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authorAkinobu Mita <mita@miraclelinux.com>2006-03-26 04:39:13 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-26 11:57:11 -0500
commit3b9ed1a5d2d121f32d2cb4f2b05f1fc57c99c946 (patch)
treed8ea52d6b490c0e3b3851e1887c01700cc0115c6 /lib/hweight.c
parent09020adb61416c4307de35941a9725a5e33d9beb (diff)
[PATCH] bitops: generic hweight{64,32,16,8}()
This patch introduces the C-language equivalents of the functions below: unsigned int hweight32(unsigned int w); unsigned int hweight16(unsigned int w); unsigned int hweight8(unsigned int w); unsigned long hweight64(__u64 w); In include/asm-generic/bitops/hweight.h This code largely copied from: include/linux/bitops.h Signed-off-by: Akinobu Mita <mita@miraclelinux.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'lib/hweight.c')
-rw-r--r--lib/hweight.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/lib/hweight.c b/lib/hweight.c
new file mode 100644
index 000000000000..721a4b8b4fb8
--- /dev/null
+++ b/lib/hweight.c
@@ -0,0 +1,54 @@
1#include <linux/module.h>
2#include <asm/types.h>
3
4/**
5 * hweightN - returns the hamming weight of a N-bit word
6 * @x: the word to weigh
7 *
8 * The Hamming Weight of a number is the total number of bits set in it.
9 */
10
11unsigned int hweight32(unsigned int w)
12{
13 unsigned int res = (w & 0x55555555) + ((w >> 1) & 0x55555555);
14 res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
15 res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
16 res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
17 return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
18}
19EXPORT_SYMBOL(hweight32);
20
21unsigned int hweight16(unsigned int w)
22{
23 unsigned int res = (w & 0x5555) + ((w >> 1) & 0x5555);
24 res = (res & 0x3333) + ((res >> 2) & 0x3333);
25 res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F);
26 return (res & 0x00FF) + ((res >> 8) & 0x00FF);
27}
28EXPORT_SYMBOL(hweight16);
29
30unsigned int hweight8(unsigned int w)
31{
32 unsigned int res = (w & 0x55) + ((w >> 1) & 0x55);
33 res = (res & 0x33) + ((res >> 2) & 0x33);
34 return (res & 0x0F) + ((res >> 4) & 0x0F);
35}
36EXPORT_SYMBOL(hweight8);
37
38unsigned long hweight64(__u64 w)
39{
40#if BITS_PER_LONG == 32
41 return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w);
42#elif BITS_PER_LONG == 64
43 u64 res;
44 res = (w & 0x5555555555555555ul) + ((w >> 1) & 0x5555555555555555ul);
45 res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
46 res = (res & 0x0F0F0F0F0F0F0F0Ful) + ((res >> 4) & 0x0F0F0F0F0F0F0F0Ful);
47 res = (res & 0x00FF00FF00FF00FFul) + ((res >> 8) & 0x00FF00FF00FF00FFul);
48 res = (res & 0x0000FFFF0000FFFFul) + ((res >> 16) & 0x0000FFFF0000FFFFul);
49 return (res & 0x00000000FFFFFFFFul) + ((res >> 32) & 0x00000000FFFFFFFFul);
50#else
51#error BITS_PER_LONG not defined
52#endif
53}
54EXPORT_SYMBOL(hweight64);