#include <stdio.h>

 #include <string.h>

 /*

 *int memcmp (const void *s1,const void *s2,size_t n);

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 *p is src, q is des, len is length of p

 *error     =-1

 *p>q     >0

 *p<q     <0

 *p==q    =0

 */

 int _memcmp(const void *p,const void *q,int len)

 {

     if(!p || !q)

     {

         return -;

     }

    // while((*(char *)p != '\0') && (*(char *)q != '\0') && (len > ))
　　　　while(len > 0)//this is strcmp , memcmp should't test \0

     {

         //printf("p %p:%d q %p:%d len %d\n",p,*(char *)p,q,*(char *)q,len);

         if((*(char *)p - *(char *)q) != )

         {

             return (*(char *)p-*(char *)q);

         }

         p++;

         q++;

         len--;

     }

     if((len >  ) && (*(char *)p != '\0'))

     {

         return ;

     }

     if((len >  ) && (*(char *)q != '\0'))

     {

         return -;

     }

     return ;

 }

 int main(int argc, char **argv)

 {

     char *p = "abcfgf";

     char *q = "abcfg";

     int val;

     val = memcmp(p,q,);

     printf("sys val is %d\n",val);    

     val = _memcmp(p,q,);

     printf("my val is %d  \n",val);

     return ;

 }