// 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 arrow_buffer::{bit_util, ArrowNativeType, MutableBuffer};

use num::{CheckedAdd, Integer};

/// extends the `buffer` to be able to hold `len` bits, setting all bits of the new size to zero.

#[inline]

pub(super) fn resize_for_bits(buffer: &mut MutableBuffer, len: usize) {

    let needed_bytes = bit_util::ceil(len, 8);

    if buffer.len() < needed_bytes {

        buffer.resize(needed_bytes, 0);

    }

}

pub(super) fn extend_offsets<T: ArrowNativeType + Integer + CheckedAdd>(

    buffer: &mut MutableBuffer,

    mut last_offset: T,

    offsets: &[T],

) {

    buffer.reserve(std::mem::size_of_val(offsets));

    
offsets21
.
windows21
(2).
for_each21
(|offsets| {

        // compute the new offset

        let length = offsets[1] - offsets[0];

        // if you hit this appending to a StringArray / BinaryArray it is because you

        // are trying to add more data than can fit into that type. Try breaking your data into

        // smaller batches or using LargeStringArray / LargeBinaryArray

        last_offset = last_offset.checked_add(&length).expect("offset overflow");

        buffer.push(last_offset);

    });

}

#[inline]

pub(super) unsafe fn get_last_offset<T: ArrowNativeType>(offset_buffer: &MutableBuffer) -> T {

    // JUSTIFICATION

    //  Benefit

    //      20% performance improvement extend of variable sized arrays (see bench `mutable_array`)

    //  Soundness

    //      * offset buffer is always extended in slices of T and aligned accordingly.

    //      * Buffer[0] is initialized with one element, 0, and thus `mutable_offsets.len() - 1` is always valid.

    let (prefix, offsets, suffix) = offset_buffer.as_slice().align_to::<T>();

    debug_assert!(prefix.is_empty() && suffix.is_empty());

    *offsets.get_unchecked(offsets.len() - 1)

}

#[cfg(test)]

mod tests {

    use crate::transform::utils::extend_offsets;

    use arrow_buffer::MutableBuffer;

    #[test]

    #[should_panic(expected = "offset overflow")]

    fn test_overflow() {

        let mut buffer = MutableBuffer::new(10);

        extend_offsets(&mut buffer, i32::MAX - 4, &[0, 5]);

    }

}