Simple memory pool implementation

Simple memory pool implementation

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Using namespace std; class MemPool {struct FreeNode * next;}; private: static const int allocNum = 8; static const int step = 4; static char * head; static char * tail; static unsigned int poolSize; static int allocSize [allocNum]; static FreeNode * FreeList [allocNum]; static void * GetFromPool (int n ); static void * PoolAlloc (int n, int & num); static int UpToFourTimes (int n); // static int IndexOfFreeLis T (int n); public: static void * alloc (int n); static void dealloc (void * p, int n) ;}; char * MemPool: head = NULL; char * MemPool: tail = NULL; unsigned int MemPool: poolSize = 0; int MemPool: allocSize [MemPool: allocNum] = {4, 8, 12, 16, 20, 24, 28, 32}; MemPool: FreeNode * MemPool: FreeList [MemPool: allocNum] = {0, 0, 0, 0, 0, 0, 0, 0, 0}; void * MemPool: GetFromPool (int n) {int num = 16; int size = UpToFourTime S (n); void * result = PoolAlloc (size, num); if (result = NULL) return NULL; if (num = 1) return result; FreeNode * next, * curr = (FreeNode *) (char *) result + size); FreeNode ** indexNode = FreeList + size/step-1; * indexNode = curr; for (int I = 1; I <num-1; I ++) {next = (FreeNode *) (char *) curr + size); curr-> next = next; curr = next;} curr-> next = NULL; return result;} void * MemPool: PoolAlloc (int n, int & num) {int NeedSize = n * num; char * result; int totalSize = tail-head; if (totalSize> = needSize) {result = head; head + = needSize; return result ;} else if (totalSize> = n) {num = totalSize/n; needSize = num * n; result = head; head + = needSize; return result ;} else {// send the remaining resources to the linked list FreeNode ** indexNode = FreeList + totalSize/step-1; if (head! = NULL) {FreeNode * temp = (FreeNode *) head; int reallocSize = 2 * needSize; temp-> next = * indexNode; * indexNode = temp; head = (char *) malloc (reallocSize); tail = head + reallocSize; poolSize + = reallocSize; temp = (FreeNode *) head; head + = needSize; return temp ;}} int MemPool :: upToFourTimes (int n) {return n % step = 0? N: n + = step-n % step;} void * MemPool: alloc (int n) {if (n> 32) return malloc (n ); int size = UpToFourTimes (n); FreeNode ** indexNode = FreeList + size/step-1; if (* indexNode = NULL) return GetFromPool (size ); freeNode * result = * indexNode; * indexNode = result-> next; return result;} void MemPool: dealloc (void * p, int n) {if (n> 32) return free (p); FreeNode * result = (FreeNode *) p; int size = UpToFourTimes (n); FreeNode ** indexNode = FreeList + size/step-1; result-> next = * indexNode; * indexNode = result; return;} int main (void) {srand (time (NULL); clock_t start, end; start = clock (); for (int I = 0; I <100000000; I ++) {int size = rand () % 32; char * a = (char *) memPool: alloc (size); MemPool: dealloc (a, size);} end = clock (); cout <my time: <end-start <MS <endl; start = clock (); for (int I = 0; I <100000000; I ++) {int size = rand () % 32; char * a = new char [size]; delete [] a;} end = clock (); cout <sys time: <end-start <MS <endl; return 0 ;}