Make some easyaccess functions conditional

This eliminates the need to have separate SWIG files for libexiv2
v0.27.3 and older.

Author: jim-easterbrook

src/interface/easyaccess.i

@@ -23,10 +23,24 @@
 
 %include "shared/preamble.i"
 %include "shared/exception.i"
+%include "shared/exv_options.i"
 
 // Catch all C++ exceptions
 EXCEPTION()
 
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::apertureValue)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::brightnessValue)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::dateTimeOriginal)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::exposureBiasValue)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::exposureIndex)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::flash)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::flashEnergy)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::lightSource)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::maxApertureValue)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::sensingMethod)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::shutterSpeedValue)
+EXV_ENABLE_EASYACCESS_FUNCTION(Exiv2::subjectArea)
+
 // Store data.end() after converting input
 %typemap(check) Exiv2::ExifData& (Exiv2::ExifData::const_iterator _global_end) %{
     _global_end = $1->end();

src/interface/shared/exv_options.i

@@ -74,3 +74,22 @@ namespace Exiv2 {
     }
 }
 %enddef // EXV_ENABLE_FILESYSTEM_FUNCTION
+
+// Macro to not call a function if libexiv2 version is <= 0.27.3
+%define EXV_ENABLE_EASYACCESS_FUNCTION(signature)
+%fragment("_set_python_exception");
+%fragment("set_EXV_ENABLE_FILESYSTEM");
+%exception signature {
+    try {
+%#if EXIV2_TEST_VERSION(0, 27, 4)
+        $action
+%#else
+        throw Exiv2::Error(Exiv2::kerFunctionNotSupported);
+%#endif
+    }
+    catch(std::exception const& e) {
+        _set_python_exception();
+        SWIG_fail;
+    }
+}
+%enddef // EXV_ENABLE_EASYACCESS_FUNCTION