Method copy_view_to_buffer

arrow-array/src/array/byte_view_array.rs:642–671

(
        &self,
        i: usize,
        buffer_idx: i32,
        data_buf: &mut Vec<u8>,
    )

    ///   into the bytes just appended at the end of `data_buf`.
    #[inline(always)]
    unsafe fn copy_view_to_buffer(
        &self,
        i: usize,
        buffer_idx: i32,
        data_buf: &mut Vec<u8>,
    ) -> u128 {
        // SAFETY: `i < self.len()` ensures this is in‑bounds.
        let raw_view = unsafe { *self.views().get_unchecked(i) };
        let mut bv = ByteView::from(raw_view);

        // Inline‑small views stay as‑is.
        if bv.length <= MAX_INLINE_VIEW_LEN {
            raw_view
        } else {
            // SAFETY: `bv.buffer_index` and `bv.offset..bv.offset+bv.length`
            // must both lie within valid ranges for `self.buffers`.
            let buffer = unsafe { self.buffers.get_unchecked(bv.buffer_index as usize) };
            let start = bv.offset as usize;
            let end = start + bv.length as usize;
            let slice = unsafe { buffer.get_unchecked(start..end) };

            // Copy out‑of‑line data into our single “0” buffer.
            let new_offset = data_buf.len() as u32;
            data_buf.extend_from_slice(slice);

            bv.buffer_index = buffer_idx as u32;
            bv.offset = new_offset;
            bv.into()
        }
    }

    /// Returns the total number of bytes of all non-null values in this array.
    ///