vertexclique commented on a change in pull request #8664: URL: https://github.com/apache/arrow/pull/8664#discussion_r526122655
########## 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. + #[inline] + pub fn as_buffer(&self) -> Buffer { + Buffer::from(self.bit_slice.as_slice()) + } + + /// + /// Count ones in the given bit view + #[inline] + pub fn count_ones(&self) -> usize { + self.bit_slice.count_ones() + } + + /// + /// Count zeros in the given bit view + #[inline] + pub fn count_zeros(&self) -> usize { + self.bit_slice.count_zeros() + } + + /// + /// Get bit value at the given index in this bit view + #[inline] + pub fn get_bit(&self, index: usize) -> bool { + *unsafe { self.bit_slice.get_unchecked(index) } + } + + /// + /// Get bits in this view as vector of booleans + #[inline] + pub fn typed_bits(&self) -> Vec<bool> { + self.bit_slice.iter().map(|e| *e).collect() + } + + /// + /// Get manipulated data as byte slice + #[inline] + pub fn to_slice(&self) -> &[u8] { + self.bit_slice.as_slice() + } +} + +impl<'a> PartialEq for BufferBitSlice<'a> { + fn eq(&self, other: &Self) -> bool { + self.bit_slice == other.bit_slice + } +} + +/// +/// Conversion from mutable slice to immutable bit slice +impl<'a> From<&'a [u8]> for BufferBitSlice<'a> { + fn from(data: &'a [u8]) -> Self { + BufferBitSlice::new(data) + } +} + +/// +/// Mutable bit slice representation of buffer data +#[derive(Debug)] +pub struct BufferBitSliceMut<'a> { + bit_slice: &'a mut BitSlice<LocalBits, u8>, +} + +impl<'a> BufferBitSliceMut<'a> { + /// + /// Creates a mutable bit slice over the given data + #[inline] + pub fn new(buffer_data: &'a mut [u8]) -> Self { + let bit_slice = BitSlice::<LocalBits, _>::from_slice_mut(buffer_data).unwrap(); + + BufferBitSliceMut { bit_slice } + } + + /// + /// Returns mutable 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(&'a mut self, offset_in_bits: usize, len_in_bits: usize) -> Self { + Self { + bit_slice: &mut self.bit_slice[offset_in_bits..offset_in_bits + len_in_bits], + } + } + + /// + /// Set given bit at the position to a given value + #[inline] + pub fn set_bit_all(&mut self, value: bool) { + self.bit_slice.set_all(value) + } + + /// + /// Count zeros in the given bit view + #[inline] + pub fn set_bit(&mut self, index: usize, value: bool) { + unsafe { self.bit_slice.set_unchecked(index, value) } + } + + /// + /// Converts the bit view into the Buffer. + /// Buffer is always byte-aligned and well-aligned. + #[inline] + pub fn as_buffer(&self) -> Buffer { + Buffer::from(self.bit_slice.as_slice()) + } + + /// + /// Count ones in the given bit view + #[inline] + pub fn count_ones(&self) -> usize { + self.bit_slice.count_ones() + } + + /// + /// Count zeros in the given bit view + #[inline] + pub fn count_zeros(&self) -> usize { + self.bit_slice.count_zeros() + } + + /// + /// Get bit value at the given index in this bit view + #[inline] + pub fn get_bit(&self, index: usize) -> bool { + *unsafe { self.bit_slice.get_unchecked(index) } + } + + /// + /// Get bits in this view as vector of booleans + #[inline] + pub fn typed_bits(&self) -> Vec<bool> { + self.bit_slice.iter().map(|e| *e).collect() + } + + /// + /// Get manipulated data as byte slice + #[inline] + pub fn to_slice(&self) -> &[u8] { + self.bit_slice.as_slice() + } +} + +impl<'a> PartialEq for BufferBitSliceMut<'a> { + fn eq(&self, other: &Self) -> bool { + self.bit_slice == other.bit_slice + } +} + +/// +/// Conversion from mutable slice to mutable bit slice +impl<'a> From<&'a mut [u8]> for BufferBitSliceMut<'a> { + fn from(data: &'a mut [u8]) -> Self { + BufferBitSliceMut::new(data) + } +} + +/// +/// Exact chunk view over the bit slice +#[derive(Clone, Debug)] +pub struct BufferBitChunksExact<'a, T> +where + T: BitMemory, Review comment: Wrote a doccomment and doctest there to make understanding and design rationale a little bit easier. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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