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// SPDX-License-Identifier: GPL-2.0
use super::Vmalloc;
use crate::page;
use core::marker::PhantomData;
use core::ptr::NonNull;
/// An [`Iterator`] of [`page::BorrowedPage`] items owned by a [`Vmalloc`] allocation.
///
/// # Guarantees
///
/// The pages iterated by the [`Iterator`] appear in the order as they are mapped in the CPU's
/// virtual address space ascendingly.
///
/// # Invariants
///
/// - `buf` is a valid and [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
/// - `size` is the number of bytes from `buf` until the end of the [`Vmalloc`] allocation `buf`
/// points to.
pub struct VmallocPageIter<'a> {
/// The base address of the [`Vmalloc`] buffer.
buf: NonNull<u8>,
/// The size of the buffer pointed to by `buf` in bytes.
size: usize,
/// The current page index of the [`Iterator`].
index: usize,
_p: PhantomData<page::BorrowedPage<'a>>,
}
impl<'a> Iterator for VmallocPageIter<'a> {
type Item = page::BorrowedPage<'a>;
fn next(&mut self) -> Option<Self::Item> {
let offset = self.index.checked_mul(page::PAGE_SIZE)?;
// Even though `self.size()` may be smaller than `Self::page_count() * page::PAGE_SIZE`, it
// is always a number between `(Self::page_count() - 1) * page::PAGE_SIZE` and
// `Self::page_count() * page::PAGE_SIZE`, hence the check below is sufficient.
if offset < self.size() {
self.index += 1;
} else {
return None;
}
// TODO: Use `NonNull::add()` instead, once the minimum supported compiler version is
// bumped to 1.80 or later.
//
// SAFETY: `offset` is in the interval `[0, (self.page_count() - 1) * page::PAGE_SIZE]`,
// hence the resulting pointer is guaranteed to be within the same allocation.
let ptr = unsafe { self.buf.as_ptr().add(offset) };
// SAFETY: `ptr` is guaranteed to be non-null given that it is derived from `self.buf`.
let ptr = unsafe { NonNull::new_unchecked(ptr) };
// SAFETY:
// - `ptr` is a valid pointer to a `Vmalloc` allocation.
// - `ptr` is valid for the duration of `'a`.
Some(unsafe { Vmalloc::to_page(ptr) })
}
fn size_hint(&self) -> (usize, Option<usize>) {
let remaining = self.page_count().saturating_sub(self.index);
(remaining, Some(remaining))
}
}
impl<'a> VmallocPageIter<'a> {
/// Creates a new [`VmallocPageIter`] instance.
///
/// # Safety
///
/// - `buf` must be a [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
/// - `buf` must be valid for at least the lifetime of `'a`.
/// - `size` must be the number of bytes from `buf` until the end of the [`Vmalloc`] allocation
/// `buf` points to.
pub unsafe fn new(buf: NonNull<u8>, size: usize) -> Self {
// INVARIANT: By the safety requirements, `buf` is a valid and `page::PAGE_SIZE` aligned
// pointer into a [`Vmalloc`] allocation.
Self {
buf,
size,
index: 0,
_p: PhantomData,
}
}
/// Returns the size of the backing [`Vmalloc`] allocation in bytes.
///
/// Note that this is the size the [`Vmalloc`] allocation has been allocated with. Hence, this
/// number may be smaller than `[`Self::page_count`] * [`page::PAGE_SIZE`]`.
#[inline]
pub fn size(&self) -> usize {
self.size
}
/// Returns the number of pages owned by the backing [`Vmalloc`] allocation.
#[inline]
pub fn page_count(&self) -> usize {
self.size().div_ceil(page::PAGE_SIZE)
}
}
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