From 16ef34f9c5c49c205802937a76f219eb561b6f9f Mon Sep 17 00:00:00 2001
From: Christophe Riccio <mail@g-truc.net>
Date: Thu, 13 Oct 2011 18:36:44 +0100
Subject: [PATCH] Added log2 for int types

---
 glm/core/_detail.hpp          | 85 +++++++++++++++++++++++++++++++++++
 glm/core/func_exponential.inl | 28 ++++++++++--
 glm/glm.hpp                   |  1 +
 glm/gtx/integer.hpp           |  3 +-
 glm/gtx/integer.inl           | 24 +++++-----
 5 files changed, 124 insertions(+), 17 deletions(-)

diff --git a/glm/core/_detail.hpp b/glm/core/_detail.hpp
index e6d2e128..ce933aa0 100644
--- a/glm/core/_detail.hpp
+++ b/glm/core/_detail.hpp
@@ -345,6 +345,91 @@ namespace detail
 	typedef float								float32;
 	typedef double								float64;
 	
+	//////////////////
+	// float_or_int_trait 
+
+	struct float_or_int_value
+	{
+		enum
+		{
+			ERROR,
+			FLOAT,
+			INT
+		};
+	};
+
+	template <typename T>
+	struct float_or_int_trait
+	{
+		enum{ID = float_or_int_value::ERROR};
+	};
+
+	template <>
+	struct float_or_int_trait<int8>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<int16>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<int32>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<int64>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<uint8>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<uint16>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<uint32>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<uint64>
+	{
+		enum{ID = float_or_int_value::INT};
+	};
+
+	template <>
+	struct float_or_int_trait<float16>
+	{
+		enum{ID = float_or_int_value::FLOAT};
+	};
+
+	template <>
+	struct float_or_int_trait<float32>
+	{
+		enum{ID = float_or_int_value::FLOAT};
+	};
+
+	template <>
+	struct float_or_int_trait<float64>
+	{
+		enum{ID = float_or_int_value::FLOAT};
+	};
+
 }//namespace detail
 
 }//namespace glm
diff --git a/glm/core/func_exponential.inl b/glm/core/func_exponential.inl
index c8c385f7..c1ffee92 100644
--- a/glm/core/func_exponential.inl
+++ b/glm/core/func_exponential.inl
@@ -224,6 +224,30 @@ namespace glm
             exp2(x.w));
     }
 
+namespace detail
+{
+	template <int PATH = float_or_int_value::ERROR>
+	struct compute_log2
+	{
+		template <typename T>
+		T operator() (T const & Value) const
+		{
+			static_assert(0, "'log2' parameter has an invalid template parameter type");
+			return Value;
+		}
+	};
+
+	template <>
+	struct compute_log2<float_or_int_value::FLOAT>
+	{
+		template <typename T>
+		T operator() (T const & Value) const
+		{
+			return ::std::log(Value) / T(0.69314718055994530941723212145818);
+		}
+	};
+}//namespace detail
+
     // log2, ln2 = 0.69314718055994530941723212145818f
     template <typename genType>
     GLM_FUNC_QUALIFIER genType log2
@@ -231,9 +255,7 @@ namespace glm
 		genType const & x
 	)
     {
-		GLM_STATIC_ASSERT(detail::type<genType>::is_float, "'log2' only accept floating-point input");
-
-        return ::std::log(x) / genType(0.69314718055994530941723212145818);
+		return detail::compute_log2<detail::float_or_int_trait<genType>::ID>()(x);
     }
 
     template <typename T>
diff --git a/glm/glm.hpp b/glm/glm.hpp
index 7380a718..79e1d878 100644
--- a/glm/glm.hpp
+++ b/glm/glm.hpp
@@ -84,6 +84,7 @@
 #include <climits>
 #include <cfloat>
 #include <limits>
+#include <type_traits>
 #include "core/setup.hpp"
 
 #if(defined(GLM_MESSAGES) && !defined(GLM_MESSAGE_CORE_INCLUDED_DISPLAYED))
diff --git a/glm/gtx/integer.hpp b/glm/gtx/integer.hpp
index 9369bd43..7d374098 100644
--- a/glm/gtx/integer.hpp
+++ b/glm/gtx/integer.hpp
@@ -60,7 +60,8 @@ namespace glm
 
 	//! Returns the log2 of x. Can be reliably using to compute mipmap count from the texture size.
 	//! From GLM_GTX_integer extension.
-	unsigned int log2(unsigned int x);
+	template <typename genType>
+	genType log2(genType const & x);
 
 	//! Returns the floor log2 of x.
 	//! From GLM_GTX_integer extension.
diff --git a/glm/gtx/integer.inl b/glm/gtx/integer.inl
index 8c883728..870887a7 100644
--- a/glm/gtx/integer.inl
+++ b/glm/gtx/integer.inl
@@ -53,23 +53,21 @@ namespace detail
 		x += (x >> 16);
 		return(x & 0x0000003f);
 	}
-}//namespace detail
 
+	template <>
+	struct compute_log2<float_or_int_value::INT>
+	{
+		template <typename T>
+		T operator() (T const & Value) const
+		{
 #if(GLM_COMPILER & (GLM_COMPILER_VC | GLM_COMPILER_GCC))
-
-GLM_FUNC_QUALIFIER unsigned int log2(unsigned int x)
-{
-	return x <= 1 ? 0 : unsigned(32) - nlz(x - 1u);
-}
-
+			return Value <= T(1) ? T(0) : T(32) - nlz(Value - T(1));
 #else
-
-GLM_FUNC_QUALIFIER unsigned int log2(unsigned int x)
-{
-	return unsigned(32) - nlz(x - 1u);
-}
-
+			return T(32) - nlz(Value - T(1));
 #endif
+		}
+	};
+}//namespace detail
 
 // Henry Gordon Dietz: http://aggregate.org/MAGIC/
 unsigned int floor_log2(unsigned int x)