Add class to translate from bisection ids to cell ids

include/util/msb.hpp

@@ -0,0 +1,44 @@
+#ifndef OSRM_UTIL_MSB_HPP
+#define OSRM_UTIL_MSB_HPP
+
+#include <boost/assert.hpp>
+
+#include <cstdint>
+#include <utility>
+
+namespace osrm
+{
+namespace util
+{
+
+// get the msb of an integer
+// return 0 for integers without msb
+template <typename T> std::size_t msb(T value)
+{
+    static_assert(std::is_integral<T>::value, "Integer required.");
+    std::size_t msb = 0;
+    while (value > 0)
+    {
+        value >>= 1u;
+        msb++;
+    }
+    return msb;
+}
+
+#if (defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)) && __x86_64__
+inline std::size_t msb(std::uint64_t v)
+{
+    BOOST_ASSERT(v > 0);
+    return 63UL - __builtin_clzl(v);
+}
+inline std::size_t msb(std::uint32_t v)
+{
+    BOOST_ASSERT(v > 0);
+    return 31UL - __builtin_clz(v);
+}
+#endif
+
+}
+}
+
+#endif