Function zero_tail

nodedb-wal/src/double_write.rs:422–432

Fill the unwritten tail of `buf` with zero bytes so an O_DIRECT write of the entire aligned slot does not leak stale buffer contents to disk.

(buf: &mut AlignedBuf)

/// Fill the unwritten tail of `buf` with zero bytes so an O_DIRECT write of
/// the entire aligned slot does not leak stale buffer contents to disk.
fn zero_tail(buf: &mut AlignedBuf) {
    let written = buf.len();
    let cap = buf.capacity();
    if written < cap {
        // SAFETY: `as_mut_ptr` is valid for `capacity` bytes; we write only
        // the uninitialized tail between `written..capacity`.
        unsafe {
            std::ptr::write_bytes(buf.as_mut_ptr().add(written), 0, cap - written);
        }
    }
}

/// View the entire allocated capacity of `buf` as a byte slice. Requires
/// that the caller has zeroed any unwritten tail (see `zero_tail`).