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Remove bound checks from BorrowedBuf and BorrowedCursor methods #123786

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Merged
merged 1 commit into from
May 19, 2024
Merged

Remove bound checks from BorrowedBuf and BorrowedCursor methods #123786

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24 changes: 18 additions & 6 deletions library/core/src/io/borrowed_buf.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -92,14 +92,20 @@ impl<'data> BorrowedBuf<'data> {
#[inline]
pub fn filled(&self) -> &[u8] {
// 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.
#[inline]
pub fn filled_mut(&mut self) -> &mut [u8] {
// 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.
Expand Down Expand Up @@ -205,15 +211,19 @@ impl<'a> BorrowedCursor<'a> {
#[inline]
pub fn init_ref(&self) -> &[u8] {
// 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.
#[inline]
pub fn init_mut(&mut self) -> &mut [u8] {
// SAFETY: We only slice the initialized part of the buffer, which is always valid
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)
}
}

Expand All @@ -222,7 +232,8 @@ impl<'a> BorrowedCursor<'a> {
/// It is safe to uninitialize any of these bytes.
#[inline]
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.
Expand All @@ -232,7 +243,8 @@ impl<'a> BorrowedCursor<'a> {
/// The caller must not uninitialize any bytes in the initialized portion of the cursor.
#[inline]
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.
Expand Down
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