e955c94ed3
Listing the "Blender Foundation" as copyright holder implied the Blender Foundation holds copyright to files which may include work from many developers. While keeping copyright on headers makes sense for isolated libraries, Blender's own code may be refactored or moved between files in a way that makes the per file copyright holders less meaningful. Copyright references to the "Blender Foundation" have been replaced with "Blender Authors", with the exception of `./extern/` since these this contains libraries which are more isolated, any changed to license headers there can be handled on a case-by-case basis. Some directories in `./intern/` have also been excluded: - `./intern/cycles/` it's own `AUTHORS` file is planned. - `./intern/opensubdiv/`. An "AUTHORS" file has been added, using the chromium projects authors file as a template. Design task: #110784 Ref !110783.
110 lines
3.0 KiB
C++
110 lines
3.0 KiB
C++
/* SPDX-FileCopyrightText: 2023 Blender Authors
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*
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* SPDX-License-Identifier: GPL-2.0-or-later */
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#pragma once
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#include "BLI_bit_vector.hh"
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namespace blender::bits {
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/**
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* A #BitGroupVector is a compact data structure that allows storing an arbitrary but fixed number
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* of bits per element. For example, it could be used to compactly store 5 bits per vertex in a
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* mesh. The data structure stores the bits in a way so that the #BitSpan for every element is
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* bounded according to #is_bounded_span. The makes sure that operations on entire groups can be
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* implemented efficiently. For example, one can easy `or` one group into another.
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*/
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template<int64_t InlineBufferCapacity = 64, typename Allocator = GuardedAllocator>
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class BitGroupVector {
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private:
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/**
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* Number of bits per group.
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*/
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int64_t group_size_ = 0;
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/**
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* Actually stored number of bits per group so that individual groups are bounded according to
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* #is_bounded_span.
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*/
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int64_t aligned_group_size_ = 0;
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BitVector<InlineBufferCapacity, Allocator> data_;
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static int64_t align_group_size(const int64_t group_size)
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{
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if (group_size < 64) {
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/* Align to next power of two so that a single group never spans across two ints. */
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return int64_t(power_of_2_max_u(uint32_t(group_size)));
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}
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/* Align to multiple of BitsPerInt. */
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return (group_size + BitsPerInt - 1) & ~(BitsPerInt - 1);
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}
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public:
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BitGroupVector() = default;
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BitGroupVector(const int64_t size_in_groups,
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const int64_t group_size,
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const bool value = false,
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Allocator allocator = {})
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: group_size_(group_size),
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aligned_group_size_(align_group_size(group_size)),
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data_(size_in_groups * aligned_group_size_, value, allocator)
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{
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BLI_assert(group_size >= 0);
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BLI_assert(size_in_groups >= 0);
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}
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/** Get all the bits at an index. */
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BoundedBitSpan operator[](const int64_t i) const
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{
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const int64_t offset = aligned_group_size_ * i;
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return {data_.data() + (offset >> BitToIntIndexShift),
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IndexRange(offset & BitIndexMask, group_size_)};
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}
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/** Get all the bits at an index. */
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MutableBoundedBitSpan operator[](const int64_t i)
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{
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const int64_t offset = aligned_group_size_ * i;
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return {data_.data() + (offset >> BitToIntIndexShift),
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IndexRange(offset & BitIndexMask, group_size_)};
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}
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/** Number of groups. */
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int64_t size() const
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{
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return aligned_group_size_ == 0 ? 0 : data_.size() / aligned_group_size_;
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}
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/** Number of bits per group. */
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int64_t group_size() const
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{
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return group_size_;
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}
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IndexRange index_range() const
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{
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return IndexRange{this->size()};
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}
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/**
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* Get all stored bits. Note that this may also contain padding bits. This can be used to e.g.
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* mix multiple #BitGroupVector.
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*/
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BoundedBitSpan all_bits() const
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{
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return data_;
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}
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MutableBoundedBitSpan all_bits()
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{
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return data_;
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}
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};
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} // namespace blender::bits
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namespace blender {
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using bits::BitGroupVector;
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}
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