arrow 19.0.0

Rust implementation of Apache Arrow
Documentation 
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// 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::{Buffer, MutableBuffer};
use crate::util::bit_util::ceil;

/// Apply a bitwise operation `op` to two inputs and return the result as a Buffer.
/// The inputs are treated as bitmaps, meaning that offsets and length are specified in number of bits.
pub fn bitwise_bin_op_helper<F>(
    left: &Buffer,
    left_offset_in_bits: usize,
    right: &Buffer,
    right_offset_in_bits: usize,
    len_in_bits: usize,
    op: F,
) -> Buffer
where
    F: Fn(u64, u64) -> u64,
{
    let left_chunks = left.bit_chunks(left_offset_in_bits, len_in_bits);
    let right_chunks = right.bit_chunks(right_offset_in_bits, len_in_bits);

    let chunks = left_chunks
        .iter()
        .zip(right_chunks.iter())
        .map(|(left, right)| op(left, right));
    // Soundness: `BitChunks` is a `BitChunks` iterator which
    // correctly reports its upper bound
    let mut buffer = unsafe { MutableBuffer::from_trusted_len_iter(chunks) };

    let remainder_bytes = ceil(left_chunks.remainder_len(), 8);
    let rem = op(left_chunks.remainder_bits(), right_chunks.remainder_bits());
    // we are counting its starting from the least significant bit, to to_le_bytes should be correct
    let rem = &rem.to_le_bytes()[0..remainder_bytes];
    buffer.extend_from_slice(rem);

    buffer.into()
}

/// Apply a bitwise operation `op` to one input and return the result as a Buffer.
/// The input is treated as a bitmap, meaning that offset and length are specified in number of bits.
pub fn bitwise_unary_op_helper<F>(
    left: &Buffer,
    offset_in_bits: usize,
    len_in_bits: usize,
    op: F,
) -> Buffer
where
    F: Fn(u64) -> u64,
{
    // reserve capacity and set length so we can get a typed view of u64 chunks
    let mut result =
        MutableBuffer::new(ceil(len_in_bits, 8)).with_bitset(len_in_bits / 64 * 8, false);

    let left_chunks = left.bit_chunks(offset_in_bits, len_in_bits);

    let result_chunks = result.typed_data_mut::<u64>().iter_mut();

    result_chunks
        .zip(left_chunks.iter())
        .for_each(|(res, left)| {
            *res = op(left);
        });

    let remainder_bytes = ceil(left_chunks.remainder_len(), 8);
    let rem = op(left_chunks.remainder_bits());
    // we are counting its starting from the least significant bit, to to_le_bytes should be correct
    let rem = &rem.to_le_bytes()[0..remainder_bytes];
    result.extend_from_slice(rem);

    result.into()
}

pub fn buffer_bin_and(
    left: &Buffer,
    left_offset_in_bits: usize,
    right: &Buffer,
    right_offset_in_bits: usize,
    len_in_bits: usize,
) -> Buffer {
    bitwise_bin_op_helper(
        left,
        left_offset_in_bits,
        right,
        right_offset_in_bits,
        len_in_bits,
        |a, b| a & b,
    )
}

pub fn buffer_bin_or(
    left: &Buffer,
    left_offset_in_bits: usize,
    right: &Buffer,
    right_offset_in_bits: usize,
    len_in_bits: usize,
) -> Buffer {
    bitwise_bin_op_helper(
        left,
        left_offset_in_bits,
        right,
        right_offset_in_bits,
        len_in_bits,
        |a, b| a | b,
    )
}

pub fn buffer_unary_not(
    left: &Buffer,
    offset_in_bits: usize,
    len_in_bits: usize,
) -> Buffer {
    bitwise_unary_op_helper(left, offset_in_bits, len_in_bits, |a| !a)
}