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#pragma once
#include "glArrays.h"
#include <cassert>
#include <iterator>
#include <span>
#include <special_members.h>
#include <utility>
#include <vector>
template<typename T> class InstanceVertices {
public:
InstanceVertices(size_t initialSize = 16)
{
allocBuffer(initialSize);
}
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->at(index) = std::forward<U>(v);
}
[[nodiscard]]
operator T &()
{
return instances->at(index);
}
[[nodiscard]] operator const T &() const
{
return instances->at(index);
}
[[nodiscard]] T *
get()
{
return &instances->at(index);
}
[[nodiscard]] const T *
get() const
{
return &instances->at(index);
}
[[nodiscard]] T *
operator->()
{
return get();
}
[[nodiscard]] const T *
operator->() const
{
return get();
}
[[nodiscard]] T &
operator*()
{
return instances->at(index);
}
[[nodiscard]] const T &
operator*() const
{
return instances->at(index);
}
private:
InstanceVertices<T> * instances;
std::size_t index;
};
template<typename... Params>
[[nodiscard]] InstanceProxy
acquire(Params &&... params)
{
map();
if (!unused.empty()) {
auto idx = unused.back();
unused.pop_back();
index[idx] = next++;
new (&at(idx)) T(std::forward<Params>(params)...);
return InstanceProxy {this, idx};
}
if (next >= capacity) {
resize(capacity * 2);
}
index.emplace_back(next++);
new (data + index.back()) T(std::forward<Params>(params)...);
return InstanceProxy {this, index.size() - 1};
}
[[nodiscard]] const auto &
bufferName() const
{
return buffer;
}
[[nodiscard]] auto
count() const
{
unmap();
return next;
}
protected:
friend InstanceProxy;
void
release(const size_t pidx)
{
// Destroy p's object
at(pidx).~T();
if (--next != index[pidx]) {
// Move last object into p's slot
new (&at(pidx)) T {std::move(data[next])};
(data[next]).~T();
*std::find_if(index.begin(), index.end(), [this](const auto & i) {
return i == next && !std::binary_search(unused.begin(), unused.end(), &i - index.data());
}) = index[pidx];
}
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);
}
}
void
allocBuffer(std::size_t newCapacity)
{
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, static_cast<GLsizeiptr>(sizeof(T) * newCapacity), nullptr, GL_DYNAMIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
capacity = newCapacity;
data = nullptr;
}
void
resize(size_t newCapacity)
{
const auto maintain = std::min(newCapacity, capacity);
std::vector<T> existing;
const auto maintaind = static_cast<typename decltype(existing)::difference_type>(maintain);
existing.reserve(maintain);
map();
std::move(data, data + maintain, std::back_inserter(existing));
allocBuffer(newCapacity);
map();
std::move(existing.begin(), existing.begin() + maintaind, data);
capacity = newCapacity;
}
[[nodiscard]] T &
at(size_t pindex)
{
map();
return data[index[pindex]];
}
void
map() const
{
if (!data) {
data = static_cast<T *>(glMapNamedBuffer(buffer, GL_READ_WRITE));
assert(data);
}
}
void
unmap() const
{
if (data) {
glUnmapNamedBuffer(buffer);
data = nullptr;
}
}
glBuffer buffer;
mutable T * data {};
// Size of buffer
std::size_t capacity {};
// # used of capacity
std::size_t next {};
// 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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