diff --git a/bitwise.hpp b/bitwise.hpp
index 0743cb45..3e76f76e 100644
--- a/bitwise.hpp
+++ b/bitwise.hpp
@@ -11,11 +11,14 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
- * Copyright 2011 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2011-2018 Danny Robson <danny@nerdcruft.net>
  */
 
-#ifndef __UTIL_BITWISE_HPP
-#define __UTIL_BITWISE_HPP
+#ifndef CRUFT_UTIL_BITWISE_HPP
+#define CRUFT_UTIL_BITWISE_HPP
+
+#include "types/bits.hpp"
+#include "debug.hpp"
 
 #include <type_traits>
 #include <cstdint>
@@ -87,6 +90,26 @@ namespace util {
     {
         return __builtin_popcount (t);
     }
+
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// returns the integral value composed of the bits from `val' in the
+    /// inclusive range [lo, hi].
+    template <typename ValueT, typename IndexT>
+    constexpr ValueT
+    from_bits (ValueT val, IndexT hi, IndexT lo)
+    {
+        CHECK_LT (hi, IndexT (sizeof (ValueT) * 8));
+        CHECK_LT (lo, IndexT (sizeof (ValueT) * 8));
+        CHECK_GE (hi, 0);
+        CHECK_GE (lo, 1);
+        CHECK_GE (hi, lo);
+
+        ValueT zero = 0;
+        ValueT ones = ~zero;
+
+        return (val >> lo) & (ones >> (sizeof (ValueT) * 8 - (hi - lo + 1)));
+    }
 }
 
 #endif