pub fn peek(&self) -> &[u8] {
        let (slice, _) = self.peek_internal(false);
        slice
    }
Returns a slice into the buffer containing available data.
This will be the longest possible contiguous slice into the buffer that
contains data that is available to read.

Note: This function ignores EOFs, see [Self::peek_until_eof] if you need
EOF support.
esp-hal/src/dma/buffers.rs