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IlmThreadNamespace.h
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34 
35 #ifndef INCLUDED_ILMTHREADNAMESPACE_H
36 #define INCLUDED_ILMTHREADNAMESPACE_H
37 
38 //
39 // The purpose of this file is to make it possible to specify an
40 // ILMTHREAD_INTERNAL_NAMESPACE as a preprocessor definition and have all of
41 // the IlmThread symbols defined within that namespace rather than the
42 // standard IlmThread namespace. Those symbols are made available to client
43 // code through the ILMTHREAD_NAMESPACE in addition to the
44 // ILMTHREAD_INTERNAL_NAMESPACE.
45 //
46 // To ensure source code compatibility, the ILMTHREAD_NAMESPACE defaults to
47 // IlmThread and then "using namespace ILMTHREAD_INTERNAL_NAMESPACE;" brings
48 // all of the declarations from the ILMTHREAD_INTERNAL_NAMESPACE into the
49 // ILMTHREAD_NAMESPACE. This means that client code can continue to use
50 // syntax like IlmThread::Thread, but at link time it will resolve to a
51 // mangled symbol based on the ILMTHREAD_INTERNAL_NAMESPACE.
52 //
53 // As an example, if one needed to build against a newer version of IlmThread
54 // and have it run alongside an older version in the same application, it is
55 // now possible to use an internal namespace to prevent collisions between
56 // the older versions of IlmThread symbols and the newer ones. To do this,
57 // the following could be defined at build time:
58 //
59 // ILMTHREAD_INTERNAL_NAMESPACE = IlmThread_v2
60 //
61 // This means that declarations inside IlmThread headers look like this
62 // (after the preprocessor has done its work):
63 //
64 // namespace IlmThread_v2 {
65 // ...
66 // class declarations
67 // ...
68 // }
69 //
70 // namespace IlmThread {
71 // using namespace IlmThread_v2;
72 // }
73 //
74 
75 //
76 // Open Source version of this file pulls in the IlmBaseConfig.h file
77 // for the configure time options.
78 //
79 #include "IlmBaseConfig.h"
80 
81 #ifndef ILMTHREAD_NAMESPACE
82 #define ILMTHREAD_NAMESPACE IlmThread
83 #endif
84 
85 #ifndef ILMTHREAD_INTERNAL_NAMESPACE
86 #define ILMTHREAD_INTERNAL_NAMESPACE ILMTHREAD_NAMESPACE
87 #endif
88 
89 //
90 // We need to be sure that we import the internal namespace into the public one.
91 // To do this, we use the small bit of code below which initially defines
92 // ILMTHREAD_INTERNAL_NAMESPACE (so it can be referenced) and then defines
93 // ILMTHREAD_NAMESPACE and pulls the internal symbols into the public
94 // namespace.
95 //
96 
99  using namespace ILMTHREAD_INTERNAL_NAMESPACE;
100 }
101 
102 //
103 // There are identical pairs of HEADER/SOURCE ENTER/EXIT macros so that
104 // future extension to the namespace mechanism is possible without changing
105 // project source code.
106 //
107 
108 #define ILMTHREAD_INTERNAL_NAMESPACE_HEADER_ENTER namespace ILMTHREAD_INTERNAL_NAMESPACE {
109 #define ILMTHREAD_INTERNAL_NAMESPACE_HEADER_EXIT }
110 
111 #define ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_ENTER namespace ILMTHREAD_INTERNAL_NAMESPACE {
112 #define ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_EXIT }
113 
114 #endif // INCLUDED_ILMTHREADNAMESPACE_H
#define ILMTHREAD_NAMESPACE
Definition: IlmBaseConfig.h:11
#define ILMTHREAD_INTERNAL_NAMESPACE
Definition: IlmBaseConfig.h:8