92 lines
3.0 KiB
C++
92 lines
3.0 KiB
C++
//
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// SPDX-License-Identifier: BSD-3-Clause
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// Copyright (c) Contributors to the OpenEXR Project.
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//
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#ifndef INCLUDED_ILMTHREADNAMESPACE_H
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#define INCLUDED_ILMTHREADNAMESPACE_H
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//
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// The purpose of this file is to make it possible to specify an
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// ILMTHREAD_INTERNAL_NAMESPACE as a preprocessor definition and have all of
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// the IlmThread symbols defined within that namespace rather than the
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// standard IlmThread namespace. Those symbols are made available to client
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// code through the ILMTHREAD_NAMESPACE in addition to the
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// ILMTHREAD_INTERNAL_NAMESPACE.
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//
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// To ensure source code compatibility, the ILMTHREAD_NAMESPACE defaults to
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// IlmThread and then "using namespace ILMTHREAD_INTERNAL_NAMESPACE;" brings
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// all of the declarations from the ILMTHREAD_INTERNAL_NAMESPACE into the
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// ILMTHREAD_NAMESPACE. This means that client code can continue to use
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// syntax like IlmThread::Thread, but at link time it will resolve to a
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// mangled symbol based on the ILMTHREAD_INTERNAL_NAMESPACE.
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//
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// As an example, if one needed to build against a newer version of IlmThread
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// and have it run alongside an older version in the same application, it is
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// now possible to use an internal namespace to prevent collisions between
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// the older versions of IlmThread symbols and the newer ones. To do this,
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// the following could be defined at build time:
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//
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// ILMTHREAD_INTERNAL_NAMESPACE = IlmThread_v2
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//
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// This means that declarations inside IlmThread headers look like this
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// (after the preprocessor has done its work):
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//
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// namespace IlmThread_v2 {
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// ...
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// class declarations
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// ...
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// }
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//
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// namespace IlmThread {
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// using namespace IlmThread_v2;
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// }
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//
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//
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// Open Source version of this file pulls in the IlmThreadConfig.h file
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// for the configure time options.
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//
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#include "IlmThreadConfig.h"
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#ifndef ILMTHREAD_NAMESPACE
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# define ILMTHREAD_NAMESPACE IlmThread
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#endif
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#ifndef ILMTHREAD_INTERNAL_NAMESPACE
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# define ILMTHREAD_INTERNAL_NAMESPACE ILMTHREAD_NAMESPACE
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#endif
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//
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// We need to be sure that we import the internal namespace into the public one.
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// To do this, we use the small bit of code below which initially defines
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// ILMTHREAD_INTERNAL_NAMESPACE (so it can be referenced) and then defines
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// ILMTHREAD_NAMESPACE and pulls the internal symbols into the public
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// namespace.
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//
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namespace ILMTHREAD_INTERNAL_NAMESPACE
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{}
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namespace ILMTHREAD_NAMESPACE
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{
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using namespace ILMTHREAD_INTERNAL_NAMESPACE;
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}
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//
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// There are identical pairs of HEADER/SOURCE ENTER/EXIT macros so that
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// future extension to the namespace mechanism is possible without changing
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// project source code.
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//
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#define ILMTHREAD_INTERNAL_NAMESPACE_HEADER_ENTER \
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namespace ILMTHREAD_INTERNAL_NAMESPACE \
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{
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#define ILMTHREAD_INTERNAL_NAMESPACE_HEADER_EXIT }
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#define ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_ENTER \
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namespace ILMTHREAD_INTERNAL_NAMESPACE \
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{
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#define ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_EXIT }
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#endif // INCLUDED_ILMTHREADNAMESPACE_H
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