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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef __FN_ARRAY_SPANS_HH__
#define __FN_ARRAY_SPANS_HH__
/** \file
* \ingroup fn
*
* An ArraySpan is a span where every element contains an array (instead of a single element as is
* the case in a normal span). It's main use case is to reference many small arrays.
*/
#include "FN_spans.hh"
namespace blender::fn {
/**
* Depending on the use case, the referenced data might have a different structure. More
* categories can be added when necessary.
*/
enum class VArraySpanCategory {
SingleArray,
StartsAndSizes,
};
template<typename T> class VArraySpanBase {
protected:
uint virtual_size_;
VArraySpanCategory category_;
union {
struct {
const T *start;
uint size;
} single_array;
struct {
const T *const *starts;
const uint *sizes;
} starts_and_sizes;
} data_;
public:
bool is_single_array() const
{
switch (category_) {
case VArraySpanCategory::SingleArray:
return true;
case VArraySpanCategory::StartsAndSizes:
return virtual_size_ == 1;
}
BLI_assert(false);
return false;
}
bool is_empty() const
{
return this->virtual_size_ == 0;
}
uint size() const
{
return this->virtual_size_;
}
};
/**
* A virtual array span. Every element of this span contains a virtual span. So it behaves like
* a blender::Span, but might not be backed up by an actual array.
*/
template<typename T> class VArraySpan : public VArraySpanBase<T> {
private:
friend class GVArraySpan;
VArraySpan(const VArraySpanBase<void> &other)
{
memcpy(this, &other, sizeof(VArraySpanBase<void>));
}
public:
VArraySpan()
{
this->virtual_size_ = 0;
this->category_ = VArraySpanCategory::StartsAndSizes;
this->data_.starts_and_sizes.starts = nullptr;
this->data_.starts_and_sizes.sizes = nullptr;
}
VArraySpan(Span<T> span, uint virtual_size)
{
this->virtual_size_ = virtual_size;
this->category_ = VArraySpanCategory::SingleArray;
this->data_.single_array.start = span.data();
this->data_.single_array.size = span.size();
}
VArraySpan(Span<const T *> starts, Span<uint> sizes)
{
BLI_assert(starts.size() == sizes.size());
this->virtual_size_ = starts.size();
this->category_ = VArraySpanCategory::StartsAndSizes;
this->data_.starts_and_sizes.starts = starts.begin();
this->data_.starts_and_sizes.sizes = sizes.begin();
}
VSpan<T> operator[](uint index) const
{
BLI_assert(index < this->virtual_size_);
switch (this->category_) {
case VArraySpanCategory::SingleArray:
return VSpan<T>(Span<T>(this->data_.single_array.start, this->data_.single_array.size));
case VArraySpanCategory::StartsAndSizes:
return VSpan<T>(Span<T>(this->data_.starts_and_sizes.starts[index],
this->data_.starts_and_sizes.sizes[index]));
}
BLI_assert(false);
return {};
}
};
/**
* A generic virtual array span. It's just like a VArraySpan, but the type is only known at
* run-time.
*/
class GVArraySpan : public VArraySpanBase<void> {
private:
const CPPType *type_;
GVArraySpan() = default;
public:
GVArraySpan(const CPPType &type)
{
this->type_ = &type;
this->virtual_size_ = 0;
this->category_ = VArraySpanCategory::StartsAndSizes;
this->data_.starts_and_sizes.starts = nullptr;
this->data_.starts_and_sizes.sizes = nullptr;
}
GVArraySpan(GSpan array, uint virtual_size)
{
this->type_ = &array.type();
this->virtual_size_ = virtual_size;
this->category_ = VArraySpanCategory::SingleArray;
this->data_.single_array.start = array.buffer();
this->data_.single_array.size = array.size();
}
GVArraySpan(const CPPType &type, Span<const void *> starts, Span<uint> sizes)
{
BLI_assert(starts.size() == sizes.size());
this->type_ = &type;
this->virtual_size_ = starts.size();
this->category_ = VArraySpanCategory::StartsAndSizes;
this->data_.starts_and_sizes.starts = (void **)starts.begin();
this->data_.starts_and_sizes.sizes = sizes.begin();
}
template<typename T> GVArraySpan(VArraySpan<T> other)
{
this->type_ = &CPPType::get<T>();
memcpy(this, &other, sizeof(VArraySpanBase<void>));
}
const CPPType &type() const
{
return *this->type_;
}
template<typename T> VArraySpan<T> typed() const
{
BLI_assert(type_->is<T>());
return VArraySpan<T>(*this);
}
GVSpan operator[](uint index) const
{
BLI_assert(index < virtual_size_);
switch (category_) {
case VArraySpanCategory::SingleArray:
return GVSpan(GSpan(*type_, data_.single_array.start, data_.single_array.size));
case VArraySpanCategory::StartsAndSizes:
return GVSpan(GSpan(
*type_, data_.starts_and_sizes.starts[index], data_.starts_and_sizes.sizes[index]));
}
BLI_assert(false);
return GVSpan(*type_);
}
};
} // namespace blender::fn
#endif /* __FN_ARRAY_SPANS_HH__ */
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