From 2ee6151a40f99a8a31349f0743eef50a9007da9f Mon Sep 17 00:00:00 2001
From: Carsten Neumann <cpneumann@ualr.edu>
Date: Mon, 18 May 2015 12:20:55 -0500
Subject: [PATCH] Use unions for type punning

Fixes #334
---
 glm/detail/func_packing.inl | 162 +++++++++++++++++++++++++++++-------
 1 file changed, 132 insertions(+), 30 deletions(-)

diff --git a/glm/detail/func_packing.inl b/glm/detail/func_packing.inl
index 3132a279..fff9e703 100644
--- a/glm/detail/func_packing.inl
+++ b/glm/detail/func_packing.inl
@@ -38,82 +38,184 @@ namespace glm
 {
 	GLM_FUNC_QUALIFIER uint packUnorm2x16(vec2 const & v)
 	{
-		u16vec2 const Topack(round(clamp(v, 0.0f, 1.0f) * 65535.0f));
-		return reinterpret_cast<uint const &>(Topack);
+		union
+		{
+			u16  in[2];
+			uint out;
+		} u;
+
+		u.in[0] = round(clamp(v[0], 0.0f, 1.0f) * 65535.0f);
+		u.in[1] = round(clamp(v[1], 0.0f, 1.0f) * 65535.0f);
+
+		return u.out;
 	}
 
 	GLM_FUNC_QUALIFIER vec2 unpackUnorm2x16(uint p)
 	{
-		vec2 Unpack(reinterpret_cast<u16vec2 const &>(p));
-		return Unpack * float(1.5259021896696421759365224689097e-5); // 1.0 / 65535.0
+		union
+		{
+			uint in;
+			u16  out[2];
+		} u;
+
+		u.in = p;
+
+		return vec2(
+			u.out[0] * 1.5259021896696421759365224689097e-5f,
+			u.out[1] * 1.5259021896696421759365224689097e-5f);
 	}
 
 	GLM_FUNC_QUALIFIER uint packSnorm2x16(vec2 const & v)
 	{
-		i16vec2 const Topack(round(clamp(v ,-1.0f, 1.0f) * 32767.0f));
-		return reinterpret_cast<uint const &>(Topack);
+		union
+		{
+			i16  in[2];
+			uint out;
+		} u;
+
+		u.in[0] = round(clamp(v[0], -1.0f, 1.0f) * 32767.0f);
+		u.in[1] = round(clamp(v[1], -1.0f, 1.0f) * 32767.0f);
+
+		return u.out;
 	}
 
 	GLM_FUNC_QUALIFIER vec2 unpackSnorm2x16(uint p)
 	{
-		vec2 const Unpack(reinterpret_cast<i16vec2 const &>(p));
-		return clamp(
-			Unpack * 3.0518509475997192297128208258309e-5f, //1.0f / 32767.0f,
-			-1.0f, 1.0f);
+		union
+		{
+			uint in;
+			i16  out[2];
+		} u;
+
+		u.in = p;
+
+		return vec2(
+			clamp(u.out[0] * 3.0518509475997192297128208258309e-5f,
+				-1.0f, 1.0f),
+			clamp(u.out[1] * 3.0518509475997192297128208258309e-5f,
+				-1.0f, 1.0f));
 	}
 
 	GLM_FUNC_QUALIFIER uint packUnorm4x8(vec4 const & v)
 	{
-		u8vec4 const Topack(round(clamp(v, 0.0f, 1.0f) * 255.0f));
-		return reinterpret_cast<uint const &>(Topack);
+		union
+		{
+			u8   in[4];
+			uint out;
+		} u;
+
+		u.in[0] = round(clamp(v[0], 0.0f, 1.0f) * 255.0f);
+		u.in[1] = round(clamp(v[1], 0.0f, 1.0f) * 255.0f);
+		u.in[2] = round(clamp(v[2], 0.0f, 1.0f) * 255.0f);
+		u.in[3] = round(clamp(v[3], 0.0f, 1.0f) * 255.0f);
+
+		return u.out;
 	}
 
 	GLM_FUNC_QUALIFIER vec4 unpackUnorm4x8(uint p)
 	{
-		vec4 const Unpack(reinterpret_cast<u8vec4 const&>(p));
-		return Unpack * float(0.0039215686274509803921568627451); // 1 / 255
+		union
+		{
+			uint in;
+			u8   out[4];
+		} u;
+
+		u.in = p;
+
+		return vec4(
+			u.out[0] * 0.0039215686274509803921568627451f,
+			u.out[1] * 0.0039215686274509803921568627451f,
+			u.out[2] * 0.0039215686274509803921568627451f,
+			u.out[3] * 0.0039215686274509803921568627451f);
 	}
 	
 	GLM_FUNC_QUALIFIER uint packSnorm4x8(vec4 const & v)
 	{
-		i8vec4 const Topack(round(clamp(v ,-1.0f, 1.0f) * 127.0f));
-		return reinterpret_cast<uint const &>(Topack);
+		union
+		{
+			i8   in[4];
+			uint out;
+		} u;
+
+		u.in[0] = round(clamp(v[0], -1.0f, 1.0f) * 127.0f);
+		u.in[1] = round(clamp(v[1], -1.0f, 1.0f) * 127.0f);
+		u.in[2] = round(clamp(v[2], -1.0f, 1.0f) * 127.0f);
+		u.in[3] = round(clamp(v[3], -1.0f, 1.0f) * 127.0f);
+
+		return u.out;
 	}
 	
 	GLM_FUNC_QUALIFIER glm::vec4 unpackSnorm4x8(uint p)
 	{
-		vec4 const Unpack(reinterpret_cast<i8vec4 const &>(p));
-		return clamp(
-			Unpack * 0.0078740157480315f, // 1.0f / 127.0f
-			-1.0f, 1.0f);
+		union
+		{
+			uint in;
+			i8   out[4];
+		} u;
+
+		u.in = p;
+
+		return vec4(
+			clamp(u.out[0] * 0.0078740157480315f, -1.0f, 1.0f),
+			clamp(u.out[1] * 0.0078740157480315f, -1.0f, 1.0f),
+			clamp(u.out[2] * 0.0078740157480315f, -1.0f, 1.0f),
+			clamp(u.out[3] * 0.0078740157480315f, -1.0f, 1.0f));
 	}
 
 	GLM_FUNC_QUALIFIER double packDouble2x32(uvec2 const & v)
 	{
-		return reinterpret_cast<double const &>(v);
+		union
+		{
+			uint   in[2];
+			double out;
+		} u;
+
+		u.in[0] = v[0];
+		u.in[1] = v[1];
+
+		return u.out;
 	}
 
 	GLM_FUNC_QUALIFIER uvec2 unpackDouble2x32(double v)
 	{
-		return reinterpret_cast<uvec2 const &>(v);
+		union
+		{
+			double in;
+			uint   out[2];
+		} u;
+
+		u.in = v;
+
+		return uvec2(u.out[0], u.out[1]);
 	}
 
 	GLM_FUNC_QUALIFIER uint packHalf2x16(vec2 const & v)
 	{
-		i16vec2 const Unpack(
-			detail::toFloat16(v.x),
-			detail::toFloat16(v.y));
+		union
+		{
+			i16  in[2];
+			uint out;
+		} u;
 
-		return reinterpret_cast<uint const &>(Unpack);
+		u.in[0] = detail::toFloat16(v.x);
+		u.in[1] = detail::toFloat16(v.y);
+
+		return u.out;
 	}
 
 	GLM_FUNC_QUALIFIER vec2 unpackHalf2x16(uint v)
 	{
-		i16vec2 const Unpack(reinterpret_cast<i16vec2 const &>(v));
-	
+		union
+		{
+			uint in;
+			i16  out[2];
+		} u;
+
+		u.in = v;
+
 		return vec2(
-			detail::toFloat32(Unpack.x), 
-			detail::toFloat32(Unpack.y));
+			detail::toFloat32(u.out[0]),
+			detail::toFloat32(u.out[1]));
 	}
 }//namespace glm