1 files changed, 177 insertions, 0 deletions
diff --git a/src/libjin/common/je_pool.hpp b/src/libjin/common/je_pool.hpp
new file mode 100644
index 0000000..cb96c5b
--- /dev/null
+++ b/src/libjin/common/je_pool.hpp
@@ -0,0 +1,177 @@
+/// 
+/// An O(1) Object Pool. Original from https://www.codeproject.com/Articles/746630/O-Object-Pool-in-Cplusplus
+/// 
+#ifndef __JE_POOL_H__
+#define __JE_POOL_H__
+
+#include <stdlib.h>
+#include <iostream>
+
+#include "je_types.h"
+
+namespace JinEngine
+{
+
+    class DefaultMemoryAllocator
+    {
+    public:
+        static inline void *Allocate(size_t size)
+        {
+            return ::operator new(size, ::std::nothrow);
+        }
+        static inline void Deallocate(void *pointer, size_t size)
+        {
+            ::operator delete(pointer);
+        }
+    };
+
+    template<typename T, class TMemoryAllocator = DefaultMemoryAllocator>
+    class Pool
+    {
+    private:
+        struct _Node
+        {
+            void *_memory;
+            size_t _capacity;
+            _Node *_nextNode;
+
+            _Node(size_t capacity)
+            {
+                if (capacity < 1)
+                    throw std::invalid_argument("capacity must be at least 1.");
+
+                _memory = TMemoryAllocator::Allocate(_itemSize * capacity);
+                if (_memory == NULL)
+                    throw std::bad_alloc();
+
+                _capacity = capacity;
+                _nextNode = NULL;
+            }
+            ~_Node()
+            {
+                TMemoryAllocator::Deallocate(_memory, _itemSize * _capacity);
+            }
+        };
+
+        void *_nodeMemory;
+        T *_firstDeleted;
+        size_t _countInNode;
+        size_t _nodeCapacity;
+        _Node _firstNode;
+        _Node *_lastNode;
+        size_t _maxBlockLength;
+
+        static const size_t _itemSize;
+
+        Pool(const Pool<T, TMemoryAllocator> &source);
+        void operator = (const Pool<T, TMemoryAllocator> &source);
+
+        void _AllocateNewNode()
+        {
+            size_t size = _countInNode;
+            if (size >= _maxBlockLength)
+                size = _maxBlockLength;
+            else
+            {
+                size *= 2;
+
+                if (size < _countInNode)
+                    throw std::overflow_error("size became too big.");
+
+                if (size >= _maxBlockLength)
+                    size = _maxBlockLength;
+            }
+
+            _Node *newNode = new _Node(size);
+            _lastNode->_nextNode = newNode;
+            _lastNode = newNode;
+            _nodeMemory = newNode->_memory;
+            _countInNode = 0;
+            _nodeCapacity = size;
+        }
+
+    public:
+        explicit Pool(size_t initialCapacity = 32, size_t maxBlockLength = 1000000) 
+            : _firstDeleted(NULL)
+            , _countInNode(0)
+            , _nodeCapacity(initialCapacity)
+            , _firstNode(initialCapacity)
+            , _maxBlockLength(maxBlockLength)
+        {
+            if (maxBlockLength < 1)
+                throw std::invalid_argument("maxBlockLength must be at least 1.");
+
+            _nodeMemory = _firstNode._memory;
+            _lastNode = &_firstNode;
+        }
+        ~Pool()
+        {
+            _Node *node = _firstNode._nextNode;
+            while (node)
+            {
+                _Node *nextNode = node->_nextNode;
+                delete node;
+                node = nextNode;
+            }
+        }
+
+        T *New()
+        {
+            if (_firstDeleted)
+            {
+                T *result = _firstDeleted;
+                _firstDeleted = *((T **)_firstDeleted);
+                new(result) T();
+                return result;
+            }
+
+            if (_countInNode >= _nodeCapacity)
+                _AllocateNewNode();
+
+            char *address = (char *)_nodeMemory;
+            address += _countInNode * _itemSize;
+            T *result = new(address) T();
+            _countInNode++;
+            return result;
+        }
+
+        // This method is useful if you want to call a non-default constructor.
+        // It should be used like this:
+        // new (pool.GetNextWithoutInitializing()) ObjectType(... parameters ...);
+        T *GetNextWithoutInitializing()
+        {
+            if (_firstDeleted)
+            {
+                T *result = (T *)_firstDeleted;
+                _firstDeleted = *((T **)_firstDeleted);
+                return result;
+            }
+
+            if (_countInNode >= _nodeCapacity)
+                _AllocateNewNode();
+
+            char *address = (char *)_nodeMemory;
+            address += _countInNode * _itemSize;
+            _countInNode++;
+            return (T *)address;
+        }
+        void Delete(T *content)
+        {
+            content->~T();
+
+            *((T **)content) = _firstDeleted;
+            _firstDeleted = content;
+        }
+        void DeleteWithoutDestroying(T *content)
+        {
+            *((T **)content) = _firstDeleted;
+            _firstDeleted = content;
+        }
+    };
+
+    template<typename T, class TMemoryAllocator>
+    const size_t Pool<T, TMemoryAllocator>::_itemSize = ((sizeof(T) + sizeof(void *) - 1) / sizeof(void *)) * sizeof(void *);
+
+} // namespace JinEngine
+
+#endif
+\ No newline at end of file