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Auto merge of #123786 - a1phyr:cursor_unsafe, r=joboet

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Remove bound checks from `BorrowedBuf` and `BorrowedCursor` methods
This commit is contained in:
bors 2024-05-19 17:16:12 +00:00
commit 959a67a7f2
1 changed files with 18 additions and 6 deletions
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24
library/core/src/io/borrowed_buf.rs
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@ -92,14 +92,20 @@ pub fn init_len(&self) -> usize {
#[inline] #[inline]
pub fn filled(&self) -> &[u8] { pub fn filled(&self) -> &[u8] {
// SAFETY: We only slice the filled part of the buffer, which is always valid // SAFETY: We only slice the filled part of the buffer, which is always valid
unsafe { MaybeUninit::slice_assume_init_ref(&self.buf[0..self.filled]) } unsafe {
let buf = self.buf.get_unchecked(..self.filled);
MaybeUninit::slice_assume_init_ref(buf)
}
} }
/// Returns a mutable reference to the filled portion of the buffer. /// Returns a mutable reference to the filled portion of the buffer.
#[inline] #[inline]
pub fn filled_mut(&mut self) -> &mut [u8] { pub fn filled_mut(&mut self) -> &mut [u8] {
// SAFETY: We only slice the filled part of the buffer, which is always valid // SAFETY: We only slice the filled part of the buffer, which is always valid
unsafe { MaybeUninit::slice_assume_init_mut(&mut self.buf[0..self.filled]) } unsafe {
let buf = self.buf.get_unchecked_mut(..self.filled);
MaybeUninit::slice_assume_init_mut(buf)
}
} }
/// Returns a cursor over the unfilled part of the buffer. /// Returns a cursor over the unfilled part of the buffer.
@ -205,7 +211,10 @@ pub fn written(&self) -> usize {
#[inline] #[inline]
pub fn init_ref(&self) -> &[u8] { pub fn init_ref(&self) -> &[u8] {
// SAFETY: We only slice the initialized part of the buffer, which is always valid // SAFETY: We only slice the initialized part of the buffer, which is always valid
unsafe { MaybeUninit::slice_assume_init_ref(&self.buf.buf[self.buf.filled..self.buf.init]) } unsafe {
let buf = self.buf.buf.get_unchecked(self.buf.filled..self.buf.init);
MaybeUninit::slice_assume_init_ref(buf)
}
} }
/// Returns a mutable reference to the initialized portion of the cursor. /// Returns a mutable reference to the initialized portion of the cursor.
@ -213,7 +222,8 @@ pub fn init_ref(&self) -> &[u8] {
pub fn init_mut(&mut self) -> &mut [u8] { pub fn init_mut(&mut self) -> &mut [u8] {
// SAFETY: We only slice the initialized part of the buffer, which is always valid // SAFETY: We only slice the initialized part of the buffer, which is always valid
unsafe { unsafe {
MaybeUninit::slice_assume_init_mut(&mut self.buf.buf[self.buf.filled..self.buf.init]) let buf = self.buf.buf.get_unchecked_mut(self.buf.filled..self.buf.init);
MaybeUninit::slice_assume_init_mut(buf)
} }
} }
@ -222,7 +232,8 @@ pub fn init_mut(&mut self) -> &mut [u8] {
/// It is safe to uninitialize any of these bytes. /// It is safe to uninitialize any of these bytes.
#[inline] #[inline]
pub fn uninit_mut(&mut self) -> &mut [MaybeUninit<u8>] { pub fn uninit_mut(&mut self) -> &mut [MaybeUninit<u8>] {
&mut self.buf.buf[self.buf.init..] // SAFETY: always in bounds
unsafe { self.buf.buf.get_unchecked_mut(self.buf.init..) }
} }
/// Returns a mutable reference to the whole cursor. /// Returns a mutable reference to the whole cursor.
@ -232,7 +243,8 @@ pub fn uninit_mut(&mut self) -> &mut [MaybeUninit<u8>] {
/// The caller must not uninitialize any bytes in the initialized portion of the cursor. /// The caller must not uninitialize any bytes in the initialized portion of the cursor.
#[inline] #[inline]
pub unsafe fn as_mut(&mut self) -> &mut [MaybeUninit<u8>] { pub unsafe fn as_mut(&mut self) -> &mut [MaybeUninit<u8>] {
&mut self.buf.buf[self.buf.filled..] // SAFETY: always in bounds
unsafe { self.buf.buf.get_unchecked_mut(self.buf.filled..) }
} }
/// Advance the cursor by asserting that `n` bytes have been filled. /// Advance the cursor by asserting that `n` bytes have been filled.