count_bits() moved to mysys/

1 files changed, 42 insertions, 0 deletions

diff --git a/mysys/my_bit.c b/mysys/my_bit.c
index 0ff487afe03..55dd72f5f76 100644
--- a/mysys/my_bit.c
+++ b/mysys/my_bit.c
@@ -29,3 +29,45 @@ uint my_bit_log2(ulong value)
   for (bit=0 ; value > 1 ; value>>=1, bit++) ;
   return bit;
 }
+
+static char nbits[256] = {
+  0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
+  1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+  1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+  1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+  1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+  4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
+};
+
+uint my_count_bits(ulonglong v)
+{
+#if SIZEOF_LONG_LONG > 4
+  /* The following code is a bit faster on 16 bit machines than if we would
+     only shift v */
+  ulong v2=(ulong) (v >> 32);
+  return (uint) (uchar) (nbits[(uchar)  v] +
+                         nbits[(uchar) (v >> 8)] +
+                         nbits[(uchar) (v >> 16)] +
+                         nbits[(uchar) (v >> 24)] +
+                         nbits[(uchar) (v2)] +
+                         nbits[(uchar) (v2 >> 8)] +
+                         nbits[(uchar) (v2 >> 16)] +
+                         nbits[(uchar) (v2 >> 24)]);
+#else
+  return (uint) (uchar) (nbits[(uchar)  v] +
+                         nbits[(uchar) (v >> 8)] +
+                         nbits[(uchar) (v >> 16)] +
+                         nbits[(uchar) (v >> 24)]);
+#endif
+}
+