內存池簡單實例

#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;
}

 

使用內存池的結果是：

total use 0.245 seconds

使用new，delete操作的結果是：

total use 7.256 seconds

 

結果相差近30倍，可見使用內存池對系統的性能有很大的提高

 

MemPool實現源碼參見：http://blog.csdn.net/zhangzhenghe/article/details/5437487