ImathNamespace.h

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//
// Copyright (c) 2012, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
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#ifndef INCLUDED_IMATHNAMESPACE_H
#define INCLUDED_IMATHNAMESPACE_H

//
// The purpose of this file is to make it possible to specify an
// IMATH_INTERNAL_NAMESPACE as a preprocessor definition and have all of the
// Imath symbols defined within that namespace rather than the standard
// Imath namespace.  Those symbols are made available to client code through
// the IMATH_NAMESPACE in addition to the IMATH_INTERNAL_NAMESPACE.
//
// To ensure source code compatibility, the IMATH_NAMESPACE defaults to Imath
// and then "using namespace IMATH_INTERNAL_NAMESPACE;" brings all of the
// declarations from the IMATH_INTERNAL_NAMESPACE into the IMATH_NAMESPACE.
// This means that client code can continue to use syntax like Imath::V3f,
// but at link time it will resolve to a mangled symbol based on the
// IMATH_INTERNAL_NAMESPACE.
//
// As an example, if one needed to build against a newer version of Imath and
// have it run alongside an older version in the same application, it is now
// possible to use an internal namespace to prevent collisions between the
// older versions of Imath symbols and the newer ones.  To do this, the
// following could be defined at build time:
//
// IMATH_INTERNAL_NAMESPACE = Imath_v2
//
// This means that declarations inside Imath headers look like this (after
// the preprocessor has done its work):
//
// namespace Imath_v2 {
//     ...
//     class declarations
//     ...
// }
//
// namespace Imath {
//     using namespace Imath_v2;
// }
//

//
// Open Source version of this file pulls in the IlmBaseConfig.h file
// for the configure time options.
//
#include "IlmBaseConfig.h"


#ifndef IMATH_NAMESPACE
#define IMATH_NAMESPACE Imath
#endif

#ifndef IMATH_INTERNAL_NAMESPACE
#define IMATH_INTERNAL_NAMESPACE IMATH_NAMESPACE
#endif

//
// We need to be sure that we import the internal namespace into the public one.
// To do this, we use the small bit of code below which initially defines
// IMATH_INTERNAL_NAMESPACE (so it can be referenced) and then defines
// IMATH_NAMESPACE and pulls the internal symbols into the public
// namespace.
//

namespace IMATH_INTERNAL_NAMESPACE {}
namespace IMATH_NAMESPACE {
     using namespace IMATH_INTERNAL_NAMESPACE;
}

//
// There are identical pairs of HEADER/SOURCE ENTER/EXIT macros so that
// future extension to the namespace mechanism is possible without changing
// project source code.
//

#define IMATH_INTERNAL_NAMESPACE_HEADER_ENTER namespace IMATH_INTERNAL_NAMESPACE {
#define IMATH_INTERNAL_NAMESPACE_HEADER_EXIT }

#define IMATH_INTERNAL_NAMESPACE_SOURCE_ENTER namespace IMATH_INTERNAL_NAMESPACE {
#define IMATH_INTERNAL_NAMESPACE_SOURCE_EXIT }


#endif /* INCLUDED_IMATHNAMESPACE_H */