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authorDmitry Torokhov <dtor_core@ameritech.net>2006-04-02 00:08:05 -0500
committerDmitry Torokhov <dtor_core@ameritech.net>2006-04-02 00:08:05 -0500
commit95d465fd750897ab32462a6702fbfe1b122cbbc0 (patch)
tree65c38b2f11c51bb6932e44dd6c92f15b0091abfe /lib/hweight.c
parent642fde17dceceb56c7ba2762733ac688666ae657 (diff)
parent683aa4012f53b2ada0f430487e05d37b0d94e90a (diff)
downloadlwn-95d465fd750897ab32462a6702fbfe1b122cbbc0.tar.gz
lwn-95d465fd750897ab32462a6702fbfe1b122cbbc0.zip
Manual merge with Linus.
Conflicts: arch/powerpc/kernel/setup-common.c drivers/input/keyboard/hil_kbd.c drivers/input/mouse/hil_ptr.c
Diffstat (limited to 'lib/hweight.c')
-rw-r--r--lib/hweight.c53
1 files changed, 53 insertions, 0 deletions
diff --git a/lib/hweight.c b/lib/hweight.c
new file mode 100644
index 000000000000..438257671708
--- /dev/null
+++ b/lib/hweight.c
@@ -0,0 +1,53 @@
+#include <linux/module.h>
+#include <asm/types.h>
+
+/**
+ * hweightN - returns the hamming weight of a N-bit word
+ * @x: the word to weigh
+ *
+ * The Hamming Weight of a number is the total number of bits set in it.
+ */
+
+unsigned int hweight32(unsigned int w)
+{
+ unsigned int res = w - ((w >> 1) & 0x55555555);
+ res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
+ res = (res + (res >> 4)) & 0x0F0F0F0F;
+ res = res + (res >> 8);
+ return (res + (res >> 16)) & 0x000000FF;
+}
+EXPORT_SYMBOL(hweight32);
+
+unsigned int hweight16(unsigned int w)
+{
+ unsigned int res = w - ((w >> 1) & 0x5555);
+ res = (res & 0x3333) + ((res >> 2) & 0x3333);
+ res = (res + (res >> 4)) & 0x0F0F;
+ return (res + (res >> 8)) & 0x00FF;
+}
+EXPORT_SYMBOL(hweight16);
+
+unsigned int hweight8(unsigned int w)
+{
+ unsigned int res = w - ((w >> 1) & 0x55);
+ res = (res & 0x33) + ((res >> 2) & 0x33);
+ return (res + (res >> 4)) & 0x0F;
+}
+EXPORT_SYMBOL(hweight8);
+
+unsigned long hweight64(__u64 w)
+{
+#if BITS_PER_LONG == 32
+ return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w);
+#elif BITS_PER_LONG == 64
+ __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
+ res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
+ res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
+ res = res + (res >> 8);
+ res = res + (res >> 16);
+ return (res + (res >> 32)) & 0x00000000000000FFul;
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+EXPORT_SYMBOL(hweight64);