Function apply_bitwise_binary_op

arrow-buffer/src/util/bit_util.rs:199–271

Applies a bitwise operation relative to another bit-packed byte slice (right) in place Note: applies the operation 64-bits (u64) at a time. # Arguments `left` - The mutable buffer to be modified in-place `offset_in_bits` - Starting bit offset in Self buffer `right` - slice of bit-packed bytes in LSB order `right_offset_in_bits` - Starting bit offset in the right buffer `len_in_bits` - Number of

(
    left: &mut [u8],
    left_offset_in_bits: usize,
    right: impl AsRef<[u8]>,
    right_offset_in_bits: usize,
    len_in_bits: usize,
    mut op: F,
)

///
/// If the offset or lengths exceed the buffer or slice size.
pub fn apply_bitwise_binary_op<F>(
    left: &mut [u8],
    left_offset_in_bits: usize,
    right: impl AsRef<[u8]>,
    right_offset_in_bits: usize,
    len_in_bits: usize,
    mut op: F,
) where
    F: FnMut(u64, u64) -> u64,
{
    if len_in_bits == 0 {
        return;
    }

    // offset inside a byte
    let bit_offset = left_offset_in_bits % 8;

    let is_mutable_buffer_byte_aligned = bit_offset == 0;

    if is_mutable_buffer_byte_aligned {
        byte_aligned_bitwise_bin_op_helper(
            left,
            left_offset_in_bits,
            right,
            right_offset_in_bits,
            len_in_bits,
            op,
        );
    } else {
        // If we are not byte aligned, run `op` on the first few bits to reach byte alignment
        let bits_to_next_byte = (8 - bit_offset)
            // Minimum with the amount of bits we need to process
            // to avoid reading out of bounds
            .min(len_in_bits);

        {
            let right_byte_offset = right_offset_in_bits / 8;

            // Read the same amount of bits from the right buffer
            let right_first_byte: u8 = crate::util::bit_util::read_up_to_byte_from_offset(
                &right.as_ref()[right_byte_offset..],
                bits_to_next_byte,
                // Right bit offset
                right_offset_in_bits % 8,
            );

            align_to_byte(
                left,
                // Hope it gets inlined
                &mut |left| op(left, right_first_byte as u64),
                left_offset_in_bits,
            );
        }

        let offset_in_bits = left_offset_in_bits + bits_to_next_byte;
        let right_offset_in_bits = right_offset_in_bits + bits_to_next_byte;
        let len_in_bits = len_in_bits.saturating_sub(bits_to_next_byte);