内存池简单实例

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <iostream>

using namespace std;

class MemPool
{
  public:
     MemPool();
     ~MemPool();
     void* Alloc();
     void Free(void* p);

  private:
      const static int blockSize = 1024;
      const static int itemSize = 16;

      struct ItemNode
      {
             ItemNode *next;
             char data[itemSize - sizeof(ItemNode*)];
      };

      struct BlockNode
      {
             BlockNode *next;
             ItemNode data[blockSize/itemSize];
      };

      ItemNode *freeItemNodeHead;
      BlockNode *memBlockNodeHead;
};

MemPool::MemPool():memBlockNodeHead(NULL), freeItemNodeHead(NULL)
{
}

MemPool::~MemPool()
{
    BlockNode *temp = memBlockNodeHead;
     while(temp)
     {
        memBlockNodeHead = memBlockNodeHead->next;
        delete temp;
        temp = memBlockNodeHead;
    }
}

void* MemPool::Alloc()
{
      if(freeItemNodeHead == NULL)
      {
         BlockNode *tempBlockNode = new BlockNode;
         if(tempBlockNode == NULL)
         {
                   perror("allocate memory error!\n");
                   exit(1);
         }

         if(memBlockNodeHead == NULL)
         {
                  memBlockNodeHead = tempBlockNode;
                  memBlockNodeHead->next = NULL;
         }
         else
         {
                  tempBlockNode->next = memBlockNodeHead;
                  memBlockNodeHead = tempBlockNode;
         }

         freeItemNodeHead = &(memBlockNodeHead->data[0]);

         int i = 0;
         while(i < blockSize/itemSize -1)
         {
                  tempBlockNode->data[i].next = &(tempBlockNode->data[i+1]);
                  ++i;
         }

         tempBlockNode->data[i].next = NULL;
     }

     ItemNode *allocItemNode = freeItemNodeHead;
     freeItemNodeHead = freeItemNodeHead->next;

     return allocItemNode;
}

void MemPool::Free(void* p)
{
      ItemNode *tempItemNode = static_cast<ItemNode*>(p);
      tempItemNode->next = freeItemNodeHead;
      freeItemNodeHead = tempItemNode;
}

int main()
{
     MemPool pool;
     char *p = NULL;

     clock_t start, finish;

     double duration;

     long i = 0;

     start = clock();

     while(i < 10000000)
     {
             p = static_cast<char*>(pool.Alloc());
             //p = new char[16];
             ++i;
             pool.Free(p);
             //delete p;
    }

    finish = clock();

    duration = (double)(finish - start)/CLOCKS_PER_SEC;

    cout << "total use " << duration << " seconds" << endl;

    system("pause");

    return 0;
}

 

使用内存池的结果是：

total use 0.245 seconds

使用new，delete操作的结果是：

total use 7.256 seconds

 

结果相差近30倍，可见使用内存池对系统的性能有很大的提高

 

MemPool实现源码参见：http://blog.csdn.net/zhangzhenghe/article/details/5437487