memcmp ( )【C語言庫函數原始碼】

【C語言庫函數原始碼】

【本程式在Dev C++ 4.9.9.2 下編譯通過】

/*

   Compares count bytes of memory starting at buffer1 and buffer2 and

find if equal or which one is first in lexical order.

   比較記憶體地區buffer1和buffer2的前count個位元組。當buffer1 < buffer2時，傳回值 < 0；

當buffer1 = buffer2時，傳回值 0；當buffer1 > buffer2時，傳回值 > 0。

*/

int my_memcmp(const void *buffer1,const void *buffer2,int count)

{

   if (!count)

      return(0);

   while ( --count && *(char *)buffer1 == *(char *)buffer2)

   {

      buffer1 = (char *)buffer1 + 1;

        buffer2 = (char *)buffer2 + 1;

   }

   return( *((unsigned char *)buffer1) - *((unsigned char *)buffer2) );

}

void Print(char * str1,char *str2,int t)

{

   if(t > 0)

      printf("/n%s Upper Than %s/n",str1,str2);

   else if(t < 0)

      printf("/n%s Lower Than %s/n",str1,str2);

   else

      printf("/n%s Equal %s/n",str1,str2);

     

}

int main()

{

   char *str1= "ammana";

   char *str2 = "babi";

 

   Print(str1,str2,my_memcmp(str1,str2,3));

   Print(str2,str1,my_memcmp(str2,str1,3));

   Print(str2,str2,my_memcmp(str2,str2,3));

  

   system("pause");

   return 0;

}