arrow_data/transform/
utils.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use arrow_buffer::{ArrowNativeType, MutableBuffer, bit_util};
19use num_integer::Integer;
20use num_traits::CheckedAdd;
21
22/// extends the `buffer` to be able to hold `len` bits, setting all bits of the new size to zero.
23#[inline]
24pub(super) fn resize_for_bits(buffer: &mut MutableBuffer, len: usize) {
25    let needed_bytes = bit_util::ceil(len, 8);
26    if buffer.len() < needed_bytes {
27        buffer.resize(needed_bytes, 0);
28    }
29}
30
31pub(super) fn extend_offsets<T: ArrowNativeType + Integer + CheckedAdd>(
32    buffer: &mut MutableBuffer,
33    mut last_offset: T,
34    offsets: &[T],
35) {
36    buffer.reserve(std::mem::size_of_val(offsets));
37    offsets.windows(2).for_each(|offsets| {
38        // compute the new offset
39        let length = offsets[1] - offsets[0];
40        // if you hit this appending to a StringArray / BinaryArray it is because you
41        // are trying to add more data than can fit into that type. Try breaking your data into
42        // smaller batches or using LargeStringArray / LargeBinaryArray
43        last_offset = last_offset.checked_add(&length).expect("offset overflow");
44        buffer.push(last_offset);
45    });
46}
47
48#[inline]
49pub(super) unsafe fn get_last_offset<T: ArrowNativeType>(offset_buffer: &MutableBuffer) -> T {
50    // JUSTIFICATION
51    //  Benefit
52    //      20% performance improvement extend of variable sized arrays (see bench `mutable_array`)
53    //  Soundness
54    //      * offset buffer is always extended in slices of T and aligned accordingly.
55    //      * Buffer[0] is initialized with one element, 0, and thus `mutable_offsets.len() - 1` is always valid.
56    let (prefix, offsets, suffix) = unsafe { offset_buffer.as_slice().align_to::<T>() };
57    debug_assert!(prefix.is_empty() && suffix.is_empty());
58    *unsafe { offsets.get_unchecked(offsets.len() - 1) }
59}
60
61#[cfg(test)]
62mod tests {
63    use crate::transform::utils::extend_offsets;
64    use arrow_buffer::MutableBuffer;
65
66    #[test]
67    #[should_panic(expected = "offset overflow")]
68    fn test_overflow() {
69        let mut buffer = MutableBuffer::new(10);
70        extend_offsets(&mut buffer, i32::MAX - 4, &[0, 5]);
71    }
72}
arrow_data/transform/utils.rs

arrow_data/transform/
utils.rs
