From 27aa985f450a7d2312f8731991d4e4e9ec122e8d Mon Sep 17 00:00:00 2001
From: Martin Braun <martin.braun@ettus.com>
Date: Thu, 23 Oct 2014 18:07:07 +0200
Subject: math: Added a portable log2()

---
 host/include/uhd/utils/math.hpp | 12 +++++++++++-
 host/tests/CMakeLists.txt       |  1 +
 host/tests/math_test.cpp        | 29 +++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 host/tests/math_test.cpp

diff --git a/host/include/uhd/utils/math.hpp b/host/include/uhd/utils/math.hpp
index 21825c3dc..a41a35d67 100644
--- a/host/include/uhd/utils/math.hpp
+++ b/host/include/uhd/utils/math.hpp
@@ -18,11 +18,11 @@
 #ifndef INCLUDED_UHD_UTILS_MATH_HPP
 #define INCLUDED_UHD_UTILS_MATH_HPP
 
+#include <cmath>
 #include <uhd/config.hpp>
 #include <boost/cstdint.hpp>
 #include <boost/numeric/conversion/bounds.hpp>
 
-
 namespace uhd {
 
 /*!
@@ -237,6 +237,16 @@ namespace fp_compare {
                 == fp_compare::fp_compare_delta<double>(rhs, FREQ_COMPARISON_DELTA_HZ));
     }
 
+    //! Portable log2()
+    template <typename float_t> UHD_INLINE
+    float_t log2(float_t x)
+    {
+        // C++11 defines std::log2(), when that's universally supported
+        // we can switch over.
+        return std::log(x) / std::log(2);
+    }
+
+
 } // namespace math
 } // namespace uhd
 
diff --git a/host/tests/CMakeLists.txt b/host/tests/CMakeLists.txt
index ea0b30cb8..579fd46ca 100644
--- a/host/tests/CMakeLists.txt
+++ b/host/tests/CMakeLists.txt
@@ -34,6 +34,7 @@ SET(test_sources
     fp_compare_delta_test.cpp
     fp_compare_epsilon_test.cpp
     gain_group_test.cpp
+    math_test.cpp
     msg_test.cpp
     property_test.cpp
     ranges_test.cpp
diff --git a/host/tests/math_test.cpp b/host/tests/math_test.cpp
new file mode 100644
index 000000000..6c890c484
--- /dev/null
+++ b/host/tests/math_test.cpp
@@ -0,0 +1,29 @@
+//
+// Copyright 2014 Ettus Research LLC
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#include <boost/test/unit_test.hpp>
+#include <boost/cstdint.hpp>
+#include <uhd/utils/math.hpp>
+
+// NOTE: This is not the only math test case, see e.g. special tests
+// for fp comparison.
+
+BOOST_AUTO_TEST_CASE(test_log2){
+    double y = uhd::math::log2(16.0);
+    BOOST_CHECK_EQUAL(y, 4.0);
+}
+
-- 
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