !=3D 0 { > + // SAFETY: `self.buf` was previously allocated with `A`. > + unsafe { A::free(self.buf.cast()) }; > + } > + } > +} > + > +impl IntoIterator for Vec > +where > + A: Allocator, > +{ > + type Item =3D T; > + type IntoIter =3D IntoIter; > + > + /// Consumes the `Vec` and creates an `Iterator`, which moves = each value out of the > + /// vector (from start to end). > + /// > + /// # Examples > + /// > + /// ``` > + /// let v =3D kernel::kvec![1, 2]?; > + /// let mut v_iter =3D v.into_iter(); > + /// > + /// let first_element: Option =3D v_iter.next(); > + /// > + /// assert_eq!(first_element, Some(1)); > + /// assert_eq!(v_iter.next(), Some(2)); > + /// assert_eq!(v_iter.next(), None); > + /// > + /// # Ok::<(), Error>(()) > + /// ``` > + /// > + /// ``` > + /// let v =3D kernel::kvec![]; > + /// let mut v_iter =3D v.into_iter(); > + /// > + /// let first_element: Option =3D v_iter.next(); > + /// > + /// assert_eq!(first_element, None); > + /// > + /// # Ok::<(), Error>(()) > + /// ``` > + #[inline] > + fn into_iter(self) -> Self::IntoIter { > + let (ptr, len, cap) =3D self.into_raw_parts(); > + > + IntoIter { > + ptr, > + // SAFETY: `ptr` is either a dangling pointer or a pointer t= o a valid memory > + // allocation, allocated with `A`. > + buf: unsafe { NonNull::new_unchecked(ptr) }, > + len, > + cap, > + _p: PhantomData::, > + } > + } > +} > -- > 2.46.0 >