memcpy实现

     
     
     
     

      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        

         
         
         
         void *memcpy(void *dest, const void *src, int count)
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        

         
         
         
         {
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
	
         
         
         
         void *ptr = dest;
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
 
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
	
         
         
         
         if (
         
         
         
         NULL == dest || 
         
         
         
         NULL == src || count <= 
         
         
         
         0)
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        

         
         
         
         	{
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
		
         
         
         
         return 
         
         
         
         NULL;
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        

         
         
         
         	}
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
 
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
	
         
         
         
         while (count--)
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
 
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        

         
         
         
         	*(
         
         
         
         char *)dest++ = *(
         
         
         
         char *)src++;
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
 
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        
	
         
         
         
         return ptr;
        
        
        
        
       
       
       
       
      
      
      
      

       
       
       
       

        
        
        
        

       
       
       
       
       
       
       
       

        
        
        
        

         
         
         
         }