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#pragma once
#include "glContainer.h"
#include "pack.h"
#include <cassert>
#include <special_members.h>
#include <utility>
template<typename T> class InstanceVertices : protected glContainer<T> {
using base = glContainer<T>;
public:
class [[nodiscard]] InstanceProxy {
public:
InstanceProxy(InstanceVertices * iv, std::size_t idx) : instances {iv}, index {idx} { }
InstanceProxy(InstanceProxy && other) : instances {std::exchange(other.instances, nullptr)}, index {other.index}
{
}
NO_COPY(InstanceProxy);
~InstanceProxy()
{
if (instances) {
instances->release(index);
}
}
InstanceProxy &
operator=(InstanceProxy && other)
{
if (instances) {
instances->release(index);
}
instances = std::exchange(other.instances, nullptr);
index = other.index;
return *this;
}
template<typename U>
T &
operator=(U && v)
{
return instances->lookup(index) = std::forward<U>(v);
}
[[nodiscard]]
operator T &()
{
return instances->lookup(index);
}
[[nodiscard]] operator const T &() const
{
return instances->lookup(index);
}
[[nodiscard]] T *
get()
{
return &instances->lookup(index);
}
[[nodiscard]] const T *
get() const
{
return &instances->lookup(index);
}
[[nodiscard]] T *
operator->()
{
return get();
}
[[nodiscard]] const T *
operator->() const
{
return get();
}
[[nodiscard]] T &
operator*()
{
return instances->lookup(index);
}
[[nodiscard]] const T &
operator*() const
{
return instances->lookup(index);
}
private:
InstanceVertices<T> * instances;
std::size_t index;
};
template<typename... Params>
[[nodiscard]] InstanceProxy
acquire(Params &&... params)
{
if (!unused.empty()) {
auto idx = unused.back();
unused.pop_back();
index[idx] = base::size();
base::emplace_back(std::forward<Params>(params)...);
return InstanceProxy {this, idx};
}
index.emplace_back(base::size());
base::emplace_back(std::forward<Params>(params)...);
return InstanceProxy {this, index.size() - 1};
}
using base::bufferName;
[[nodiscard]] auto
size() const
{
base::unmap();
return base::size();
}
protected:
friend InstanceProxy;
void
release(const size_t pidx)
{
if (base::size() - 1 != index[pidx]) {
lookup(pidx) = std::move(base::back());
*std::find_if(index.begin(), index.end(), [this, old = base::size() - 1](const auto & i) {
return i == old && !std::binary_search(unused.begin(), unused.end(), &i - index.data());
}) = index[pidx];
}
base::pop_back();
if (pidx == index.size() - 1) {
index.pop_back();
}
else {
// Remember p.index is free index now, keeping it sorted
unused.insert(std::upper_bound(unused.begin(), unused.end(), pidx), pidx);
}
}
[[nodiscard]] T &
lookup(size_t pindex)
{
return base::data()[index[pindex]];
}
// Index into buffer given to nth proxy
std::vector<size_t> index;
// List of free spaces in index
std::vector<size_t> unused;
};
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