From bfbbfc325f081d9523f56accc267167c82ffa495 Mon Sep 17 00:00:00 2001
From: Stanislaw Halik <sthalik@misaki.pl>
Date: Sun, 19 Mar 2023 18:20:49 +0100
Subject: src/rtree: add simple object pool impl

---
 src/RTree.cpp | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/RTree.h   | 13 ++++++-------
 src/RTree.hpp | 28 ++++++++++++++++++++++-----
 3 files changed, 90 insertions(+), 12 deletions(-)

diff --git a/src/RTree.cpp b/src/RTree.cpp
index 81677922..bee4641c 100644
--- a/src/RTree.cpp
+++ b/src/RTree.cpp
@@ -1,3 +1,64 @@
+#define RTREE_NO_EXTERN_TEMPLATE_POOL
 #include "RTree.hpp"
 
+//#define RTREE_POOL_DEBUG
+
+#ifdef RTREE_POOL_DEBUG
+#include <cstdio>
+#include <Corrade/Containers/StringView.h>
+#include <Corrade/Utility/Debug.h>
+#endif
+
+namespace floormat::detail {
+
+template<typename T> rtree_pool<T>::rtree_pool()
+{
+    free_list.reserve(128);
+}
+
+template<typename T> rtree_pool<T>::~rtree_pool()
+{
+    for (auto* ptr : free_list)
+        ::operator delete(ptr);
+    free_list.clear();
+    free_list.shrink_to_fit();
+}
+
+template<typename T> T* rtree_pool<T>::construct()
+{
+    if (free_list.empty())
+    {
+#ifdef RTREE_POOL_DEBUG
+        static unsigned i = 0; Debug{} << "rtree-pool: fresh"_s << ++i; std::fflush(stdout);
+#endif
+        return new T;
+    }
+    else
+    {
+        auto* ret = free_list.back();
+        free_list.pop_back();
+        new (ret) T();
+#ifdef RTREE_POOL_DEBUG
+        static unsigned i = 0; Debug{} << "rtree-pool: reused"_s << ++i; std::fflush(stdout);
+#endif
+        return ret;
+    }
+}
+
+template<typename T> void rtree_pool<T>::free(T* ptr)
+{
+    ptr->~T();
+    free_list.push_back(ptr);
+}
+
+using my_rtree = RTree<uint64_t, float, 2, float>;
+
+template<> std::vector<my_rtree::Node*> rtree_pool<my_rtree::Node>::free_list = {}; // NOLINT
+template<> std::vector<my_rtree::ListNode*> rtree_pool<my_rtree::ListNode>::free_list = {}; // NOLINT
+
+template struct floormat::detail::rtree_pool<my_rtree::Node>;
+template struct floormat::detail::rtree_pool<my_rtree::ListNode>;
+
+} // namespace floormat::detail
+
 template class RTree<floormat::uint64_t, float, 2, float>;
diff --git a/src/RTree.h b/src/RTree.h
index 9ef66f34..1a30a735 100644
--- a/src/RTree.h
+++ b/src/RTree.h
@@ -17,15 +17,16 @@
 // RTree.h
 //
 
-#define RTREE_DONT_USE_MEMPOOLS // This version does not contain a fixed memory allocator, fill in lines with EXAMPLE to implement one.
+//#define RTREE_DONT_USE_MEMPOOLS // This version does not contain a fixed memory allocator, fill in lines with EXAMPLE to implement one.
 #define RTREE_USE_SPHERICAL_VOLUME // Better split classification, may be slower on some systems
 
+namespace floormat::detail { template<typename T> struct rtree_pool; }
+
 #ifdef RTREE_STDIO
 // Fwd decl
 class RTFileStream;  // File I/O helper class, look below for implementation and notes.
 #endif
 
-
 /// \class RTree
 /// Implementation of RTree, a multidimensional bounding rectangle tree.
 /// Example usage: For a 3-dimensional tree use RTree<Object*, float, 3> myTree;
@@ -47,11 +48,10 @@ template<class DATATYPE, class ELEMTYPE, int NUMDIMS,
 class RTree
 {
 
-protected:
+public:
 
   struct Node;  // Fwd decl.  Used by other internal structs and iterator
-
-public:
+  struct ListNode;
 
   // These constant must be declared after Branch and before Node struct
   // Stuck up here for MSVC 6 compiler.  NSVC .NET 2003 is much happier.
@@ -184,8 +184,6 @@ public:
     ELEMTYPE m_max[NUMDIMS];                      ///< Max dimensions of bounding box
   };
 
-protected:
-
   /// May be data or may be another subtree
   /// The parents level determines this.
   /// If the parents level is 0, then this is data
@@ -214,6 +212,7 @@ protected:
     Node* m_node;                                 ///< Node
   };
 
+protected:
   /// Variables for finding a split partition
   struct PartitionVars
   {
diff --git a/src/RTree.hpp b/src/RTree.hpp
index da60a76f..45cbb378 100644
--- a/src/RTree.hpp
+++ b/src/RTree.hpp
@@ -32,6 +32,24 @@
   #define Max std::max
 #endif //Max
 
+namespace floormat::detail {
+template<typename T> struct rtree_pool final
+{
+    rtree_pool();
+    ~rtree_pool();
+    static T* construct();
+    static void free(T* pool);
+
+private:
+    static std::vector<T*> free_list; // NOLINT
+};
+
+#ifndef RTREE_NO_EXTERN_TEMPLATE_POOL
+extern template struct rtree_pool<RTree<std::uint64_t, float, 2, float>::Node>;
+extern template struct rtree_pool<RTree<std::uint64_t, float, 2, float>::ListNode>;
+#endif
+} // namespace floormat::detail
+
 #ifdef RTREE_STDIO
 // Because there is not stream support, this is a quick and dirty file I/O helper.
 // Users will likely replace its usage with a Stream implementation from their favorite API.
@@ -508,7 +526,7 @@ void RTREE_QUAL::RemoveAll()
 RTREE_TEMPLATE
 void RTREE_QUAL::Reset()
 {
-#ifdef RTREE_DONT_USE_MEMPOOLS
+#if defined RTREE_DONT_USE_MEMPOOLS || 1
   // Delete all existing nodes
   RemoveAllRec(m_root);
 #else // RTREE_DONT_USE_MEMPOOLS
@@ -542,7 +560,7 @@ typename RTREE_QUAL::Node* RTREE_QUAL::AllocNode()
 #ifdef RTREE_DONT_USE_MEMPOOLS
   newNode = new Node;
 #else // RTREE_DONT_USE_MEMPOOLS
-  // EXAMPLE
+  newNode = floormat::detail::rtree_pool<Node>::construct();
 #endif // RTREE_DONT_USE_MEMPOOLS
   InitNode(newNode);
   return newNode;
@@ -557,7 +575,7 @@ void RTREE_QUAL::FreeNode(Node* a_node)
 #ifdef RTREE_DONT_USE_MEMPOOLS
   delete a_node;
 #else // RTREE_DONT_USE_MEMPOOLS
-  // EXAMPLE
+  floormat::detail::rtree_pool<Node>::free(a_node);
 #endif // RTREE_DONT_USE_MEMPOOLS
 }
 
@@ -570,7 +588,7 @@ typename RTREE_QUAL::ListNode* RTREE_QUAL::AllocListNode()
 #ifdef RTREE_DONT_USE_MEMPOOLS
   return new ListNode;
 #else // RTREE_DONT_USE_MEMPOOLS
-  // EXAMPLE
+  return floormat::detail::rtree_pool<ListNode>::construct();
 #endif // RTREE_DONT_USE_MEMPOOLS
 }
 
@@ -581,7 +599,7 @@ void RTREE_QUAL::FreeListNode(ListNode* a_listNode)
 #ifdef RTREE_DONT_USE_MEMPOOLS
   delete a_listNode;
 #else // RTREE_DONT_USE_MEMPOOLS
-  // EXAMPLE
+  floormat::detail::rtree_pool<ListNode>::free(a_listNode);
 #endif // RTREE_DONT_USE_MEMPOOLS
 }
 
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