1 files changed, 32 insertions, 1 deletions
diff --git a/src/H5Vprivate.h b/src/H5Vprivate.h
index 52f9d6b..55047cb 100644
--- a/src/H5Vprivate.h
+++ b/src/H5Vprivate.h
@@ -300,4 +300,35 @@ H5V_vector_inc(int n, hsize_t *v1, const hsize_t *v2)
     while (n--) *v1++ += *v2++;
 }
 
-#endif
+
+/*-------------------------------------------------------------------------
+ * Function:    H5V_power_of_two
+ *
+ * Purpose:     Determines the log base two of a number (i.e. log2(n)).
+ *
+ * Note:        N must be a power of two and is limited to 32-bit quantities.
+
+ *              This is from the "Bit Twiddling Hacks" at:
+ *                  http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogDeBruijn
+ *
+ * Return:      log2(n) (always - no failure condition)
+ *
+ * Programmer:  Quincey Koziol
+ *              Monday, Febraury 27, 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+static H5_inline unsigned 
+H5V_log2(unsigned n)
+{
+    static const unsigned MultiplyDeBruijnBitPosition[32] = 
+    {
+          0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, 
+            31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
+    };
+
+    return(MultiplyDeBruijnBitPosition[(n * 0x077CB531UL) >> 27]);
+} /* H5V_log2() */
+
+#endif /* H5Vprivate_H */
+