arrow-data/src/transform/list.rs

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

use super::{
    _MutableArrayData, Extend,
    utils::{extend_offsets, get_last_offset},
};
use crate::ArrayData;
use arrow_buffer::ArrowNativeType;
use num_integer::Integer;
use num_traits::CheckedAdd;

pub(super) fn build_extend<T: ArrowNativeType + Integer + CheckedAdd>(
    array: &ArrayData,
) -> Extend<'_> {
    let offsets = array.buffer::<T>(0);
    Box::new(
        move |mutable: &mut _MutableArrayData, index: usize, start: usize, len: usize| {
            let offset_buffer = &mut mutable.buffer1;

            // this is safe due to how offset is built. See details on `get_last_offset`
            let last_offset: T = unsafe { get_last_offset(offset_buffer) };

            // offsets
            extend_offsets::<T>(offset_buffer, last_offset, &offsets[start..start + len + 1]);

            mutable.child_data[0].extend(
                index,
                offsets[start].as_usize(),
                offsets[start + len].as_usize(),
            )
        },
    )
}

pub(super) fn extend_nulls<T: ArrowNativeType>(mutable: &mut _MutableArrayData, len: usize) {
    let offset_buffer = &mut mutable.buffer1;

    // this is safe due to how offset is built. See details on `get_last_offset`
    let last_offset: T = unsafe { get_last_offset(offset_buffer) };

    (0..len).for_each(|_| offset_buffer.push(last_offset))
}