vertexclique commented on a change in pull request #8664: URL: https://github.com/apache/arrow/pull/8664#discussion_r526390939
########## File path: rust/arrow/src/util/bit_ops.rs ########## @@ -0,0 +1,407 @@ +// 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 crate::buffer::Buffer; + +use bitvec::prelude::*; +use bitvec::slice::ChunksExact; + +use std::fmt::Debug; + +/// +/// Immutable bit slice representation of buffer data +#[derive(Debug)] +pub struct BufferBitSlice<'a> { + buffer_data: &'a [u8], + bit_slice: &'a BitSlice<LocalBits, u8>, +} + +impl<'a> BufferBitSlice<'a> { + /// + /// Creates a immutable bit slice over the given data + #[inline] + pub fn new(buffer_data: &'a [u8]) -> Self { + let bit_slice = BitSlice::<LocalBits, _>::from_slice(buffer_data).unwrap(); + + BufferBitSlice { + buffer_data, + bit_slice: &bit_slice, + } + } + + /// + /// Returns immutable view with the given offset in bits and length in bits. + /// This view have zero-copy representation over the actual data. + #[inline] + pub fn view(&self, offset_in_bits: usize, len_in_bits: usize) -> Self { + Self { + buffer_data: self.buffer_data, + bit_slice: &self.bit_slice[offset_in_bits..offset_in_bits + len_in_bits], + } + } + + /// + /// Returns bit chunks in native 64-bit allocation size. + /// Native representations in Arrow follows 64-bit convention. + /// Chunks can still be reinterpreted in any primitive type lower than u64. + #[inline] + pub fn chunks<T>(&self) -> BufferBitChunksExact<T> + where + T: BitMemory, + { + let offset_size_in_bits = 8 * std::mem::size_of::<T>(); + let chunks_exact = self.bit_slice.chunks_exact(offset_size_in_bits); + let remainder_bits = chunks_exact.remainder(); + let remainder: T = if remainder_bits.len() == 0 { + T::default() + } else { + remainder_bits.load::<T>() + }; + BufferBitChunksExact { + chunks_exact, + remainder, + remainder_len_in_bits: remainder_bits.len(), + } + } + + /// + /// Converts the bit view into the Buffer. + /// Buffer is always byte-aligned and well-aligned. Review comment: Yes that's what I meant. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
