Subversion Repositories planix.SVN

#include "os.h"
#include <libsec.h>

/*
 * timing safe memcmp()
 */
int
tsmemcmp(void *a1, void *a2, ulong n)
{
        int lt, gt, c1, c2, r, m;
        uchar *s1, *s2;

        r = m = 0;
        s1 = a1;
        s2 = a2;
        while(n--){
                c1 = *s1++;
                c2 = *s2++;
                lt = (c1 - c2) >> 8;
                gt = (c2 - c1) >> 8;
                r |= (lt - gt) & ~m;
                m |= lt | gt;
        }
        return r;
}