Merge branch 'devel'

[palacios.git] / kitten / lib / hweight.c

diff --git a/kitten/lib/hweight.c b/kitten/lib/hweight.c
new file mode 100644 (file)
index 0000000..3d06cff
--- /dev/null
+++ b/kitten/lib/hweight.c
@@ -0,0 +1,53 @@
+#include <lwk/linux_compat.h>
+#include <arch/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);