diff --git a/library/std/src/io/impls.rs b/library/std/src/io/impls.rs index 85023540a816f..e388d783f111a 100644 --- a/library/std/src/io/impls.rs +++ b/library/std/src/io/impls.rs @@ -453,6 +453,29 @@ impl Read for VecDeque { Ok(n) } + fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> { + let (front, back) = self.as_slices(); + + // Use only the front buffer is big enough to fill `buf`, else use the + // back buffer too if it is big enough + match buf.split_at_mut_checked(front.len()) { + None => buf.copy_from_slice(&front[..buf.len()]), + Some((buf_front, buf_back)) => match back.split_at_checked(buf_back.len()) { + Some((back, _)) => { + buf_front.copy_from_slice(front); + buf_back.copy_from_slice(back); + } + None => { + self.clear(); + return Err(io::Error::READ_EXACT_EOF); + } + }, + } + + self.drain(..buf.len()); + Ok(()) + } + #[inline] fn read_buf(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> { let (ref mut front, _) = self.as_slices(); @@ -462,6 +485,29 @@ impl Read for VecDeque { Ok(()) } + fn read_buf_exact(&mut self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> { + let len = cursor.capacity(); + let (front, back) = self.as_slices(); + + match front.split_at_checked(cursor.capacity()) { + Some((front, _)) => cursor.append(front), + None => { + cursor.append(front); + match back.split_at_checked(cursor.capacity()) { + Some((back, _)) => cursor.append(back), + None => { + cursor.append(back); + self.clear(); + return Err(io::Error::READ_EXACT_EOF); + } + } + } + } + + self.drain(..len); + Ok(()) + } + #[inline] fn read_to_end(&mut self, buf: &mut Vec) -> io::Result { // The total len is known upfront so we can reserve it in a single call.