90 lines
2.8 KiB
C
90 lines
2.8 KiB
C
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//
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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_IEXNAMESPACE_H
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#define INCLUDED_IEXNAMESPACE_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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// IEX_INTERNAL_NAMESPACE as a preprocessor definition and have all of the
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// Iex symbols defined within that namespace rather than the standard
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// Iex namespace. Those symbols are made available to client code through
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// the IEX_NAMESPACE in addition to the IEX_INTERNAL_NAMESPACE.
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//
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// To ensure source code compatibility, the IEX_NAMESPACE defaults to Iex
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// and then "using namespace IEX_INTERNAL_NAMESPACE;" brings all of the
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// declarations from the IEX_INTERNAL_NAMESPACE into the IEX_NAMESPACE. This
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// means that client code can continue to use syntax like Iex::BaseExc, but
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// at link time it will resolve to a mangled symbol based on the
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// IEX_INTERNAL_NAMESPACE.
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//
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// As an example, if one needed to build against a newer version of Iex and
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// have it run alongside an older version in the same application, it is now
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// possible to use an internal namespace to prevent collisions between the
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// older versions of Iex symbols and the newer ones. To do this, the
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// following could be defined at build time:
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//
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// IEX_INTERNAL_NAMESPACE = Iex_v2
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//
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// This means that declarations inside Iex headers look like this (after the
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// preprocessor has done its work):
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//
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// namespace Iex_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 Iex {
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// using namespace Iex_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 IexConfig.h file
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// for the configure time options.
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//
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#include "IexConfig.h"
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#ifndef IEX_NAMESPACE
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# define IEX_NAMESPACE Iex
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#endif
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#ifndef IEX_INTERNAL_NAMESPACE
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# define IEX_INTERNAL_NAMESPACE IEX_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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// IEX_INTERNAL_NAMESPACE (so it can be referenced) and then defines
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// IEX_NAMESPACE and pulls the internal symbols into the public namespace.
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//
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namespace IEX_INTERNAL_NAMESPACE
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{}
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namespace IEX_NAMESPACE
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{
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using namespace IEX_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 IEX_INTERNAL_NAMESPACE_HEADER_ENTER \
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namespace IEX_INTERNAL_NAMESPACE \
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{
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#define IEX_INTERNAL_NAMESPACE_HEADER_EXIT }
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#define IEX_INTERNAL_NAMESPACE_SOURCE_ENTER \
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namespace IEX_INTERNAL_NAMESPACE \
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{
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#define IEX_INTERNAL_NAMESPACE_SOURCE_EXIT }
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#endif // INCLUDED_IEXNAMESPACE_H
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