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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225// SPDX-License-Identifier: GPL-2.0
use core::ops::Deref;
use kernel::prelude::*;
/// A buffer abstraction for discontiguous byte slices.////// This allows you to treat multiple non-contiguous `&mut [u8]` slices/// of the same length as a single stream-like read/write buffer.////// # Examples////// ```// let mut buf1 = [0u8; 5];/// let mut buf2 = [0u8; 5];/// let mut sbuffer = SBufferIter::new_writer([&mut buf1[..], &mut buf2[..]]);////// let data = b"hi world!";/// sbuffer.write_all(data)?;/// drop(sbuffer);////// assert_eq!(buf1, *b"hi wo");/// assert_eq!(buf2, *b"rld!\0");////// # Ok::<(), Error>(())/// ```pub(crate) struct SBufferIter<I: Iterator> { // [`Some`] if we are not at the end of the data yet. cur_slice: Option<I::Item>, // All the slices remaining after `cur_slice`. slices: I,}
impl<'a, I> SBufferIter<I>where I: Iterator,{ /// Creates a reader buffer for a discontiguous set of byte slices. /// /// # Examples /// /// ``` /// let buf1: [u8; 5] = [0, 1, 2, 3, 4]; /// let buf2: [u8; 5] = [5, 6, 7, 8, 9]; /// let sbuffer = SBufferIter::new_reader([&buf1[..], &buf2[..]]); /// let sum: u8 = sbuffer.sum(); /// assert_eq!(sum, 45); /// ``` pub(crate) fn new_reader(slices: impl IntoIterator<IntoIter = I>) -> Self where I: Iterator<Item = &'a [u8]>, { Self::new(slices) }
/// Creates a writeable buffer for a discontiguous set of byte slices. /// /// # Examples /// /// ``` /// let mut buf1 = [0u8; 5]; /// let mut buf2 = [0u8; 5]; /// let mut sbuffer = SBufferIter::new_writer([&mut buf1[..], &mut buf2[..]]); /// sbuffer.write_all(&[0u8, 1, 2, 3, 4, 5, 6, 7, 8, 9][..])?; /// drop(sbuffer); /// assert_eq!(buf1, [0, 1, 2, 3, 4]); /// assert_eq!(buf2, [5, 6, 7, 8, 9]); /// /// ``` pub(crate) fn new_writer(slices: impl IntoIterator<IntoIter = I>) -> Self where I: Iterator<Item = &'a mut [u8]>, { Self::new(slices) }
fn new(slices: impl IntoIterator<IntoIter = I>) -> Self where I::Item: Deref<Target = [u8]>, { let mut slices = slices.into_iter();
Self { // Skip empty slices. cur_slice: slices.find(|s| !s.deref().is_empty()), slices, } }
/// Returns a slice of at most `len` bytes, or [`None`] if we are at the end of the data. /// /// If a slice shorter than `len` bytes has been returned, the caller can call this method /// again until it returns [`None`] to try and obtain the remainder of the data. /// /// The closure `f` should split the slice received in it's first parameter /// at the position given in the second parameter. fn get_slice_internal( &mut self, len: usize, mut f: impl FnMut(I::Item, usize) -> (I::Item, I::Item), ) -> Option<I::Item> where I::Item: Deref<Target = [u8]>, { match self.cur_slice.take() { None => None, Some(cur_slice) => { if len >= cur_slice.len() { // Caller requested more data than is in the current slice, return it entirely // and prepare the following slice for being used. Skip empty slices to avoid // trouble. self.cur_slice = self.slices.find(|s| !s.is_empty());
Some(cur_slice) } else { // The current slice can satisfy the request, split it and return a slice of // the requested size. let (ret, next) = f(cur_slice, len); self.cur_slice = Some(next);
Some(ret) } } } }
/// Returns whether this buffer still has data available. pub(crate) fn is_empty(&self) -> bool { self.cur_slice.is_none() }}
/// Provides a way to get non-mutable slices of data to read from.impl<'a, I> SBufferIter<I>where I: Iterator<Item = &'a [u8]>,{ /// Returns a slice of at most `len` bytes, or [`None`] if we are at the end of the data. /// /// If a slice shorter than `len` bytes has been returned, the caller can call this method /// again until it returns [`None`] to try and obtain the remainder of the data. fn get_slice(&mut self, len: usize) -> Option<&'a [u8]> { self.get_slice_internal(len, |s, pos| s.split_at(pos)) }
/// Ideally we would implement `Read`, but it is not available in `core`. /// So mimic `std::io::Read::read_exact`. #[expect(unused)] pub(crate) fn read_exact(&mut self, mut dst: &mut [u8]) -> Result { while !dst.is_empty() { match self.get_slice(dst.len()) { None => return Err(EINVAL), Some(src) => { let dst_slice; (dst_slice, dst) = dst.split_at_mut(src.len()); dst_slice.copy_from_slice(src); } } }
Ok(()) }
/// Read all the remaining data into a [`KVec`]. /// /// `self` will be empty after this operation. pub(crate) fn flush_into_kvec(&mut self, flags: kernel::alloc::Flags) -> Result<KVec<u8>> { let mut buf = KVec::<u8>::new();
if let Some(slice) = core::mem::take(&mut self.cur_slice) { buf.extend_from_slice(slice, flags)?; } for slice in &mut self.slices { buf.extend_from_slice(slice, flags)?; }
Ok(buf) }}
/// Provides a way to get mutable slices of data to write into.impl<'a, I> SBufferIter<I>where I: Iterator<Item = &'a mut [u8]>,{ /// Returns a mutable slice of at most `len` bytes, or [`None`] if we are at the end of the /// data. /// /// If a slice shorter than `len` bytes has been returned, the caller can call this method /// again until it returns `None` to try and obtain the remainder of the data. fn get_slice_mut(&mut self, len: usize) -> Option<&'a mut [u8]> { self.get_slice_internal(len, |s, pos| s.split_at_mut(pos)) }
/// Ideally we would implement [`Write`], but it is not available in `core`. /// So mimic `std::io::Write::write_all`. pub(crate) fn write_all(&mut self, mut src: &[u8]) -> Result { while !src.is_empty() { match self.get_slice_mut(src.len()) { None => return Err(ETOOSMALL), Some(dst) => { let src_slice; (src_slice, src) = src.split_at(dst.len()); dst.copy_from_slice(src_slice); } } }
Ok(()) }}
impl<'a, I> Iterator for SBufferIter<I>where I: Iterator<Item = &'a [u8]>,{ type Item = u8;
fn next(&mut self) -> Option<Self::Item> { // Returned slices are guaranteed to not be empty so we can safely index the first entry. self.get_slice(1).map(|s| s[0]) }}