added simple poolallocator, increased version to 2.57

src/LinearMath/btPoolAllocator.h

@@ -0,0 +1,72 @@
+/*
+Copyright (c) 2003-2006 Gino van den Bergen / Erwin Coumans  http://continuousphysics.com/Bullet/
+
+This software is provided 'as-is', without any express or implied warranty.
+In no event will the authors be held liable for any damages arising from the use of this software.
+Permission is granted to anyone to use this software for any purpose, 
+including commercial applications, and to alter it and redistribute it freely, 
+subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+*/
+
+
+#ifndef _BT_POOL_ALLOCATOR_H
+#define _BT_POOL_ALLOCATOR_H
+
+#include "btScalar.h"
+
+class btPoolAllocator
+{
+	int				m_elemSize;
+	int				m_maxElements;
+	int				m_freeCount;
+	void*			m_firstFree;
+	unsigned char*	m_pool;
+
+public:
+
+	btPoolAllocator(int elemSize, int maxElements)
+		:m_elemSize(elemSize),
+		m_maxElements(maxElements)
+	{
+		m_pool = new unsigned char[m_elemSize*m_maxElements];
+
+		unsigned char* p = m_pool;
+        m_firstFree = p;
+        m_freeCount = m_maxElements;
+        int count = m_maxElements;
+        while (--count) {
+            *(void**)p = (p + m_elemSize);
+            p += m_elemSize;
+        }
+        *(void**)p = 0;
+    }
+
+	void*	allocate(int size)
+	{
+		btAssert(!size || size<=m_elemSize);
+		btAssert(m_freeCount>0);
+        void* result = m_firstFree;
+        m_firstFree = *(void**)m_firstFree;
+        --m_freeCount;
+        return result;
+	}
+
+	void	free(void* ptr)
+	{
+		 if (ptr) {
+            btAssert((unsigned char*)ptr >= m_pool && (unsigned char*)ptr < m_pool + m_maxElements * m_elemSize);
+
+            *(void**)ptr = m_firstFree;
+            m_firstFree = ptr;
+            ++m_freeCount;
+        }
+	}
+
+
+};
+
+#endif //_BT_POOL_ALLOCATOR_H