//find 'substr' from a fixed-length buffer

 //('full_data' will be treated as binary data buffer)

 //return NULL if not found

 char* memstr(char* full_data, int full_data_len, char* substr)

 {

     if (full_data == NULL || full_data_len <=  || substr == NULL) {

         return NULL;

     }

     if (*substr == '\0') {

         return NULL;

     }

     int sublen = strlen(substr);

     int i;

     char* cur = full_data;

     int last_possible = full_data_len - sublen + ;

     for (i = ; i < last_possible; i++) {

         if (*cur == *substr) {

             //assert(full_data_len - i >= sublen);

             if (memcmp(cur, substr, sublen) == ) {

                 //found

                 return cur;

             }

         }

         cur++;

     }

     return NULL;

 }

 char* memstr(char* full_data, int full_data_len, char* substr, int substr_len)

 {

 }