alamb commented on code in PR #8619: URL: https://github.com/apache/arrow-rs/pull/8619#discussion_r2440154447
########## 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 { + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + 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 - left_bit_offset; + + { + let right_byte_offset = right_offset_in_bits / 8; + + // Read the same amount of bits from the right buffer + let right_first_byte: u8 = read_up_to_byte_from_offset( + &right.as_slice()[right_byte_offset..], + bits_to_next_byte, + // Right bit offset + right_offset_in_bits % 8, + ); + + align_to_byte( + // Hope it gets inlined + &mut |left| op(left, right_first_byte as u64), + mutable_buffer, + left_offset_in_bits, + ); + } + + let left_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); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned Review Comment: I don't understand how you can byte align the operations if they both have an offset For example if you had `lhs_offset=1` and `rhs_offset=2` how can you byte align that operation? It seems like it would requires shifting each byte / word to get alignment and then handling the remaining bits as edge cases 🤔 However, your tests seem to cover this case ########## 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: is it worth special casing the case where both left_offset and right_offset are zero? In that case a simple loop that compared `u64` by `u64` is probably fastest (maybe even `u128` 🤔 ) ########## arrow-buffer/src/builder/boolean.rs: ########## @@ -258,6 +262,133 @@ impl BooleanBufferBuilder { } } +/// This trait is not public API so it does not leak the inner mutable buffer +impl MutableOpsBufferSupportedLhs for BooleanBufferBuilder { + fn inner_mutable_buffer(&mut self) -> &mut MutableBuffer { + &mut self.buffer + } +} + +impl Not for BooleanBufferBuilder { + type Output = BooleanBufferBuilder; + + fn not(mut self) -> Self::Output { + mutable_buffer_unary_not(&mut self.buffer, 0, self.len); + Self { + buffer: self.buffer, + len: self.len, + } + } +} + +impl BitAnd<&BooleanBuffer> for BooleanBufferBuilder { + type Output = BooleanBufferBuilder; + + fn bitand(mut self, rhs: &BooleanBuffer) -> Self::Output { + self &= rhs; + + self + } +} + +impl BitAnd<&BooleanBufferBuilder> for BooleanBufferBuilder { + type Output = BooleanBufferBuilder; + + fn bitand(mut self, rhs: &BooleanBufferBuilder) -> Self::Output { + self &= rhs; + + self + } +} + +impl BitAndAssign<&BooleanBuffer> for BooleanBufferBuilder { + fn bitand_assign(&mut self, rhs: &BooleanBuffer) { + assert_eq!(self.len, rhs.len()); Review Comment: it might be nice to document somewhere that using the bitwise operators on BooleanBuffer/Builders with the different lengths will panic ########## 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 { + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + 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 - left_bit_offset; + + { + let right_byte_offset = right_offset_in_bits / 8; + + // Read the same amount of bits from the right buffer + let right_first_byte: u8 = read_up_to_byte_from_offset( + &right.as_slice()[right_byte_offset..], + bits_to_next_byte, + // Right bit offset + right_offset_in_bits % 8, + ); + + align_to_byte( + // Hope it gets inlined + &mut |left| op(left, right_first_byte as u64), + mutable_buffer, + left_offset_in_bits, + ); + } + + let left_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); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + op, + ); + } + + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); +} + +/// Align to byte boundary by applying operation to bits before the next byte boundary. +/// +/// This function handles non-byte-aligned operations by processing bits from the current +/// position up to the next byte boundary, while preserving all other bits in the byte. +/// +/// # Arguments +/// +/// * `op` - Unary operation to apply +/// * `buffer` - The mutable buffer to modify +/// * `offset_in_bits` - Starting bit offset (not byte-aligned) +fn align_to_byte<F>(op: &mut F, buffer: &mut MutableBuffer, offset_in_bits: usize) +where + F: FnMut(u64) -> u64, +{ + let byte_offset = offset_in_bits / 8; + let bit_offset = offset_in_bits % 8; + + // 1. read the first byte from the buffer + let first_byte: u8 = buffer.as_slice()[byte_offset]; + + // 2. Shift byte by the bit offset, keeping only the relevant bits + let relevant_first_byte = first_byte >> bit_offset; + + // 3. run the op on the first byte only + let result_first_byte = op(relevant_first_byte as u64) as u8; + + // 4. Shift back the result to the original position + let result_first_byte = result_first_byte << bit_offset; + + // 5. Mask the bits that are outside the relevant bits in the byte + // so the bits until bit_offset are 1 and the rest are 0 + let mask_for_first_bit_offset = (1 << bit_offset) - 1; + + let result_first_byte = + (first_byte & mask_for_first_bit_offset) | (result_first_byte & !mask_for_first_bit_offset); + + // 6. write back the result to the buffer + buffer.as_slice_mut()[byte_offset] = result_first_byte; +} + +/// Read up to 8 bits from a byte slice starting at a given bit offset. +/// +/// This is similar to `get_8_bits_from_offset` but works with raw byte slices +/// and can read fewer than 8 bits. +/// +/// # Arguments +/// +/// * `slice` - The byte slice to read from +/// * `number_of_bits_to_read` - Number of bits to read (must be ≤ 8) +/// * `bit_offset` - Starting bit offset within the first byte +/// +/// # Returns +/// +/// A u8 containing the requested bits in the least significant positions +#[inline] +fn read_up_to_byte_from_offset( + slice: &[u8], + number_of_bits_to_read: usize, + bit_offset: usize, +) -> u8 { + assert!(number_of_bits_to_read <= 8); + assert_ne!(number_of_bits_to_read, 0); + assert_ne!(slice.len(), 0); + + let number_of_bytes_to_read = bit_util::ceil(number_of_bits_to_read + bit_offset, 8); + + // number of bytes to read + // might be one more than sizeof(u64) if the offset is in the middle of a byte + assert!(slice.len() >= number_of_bytes_to_read); + + let mut bits = slice[0] >> bit_offset; + for (i, &byte) in slice + .iter() + .take(number_of_bytes_to_read) + .enumerate() + .skip(1) + { + bits |= byte << (i * 8 - bit_offset); + } + + bits & ((1 << number_of_bits_to_read) - 1) +} + +/// Perform bitwise binary operation on byte-aligned buffers (i.e. not offsetting into a middle of a byte). +/// +/// This is the optimized path for byte-aligned operations. It processes data in +/// u64 chunks for maximum efficiency, then handles any remainder bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (must be byte-aligned) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer (must be multiple of 8) +/// * `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 +#[inline] +fn mutable_buffer_byte_aligned_bitwise_bin_op_helper<F>( + left: &mut MutableBuffer, + 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, +{ + // Must not reach here if we not byte aligned + assert_eq!( + left_offset_in_bits % 8, + 0, + "left_offset_in_bits must be byte aligned" + ); + + // 1. Prepare the buffers + let (complete_u64_chunks, remainder_bytes) = + U64UnalignedSlice::split(left, left_offset_in_bits, len_in_bits); + + let right_chunks = BitChunks::new(right.as_slice(), right_offset_in_bits, len_in_bits); + assert_eq!( + bit_util::ceil(right_chunks.remainder_len(), 8), + remainder_bytes.len() + ); + + let right_chunks_iter = right_chunks.iter(); + assert_eq!(right_chunks_iter.len(), complete_u64_chunks.len()); + + // 2. Process complete u64 chunks + complete_u64_chunks.zip_modify(right_chunks_iter, &mut op); + + // Handle remainder bits if any + if right_chunks.remainder_len() > 0 { + handle_mutable_buffer_remainder( + &mut op, + remainder_bytes, + right_chunks.remainder_bits(), + right_chunks.remainder_len(), + ) + } +} + +/// Centralized structure to handle a mutable u8 slice as a mutable u64 pointer. +/// +/// Handle the following: +/// 1. the lifetime is correct +/// 2. we read/write within the bounds +/// 3. We read and write using unaligned +/// +/// This does not deallocate the underlying pointer when dropped +/// +/// This is the only place that uses unsafe code to read and write unaligned +/// +struct U64UnalignedSlice<'a> { + /// Pointer to the start of the u64 data + /// + /// We are using raw pointer as the data came from a u8 slice so we need to read and write unaligned Review Comment: Rather than using Unsafe, would it make sense to align the pointer to `u64` instead And handle any starting / ending bytes that were not u64 aligned specially? That might make the code simpler / faster ########## 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 { + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + 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 - left_bit_offset; + + { + let right_byte_offset = right_offset_in_bits / 8; + + // Read the same amount of bits from the right buffer + let right_first_byte: u8 = read_up_to_byte_from_offset( + &right.as_slice()[right_byte_offset..], + bits_to_next_byte, + // Right bit offset + right_offset_in_bits % 8, + ); + + align_to_byte( + // Hope it gets inlined + &mut |left| op(left, right_first_byte as u64), + mutable_buffer, + left_offset_in_bits, + ); + } + + let left_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); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + op, + ); + } + + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); +} + +/// Align to byte boundary by applying operation to bits before the next byte boundary. +/// +/// This function handles non-byte-aligned operations by processing bits from the current +/// position up to the next byte boundary, while preserving all other bits in the byte. +/// +/// # Arguments +/// +/// * `op` - Unary operation to apply +/// * `buffer` - The mutable buffer to modify +/// * `offset_in_bits` - Starting bit offset (not byte-aligned) +fn align_to_byte<F>(op: &mut F, buffer: &mut MutableBuffer, offset_in_bits: usize) +where + F: FnMut(u64) -> u64, +{ + let byte_offset = offset_in_bits / 8; + let bit_offset = offset_in_bits % 8; + + // 1. read the first byte from the buffer + let first_byte: u8 = buffer.as_slice()[byte_offset]; + + // 2. Shift byte by the bit offset, keeping only the relevant bits + let relevant_first_byte = first_byte >> bit_offset; + + // 3. run the op on the first byte only + let result_first_byte = op(relevant_first_byte as u64) as u8; + + // 4. Shift back the result to the original position + let result_first_byte = result_first_byte << bit_offset; + + // 5. Mask the bits that are outside the relevant bits in the byte + // so the bits until bit_offset are 1 and the rest are 0 + let mask_for_first_bit_offset = (1 << bit_offset) - 1; + + let result_first_byte = + (first_byte & mask_for_first_bit_offset) | (result_first_byte & !mask_for_first_bit_offset); + + // 6. write back the result to the buffer + buffer.as_slice_mut()[byte_offset] = result_first_byte; +} + +/// Read up to 8 bits from a byte slice starting at a given bit offset. +/// +/// This is similar to `get_8_bits_from_offset` but works with raw byte slices +/// and can read fewer than 8 bits. +/// +/// # Arguments +/// +/// * `slice` - The byte slice to read from +/// * `number_of_bits_to_read` - Number of bits to read (must be ≤ 8) +/// * `bit_offset` - Starting bit offset within the first byte +/// +/// # Returns +/// +/// A u8 containing the requested bits in the least significant positions +#[inline] +fn read_up_to_byte_from_offset( + slice: &[u8], + number_of_bits_to_read: usize, + bit_offset: usize, +) -> u8 { + assert!(number_of_bits_to_read <= 8); + assert_ne!(number_of_bits_to_read, 0); + assert_ne!(slice.len(), 0); + + let number_of_bytes_to_read = bit_util::ceil(number_of_bits_to_read + bit_offset, 8); + + // number of bytes to read + // might be one more than sizeof(u64) if the offset is in the middle of a byte + assert!(slice.len() >= number_of_bytes_to_read); + + let mut bits = slice[0] >> bit_offset; + for (i, &byte) in slice + .iter() + .take(number_of_bytes_to_read) + .enumerate() + .skip(1) + { + bits |= byte << (i * 8 - bit_offset); + } + + bits & ((1 << number_of_bits_to_read) - 1) +} + +/// Perform bitwise binary operation on byte-aligned buffers (i.e. not offsetting into a middle of a byte). +/// +/// This is the optimized path for byte-aligned operations. It processes data in +/// u64 chunks for maximum efficiency, then handles any remainder bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (must be byte-aligned) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer (must be multiple of 8) +/// * `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 +#[inline] +fn mutable_buffer_byte_aligned_bitwise_bin_op_helper<F>( + left: &mut MutableBuffer, + 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, +{ + // Must not reach here if we not byte aligned + assert_eq!( + left_offset_in_bits % 8, + 0, + "left_offset_in_bits must be byte aligned" + ); + + // 1. Prepare the buffers + let (complete_u64_chunks, remainder_bytes) = + U64UnalignedSlice::split(left, left_offset_in_bits, len_in_bits); + + let right_chunks = BitChunks::new(right.as_slice(), right_offset_in_bits, len_in_bits); + assert_eq!( + bit_util::ceil(right_chunks.remainder_len(), 8), + remainder_bytes.len() + ); + + let right_chunks_iter = right_chunks.iter(); + assert_eq!(right_chunks_iter.len(), complete_u64_chunks.len()); + + // 2. Process complete u64 chunks + complete_u64_chunks.zip_modify(right_chunks_iter, &mut op); + + // Handle remainder bits if any + if right_chunks.remainder_len() > 0 { + handle_mutable_buffer_remainder( + &mut op, + remainder_bytes, + right_chunks.remainder_bits(), + right_chunks.remainder_len(), + ) + } +} + +/// Centralized structure to handle a mutable u8 slice as a mutable u64 pointer. +/// +/// Handle the following: +/// 1. the lifetime is correct +/// 2. we read/write within the bounds +/// 3. We read and write using unaligned +/// +/// This does not deallocate the underlying pointer when dropped +/// +/// This is the only place that uses unsafe code to read and write unaligned +/// +struct U64UnalignedSlice<'a> { + /// Pointer to the start of the u64 data + /// + /// We are using raw pointer as the data came from a u8 slice so we need to read and write unaligned + ptr: *mut u64, + + /// Number of u64 elements + len: usize, + + /// Marker to tie the lifetime of the pointer to the lifetime of the u8 slice + _marker: std::marker::PhantomData<&'a u8>, +} + +impl<'a> U64UnalignedSlice<'a> { + /// Create a new [`U64UnalignedSlice`] from a [`MutableBuffer`] + /// + /// return the [`U64UnalignedSlice`] and slice of bytes that are not part of the u64 chunks (guaranteed to be less than 8 bytes) + /// + fn split( + mutable_buffer: &'a mut MutableBuffer, + offset_in_bits: usize, + len_in_bits: usize, + ) -> (Self, &'a mut [u8]) { + // 1. Prepare the buffers + let left_buffer_mut: &mut [u8] = { + let last_offset = bit_util::ceil(offset_in_bits + len_in_bits, 8); + assert!(last_offset <= mutable_buffer.len()); + + let byte_offset = offset_in_bits / 8; + + &mut mutable_buffer.as_slice_mut()[byte_offset..last_offset] + }; + + let number_of_u64_we_can_fit = len_in_bits / (u64::BITS as usize); + + // 2. Split + let u64_len_in_bytes = number_of_u64_we_can_fit * size_of::<u64>(); + + assert!(u64_len_in_bytes <= left_buffer_mut.len()); + let (bytes_for_u64, remainder) = left_buffer_mut.split_at_mut(u64_len_in_bytes); + + let ptr = bytes_for_u64.as_mut_ptr() as *mut u64; + + let this = Self { + ptr, + len: number_of_u64_we_can_fit, + _marker: std::marker::PhantomData, + }; + + (this, remainder) + } + + fn len(&self) -> usize { + self.len + } + + /// Modify the underlying u64 data in place using a binary operation + /// with another iterator. + fn zip_modify( + mut self, + mut zip_iter: impl ExactSizeIterator<Item = u64>, + mut map: impl FnMut(u64, u64) -> u64, + ) { + assert_eq!(self.len, zip_iter.len()); + + // In order to avoid advancing the pointer at the end of the loop which will + // make the last pointer invalid, we handle the first element outside the loop + // and then advance the pointer at the start of the loop + // making sure that the iterator is not empty + if let Some(right) = zip_iter.next() { + // SAFETY: We asserted that the iterator length and the current length are the same + // and the iterator is not empty, so the pointer is valid + unsafe { + self.modify_self(right, &mut map); + } + + // Because this consumes self we don't update the length + } + + for right in zip_iter { + // Advance the pointer + // + // SAFETY: We asserted that the iterator length and the current length are the same + self.ptr = unsafe { self.ptr.add(1) }; + + // SAFETY: the pointer is valid as we are within the length + unsafe { + self.modify_self(right, &mut map); + } + + // Because this consumes self we don't update the length + } + } + + /// Centralized function to correctly read the current u64 value and write back the result + /// + /// # SAFETY + /// the caller must ensure that the pointer is valid for reads and writes + /// + #[inline] + unsafe fn modify_self(&mut self, right: u64, mut map: impl FnMut(u64, u64) -> u64) { + // Safety the caller must ensure pointer point to a valid u64 + let current_input = unsafe { + self.ptr + // Reading unaligned as we came from u8 slice + .read_unaligned() + // bit-packed buffers are stored starting with the least-significant byte first + // so when reading as u64 on a big-endian machine, the bytes need to be swapped + .to_le() + }; + + let combined = map(current_input, right); + + // Write the result back + // + // The pointer came from mutable u8 slice so the pointer is valid for writes, + // and we need to write unaligned + unsafe { self.ptr.write_unaligned(combined) } + } + + /// Modify the underlying u64 data in place using a unary operation. + fn modify(mut self, mut map: impl FnMut(u64) -> u64) { + if self.len == 0 { + return; + } + + // In order to avoid advancing the pointer at the end of the loop which will + // make the last pointer invalid, we handle the first element outside the loop + // and then advance the pointer at the start of the loop + // making sure that the iterator is not empty + unsafe { + // I hope the function get inlined and the compiler remove the dead right parameter + self.modify_self(0, &mut |left, _| map(left)); + + // Because this consumes self we don't update the length + } + + for _ in 1..self.len { + // Advance the pointer + // + // SAFETY: we only advance the pointer within the length and not beyond + self.ptr = unsafe { self.ptr.add(1) }; + + // SAFETY: the pointer is valid as we are within the length + unsafe { + // I hope the function get inlined and the compiler remove the dead right parameter + self.modify_self(0, &mut |left, _| map(left)); + } + + // Because this consumes self we don't update the length + } + } +} + +/// Handle remainder bits (< 64 bits) for binary operations. +/// +/// This function processes the bits that don't form a complete u64 chunk, +/// ensuring that bits outside the operation range are preserved. +/// +/// # Arguments +/// +/// * `op` - Binary operation to apply +/// * `start_remainder_mut_ptr` - Pointer to the start of remainder bytes +/// * `right_remainder_bits` - Right operand bits +/// * `remainder_len` - Number of remainder bits +#[inline] +fn handle_mutable_buffer_remainder<F>( + op: &mut F, + start_remainder_mut_slice: &mut [u8], + right_remainder_bits: u64, + remainder_len: usize, +) where + F: FnMut(u64, u64) -> u64, +{ + // Only read from mut pointer the number of remainder bits + let left_remainder_bits = get_remainder_bits(start_remainder_mut_slice, remainder_len); + + // Apply the operation + let rem = op(left_remainder_bits, right_remainder_bits); + + // Write only the relevant bits back the result to the mutable pointer + set_remainder_bits(start_remainder_mut_slice, rem, remainder_len); +} + +/// Write remainder bits back to buffer while preserving bits outside the range. +/// +/// This function carefully updates only the specified bits, leaving all other +/// bits in the affected bytes unchanged. +/// +/// # Arguments +/// +/// * `start_remainder_mut_slice` - the slice of bytes to write the remainder bits to +/// * `rem` - The result bits to write +/// * `remainder_len` - Number of bits to write +#[inline] +fn set_remainder_bits(start_remainder_mut_slice: &mut [u8], rem: u64, remainder_len: usize) { + assert_ne!( + start_remainder_mut_slice.len(), + 0, + "start_remainder_mut_slice must not be empty" + ); + assert!(remainder_len < 64, "remainder_len must be less than 64"); + // Need to update the remainder bytes in the mutable buffer + // but not override the bits outside the remainder + + // Update `rem` end with the current bytes in the mutable buffer + // to preserve the bits outside the remainder + let rem = { + // 1. Read the byte that we will override + let current = start_remainder_mut_slice + .last() + // Unwrap as we already validated the slice is not empty + .unwrap(); + + let current = *current as u64; + + // Mask where the bits that are inside the remainder are 1 + // and the bits outside the remainder are 0 + let inside_remainder_mask = (1 << remainder_len) - 1; + // Mask where the bits that are outside the remainder are 1 + // and the bits inside the remainder are 0 + let outside_remainder_mask = !inside_remainder_mask; + + // 2. Only keep the bits that are outside the remainder for the value from the mutable buffer + let current = current & outside_remainder_mask; + + // 3. Only keep the bits that are inside the remainder for the value from the operation + let rem = rem & inside_remainder_mask; + + // 4. Combine the two values + current | rem + }; + + // Write back the result to the mutable pointer + { + let remainder_bytes = bit_util::ceil(remainder_len, 8); + + // we are counting starting from the least significant bit, so to_le_bytes should be correct + let rem = &rem.to_le_bytes()[0..remainder_bytes]; + + // this assumes that `[ToByteSlice]` can be copied directly + // without calling `to_byte_slice` for each element, + // which is correct for all ArrowNativeType implementations including u64. + let src = rem.as_ptr(); + unsafe { + std::ptr::copy_nonoverlapping( + src, + start_remainder_mut_slice.as_mut_ptr(), + remainder_bytes, + ) + }; + } +} + +/// Read remainder bits from a pointer. +/// +/// Reads the specified number of bits from memory and returns them as a u64. +/// +/// # Arguments +/// +/// * `remainder_ptr` - Pointer to the start of the bits +/// * `remainder_len` - Number of bits to read (must be < 64) +/// +/// # Returns +/// +/// A u64 containing the bits in the least significant positions +#[inline] +fn get_remainder_bits(remainder: &[u8], remainder_len: usize) -> u64 { + assert!(remainder.len() < 64, "remainder_len must be less than 64"); + assert_eq!( + remainder.len(), + bit_util::ceil(remainder_len, 8), + "remainder and remainder len ceil must be the same" + ); + + let bits = remainder + .iter() + .enumerate() + .fold(0_u64, |acc, (index, &byte)| { + acc | (byte as u64) << (index * 8) + }); + + bits & ((1 << remainder_len) - 1) +} + +/// Perform bitwise unary operation on byte-aligned buffer. +/// +/// This is the optimized path for byte-aligned unary operations. It processes data in +/// u64 chunks for maximum efficiency, then handles any remainder bits. +/// +/// # Arguments +/// +/// * `left` - The mutable buffer (must be byte-aligned) +/// * `left_offset_in_bits` - Starting bit offset (must be multiple of 8) +/// * `len_in_bits` - Number of bits to process +/// * `op` - Unary operation to apply (e.g., `|a| !a`) +#[inline] +fn mutable_byte_aligned_bitwise_unary_op_helper<F>( + left: &mut MutableBuffer, + left_offset_in_bits: usize, + len_in_bits: usize, + mut op: F, +) where + F: FnMut(u64) -> u64, +{ + // Must not reach here if we not byte aligned + assert_eq!( + left_offset_in_bits % 8, + 0, + "left_offset_in_bits must be byte aligned" + ); + + let remainder_len = len_in_bits % 64; + + let (complete_u64_chunks, remainder_bytes) = + U64UnalignedSlice::split(left, left_offset_in_bits, len_in_bits); + + assert_eq!(bit_util::ceil(remainder_len, 8), remainder_bytes.len()); + + // 2. Process complete u64 chunks + complete_u64_chunks.modify(&mut op); + + // Handle remainder bits if any + if remainder_len > 0 { + handle_mutable_buffer_remainder_unary(&mut op, remainder_bytes, remainder_len) + } +} + +/// Handle remainder bits (< 64 bits) for unary operations. +/// +/// This function processes the bits that don't form a complete u64 chunk, +/// ensuring that bits outside the operation range are preserved. +/// +/// # Arguments +/// +/// * `op` - Unary operation to apply +/// * `start_remainder_mut` - Slice of bytes to write the remainder bits to +/// * `remainder_len` - Number of remainder bits +#[inline] +fn handle_mutable_buffer_remainder_unary<F>( + op: &mut F, + start_remainder_mut: &mut [u8], + remainder_len: usize, +) where + F: FnMut(u64) -> u64, +{ + // Only read from mut pointer the number of remainder bits + let left_remainder_bits = get_remainder_bits(start_remainder_mut, remainder_len); + + // Apply the operation + let rem = op(left_remainder_bits); + + // Write only the relevant bits back the result to the mutable pointer + set_remainder_bits(start_remainder_mut, rem, remainder_len); +} + +/// Apply a bitwise operation to a mutable buffer and update it in-place. +/// +/// This is the main entry point for unary operations. It handles both byte-aligned +/// and non-byte-aligned cases. +/// +/// The input is treated as a bitmap, meaning that offset and length are specified +/// in number of bits. +/// +/// # Arguments +/// +/// * `buffer` - The mutable buffer to modify +/// * `offset_in_bits` - Starting bit offset +/// * `len_in_bits` - Number of bits to process +/// * `op` - Unary operation to apply (e.g., `|a| !a`) +#[allow( + private_bounds, + reason = "MutableOpsBufferSupportedLhs exposes the inner internals which is the implementor choice and we dont want to leak internals" +)] +pub fn mutable_bitwise_unary_op_helper<F>( + buffer: &mut impl MutableOpsBufferSupportedLhs, + offset_in_bits: usize, + len_in_bits: usize, + mut op: F, +) where + F: FnMut(u64) -> u64, +{ + if len_in_bits == 0 { + return; + } + + let mutable_buffer = buffer.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 = offset_in_bits % 8; + + let is_mutable_buffer_byte_aligned = left_bit_offset == 0; + + if is_mutable_buffer_byte_aligned { + mutable_byte_aligned_bitwise_unary_op_helper( + mutable_buffer, + offset_in_bits, + len_in_bits, + op, + ); + } else { + // If we are not byte aligned we will read the first few bits + let bits_to_next_byte = 8 - left_bit_offset; + + align_to_byte(&mut op, mutable_buffer, offset_in_bits); + + let offset_in_bits = offset_in_bits + bits_to_next_byte; + let len_in_bits = len_in_bits.saturating_sub(bits_to_next_byte); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned + mutable_byte_aligned_bitwise_unary_op_helper( + mutable_buffer, + offset_in_bits, + len_in_bits, + op, + ); + } + + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); +} + +/// Apply a bitwise AND operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_and( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a & b, + ) +} + +/// Apply a bitwise OR operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_or( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a | b, + ) +} + +/// Apply a bitwise XOR operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_xor( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a ^ b, + ) +} + +/// Apply a bitwise NOT operation to the passed buffer. +/// +/// The buffer (mutable) is modified in-place to contain the result. +/// The input is treated as bitmap, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `buffer` - The mutable buffer (will be modified) +/// * `offset_in_bits` - Starting bit offset in the buffer +/// * `len_in_bits` - Number of bits to process +#[allow( + private_bounds, + reason = "MutableOpsBufferSupportedLhs exposes the inner internals which is the implementor choice and we dont want to leak internals" +)] +pub fn mutable_buffer_unary_not( + buffer: &mut impl MutableOpsBufferSupportedLhs, + offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_unary_op_helper(buffer, offset_in_bits, len_in_bits, |a| !a) +} + +#[cfg(test)] +mod tests { + use crate::bit_iterator::BitIterator; + use crate::{BooleanBuffer, BooleanBufferBuilder}; + + fn test_mutable_buffer_bin_op_helper<F, G>( + left_data: &[bool], + right_data: &[bool], + left_offset_in_bits: usize, + right_offset_in_bits: usize, + len_in_bits: usize, + op: F, + mut expected_op: G, + ) where + F: FnMut(u64, u64) -> u64, + G: FnMut(bool, bool) -> bool, + { + let mut left_buffer = BooleanBufferBuilder::from(left_data); + let right_buffer = BooleanBuffer::from(right_data); + + let expected: Vec<bool> = left_data + .iter() + .skip(left_offset_in_bits) + .zip(right_data.iter().skip(right_offset_in_bits)) + .take(len_in_bits) + .map(|(l, r)| expected_op(*l, *r)) + .collect(); + + super::mutable_bitwise_bin_op_helper( + &mut left_buffer, + left_offset_in_bits, + right_buffer.inner(), + right_offset_in_bits, + len_in_bits, + op, + ); + + let result: Vec<bool> = + BitIterator::new(left_buffer.as_slice(), left_offset_in_bits, len_in_bits).collect(); + + assert_eq!( + result, expected, + "Failed with left_offset={}, right_offset={}, len={}", + left_offset_in_bits, right_offset_in_bits, len_in_bits + ); + } + + fn test_mutable_buffer_unary_op_helper<F, G>( + data: &[bool], + offset_in_bits: usize, + len_in_bits: usize, + op: F, + mut expected_op: G, + ) where + F: FnMut(u64) -> u64, + G: FnMut(bool) -> bool, + { + let mut buffer = BooleanBufferBuilder::from(data); + + let expected: Vec<bool> = data + .iter() + .skip(offset_in_bits) + .take(len_in_bits) + .map(|b| expected_op(*b)) + .collect(); + + super::mutable_bitwise_unary_op_helper(&mut buffer, offset_in_bits, len_in_bits, op); + + let result: Vec<bool> = + BitIterator::new(buffer.as_slice(), offset_in_bits, len_in_bits).collect(); + + assert_eq!( + result, expected, + "Failed with offset={}, len={}", + offset_in_bits, len_in_bits + ); + } + + // Helper to create test data of specific length + fn create_test_data(len: usize) -> (Vec<bool>, Vec<bool>) { + let left: Vec<bool> = (0..len).map(|i| i % 2 == 0).collect(); Review Comment: Can you please add more randomness in these patterns? I worry these repeating patterns don't cover all the cases Perhaps something like this (I tried this locally and all the tests still pass) ```rust // Helper to create test data of specific length fn create_test_data(len: usize) -> (Vec<bool>, Vec<bool>) { let mut rng = rand::rng(); let left: Vec<bool> = (0..len).map(|_| rng.random_bool(0.5)).collect(); let right: Vec<bool> = (0..len).map(|_| rng.random_bool(0.5)).collect(); (left, right) } ``` ########## 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 { + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + 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 - left_bit_offset; + + { + let right_byte_offset = right_offset_in_bits / 8; + + // Read the same amount of bits from the right buffer + let right_first_byte: u8 = read_up_to_byte_from_offset( + &right.as_slice()[right_byte_offset..], + bits_to_next_byte, + // Right bit offset + right_offset_in_bits % 8, + ); + + align_to_byte( + // Hope it gets inlined + &mut |left| op(left, right_first_byte as u64), + mutable_buffer, + left_offset_in_bits, + ); + } + + let left_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); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + op, + ); + } + + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); +} + +/// Align to byte boundary by applying operation to bits before the next byte boundary. +/// +/// This function handles non-byte-aligned operations by processing bits from the current +/// position up to the next byte boundary, while preserving all other bits in the byte. +/// +/// # Arguments +/// +/// * `op` - Unary operation to apply +/// * `buffer` - The mutable buffer to modify +/// * `offset_in_bits` - Starting bit offset (not byte-aligned) +fn align_to_byte<F>(op: &mut F, buffer: &mut MutableBuffer, offset_in_bits: usize) +where + F: FnMut(u64) -> u64, +{ + let byte_offset = offset_in_bits / 8; + let bit_offset = offset_in_bits % 8; + + // 1. read the first byte from the buffer + let first_byte: u8 = buffer.as_slice()[byte_offset]; + + // 2. Shift byte by the bit offset, keeping only the relevant bits + let relevant_first_byte = first_byte >> bit_offset; + + // 3. run the op on the first byte only + let result_first_byte = op(relevant_first_byte as u64) as u8; + + // 4. Shift back the result to the original position + let result_first_byte = result_first_byte << bit_offset; + + // 5. Mask the bits that are outside the relevant bits in the byte + // so the bits until bit_offset are 1 and the rest are 0 + let mask_for_first_bit_offset = (1 << bit_offset) - 1; + + let result_first_byte = + (first_byte & mask_for_first_bit_offset) | (result_first_byte & !mask_for_first_bit_offset); + + // 6. write back the result to the buffer + buffer.as_slice_mut()[byte_offset] = result_first_byte; +} + +/// Read up to 8 bits from a byte slice starting at a given bit offset. +/// +/// This is similar to `get_8_bits_from_offset` but works with raw byte slices +/// and can read fewer than 8 bits. +/// +/// # Arguments +/// +/// * `slice` - The byte slice to read from +/// * `number_of_bits_to_read` - Number of bits to read (must be ≤ 8) +/// * `bit_offset` - Starting bit offset within the first byte +/// +/// # Returns +/// +/// A u8 containing the requested bits in the least significant positions +#[inline] +fn read_up_to_byte_from_offset( + slice: &[u8], + number_of_bits_to_read: usize, + bit_offset: usize, +) -> u8 { + assert!(number_of_bits_to_read <= 8); + assert_ne!(number_of_bits_to_read, 0); + assert_ne!(slice.len(), 0); + + let number_of_bytes_to_read = bit_util::ceil(number_of_bits_to_read + bit_offset, 8); + + // number of bytes to read + // might be one more than sizeof(u64) if the offset is in the middle of a byte + assert!(slice.len() >= number_of_bytes_to_read); + + let mut bits = slice[0] >> bit_offset; + for (i, &byte) in slice + .iter() + .take(number_of_bytes_to_read) + .enumerate() + .skip(1) + { + bits |= byte << (i * 8 - bit_offset); + } + + bits & ((1 << number_of_bits_to_read) - 1) +} + +/// Perform bitwise binary operation on byte-aligned buffers (i.e. not offsetting into a middle of a byte). +/// +/// This is the optimized path for byte-aligned operations. It processes data in +/// u64 chunks for maximum efficiency, then handles any remainder bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (must be byte-aligned) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer (must be multiple of 8) +/// * `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 +#[inline] +fn mutable_buffer_byte_aligned_bitwise_bin_op_helper<F>( + left: &mut MutableBuffer, + 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, +{ + // Must not reach here if we not byte aligned + assert_eq!( + left_offset_in_bits % 8, + 0, + "left_offset_in_bits must be byte aligned" + ); + + // 1. Prepare the buffers + let (complete_u64_chunks, remainder_bytes) = + U64UnalignedSlice::split(left, left_offset_in_bits, len_in_bits); + + let right_chunks = BitChunks::new(right.as_slice(), right_offset_in_bits, len_in_bits); + assert_eq!( + bit_util::ceil(right_chunks.remainder_len(), 8), + remainder_bytes.len() + ); + + let right_chunks_iter = right_chunks.iter(); + assert_eq!(right_chunks_iter.len(), complete_u64_chunks.len()); + + // 2. Process complete u64 chunks + complete_u64_chunks.zip_modify(right_chunks_iter, &mut op); + + // Handle remainder bits if any + if right_chunks.remainder_len() > 0 { + handle_mutable_buffer_remainder( + &mut op, + remainder_bytes, + right_chunks.remainder_bits(), + right_chunks.remainder_len(), + ) + } +} + +/// Centralized structure to handle a mutable u8 slice as a mutable u64 pointer. +/// +/// Handle the following: +/// 1. the lifetime is correct +/// 2. we read/write within the bounds +/// 3. We read and write using unaligned +/// +/// This does not deallocate the underlying pointer when dropped +/// +/// This is the only place that uses unsafe code to read and write unaligned +/// +struct U64UnalignedSlice<'a> { + /// Pointer to the start of the u64 data + /// + /// We are using raw pointer as the data came from a u8 slice so we need to read and write unaligned + ptr: *mut u64, + + /// Number of u64 elements + len: usize, + + /// Marker to tie the lifetime of the pointer to the lifetime of the u8 slice + _marker: std::marker::PhantomData<&'a u8>, +} + +impl<'a> U64UnalignedSlice<'a> { + /// Create a new [`U64UnalignedSlice`] from a [`MutableBuffer`] + /// + /// return the [`U64UnalignedSlice`] and slice of bytes that are not part of the u64 chunks (guaranteed to be less than 8 bytes) + /// + fn split( + mutable_buffer: &'a mut MutableBuffer, + offset_in_bits: usize, + len_in_bits: usize, + ) -> (Self, &'a mut [u8]) { + // 1. Prepare the buffers + let left_buffer_mut: &mut [u8] = { + let last_offset = bit_util::ceil(offset_in_bits + len_in_bits, 8); + assert!(last_offset <= mutable_buffer.len()); + + let byte_offset = offset_in_bits / 8; + + &mut mutable_buffer.as_slice_mut()[byte_offset..last_offset] + }; + + let number_of_u64_we_can_fit = len_in_bits / (u64::BITS as usize); + + // 2. Split + let u64_len_in_bytes = number_of_u64_we_can_fit * size_of::<u64>(); + + assert!(u64_len_in_bytes <= left_buffer_mut.len()); + let (bytes_for_u64, remainder) = left_buffer_mut.split_at_mut(u64_len_in_bytes); + + let ptr = bytes_for_u64.as_mut_ptr() as *mut u64; + + let this = Self { + ptr, + len: number_of_u64_we_can_fit, + _marker: std::marker::PhantomData, + }; + + (this, remainder) + } + + fn len(&self) -> usize { + self.len + } + + /// Modify the underlying u64 data in place using a binary operation + /// with another iterator. + fn zip_modify( + mut self, + mut zip_iter: impl ExactSizeIterator<Item = u64>, + mut map: impl FnMut(u64, u64) -> u64, + ) { + assert_eq!(self.len, zip_iter.len()); + + // In order to avoid advancing the pointer at the end of the loop which will + // make the last pointer invalid, we handle the first element outside the loop + // and then advance the pointer at the start of the loop + // making sure that the iterator is not empty + if let Some(right) = zip_iter.next() { + // SAFETY: We asserted that the iterator length and the current length are the same + // and the iterator is not empty, so the pointer is valid + unsafe { + self.modify_self(right, &mut map); + } + + // Because this consumes self we don't update the length + } + + for right in zip_iter { + // Advance the pointer + // + // SAFETY: We asserted that the iterator length and the current length are the same + self.ptr = unsafe { self.ptr.add(1) }; + + // SAFETY: the pointer is valid as we are within the length + unsafe { + self.modify_self(right, &mut map); + } + + // Because this consumes self we don't update the length + } + } + + /// Centralized function to correctly read the current u64 value and write back the result + /// + /// # SAFETY + /// the caller must ensure that the pointer is valid for reads and writes + /// + #[inline] + unsafe fn modify_self(&mut self, right: u64, mut map: impl FnMut(u64, u64) -> u64) { + // Safety the caller must ensure pointer point to a valid u64 + let current_input = unsafe { + self.ptr + // Reading unaligned as we came from u8 slice + .read_unaligned() + // bit-packed buffers are stored starting with the least-significant byte first + // so when reading as u64 on a big-endian machine, the bytes need to be swapped + .to_le() + }; + + let combined = map(current_input, right); + + // Write the result back + // + // The pointer came from mutable u8 slice so the pointer is valid for writes, + // and we need to write unaligned + unsafe { self.ptr.write_unaligned(combined) } + } + + /// Modify the underlying u64 data in place using a unary operation. + fn modify(mut self, mut map: impl FnMut(u64) -> u64) { + if self.len == 0 { + return; + } + + // In order to avoid advancing the pointer at the end of the loop which will + // make the last pointer invalid, we handle the first element outside the loop + // and then advance the pointer at the start of the loop + // making sure that the iterator is not empty + unsafe { + // I hope the function get inlined and the compiler remove the dead right parameter + self.modify_self(0, &mut |left, _| map(left)); + + // Because this consumes self we don't update the length + } + + for _ in 1..self.len { + // Advance the pointer + // + // SAFETY: we only advance the pointer within the length and not beyond + self.ptr = unsafe { self.ptr.add(1) }; + + // SAFETY: the pointer is valid as we are within the length + unsafe { + // I hope the function get inlined and the compiler remove the dead right parameter + self.modify_self(0, &mut |left, _| map(left)); + } + + // Because this consumes self we don't update the length + } + } +} + +/// Handle remainder bits (< 64 bits) for binary operations. +/// +/// This function processes the bits that don't form a complete u64 chunk, +/// ensuring that bits outside the operation range are preserved. +/// +/// # Arguments +/// +/// * `op` - Binary operation to apply +/// * `start_remainder_mut_ptr` - Pointer to the start of remainder bytes +/// * `right_remainder_bits` - Right operand bits +/// * `remainder_len` - Number of remainder bits +#[inline] +fn handle_mutable_buffer_remainder<F>( + op: &mut F, + start_remainder_mut_slice: &mut [u8], + right_remainder_bits: u64, + remainder_len: usize, +) where + F: FnMut(u64, u64) -> u64, +{ + // Only read from mut pointer the number of remainder bits + let left_remainder_bits = get_remainder_bits(start_remainder_mut_slice, remainder_len); + + // Apply the operation + let rem = op(left_remainder_bits, right_remainder_bits); + + // Write only the relevant bits back the result to the mutable pointer + set_remainder_bits(start_remainder_mut_slice, rem, remainder_len); +} + +/// Write remainder bits back to buffer while preserving bits outside the range. +/// +/// This function carefully updates only the specified bits, leaving all other +/// bits in the affected bytes unchanged. +/// +/// # Arguments +/// +/// * `start_remainder_mut_slice` - the slice of bytes to write the remainder bits to +/// * `rem` - The result bits to write +/// * `remainder_len` - Number of bits to write +#[inline] +fn set_remainder_bits(start_remainder_mut_slice: &mut [u8], rem: u64, remainder_len: usize) { + assert_ne!( + start_remainder_mut_slice.len(), + 0, + "start_remainder_mut_slice must not be empty" + ); + assert!(remainder_len < 64, "remainder_len must be less than 64"); + // Need to update the remainder bytes in the mutable buffer + // but not override the bits outside the remainder + + // Update `rem` end with the current bytes in the mutable buffer + // to preserve the bits outside the remainder + let rem = { + // 1. Read the byte that we will override + let current = start_remainder_mut_slice + .last() + // Unwrap as we already validated the slice is not empty + .unwrap(); + + let current = *current as u64; + + // Mask where the bits that are inside the remainder are 1 + // and the bits outside the remainder are 0 + let inside_remainder_mask = (1 << remainder_len) - 1; + // Mask where the bits that are outside the remainder are 1 + // and the bits inside the remainder are 0 + let outside_remainder_mask = !inside_remainder_mask; + + // 2. Only keep the bits that are outside the remainder for the value from the mutable buffer + let current = current & outside_remainder_mask; + + // 3. Only keep the bits that are inside the remainder for the value from the operation + let rem = rem & inside_remainder_mask; + + // 4. Combine the two values + current | rem + }; + + // Write back the result to the mutable pointer + { + let remainder_bytes = bit_util::ceil(remainder_len, 8); + + // we are counting starting from the least significant bit, so to_le_bytes should be correct + let rem = &rem.to_le_bytes()[0..remainder_bytes]; + + // this assumes that `[ToByteSlice]` can be copied directly + // without calling `to_byte_slice` for each element, + // which is correct for all ArrowNativeType implementations including u64. + let src = rem.as_ptr(); + unsafe { + std::ptr::copy_nonoverlapping( + src, + start_remainder_mut_slice.as_mut_ptr(), + remainder_bytes, + ) + }; + } +} + +/// Read remainder bits from a pointer. +/// +/// Reads the specified number of bits from memory and returns them as a u64. +/// +/// # Arguments +/// +/// * `remainder_ptr` - Pointer to the start of the bits +/// * `remainder_len` - Number of bits to read (must be < 64) +/// +/// # Returns +/// +/// A u64 containing the bits in the least significant positions +#[inline] +fn get_remainder_bits(remainder: &[u8], remainder_len: usize) -> u64 { + assert!(remainder.len() < 64, "remainder_len must be less than 64"); + assert_eq!( + remainder.len(), + bit_util::ceil(remainder_len, 8), + "remainder and remainder len ceil must be the same" + ); + + let bits = remainder + .iter() + .enumerate() + .fold(0_u64, |acc, (index, &byte)| { + acc | (byte as u64) << (index * 8) + }); + + bits & ((1 << remainder_len) - 1) +} + +/// Perform bitwise unary operation on byte-aligned buffer. +/// +/// This is the optimized path for byte-aligned unary operations. It processes data in +/// u64 chunks for maximum efficiency, then handles any remainder bits. +/// +/// # Arguments +/// +/// * `left` - The mutable buffer (must be byte-aligned) +/// * `left_offset_in_bits` - Starting bit offset (must be multiple of 8) +/// * `len_in_bits` - Number of bits to process +/// * `op` - Unary operation to apply (e.g., `|a| !a`) +#[inline] +fn mutable_byte_aligned_bitwise_unary_op_helper<F>( + left: &mut MutableBuffer, + left_offset_in_bits: usize, + len_in_bits: usize, + mut op: F, +) where + F: FnMut(u64) -> u64, +{ + // Must not reach here if we not byte aligned + assert_eq!( + left_offset_in_bits % 8, + 0, + "left_offset_in_bits must be byte aligned" + ); + + let remainder_len = len_in_bits % 64; + + let (complete_u64_chunks, remainder_bytes) = + U64UnalignedSlice::split(left, left_offset_in_bits, len_in_bits); + + assert_eq!(bit_util::ceil(remainder_len, 8), remainder_bytes.len()); + + // 2. Process complete u64 chunks + complete_u64_chunks.modify(&mut op); + + // Handle remainder bits if any + if remainder_len > 0 { + handle_mutable_buffer_remainder_unary(&mut op, remainder_bytes, remainder_len) + } +} + +/// Handle remainder bits (< 64 bits) for unary operations. +/// +/// This function processes the bits that don't form a complete u64 chunk, +/// ensuring that bits outside the operation range are preserved. +/// +/// # Arguments +/// +/// * `op` - Unary operation to apply +/// * `start_remainder_mut` - Slice of bytes to write the remainder bits to +/// * `remainder_len` - Number of remainder bits +#[inline] +fn handle_mutable_buffer_remainder_unary<F>( + op: &mut F, + start_remainder_mut: &mut [u8], + remainder_len: usize, +) where + F: FnMut(u64) -> u64, +{ + // Only read from mut pointer the number of remainder bits + let left_remainder_bits = get_remainder_bits(start_remainder_mut, remainder_len); + + // Apply the operation + let rem = op(left_remainder_bits); + + // Write only the relevant bits back the result to the mutable pointer + set_remainder_bits(start_remainder_mut, rem, remainder_len); +} + +/// Apply a bitwise operation to a mutable buffer and update it in-place. +/// +/// This is the main entry point for unary operations. It handles both byte-aligned +/// and non-byte-aligned cases. +/// +/// The input is treated as a bitmap, meaning that offset and length are specified +/// in number of bits. +/// +/// # Arguments +/// +/// * `buffer` - The mutable buffer to modify +/// * `offset_in_bits` - Starting bit offset +/// * `len_in_bits` - Number of bits to process +/// * `op` - Unary operation to apply (e.g., `|a| !a`) +#[allow( + private_bounds, + reason = "MutableOpsBufferSupportedLhs exposes the inner internals which is the implementor choice and we dont want to leak internals" +)] +pub fn mutable_bitwise_unary_op_helper<F>( + buffer: &mut impl MutableOpsBufferSupportedLhs, + offset_in_bits: usize, + len_in_bits: usize, + mut op: F, +) where + F: FnMut(u64) -> u64, +{ + if len_in_bits == 0 { + return; + } + + let mutable_buffer = buffer.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 = offset_in_bits % 8; + + let is_mutable_buffer_byte_aligned = left_bit_offset == 0; + + if is_mutable_buffer_byte_aligned { + mutable_byte_aligned_bitwise_unary_op_helper( + mutable_buffer, + offset_in_bits, + len_in_bits, + op, + ); + } else { + // If we are not byte aligned we will read the first few bits + let bits_to_next_byte = 8 - left_bit_offset; + + align_to_byte(&mut op, mutable_buffer, offset_in_bits); + + let offset_in_bits = offset_in_bits + bits_to_next_byte; + let len_in_bits = len_in_bits.saturating_sub(bits_to_next_byte); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned + mutable_byte_aligned_bitwise_unary_op_helper( + mutable_buffer, + offset_in_bits, + len_in_bits, + op, + ); + } + + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); +} + +/// Apply a bitwise AND operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_and( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a & b, + ) +} + +/// Apply a bitwise OR operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_or( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a | b, + ) +} + +/// Apply a bitwise XOR operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_xor( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a ^ b, + ) +} + +/// Apply a bitwise NOT operation to the passed buffer. +/// +/// The buffer (mutable) is modified in-place to contain the result. +/// The input is treated as bitmap, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `buffer` - The mutable buffer (will be modified) +/// * `offset_in_bits` - Starting bit offset in the buffer +/// * `len_in_bits` - Number of bits to process +#[allow( + private_bounds, + reason = "MutableOpsBufferSupportedLhs exposes the inner internals which is the implementor choice and we dont want to leak internals" +)] +pub fn mutable_buffer_unary_not( + buffer: &mut impl MutableOpsBufferSupportedLhs, + offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_unary_op_helper(buffer, offset_in_bits, len_in_bits, |a| !a) +} + +#[cfg(test)] +mod tests { + use crate::bit_iterator::BitIterator; + use crate::{BooleanBuffer, BooleanBufferBuilder}; + + fn test_mutable_buffer_bin_op_helper<F, G>( + left_data: &[bool], + right_data: &[bool], + left_offset_in_bits: usize, + right_offset_in_bits: usize, + len_in_bits: usize, + op: F, + mut expected_op: G, + ) where + F: FnMut(u64, u64) -> u64, + G: FnMut(bool, bool) -> bool, + { + let mut left_buffer = BooleanBufferBuilder::from(left_data); + let right_buffer = BooleanBuffer::from(right_data); + + let expected: Vec<bool> = left_data + .iter() + .skip(left_offset_in_bits) + .zip(right_data.iter().skip(right_offset_in_bits)) + .take(len_in_bits) + .map(|(l, r)| expected_op(*l, *r)) + .collect(); + + super::mutable_bitwise_bin_op_helper( + &mut left_buffer, + left_offset_in_bits, + right_buffer.inner(), + right_offset_in_bits, + len_in_bits, + op, + ); + + let result: Vec<bool> = + BitIterator::new(left_buffer.as_slice(), left_offset_in_bits, len_in_bits).collect(); + + assert_eq!( + result, expected, + "Failed with left_offset={}, right_offset={}, len={}", + left_offset_in_bits, right_offset_in_bits, len_in_bits + ); + } + + fn test_mutable_buffer_unary_op_helper<F, G>( + data: &[bool], + offset_in_bits: usize, + len_in_bits: usize, + op: F, + mut expected_op: G, + ) where + F: FnMut(u64) -> u64, + G: FnMut(bool) -> bool, + { + let mut buffer = BooleanBufferBuilder::from(data); + + let expected: Vec<bool> = data + .iter() + .skip(offset_in_bits) + .take(len_in_bits) + .map(|b| expected_op(*b)) + .collect(); + + super::mutable_bitwise_unary_op_helper(&mut buffer, offset_in_bits, len_in_bits, op); + + let result: Vec<bool> = + BitIterator::new(buffer.as_slice(), offset_in_bits, len_in_bits).collect(); + + assert_eq!( + result, expected, + "Failed with offset={}, len={}", + offset_in_bits, len_in_bits + ); + } + + // Helper to create test data of specific length + fn create_test_data(len: usize) -> (Vec<bool>, Vec<bool>) { + let left: Vec<bool> = (0..len).map(|i| i % 2 == 0).collect(); + let right: Vec<bool> = (0..len).map(|i| (i / 2) % 2 == 0).collect(); + (left, right) + } + + /// Test all binary operations (AND, OR, XOR) with the given parameters + fn test_all_binary_ops( + left_data: &[bool], + right_data: &[bool], + left_offset_in_bits: usize, + right_offset_in_bits: usize, + len_in_bits: usize, + ) { + // Test AND + test_mutable_buffer_bin_op_helper( + left_data, + right_data, + left_offset_in_bits, + right_offset_in_bits, + len_in_bits, + |a, b| a & b, + |a, b| a & b, + ); + + // Test OR + test_mutable_buffer_bin_op_helper( + left_data, + right_data, + left_offset_in_bits, + right_offset_in_bits, + len_in_bits, + |a, b| a | b, + |a, b| a | b, + ); + + // Test XOR + test_mutable_buffer_bin_op_helper( + left_data, + right_data, + left_offset_in_bits, + right_offset_in_bits, + len_in_bits, + |a, b| a ^ b, + |a, b| a ^ b, + ); + } + + // ===== Combined Binary Operation Tests ===== + + #[test] + fn test_binary_ops_less_than_byte() { + let (left, right) = create_test_data(4); + test_all_binary_ops(&left, &right, 0, 0, 4); + } + + #[test] + fn test_binary_ops_less_than_byte_across_boundary() { + let (left, right) = create_test_data(16); + test_all_binary_ops(&left, &right, 6, 6, 4); + } + + #[test] + fn test_binary_ops_exactly_byte() { + let (left, right) = create_test_data(16); + test_all_binary_ops(&left, &right, 0, 0, 8); + } + + #[test] + fn test_binary_ops_more_than_byte_less_than_u64() { + let (left, right) = create_test_data(64); + test_all_binary_ops(&left, &right, 0, 0, 32); + } + + #[test] + fn test_binary_ops_exactly_u64() { + let (left, right) = create_test_data(180); + test_all_binary_ops(&left, &right, 0, 0, 64); + test_all_binary_ops(&left, &right, 64, 9, 64); + test_all_binary_ops(&left, &right, 8, 100, 64); + test_all_binary_ops(&left, &right, 1, 15, 64); + test_all_binary_ops(&left, &right, 12, 10, 64); + test_all_binary_ops(&left, &right, 180 - 64, 2, 64); + } + + #[test] + fn test_binary_ops_more_than_u64_not_multiple() { + let (left, right) = create_test_data(200); + test_all_binary_ops(&left, &right, 0, 0, 100); + } + + #[test] + fn test_binary_ops_exactly_multiple_u64() { + let (left, right) = create_test_data(256); + test_all_binary_ops(&left, &right, 0, 0, 128); + } + + #[test] + fn test_binary_ops_more_than_multiple_u64() { + let (left, right) = create_test_data(300); + test_all_binary_ops(&left, &right, 0, 0, 200); + } + + #[test] + fn test_binary_ops_byte_aligned_no_remainder() { + let (left, right) = create_test_data(200); + test_all_binary_ops(&left, &right, 0, 0, 128); + } + + #[test] + fn test_binary_ops_byte_aligned_with_remainder() { + let (left, right) = create_test_data(200); + test_all_binary_ops(&left, &right, 0, 0, 100); + } + + #[test] + fn test_binary_ops_not_byte_aligned_no_remainder() { + let (left, right) = create_test_data(200); + test_all_binary_ops(&left, &right, 3, 3, 128); + } + + #[test] + fn test_binary_ops_not_byte_aligned_with_remainder() { + let (left, right) = create_test_data(200); + test_all_binary_ops(&left, &right, 5, 5, 100); + } + + #[test] + fn test_binary_ops_different_offsets() { + let (left, right) = create_test_data(200); + test_all_binary_ops(&left, &right, 3, 7, 50); Review Comment: can you please also test an offset that is greater than 1 byte but less than 8 bytes? Something like this perhaps? `test_all_binary_ops(&left, &right, 13, 27, 100);` ########## 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 { + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + 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 - left_bit_offset; + + { + let right_byte_offset = right_offset_in_bits / 8; + + // Read the same amount of bits from the right buffer + let right_first_byte: u8 = read_up_to_byte_from_offset( + &right.as_slice()[right_byte_offset..], + bits_to_next_byte, + // Right bit offset + right_offset_in_bits % 8, + ); + + align_to_byte( + // Hope it gets inlined + &mut |left| op(left, right_first_byte as u64), + mutable_buffer, + left_offset_in_bits, + ); + } + + let left_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); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned + mutable_buffer_byte_aligned_bitwise_bin_op_helper( + mutable_buffer, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + op, + ); + } + + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); +} + +/// Align to byte boundary by applying operation to bits before the next byte boundary. +/// +/// This function handles non-byte-aligned operations by processing bits from the current +/// position up to the next byte boundary, while preserving all other bits in the byte. +/// +/// # Arguments +/// +/// * `op` - Unary operation to apply +/// * `buffer` - The mutable buffer to modify +/// * `offset_in_bits` - Starting bit offset (not byte-aligned) +fn align_to_byte<F>(op: &mut F, buffer: &mut MutableBuffer, offset_in_bits: usize) +where + F: FnMut(u64) -> u64, +{ + let byte_offset = offset_in_bits / 8; + let bit_offset = offset_in_bits % 8; + + // 1. read the first byte from the buffer + let first_byte: u8 = buffer.as_slice()[byte_offset]; + + // 2. Shift byte by the bit offset, keeping only the relevant bits + let relevant_first_byte = first_byte >> bit_offset; + + // 3. run the op on the first byte only + let result_first_byte = op(relevant_first_byte as u64) as u8; + + // 4. Shift back the result to the original position + let result_first_byte = result_first_byte << bit_offset; + + // 5. Mask the bits that are outside the relevant bits in the byte + // so the bits until bit_offset are 1 and the rest are 0 + let mask_for_first_bit_offset = (1 << bit_offset) - 1; + + let result_first_byte = + (first_byte & mask_for_first_bit_offset) | (result_first_byte & !mask_for_first_bit_offset); + + // 6. write back the result to the buffer + buffer.as_slice_mut()[byte_offset] = result_first_byte; +} + +/// Read up to 8 bits from a byte slice starting at a given bit offset. +/// +/// This is similar to `get_8_bits_from_offset` but works with raw byte slices +/// and can read fewer than 8 bits. +/// +/// # Arguments +/// +/// * `slice` - The byte slice to read from +/// * `number_of_bits_to_read` - Number of bits to read (must be ≤ 8) +/// * `bit_offset` - Starting bit offset within the first byte +/// +/// # Returns +/// +/// A u8 containing the requested bits in the least significant positions +#[inline] +fn read_up_to_byte_from_offset( + slice: &[u8], + number_of_bits_to_read: usize, + bit_offset: usize, +) -> u8 { + assert!(number_of_bits_to_read <= 8); + assert_ne!(number_of_bits_to_read, 0); + assert_ne!(slice.len(), 0); + + let number_of_bytes_to_read = bit_util::ceil(number_of_bits_to_read + bit_offset, 8); + + // number of bytes to read + // might be one more than sizeof(u64) if the offset is in the middle of a byte + assert!(slice.len() >= number_of_bytes_to_read); + + let mut bits = slice[0] >> bit_offset; + for (i, &byte) in slice + .iter() + .take(number_of_bytes_to_read) + .enumerate() + .skip(1) + { + bits |= byte << (i * 8 - bit_offset); + } + + bits & ((1 << number_of_bits_to_read) - 1) +} + +/// Perform bitwise binary operation on byte-aligned buffers (i.e. not offsetting into a middle of a byte). +/// +/// This is the optimized path for byte-aligned operations. It processes data in +/// u64 chunks for maximum efficiency, then handles any remainder bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (must be byte-aligned) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer (must be multiple of 8) +/// * `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 +#[inline] +fn mutable_buffer_byte_aligned_bitwise_bin_op_helper<F>( + left: &mut MutableBuffer, + 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, +{ + // Must not reach here if we not byte aligned + assert_eq!( + left_offset_in_bits % 8, + 0, + "left_offset_in_bits must be byte aligned" + ); + + // 1. Prepare the buffers + let (complete_u64_chunks, remainder_bytes) = + U64UnalignedSlice::split(left, left_offset_in_bits, len_in_bits); + + let right_chunks = BitChunks::new(right.as_slice(), right_offset_in_bits, len_in_bits); + assert_eq!( + bit_util::ceil(right_chunks.remainder_len(), 8), + remainder_bytes.len() + ); + + let right_chunks_iter = right_chunks.iter(); + assert_eq!(right_chunks_iter.len(), complete_u64_chunks.len()); + + // 2. Process complete u64 chunks + complete_u64_chunks.zip_modify(right_chunks_iter, &mut op); + + // Handle remainder bits if any + if right_chunks.remainder_len() > 0 { + handle_mutable_buffer_remainder( + &mut op, + remainder_bytes, + right_chunks.remainder_bits(), + right_chunks.remainder_len(), + ) + } +} + +/// Centralized structure to handle a mutable u8 slice as a mutable u64 pointer. +/// +/// Handle the following: +/// 1. the lifetime is correct +/// 2. we read/write within the bounds +/// 3. We read and write using unaligned +/// +/// This does not deallocate the underlying pointer when dropped +/// +/// This is the only place that uses unsafe code to read and write unaligned +/// +struct U64UnalignedSlice<'a> { + /// Pointer to the start of the u64 data + /// + /// We are using raw pointer as the data came from a u8 slice so we need to read and write unaligned + ptr: *mut u64, + + /// Number of u64 elements + len: usize, + + /// Marker to tie the lifetime of the pointer to the lifetime of the u8 slice + _marker: std::marker::PhantomData<&'a u8>, +} + +impl<'a> U64UnalignedSlice<'a> { + /// Create a new [`U64UnalignedSlice`] from a [`MutableBuffer`] + /// + /// return the [`U64UnalignedSlice`] and slice of bytes that are not part of the u64 chunks (guaranteed to be less than 8 bytes) + /// + fn split( + mutable_buffer: &'a mut MutableBuffer, + offset_in_bits: usize, + len_in_bits: usize, + ) -> (Self, &'a mut [u8]) { + // 1. Prepare the buffers + let left_buffer_mut: &mut [u8] = { + let last_offset = bit_util::ceil(offset_in_bits + len_in_bits, 8); + assert!(last_offset <= mutable_buffer.len()); + + let byte_offset = offset_in_bits / 8; + + &mut mutable_buffer.as_slice_mut()[byte_offset..last_offset] + }; + + let number_of_u64_we_can_fit = len_in_bits / (u64::BITS as usize); + + // 2. Split + let u64_len_in_bytes = number_of_u64_we_can_fit * size_of::<u64>(); + + assert!(u64_len_in_bytes <= left_buffer_mut.len()); + let (bytes_for_u64, remainder) = left_buffer_mut.split_at_mut(u64_len_in_bytes); + + let ptr = bytes_for_u64.as_mut_ptr() as *mut u64; + + let this = Self { + ptr, + len: number_of_u64_we_can_fit, + _marker: std::marker::PhantomData, + }; + + (this, remainder) + } + + fn len(&self) -> usize { + self.len + } + + /// Modify the underlying u64 data in place using a binary operation + /// with another iterator. + fn zip_modify( + mut self, + mut zip_iter: impl ExactSizeIterator<Item = u64>, + mut map: impl FnMut(u64, u64) -> u64, + ) { + assert_eq!(self.len, zip_iter.len()); + + // In order to avoid advancing the pointer at the end of the loop which will + // make the last pointer invalid, we handle the first element outside the loop + // and then advance the pointer at the start of the loop + // making sure that the iterator is not empty + if let Some(right) = zip_iter.next() { + // SAFETY: We asserted that the iterator length and the current length are the same + // and the iterator is not empty, so the pointer is valid + unsafe { + self.modify_self(right, &mut map); + } + + // Because this consumes self we don't update the length + } + + for right in zip_iter { + // Advance the pointer + // + // SAFETY: We asserted that the iterator length and the current length are the same + self.ptr = unsafe { self.ptr.add(1) }; + + // SAFETY: the pointer is valid as we are within the length + unsafe { + self.modify_self(right, &mut map); + } + + // Because this consumes self we don't update the length + } + } + + /// Centralized function to correctly read the current u64 value and write back the result + /// + /// # SAFETY + /// the caller must ensure that the pointer is valid for reads and writes + /// + #[inline] + unsafe fn modify_self(&mut self, right: u64, mut map: impl FnMut(u64, u64) -> u64) { + // Safety the caller must ensure pointer point to a valid u64 + let current_input = unsafe { + self.ptr + // Reading unaligned as we came from u8 slice + .read_unaligned() + // bit-packed buffers are stored starting with the least-significant byte first + // so when reading as u64 on a big-endian machine, the bytes need to be swapped + .to_le() + }; + + let combined = map(current_input, right); + + // Write the result back + // + // The pointer came from mutable u8 slice so the pointer is valid for writes, + // and we need to write unaligned + unsafe { self.ptr.write_unaligned(combined) } + } + + /// Modify the underlying u64 data in place using a unary operation. + fn modify(mut self, mut map: impl FnMut(u64) -> u64) { + if self.len == 0 { + return; + } + + // In order to avoid advancing the pointer at the end of the loop which will + // make the last pointer invalid, we handle the first element outside the loop + // and then advance the pointer at the start of the loop + // making sure that the iterator is not empty + unsafe { + // I hope the function get inlined and the compiler remove the dead right parameter + self.modify_self(0, &mut |left, _| map(left)); + + // Because this consumes self we don't update the length + } + + for _ in 1..self.len { + // Advance the pointer + // + // SAFETY: we only advance the pointer within the length and not beyond + self.ptr = unsafe { self.ptr.add(1) }; + + // SAFETY: the pointer is valid as we are within the length + unsafe { + // I hope the function get inlined and the compiler remove the dead right parameter + self.modify_self(0, &mut |left, _| map(left)); + } + + // Because this consumes self we don't update the length + } + } +} + +/// Handle remainder bits (< 64 bits) for binary operations. +/// +/// This function processes the bits that don't form a complete u64 chunk, +/// ensuring that bits outside the operation range are preserved. +/// +/// # Arguments +/// +/// * `op` - Binary operation to apply +/// * `start_remainder_mut_ptr` - Pointer to the start of remainder bytes +/// * `right_remainder_bits` - Right operand bits +/// * `remainder_len` - Number of remainder bits +#[inline] +fn handle_mutable_buffer_remainder<F>( + op: &mut F, + start_remainder_mut_slice: &mut [u8], + right_remainder_bits: u64, + remainder_len: usize, +) where + F: FnMut(u64, u64) -> u64, +{ + // Only read from mut pointer the number of remainder bits + let left_remainder_bits = get_remainder_bits(start_remainder_mut_slice, remainder_len); + + // Apply the operation + let rem = op(left_remainder_bits, right_remainder_bits); + + // Write only the relevant bits back the result to the mutable pointer + set_remainder_bits(start_remainder_mut_slice, rem, remainder_len); +} + +/// Write remainder bits back to buffer while preserving bits outside the range. +/// +/// This function carefully updates only the specified bits, leaving all other +/// bits in the affected bytes unchanged. +/// +/// # Arguments +/// +/// * `start_remainder_mut_slice` - the slice of bytes to write the remainder bits to +/// * `rem` - The result bits to write +/// * `remainder_len` - Number of bits to write +#[inline] +fn set_remainder_bits(start_remainder_mut_slice: &mut [u8], rem: u64, remainder_len: usize) { + assert_ne!( + start_remainder_mut_slice.len(), + 0, + "start_remainder_mut_slice must not be empty" + ); + assert!(remainder_len < 64, "remainder_len must be less than 64"); + // Need to update the remainder bytes in the mutable buffer + // but not override the bits outside the remainder + + // Update `rem` end with the current bytes in the mutable buffer + // to preserve the bits outside the remainder + let rem = { + // 1. Read the byte that we will override + let current = start_remainder_mut_slice + .last() + // Unwrap as we already validated the slice is not empty + .unwrap(); + + let current = *current as u64; + + // Mask where the bits that are inside the remainder are 1 + // and the bits outside the remainder are 0 + let inside_remainder_mask = (1 << remainder_len) - 1; + // Mask where the bits that are outside the remainder are 1 + // and the bits inside the remainder are 0 + let outside_remainder_mask = !inside_remainder_mask; + + // 2. Only keep the bits that are outside the remainder for the value from the mutable buffer + let current = current & outside_remainder_mask; + + // 3. Only keep the bits that are inside the remainder for the value from the operation + let rem = rem & inside_remainder_mask; + + // 4. Combine the two values + current | rem + }; + + // Write back the result to the mutable pointer + { + let remainder_bytes = bit_util::ceil(remainder_len, 8); + + // we are counting starting from the least significant bit, so to_le_bytes should be correct + let rem = &rem.to_le_bytes()[0..remainder_bytes]; + + // this assumes that `[ToByteSlice]` can be copied directly + // without calling `to_byte_slice` for each element, + // which is correct for all ArrowNativeType implementations including u64. + let src = rem.as_ptr(); + unsafe { + std::ptr::copy_nonoverlapping( + src, + start_remainder_mut_slice.as_mut_ptr(), + remainder_bytes, + ) + }; + } +} + +/// Read remainder bits from a pointer. +/// +/// Reads the specified number of bits from memory and returns them as a u64. +/// +/// # Arguments +/// +/// * `remainder_ptr` - Pointer to the start of the bits +/// * `remainder_len` - Number of bits to read (must be < 64) +/// +/// # Returns +/// +/// A u64 containing the bits in the least significant positions +#[inline] +fn get_remainder_bits(remainder: &[u8], remainder_len: usize) -> u64 { + assert!(remainder.len() < 64, "remainder_len must be less than 64"); + assert_eq!( + remainder.len(), + bit_util::ceil(remainder_len, 8), + "remainder and remainder len ceil must be the same" + ); + + let bits = remainder + .iter() + .enumerate() + .fold(0_u64, |acc, (index, &byte)| { + acc | (byte as u64) << (index * 8) + }); + + bits & ((1 << remainder_len) - 1) +} + +/// Perform bitwise unary operation on byte-aligned buffer. +/// +/// This is the optimized path for byte-aligned unary operations. It processes data in +/// u64 chunks for maximum efficiency, then handles any remainder bits. +/// +/// # Arguments +/// +/// * `left` - The mutable buffer (must be byte-aligned) +/// * `left_offset_in_bits` - Starting bit offset (must be multiple of 8) +/// * `len_in_bits` - Number of bits to process +/// * `op` - Unary operation to apply (e.g., `|a| !a`) +#[inline] +fn mutable_byte_aligned_bitwise_unary_op_helper<F>( + left: &mut MutableBuffer, + left_offset_in_bits: usize, + len_in_bits: usize, + mut op: F, +) where + F: FnMut(u64) -> u64, +{ + // Must not reach here if we not byte aligned + assert_eq!( + left_offset_in_bits % 8, + 0, + "left_offset_in_bits must be byte aligned" + ); + + let remainder_len = len_in_bits % 64; + + let (complete_u64_chunks, remainder_bytes) = + U64UnalignedSlice::split(left, left_offset_in_bits, len_in_bits); + + assert_eq!(bit_util::ceil(remainder_len, 8), remainder_bytes.len()); + + // 2. Process complete u64 chunks + complete_u64_chunks.modify(&mut op); + + // Handle remainder bits if any + if remainder_len > 0 { + handle_mutable_buffer_remainder_unary(&mut op, remainder_bytes, remainder_len) + } +} + +/// Handle remainder bits (< 64 bits) for unary operations. +/// +/// This function processes the bits that don't form a complete u64 chunk, +/// ensuring that bits outside the operation range are preserved. +/// +/// # Arguments +/// +/// * `op` - Unary operation to apply +/// * `start_remainder_mut` - Slice of bytes to write the remainder bits to +/// * `remainder_len` - Number of remainder bits +#[inline] +fn handle_mutable_buffer_remainder_unary<F>( + op: &mut F, + start_remainder_mut: &mut [u8], + remainder_len: usize, +) where + F: FnMut(u64) -> u64, +{ + // Only read from mut pointer the number of remainder bits + let left_remainder_bits = get_remainder_bits(start_remainder_mut, remainder_len); + + // Apply the operation + let rem = op(left_remainder_bits); + + // Write only the relevant bits back the result to the mutable pointer + set_remainder_bits(start_remainder_mut, rem, remainder_len); +} + +/// Apply a bitwise operation to a mutable buffer and update it in-place. +/// +/// This is the main entry point for unary operations. It handles both byte-aligned +/// and non-byte-aligned cases. +/// +/// The input is treated as a bitmap, meaning that offset and length are specified +/// in number of bits. +/// +/// # Arguments +/// +/// * `buffer` - The mutable buffer to modify +/// * `offset_in_bits` - Starting bit offset +/// * `len_in_bits` - Number of bits to process +/// * `op` - Unary operation to apply (e.g., `|a| !a`) +#[allow( + private_bounds, + reason = "MutableOpsBufferSupportedLhs exposes the inner internals which is the implementor choice and we dont want to leak internals" +)] +pub fn mutable_bitwise_unary_op_helper<F>( + buffer: &mut impl MutableOpsBufferSupportedLhs, + offset_in_bits: usize, + len_in_bits: usize, + mut op: F, +) where + F: FnMut(u64) -> u64, +{ + if len_in_bits == 0 { + return; + } + + let mutable_buffer = buffer.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 = offset_in_bits % 8; + + let is_mutable_buffer_byte_aligned = left_bit_offset == 0; + + if is_mutable_buffer_byte_aligned { + mutable_byte_aligned_bitwise_unary_op_helper( + mutable_buffer, + offset_in_bits, + len_in_bits, + op, + ); + } else { + // If we are not byte aligned we will read the first few bits + let bits_to_next_byte = 8 - left_bit_offset; + + align_to_byte(&mut op, mutable_buffer, offset_in_bits); + + let offset_in_bits = offset_in_bits + bits_to_next_byte; + let len_in_bits = len_in_bits.saturating_sub(bits_to_next_byte); + + if len_in_bits == 0 { + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); + + return; + } + + // We are now byte aligned + mutable_byte_aligned_bitwise_unary_op_helper( + mutable_buffer, + offset_in_bits, + len_in_bits, + op, + ); + } + + // Making sure that our guarantee that the length and capacity of the mutable buffer + // will not change is upheld + assert_eq!( + mutable_buffer.len(), + mutable_buffer_len, + "The length of the mutable buffer must not change" + ); + assert_eq!( + mutable_buffer.capacity(), + mutable_buffer_cap, + "The capacity of the mutable buffer must not change" + ); +} + +/// Apply a bitwise AND operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_and( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a & b, + ) +} + +/// Apply a bitwise OR operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_or( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a | b, + ) +} + +/// Apply a bitwise XOR operation to two buffers. +/// +/// The left buffer (mutable) is modified in-place to contain the result. +/// The inputs are treated as bitmaps, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `left` - The left mutable buffer (will be modified) +/// * `left_offset_in_bits` - Starting bit offset in the left buffer +/// * `right` - The right buffer +/// * `right_offset_in_bits` - Starting bit offset in the right buffer +/// * `len_in_bits` - Number of bits to process +#[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_buffer_bin_xor( + left: &mut impl MutableOpsBufferSupportedLhs, + left_offset_in_bits: usize, + right: &impl BufferSupportedRhs, + right_offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_bin_op_helper( + left, + left_offset_in_bits, + right, + right_offset_in_bits, + len_in_bits, + |a, b| a ^ b, + ) +} + +/// Apply a bitwise NOT operation to the passed buffer. +/// +/// The buffer (mutable) is modified in-place to contain the result. +/// The input is treated as bitmap, meaning that offsets and length are +/// specified in number of bits. +/// +/// # Arguments +/// +/// * `buffer` - The mutable buffer (will be modified) +/// * `offset_in_bits` - Starting bit offset in the buffer +/// * `len_in_bits` - Number of bits to process +#[allow( + private_bounds, + reason = "MutableOpsBufferSupportedLhs exposes the inner internals which is the implementor choice and we dont want to leak internals" +)] +pub fn mutable_buffer_unary_not( + buffer: &mut impl MutableOpsBufferSupportedLhs, + offset_in_bits: usize, + len_in_bits: usize, +) { + mutable_bitwise_unary_op_helper(buffer, offset_in_bits, len_in_bits, |a| !a) +} + +#[cfg(test)] +mod tests { + use crate::bit_iterator::BitIterator; + use crate::{BooleanBuffer, BooleanBufferBuilder}; + + fn test_mutable_buffer_bin_op_helper<F, G>( + left_data: &[bool], + right_data: &[bool], + left_offset_in_bits: usize, + right_offset_in_bits: usize, + len_in_bits: usize, + op: F, + mut expected_op: G, + ) where + F: FnMut(u64, u64) -> u64, + G: FnMut(bool, bool) -> bool, + { + let mut left_buffer = BooleanBufferBuilder::from(left_data); + let right_buffer = BooleanBuffer::from(right_data); + + let expected: Vec<bool> = left_data + .iter() + .skip(left_offset_in_bits) + .zip(right_data.iter().skip(right_offset_in_bits)) + .take(len_in_bits) + .map(|(l, r)| expected_op(*l, *r)) + .collect(); + + super::mutable_bitwise_bin_op_helper( Review Comment: this is a nice test ########## 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` Review Comment: I don't understand this rationale. It seems to me that this code does expose the inner `MutableBuffer` for `BooleanBufferBuilder` (other code can modify the MutableBuffer) it just does so via a trait. I am not sure how that is different than just passing in mutable buffer directly I wonder why you can't just pass `&mut [u8]` (aka pass in the mutable slices directly) as none of the APIs seem to change the length of the underlying buffers 🤔 if it is absolutely required to use a `MutableBuffer` directly from `BooleanBufferBuilder` perhaps we can make an unsafe API instead: ```rust impl BooleanBufferBuilder { /// returns a mutable reference to the buffer and length. Callers must ensure if they change the length /// the buffer, they also update len pub unsafe fn inner(&mut self) -> (&mut MutableBuffer, &mut usize) { ... } } ``` 🤔 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
