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/* $OpenBSD: ffs.c,v 1.6 2004/08/07 00:38:32 deraadt Exp $ */
/*
* Public domain.
* Written by Dale Rahn.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char *rcsid = "$OpenBSD: ffs.c,v 1.6 2004/08/07 00:38:32 deraadt Exp $";
#endif /* LIBC_SCCS and not lint */
#if !defined(_KERNEL) && !defined(_STANDALONE)
#include <string.h>
#else
#include <lib/libkern/libkern.h>
#endif
/*
* 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 ]);
}
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