191 lines
5.3 KiB
C++
191 lines
5.3 KiB
C++
|
/* SPDX-FileCopyrightText: 2024 Blender Authors
|
||
|
*
|
||
|
* SPDX-License-Identifier: GPL-2.0-or-later */
|
||
|
|
||
|
#pragma once
|
||
|
|
||
|
#include <array>
|
||
|
|
||
|
#include "BLI_linear_allocator.hh"
|
||
|
#include "BLI_struct_equality_utils.hh"
|
||
|
#include "BLI_utility_mixins.hh"
|
||
|
|
||
|
namespace blender::linear_allocator {
|
||
|
|
||
|
/**
|
||
|
* The list is a linked list of segments containing multiple elements. The capacity of each segment
|
||
|
* is a template parameter because that removes the need to store it for every segment.
|
||
|
*/
|
||
|
template<typename T, int64_t Capacity> struct ChunkedListSegment {
|
||
|
/** Pointer to the next segment in the list. */
|
||
|
ChunkedListSegment *next = nullptr;
|
||
|
/**
|
||
|
* Number of constructed elements in this segment. The constructed elements are always at the
|
||
|
* beginning of the array below.
|
||
|
*/
|
||
|
int64_t size = 0;
|
||
|
/**
|
||
|
* The memory that actually contains the values in the end. The values are constructed and
|
||
|
* destructed by higher level code.
|
||
|
*/
|
||
|
std::array<TypedBuffer<T>, Capacity> values;
|
||
|
};
|
||
|
|
||
|
/**
|
||
|
* This is a special purpose container data structure that can be used to efficiently gather many
|
||
|
* elements into many (small) lists for later retrieval. Insertion order is *not* maintained.
|
||
|
*
|
||
|
* To use this data structure, one has to have a separate #LinearAllocator which is passed to the
|
||
|
* `append` function. This allows the same allocator to be used by many lists. Passing it into the
|
||
|
* append function also removes the need to store the allocator pointer in every list.
|
||
|
*
|
||
|
* It is an improvement over #Vector because it does not require any reallocations. #VectorList
|
||
|
* could also be used to overcome the reallocation issue.
|
||
|
*
|
||
|
* This data structure is also an improvement over #VectorList because:
|
||
|
* - It has a much lower memory footprint when empty.
|
||
|
* - Allows using a #LinearAllocator for all allocations, without storing the pointer to it in
|
||
|
* every vector.
|
||
|
* - It wastes less memory due to over-allocations.
|
||
|
*/
|
||
|
template<typename T, int64_t SegmentCapacity = 4> class ChunkedList : NonCopyable {
|
||
|
private:
|
||
|
using Segment = ChunkedListSegment<T, SegmentCapacity>;
|
||
|
Segment *current_segment_ = nullptr;
|
||
|
|
||
|
public:
|
||
|
ChunkedList() = default;
|
||
|
|
||
|
ChunkedList(ChunkedList &&other)
|
||
|
{
|
||
|
current_segment_ = other.current_segment_;
|
||
|
other.current_segment_ = nullptr;
|
||
|
}
|
||
|
|
||
|
~ChunkedList()
|
||
|
{
|
||
|
/* This code assumes that the #ChunkedListSegment does not have to be destructed if the
|
||
|
* contained type is trivially destructible. */
|
||
|
static_assert(std::is_trivially_destructible_v<ChunkedListSegment<int, 4>>);
|
||
|
if constexpr (!std::is_trivially_destructible_v<T>) {
|
||
|
for (Segment *segment = current_segment_; segment; segment = segment->next) {
|
||
|
for (const int64_t i : IndexRange(segment->size)) {
|
||
|
T &value = *segment->values[i];
|
||
|
std::destroy_at(&value);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
ChunkedList &operator=(ChunkedList &&other)
|
||
|
{
|
||
|
if (this == &other) {
|
||
|
return *this;
|
||
|
}
|
||
|
std::destroy_at(this);
|
||
|
new (this) ChunkedList(std::move(other));
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
/**
|
||
|
* Add an element to the list. The insertion order is not maintained. The given allocator is used
|
||
|
* to allocate any extra memory that may be needed.
|
||
|
*/
|
||
|
void append(LinearAllocator<> &allocator, const T &value)
|
||
|
{
|
||
|
this->append_as(allocator, value);
|
||
|
}
|
||
|
|
||
|
void append(LinearAllocator<> &allocator, T &&value)
|
||
|
{
|
||
|
this->append_as(allocator, std::move(value));
|
||
|
}
|
||
|
|
||
|
template<typename... Args> void append_as(LinearAllocator<> &allocator, Args &&...args)
|
||
|
{
|
||
|
if (current_segment_ == nullptr || current_segment_->size == SegmentCapacity) {
|
||
|
/* Allocate a new segment if necessary. */
|
||
|
static_assert(std::is_trivially_destructible_v<Segment>);
|
||
|
Segment *new_segment = allocator.construct<Segment>().release();
|
||
|
new_segment->next = current_segment_;
|
||
|
current_segment_ = new_segment;
|
||
|
}
|
||
|
T *value = &*current_segment_->values[current_segment_->size++];
|
||
|
new (value) T(std::forward<Args>(args)...);
|
||
|
}
|
||
|
|
||
|
class ConstIterator {
|
||
|
private:
|
||
|
const Segment *segment_ = nullptr;
|
||
|
int64_t index_ = 0;
|
||
|
|
||
|
public:
|
||
|
ConstIterator(const Segment *segment, int64_t index = 0) : segment_(segment), index_(index) {}
|
||
|
|
||
|
ConstIterator &operator++()
|
||
|
{
|
||
|
index_++;
|
||
|
if (index_ == segment_->size) {
|
||
|
segment_ = segment_->next;
|
||
|
index_ = 0;
|
||
|
}
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
const T &operator*() const
|
||
|
{
|
||
|
return *segment_->values[index_];
|
||
|
}
|
||
|
|
||
|
BLI_STRUCT_EQUALITY_OPERATORS_2(ConstIterator, segment_, index_)
|
||
|
};
|
||
|
|
||
|
class MutableIterator {
|
||
|
private:
|
||
|
Segment *segment_ = nullptr;
|
||
|
int64_t index_ = 0;
|
||
|
|
||
|
public:
|
||
|
MutableIterator(Segment *segment, int64_t index = 0) : segment_(segment), index_(index) {}
|
||
|
|
||
|
MutableIterator &operator++()
|
||
|
{
|
||
|
index_++;
|
||
|
if (index_ == segment_->size) {
|
||
|
segment_ = segment_->next;
|
||
|
index_ = 0;
|
||
|
}
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
T &operator*()
|
||
|
{
|
||
|
return *segment_->values[index_];
|
||
|
}
|
||
|
|
||
|
BLI_STRUCT_EQUALITY_OPERATORS_2(MutableIterator, segment_, index_)
|
||
|
};
|
||
|
|
||
|
ConstIterator begin() const
|
||
|
{
|
||
|
return ConstIterator(current_segment_, 0);
|
||
|
}
|
||
|
|
||
|
ConstIterator end() const
|
||
|
{
|
||
|
return ConstIterator(nullptr, 0);
|
||
|
}
|
||
|
|
||
|
MutableIterator begin()
|
||
|
{
|
||
|
return MutableIterator(current_segment_, 0);
|
||
|
}
|
||
|
|
||
|
MutableIterator end()
|
||
|
{
|
||
|
return MutableIterator(nullptr, 0);
|
||
|
}
|
||
|
};
|
||
|
|
||
|
} // namespace blender::linear_allocator
|