实现一个内存池管理的类方法

union obj{ union obj* next; char p[1];   };class MemoryPool{    public:      MemoryPool()      {        union obj* temp;        m_memory.assign(5,(union obj*)NULL);             for(int i=0;i<m_memory.size();i++)        {          for(int j=0;j<m_memory.size();j++)          {           temp = (obj*)malloc(sizeof(char)*(1<<(i+3)));              temp->next = m_memory[i];           m_memory[i] = temp;           }        }      }      char* mem_get(int size)      {        int j;        if( size > 128)        {         char* start = (char*)malloc(sizeof(char)*size);         return start;         }        int index = freelist_index(size);        obj* temp = m_memory[index];        if(temp == NULL) //        {         for(j = index+1;j<m_memory.size();j++)         {           temp = m_memory[j];           if(temp != NULL)           {            m_memory[j] = temp->next;            break;               }            }         if(j>= m_memory.size())         {           for(int j=0;j<m_memory.size();j++)          {           temp = (obj*)malloc(sizeof(char)*(1<<(index+3)));              temp->next = m_memory[index];           m_memory[index] = temp;           }           temp = m_memory[index];          m_memory[index] = temp->next;          return (char*)temp;         }         else         {           obj* cur;                     int up_size = round_up(size);           for(int i=0;i<(1<<(j-index));i++)           {            cur = temp;            cur->next = m_memory[index];            m_memory[index] = cur;            temp = cur+up_size;                    }            temp = m_memory[index];           m_memory[index] = temp->next;           return (char*)temp;         }           }        else        {          m_memory[index] = temp->next;         return (char*)temp;         }      }      void mem_free(void* p,int size)      {       if(size > 128)       {        free(p);        return ;         }         obj* temp = (obj*)p;       int index = freelist_index(size);       temp->next = m_memory[index];       m_memory[index] = temp;      }   private:       enum {_ALIGN = 8};//       int freelist_index(int __bytes)        {         return (((__bytes) + (int)_ALIGN-1)/(size_t)_ALIGN - 1);       }       int round_up(int __bytes)        {         return (((__bytes) + (int) _ALIGN-1) & ~((int) _ALIGN - 1));        }       vector<union obj*> m_memory;    };