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IexNamespace.h
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34 
35 #ifndef INCLUDED_IEXNAMESPACE_H
36 #define INCLUDED_IEXNAMESPACE_H
37 
38 //
39 // The purpose of this file is to make it possible to specify an
40 // IEX_INTERNAL_NAMESPACE as a preprocessor definition and have all of the
41 // Iex symbols defined within that namespace rather than the standard
42 // Iex namespace. Those symbols are made available to client code through
43 // the IEX_NAMESPACE in addition to the IEX_INTERNAL_NAMESPACE.
44 //
45 // To ensure source code compatibility, the IEX_NAMESPACE defaults to Iex
46 // and then "using namespace IEX_INTERNAL_NAMESPACE;" brings all of the
47 // declarations from the IEX_INTERNAL_NAMESPACE into the IEX_NAMESPACE. This
48 // means that client code can continue to use syntax like Iex::BaseExc, but
49 // at link time it will resolve to a mangled symbol based on the
50 // IEX_INTERNAL_NAMESPACE.
51 //
52 // As an example, if one needed to build against a newer version of Iex and
53 // have it run alongside an older version in the same application, it is now
54 // possible to use an internal namespace to prevent collisions between the
55 // older versions of Iex symbols and the newer ones. To do this, the
56 // following could be defined at build time:
57 //
58 // IEX_INTERNAL_NAMESPACE = Iex_v2
59 //
60 // This means that declarations inside Iex headers look like this (after the
61 // preprocessor has done its work):
62 //
63 // namespace Iex_v2 {
64 // ...
65 // class declarations
66 // ...
67 // }
68 //
69 // namespace Iex {
70 // using namespace Iex_v2;
71 // }
72 //
73 
74 //
75 // Open Source version of this file pulls in the IlmBaseConfig.h file
76 // for the configure time options.
77 //
78 #include "IlmBaseConfig.h"
79 
80 #ifndef IEX_NAMESPACE
81 #define IEX_NAMESPACE Iex
82 #endif
83 
84 #ifndef IEX_INTERNAL_NAMESPACE
85 #define IEX_INTERNAL_NAMESPACE IEX_NAMESPACE
86 #endif
87 
88 //
89 // We need to be sure that we import the internal namespace into the public one.
90 // To do this, we use the small bit of code below which initially defines
91 // IEX_INTERNAL_NAMESPACE (so it can be referenced) and then defines
92 // IEX_NAMESPACE and pulls the internal symbols into the public namespace.
93 //
94 
96 namespace IEX_NAMESPACE {
97  using namespace IEX_INTERNAL_NAMESPACE;
98 }
99 
100 //
101 // There are identical pairs of HEADER/SOURCE ENTER/EXIT macros so that
102 // future extension to the namespace mechanism is possible without changing
103 // project source code.
104 //
105 
106 #define IEX_INTERNAL_NAMESPACE_HEADER_ENTER namespace IEX_INTERNAL_NAMESPACE {
107 #define IEX_INTERNAL_NAMESPACE_HEADER_EXIT }
108 
109 #define IEX_INTERNAL_NAMESPACE_SOURCE_ENTER namespace IEX_INTERNAL_NAMESPACE {
110 #define IEX_INTERNAL_NAMESPACE_SOURCE_EXIT }
111 
112 #endif // INCLUDED_IEXNAMESPACE_H
#define IEX_INTERNAL_NAMESPACE
Definition: IlmBaseConfig.h:7
#define IEX_NAMESPACE
Definition: IlmBaseConfig.h:10