实现一个内存池管理的类方法

模拟STL中的freelist,有这个思想在内。

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;inext = 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;jnext;
     break;    
    }   
  }
  if(j>= m_memory.size())
  {
    for(int j=0;jnext = 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 m_memory; 
   };

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