From 755e0d92cb9121938d63952d80f61338c179ca15 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 11 Sep 2014 15:34:59 +1000
Subject: [PATCH] maths: add log2

---
 maths.cpp | 20 ++++++++++++++++++++
 maths.hpp |  5 +++++
 2 files changed, 25 insertions(+)

diff --git a/maths.cpp b/maths.cpp
index b679468d..8c9d49a1 100644
--- a/maths.cpp
+++ b/maths.cpp
@@ -40,6 +40,26 @@ template bool is_pow2 (uint32_t);
 template bool is_pow2 (uint64_t);
 
 
+//-----------------------------------------------------------------------------
+template <typename T>
+T
+log2 (T v) {
+    static_assert (std::is_integral<T>::value,
+                   "log2 is only implemented for integers");
+
+    T l = 0;
+    while (v) {
+        v >>= 1;
+        l  += 1;
+    }
+
+    return l;
+}
+
+template uint32_t log2 (uint32_t);
+template uint64_t log2 (uint64_t);
+
+
 //-----------------------------------------------------------------------------
 template <typename T>
 double
diff --git a/maths.hpp b/maths.hpp
index 815f3987..19c44d75 100644
--- a/maths.hpp
+++ b/maths.hpp
@@ -36,6 +36,11 @@ bool
 is_pow2 (T value) pure;
 
 
+template <typename T>
+T
+log2 (T val) pure;
+
+
 template <typename T>
 double
 rootsquare (T a, T b) pure;