NAME
ffs32
, ffs64
,
fls32
, fls64
—
find first or last bit set
SYNOPSIS
#include
<sys/bitops.h>
int
ffs32
(uint32_t
n);
int
ffs64
(uint64_t
n);
int
fls32
(uint32_t
n);
int
fls64
(uint64_t
n);
DESCRIPTION
Theffs32
()
and
ffs64
()
functions find the first bit set in n and return the
index of that bit. Conversely, the
fls32
()
and
fls64
()
functions find the last bit set in n, returning the
index of the bit.
The search always starts from the bit 1 (the least significant bit). If the argument n is zero, each function returns zero.
IMPLEMENTATION NOTES
The described functions are implemented as
static
inline functions in the
<sys/bitops.h>
header. The
standard C library includes a more portable
ffs(3) for user applications.
EXAMPLES
In the following example f = 3 and l = 7:
uint32_t n = 0x44; /* 01000100 */ int f, l; f = ffs32(n); l = fls32(n);
SEE ALSO
HISTORY
These functions first appeared in NetBSD 5.0.