1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
/* $OpenBSD: ffs.c,v 1.10 2018/01/18 08:23:44 guenther Exp $ */
/*
* Public domain.
* Written by Dale Rahn.
*/
#include <string.h>
/*
* ffs -- vax ffs instruction
*/
int
ffs(int mask)
{
int bit;
unsigned int r = mask;
static const signed char t[16] = {
-28, 1, 2, 1,
3, 1, 2, 1,
4, 1, 2, 1,
3, 1, 2, 1
};
bit = 0;
if (!(r & 0xffff)) {
bit += 16;
r >>= 16;
}
if (!(r & 0xff)) {
bit += 8;
r >>= 8;
}
if (!(r & 0xf)) {
bit += 4;
r >>= 4;
}
return (bit + t[ r & 0xf ]);
}
|
