两个字符串函数[c/c++]

//从字符串末尾向首部进行比较

int strendcmp(const char* a, const char* b)
{
    int alen = strlen(a);
    int blen = strlen(b);

    int maxlen = alen < blen ? alen : blen;

    char* apos = (char*)a + alen - 1;
    char* bpos = (char*)b + blen - 1;

    unsigned char achar;
    unsigned char bchar;


    while(maxlen > 0)
    {
        achar = *apos ;
        bchar = *bpos ;
        if (achar > bchar)
        {
            return 1;
        }
        if (achar < bchar)
        {
            return -1;
        }
        maxlen --;
        apos --;
        bpos --;
   }

   if (alen > blen)
   {
        return 1;
   }
   if (alen < blen)
   {
        return -1;
   }
   return 0; // both equal

}

//安全的strcat函数

//max_len为dst的数组长度。

char * strcat_s(char * dst, char * src,int max_len)
{
  char * cp = dst;

  while( *cp ) ++cp; /* Find end of dst */

  while( (int)(cp - dst) < max_len )
  {
    if( (*cp++ = *src++) == 0 ) /* Copy src to end of dst */
        break;
  }

  dst[max_len -1] = 0;

  return dst;
}