You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
43 lines
720 B
43 lines
720 B
2 months ago
|
/*
|
||
|
|
* UCW Library -- Find Highest Set Bit
|
||
|
|
*
|
||
|
|
* (c) 1997-2005 Martin Mares <mj@ucw.cz>
|
||
|
|
*
|
||
|
|
* This software may be freely distributed and used according to the terms
|
||
|
|
* of the GNU Lesser General Public License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <ucw/lib.h>
|
||
|
|
#include <ucw/bitops.h>
|
||
|
|
|
||
|
|
int
|
||
|
|
bit_fls(u32 x)
|
||
|
|
{
|
||
|
|
uint l;
|
||
|
|
|
||
|
|
if (!x)
|
||
|
|
return -1;
|
||
|
|
|
||
|
|
l = 0;
|
||
|
|
if (x & 0xffff0000) { l += 16; x &= 0xffff0000; }
|
||
|
|
if (x & 0xff00ff00) { l += 8; x &= 0xff00ff00; }
|
||
|
|
if (x & 0xf0f0f0f0) { l += 4; x &= 0xf0f0f0f0; }
|
||
|
|
if (x & 0xcccccccc) { l += 2; x &= 0xcccccccc; }
|
||
|
|
if (x & 0xaaaaaaaa) l++;
|
||
|
|
return l;
|
||
|
|
}
|
||
|
|
|
||
|
|
#ifdef TEST
|
||
|
|
|
||
|
|
#include <stdio.h>
|
||
|
|
|
||
|
|
int main(void)
|
||
|
|
{
|
||
|
|
uint i;
|
||
|
|
while (scanf("%x", &i) == 1)
|
||
|
|
printf("%d\n", bit_fls(i));
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif
|