rluvaton commented on code in PR #8619: URL: https://github.com/apache/arrow-rs/pull/8619#discussion_r2464104526
########## arrow-buffer/src/buffer/mutable_ops.rs: ########## @@ -0,0 +1,1256 @@ +// 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::BooleanBufferBuilder; +use crate::bit_chunk_iterator::BitChunks; +use crate::util::bit_util; + +/// What can be used as the right-hand side (RHS) buffer in mutable operations. +/// +/// this is not mutated. +/// +/// # Implementation notes +/// +/// ## Why `pub(crate)`? +/// This is because we don't want this trait to expose the inner buffer to the public. +/// this is the trait implementor choice. +/// +pub(crate) trait BufferSupportedRhs { + fn as_slice(&self) -> &[u8]; +} + +impl BufferSupportedRhs for Buffer { + fn as_slice(&self) -> &[u8] { + self.as_slice() + } +} + +impl BufferSupportedRhs for MutableBuffer { + fn as_slice(&self) -> &[u8] { + self.as_slice() + } +} + +impl BufferSupportedRhs for BooleanBufferBuilder { + fn as_slice(&self) -> &[u8] { + self.as_slice() + } +} + +/// Trait that will be operated on as the left-hand side (LHS) buffer in mutable operations. +/// +/// This consumer of the trait must satisfies the following guarantees: +/// 1. It will not change the length of the buffer. +/// +/// # Implementation notes +/// +/// ## Why is this trait `pub(crate)`? +/// Because we don't wanna expose the inner mutable buffer to the public. +/// as this is the choice of the implementor of the trait and sometimes it is not desirable +/// (e.g. `BooleanBufferBuilder`). +/// +/// ## Why this trait is needed, can't we just use `MutableBuffer` directly? +/// Sometimes we don't want to expose the inner `MutableBuffer` +/// so it can't be misused. +/// +/// For example, [`BooleanBufferBuilder`] does not expose the inner `MutableBuffer` +/// as exposing it will allow the user to change the length of the buffer that will make the +/// `BooleanBufferBuilder` invalid. +/// +pub(crate) trait MutableOpsBufferSupportedLhs { + /// Get a mutable reference to the inner `MutableBuffer`. + /// + /// This is used to perform in-place operations on the buffer. + /// + /// the caller must ensure that the length of the buffer is not changed. + fn inner_mutable_buffer(&mut self) -> &mut MutableBuffer; +} + +impl MutableOpsBufferSupportedLhs for MutableBuffer { + fn inner_mutable_buffer(&mut self) -> &mut MutableBuffer { + self + } +} + +/// Apply a binary bitwise operation to two bit-packed buffers. +/// +/// This is the main entry point for binary operations. It handles both byte-aligned +/// and non-byte-aligned cases by delegating to specialized helper functions. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer to be modified in-place +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer (as byte slice) +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +/// * `op` - Binary operation to apply (e.g., `|a, b| a & b`) +/// +#[allow( + private_bounds, + reason = "MutableOpsBufferSupportedLhs and BufferSupportedRhs exposes the inner internals which is the implementor choice and we dont want to leak internals" +)] +pub fn mutable_bitwise_bin_op_helper<F>( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, + mut op: F, +) where + F: FnMut(u64, u64) -> u64, +{ + if len_in_bits == 0 { + return; + } + + let mutable_buffer = left.inner_mutable_buffer(); + + let mutable_buffer_len = mutable_buffer.len(); + let mutable_buffer_cap = mutable_buffer.capacity(); + + // offset inside a byte + let left_bit_offset = left_offset_in_bits % 8; + + let is_mutable_buffer_byte_aligned = left_bit_offset == 0; + + if is_mutable_buffer_byte_aligned { Review Comment: in order to be `u128` we would want to change the function to get `u128`, but I wanted to keep similar API to `Buffer` ops. do you think we should change it? and the special case can be added later -- This is an automated message from the Apache Git Service. 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