Function advance

src/fs/file_io_ext.rs:342–369

This will be obviated by [rust-lang/rust#62726]. [rust-lang/rust#62726]: https://github.com/rust-lang/rust/issues/62726.

(bufs: &'b mut [IoSlice<'a>], n: usize)

///
/// [rust-lang/rust#62726]: https://github.com/rust-lang/rust/issues/62726.
fn advance<'a, 'b>(bufs: &'b mut [IoSlice<'a>], n: usize) -> &'b mut [IoSlice<'a>] {
    // Number of buffers to remove.
    let mut remove = 0;
    // Total length of all the to be removed buffers.
    let mut accumulated_len = 0;
    for buf in bufs.iter() {
        if accumulated_len + buf.len() > n {
            break;
        } else {
            accumulated_len += buf.len();
            remove += 1;
        }
    }

    #[allow(clippy::indexing_slicing)]
    let bufs = &mut bufs[remove..];
    if let Some(first) = bufs.first_mut() {
        let advance_by = n - accumulated_len;
        let mut ptr = first.as_ptr();
        let mut len = first.len();
        unsafe {
            ptr = ptr.add(advance_by);
            len -= advance_by;
            *first = IoSlice::<'a>::new(slice::from_raw_parts::<'a>(ptr, len));
        }
    }
    bufs
}

/// This will be obviated by [rust-lang/rust#62726].
///