Continuation of the MemoryPool class

git-svn-id: https://reactphysics3d.googlecode.com/svn/trunk@441 92aac97c-a6ce-11dd-a772-7fcde58d38e6

src/memory/MemoryPool.h

@@ -28,6 +28,9 @@
 // Libraries
 #include "../constants.h"
 #include <cstddef>
+#include <cstdlib>
+#include <cassert>
+#include <new>
 
 // ReactPhysics3D namespace
 namespace reactphysics3d {
@@ -40,7 +43,7 @@ namespace reactphysics3d {
         and deallocation.
     -------------------------------------------------------------------
 */
-template<typename T>    // TODO : Check if we need to use a template here
+template<class T>    // TODO : Check if we need to use a template here
 class MemoryPool {
     private:
 
@@ -54,6 +57,8 @@ class MemoryPool {
         struct Unit* pAllocatedLinkedList;      // Pointer to the linked list of allocated memory units
         struct Unit* pFreeLinkedList;           // Pointer to the linked list of free memory units
         size_t memorySize;                      // Total allocated memory in the pool
+        uint currentNbObjects;                  // Current number of objects in the pool
+        const uint initNbAllocatedObjects;      // Number of objects allocated at the beginning (used for reallocation)
 
     public:
         MemoryPool(uint nbObjectsToAllocate) throw(std::bad_alloc);     // Constructor
@@ -64,6 +69,108 @@ class MemoryPool {
 };
 
 
+// Constructor
+// Allocate a large block of memory in order to contain
+// a given number of object of the template type T
+template<class T>
+MemoryPool<T>::MemoryPool(uint nbObjectsToAllocate) throw(std::bad_alloc)
+              : initNbAllocatedObjects(nbObjectsToAllocate), currentNbObjects(0)  {
+    pMemoryBlock = NULL;
+    pAllocatedLinkedList = NULL;
+    pFreeLinkedList = NULL;
+    
+    // Compute the total memory size that need to be allocated
+    memorySize = nbObjectsToAllocate * (sizeof(struct Unit) + sizeof(T));
+
+    // Allocate the whole memory block
+    pMemoryBlock = malloc(memorySize);
+
+    // Check that the allocation didn't fail
+    if (!pMemoryBlock) throw std::bad_alloc();
+
+    // For each allocated memory unit
+    for (uint i=0; i<nbObjectsToAllocate; i++) {
+        // Get the adress of a memory unit
+        struct Unit* currentUnit = (struct Unit*)( (char*)pMemoryBlock + i * (sizeof(T) + sizeof(struct Unit)) );
+
+        currentUnit->pPrevious = NULL;
+        currentUnit->pNext = pFreeLinkedList;
+
+        if (pFreeLinkedList) {
+            pFreeLinkedList->pPrevious = currentUnit;
+        }
+
+        pFreeLinkedList = currentUnit;
+    }
+
+}
+
+// Destructor
+// Deallocate the block of memory that has been allocated previously
+template<class T>
+MemoryPool<T>::~MemoryPool() {
+    // Release the whole memory block
+    free(pMemoryBlock);
+}
+
+// Return a pointer to an memory allocated location to store a new object
+// This method does not allocate memory because it has already been done at the
+// beginning but it returns a pointer to a location in the allocated block of
+// memory where a new object can be stored
+template<class T>
+void* MemoryPool<T>::allocateObject() {
+    // If no memory unit is available in the current allocated memory block
+    if (!pFreeLinkedList) {
+        // TODO : REALLOCATE MEMORY HERE
+        assert(false);
+    }
+
+    assert(pFreeLinkedList);
+    struct Unit* currentUnit = pFreeLinkedList;
+    pFreeLinkedList = currentUnit->pNext;
+    if (pFreeLinkedList) {
+        pFreeLinkedList->pPrevious = NULL;
+    }
+
+    currentUnit->pNext = pAllocatedLinkedList;
+    if (pAllocatedLinkedList) {
+        pAllocatedLinkedList->pPrevious = currentUnit;
+    }
+    pAllocatedLinkedList = currentUnit;
+    
+    currentNbObjects++;
+
+    // Return a pointer to the allocated memory unit
+    return (void*)((char*)currentUnit + sizeof(struct Unit));
+}
+
+// Tell the pool that an object doesn't need to be store in the pool anymore
+// This method does not deallocate memory because it will be done only at the
+// end but it informs the memory pool that an object that was stored in the heap
+// does not need to be stored anymore and therefore we can use the corresponding
+// location in the pool for another object
+template<class T>
+void MemoryPool<T>::freeObject(void* pObjectToFree) {
+    // The pointer location must be inside the memory block
+    assert(pMemoryBlock<pObjectToFree && pObjectToFree<(void*)((char*)pMemoryBlock + memorySize));
+
+    struct Unit* currentUnit = (struct Unit*)((char*)pObjectToFree - sizeof(struct Unit));
+    pAllocatedLinkedList = currentUnit->pNext;
+    if (pAllocatedLinkedList) {
+        pAllocatedLinkedList->pPrevious = NULL;
+    }
+
+    currentUnit->pNext = pFreeLinkedList;
+    if (pFreeLinkedList) {
+        pFreeLinkedList->pPrevious = currentUnit;
+    }
+    pFreeLinkedList = currentUnit;
+    
+    currentNbObjects--;
+}
+
+
+
 }
 
 #endif