| // 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::{array::OffsetSizeTrait, buffer::MutableBuffer, util::bit_util}; |
| |
| /// extends the `buffer` to be able to hold `len` bits, setting all bits of the new size to zero. |
| #[inline] |
| pub(super) fn resize_for_bits(buffer: &mut MutableBuffer, len: usize) { |
| let needed_bytes = bit_util::ceil(len, 8); |
| if buffer.len() < needed_bytes { |
| buffer.resize(needed_bytes, 0); |
| } |
| } |
| |
| /// sets all bits on `write_data` on the range `[offset_write..offset_write+len]` to be equal to the |
| /// bits on `data` on the range `[offset_read..offset_read+len]` |
| pub(super) fn set_bits( |
| write_data: &mut [u8], |
| data: &[u8], |
| offset_write: usize, |
| offset_read: usize, |
| len: usize, |
| ) -> usize { |
| let mut count = 0; |
| (0..len).for_each(|i| { |
| if bit_util::get_bit(data, offset_read + i) { |
| bit_util::set_bit(write_data, offset_write + i); |
| } else { |
| count += 1; |
| } |
| }); |
| count |
| } |
| |
| pub(super) fn extend_offsets<T: OffsetSizeTrait>( |
| buffer: &mut MutableBuffer, |
| mut last_offset: T, |
| offsets: &[T], |
| ) { |
| buffer.reserve(offsets.len() * std::mem::size_of::<T>()); |
| offsets.windows(2).for_each(|offsets| { |
| // compute the new offset |
| let length = offsets[1] - offsets[0]; |
| last_offset += length; |
| buffer.push(last_offset); |
| }); |
| } |
| |
| #[inline] |
| pub(super) unsafe fn get_last_offset<T: OffsetSizeTrait>( |
| offset_buffer: &MutableBuffer, |
| ) -> T { |
| // JUSTIFICATION |
| // Benefit |
| // 20% performance improvement extend of variable sized arrays (see bench `mutable_array`) |
| // Soundness |
| // * offset buffer is always extended in slices of T and aligned accordingly. |
| // * Buffer[0] is initialized with one element, 0, and thus `mutable_offsets.len() - 1` is always valid. |
| let (prefix, offsets, suffix) = offset_buffer.as_slice().align_to::<T>(); |
| debug_assert!(prefix.is_empty() && suffix.is_empty()); |
| *offsets.get_unchecked(offsets.len() - 1) |
| } |