From db99fa5da911089890a3aeb0b5a5a54a4b0cea1f Mon Sep 17 00:00:00 2001
From: iris <iris-engine-dev@gmail.com>
Date: Tue, 23 Aug 2022 20:47:10 +0100
Subject: [PATCH] wip

---
 include/iris/graphics/constant_buffer_pool.h | 83 ++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 include/iris/graphics/constant_buffer_pool.h

diff --git a/include/iris/graphics/constant_buffer_pool.h b/include/iris/graphics/constant_buffer_pool.h
new file mode 100644
index 00000000..f95edc38
--- /dev/null
+++ b/include/iris/graphics/constant_buffer_pool.h
@@ -0,0 +1,83 @@
+////////////////////////////////////////////////////////////////////////////////
+//         Distributed under the Boost Software License, Version 1.0.         //
+//            (See accompanying file LICENSE or copy at                       //
+//                 https://www.boost.org/LICENSE_1_0.txt)                     //
+////////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include <memory>
+
+#include "core/error_handling.h"
+
+namespace iris
+{
+
+template <class T, std::size_t N = 1000, class Allocator = std::allocator<T>>
+class ConstantBufferPool
+{
+  public:
+    ConstantBufferPool()
+        : chunk_alloc_()
+        , chunks_(nullptr)
+        , free_list_(nullptr)
+    {
+        chunks_ = chunk_alloc_.allocate(N);
+
+        auto *cursor = chunks_;
+        for (auto i = 0u; i < N; i++)
+        {
+            ::new (std::addressof(cursor->buffer)) T(1024u * 8u);
+            ++cursor;
+        }
+
+        free_list_ = chunks_;
+    }
+
+    T *next()
+    {
+        ensure(free_list_ != nullptr, "pool has been drained");
+
+        auto *object = std::addressof(free_list_->buffer);
+
+        if (free_list_->next == nullptr)
+        {
+            ++free_list_;
+        }
+        else
+        {
+            free_list_ = free_list_->next;
+        }
+
+        return object;
+    }
+
+    void release(T *object)
+    {
+        auto *chunk = reinterpret_cast<Chunk *>(object) - 1u;
+
+        chunk->next = free_list_;
+        free_list_ = chunk;
+    }
+
+  private:
+    struct Chunk
+    {
+        Chunk(std::size_t size)
+            : next(nullptr)
+            , buffer(size)
+        {
+        }
+
+        Chunk *next;
+        T buffer;
+    };
+
+    typename std::allocator_traits<Allocator>::template rebind_alloc<Chunk> chunk_alloc_;
+
+    Chunk *chunks_;
+
+    Chunk *free_list_;
+};
+
+}