Enumerated Type

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Another facet that is frequently applied to XSD string-based types is enumeration. This results in the generation of a C enum typedef that enumerates all of the identifiers that can be used in the type. The actual C typedef that is generated for the item is of type OSUINT16. The reasons for not directly using the generated enum type are:

• The use of OSUINT16 provides for a consistent size of the data variable. Use of enum can produce different sized variables on different platform/compiler combinations, and
• The variable is capable of storing enumerated types that were not defined in the original set. This makes the type extensible in the event a newer version of the schema is produced that contains additional enumeration items that were not in the original version.

The general mapping is as follows:

XSD type:	<xsd:simpleType name="TypeName"> <restriction base="xsd:string"> <xsd:enumeration value="enum1"/> <xsd:enumeration value="enum2"/> ... <xsd:enumeration value="enumN"/> </xsd:restriction> </xsd:simpleType>
Generated C code:	typedef enum { TypeName_enum1 = 0, TypeName_enum2 = 1, ... TypeName_enumN = N - 1, } TypeName_ENUM; typedef OSUINT16 TypeName;
Generated C++ code:	class TypeName : public OSBaseType { public: enum { enum1 = 0, enum2 = 1, ... enumN = N - 1, } ; OSUINT16 value; ... } ;

Note that for C, TypeName is used on the enumerated identifiers as a namespace mechanism in order to prevent name clashes if two or more enumerated types use the same identifier names. In this case, the type name may only be a partial fragment of the full name to keep the names shorter. This is not a problem in C++ as the class provides a namespace for the enumeration constants defined within (for example, enum1 would be referenced as TypeName::enum1 outside the class).