memicmp ( )【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】

/*

 memicmp perform a case-insensitive memory comparision.
For differences,upper case letters are mapped to lower case.Thus, "abc_" < "ABCD" since "_" < "d".

   (與memcmp區別就是在比較的時候不區分大小寫)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_tolower(char ch)

{

   if(ch >= 'A' && ch <= 'Z')

      return (ch + 0x20);

   return ch;

}

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

{

    int f = 0;

    int l = 0;

    while (count--)

    {

        if ( (*(unsigned char *)buffer1 == *(unsigned char *)buffer2) ||

                ((f = my_tolower( *(unsigned char *)buffer1 )) ==

                (l =  my_tolower( *(unsigned char *)buffer2 ))) )

        {

        buffer1 = (char *)buffer1 + 1;

        buffer2 = (char *)buffer2 + 1;

        }

        else

            break;

    }

    return ( f - l );

}

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";

   char *str3 = "AMMANA";

   char *str4 = "bab_";

 

   Print(str1,str2,my_memicmp(str1,str2,4));

   Print(str3,str1,my_memicmp(str3,str1,4));

   Print(str4,str2,my_memicmp(str4,str2,4));

  

   system("pause");

   return 0;

}