C++ Representation: Translation Rules

When an ASN.1 specification is processed by the ASN.1/C++ Compiler, C++ code is created that contains C++ representations of the ASN.1 types in the specification. The rules used to create these representations follow, with examples.

1. A typedef is generated for each simple type reference that can be represented by a primitive C++ type.

   ASN.1	C++
   Age ::= INTEGER	typedef OSS_INT32 Age;

2. A typedef is generated for each type reference that can be represented by an ASN.1/C++ runtime class.

   ASN.1	C++
   Text ::= IA5String	typedef OssString Text;

3. A class is generated for each constructed type (SEQUENCE, SET, CHOICE, SEQUENCE OF, or SET OF) that contains the accessors and mutators required by the type components.

   ASN.1

   C++

   Personal ::= SEQUENCE { married BOOLEAN, age INTEGER, weight INTEGER OPTIONAL, name IA5String DEFAULT "No name" }

   class OSS_PUBLIC Personal /* SEQUENCE */ { public: void * operator new(size_t size); void operator delete(void *ptr); typedef ossBoolean married; typedef OSS_INT32 age; typedef OSS_INT32 weight; typedef OssString name; static const name & default_name; static const name& get_default_name(); Personal(); Personal(const Personal &); Personal(married, age, weight, const name &); Personal(married, age); ~Personal(); Personal & operator = (const Personal &); int operator == (const Personal &) const; int operator != (const Personal &) const; married & get_married(); married get_married() const; void set_married(married); age & get_age(); age get_age() const; void set_age(age); weight *get_weight(); const weight *get_weight() const; void set_weight(weight); int weight_is_present() const; void omit_weight(); name *get_name(); const name *get_name() const; void set_name(const name &); int name_is_default() const; void set_default_name(); private: OSS_UINT32 bit_mask; married married_field; age age_field; weight weight_field; name name_field; };

4. Additional methods to transfer ownership are generated for elements of constructed types that have --<POINTER>-- directives applied. Using these methods, you can access or modify an element without a deep copy of the element's information.

   ASN.1

   C++

   Personal ::= SEQUENCE { married BOOLEAN, age INTEGER, name IA5String --<POINTER>-- }

   class OSS_PUBLIC Personal /* SEQUENCE */ { public: void * operator new(size_t size); void operator delete(void *ptr); typedef ossBoolean married; typedef OSS_INT32 age; typedef OssString name; Personal(); Personal(const Personal &); Personal(married, age, const name &); Personal(married, age, name *); ~Personal(); Personal & operator = (const Personal &); int operator == (const Personal &) const; int operator != (const Personal &) const; married & get_married(); married get_married() const; void set_married(married); age & get_age(); age get_age() const; void set_age(age); name & get_name(); const name & get_name() const; void set_name(const name &); void set_name(name *); name *release_name(); private: married married_field; age age_field; name *name_field; };

5. An additional set of accessor/mutator methods is generated when a SET/SEQUENCE/CHOICE type is extensible and the -relaySafe compiler option is specified. Use these methods to get unknown extension additions (probably from a later protocol version) in unencoded form to edit or delete as needed. If -relaySafe is not specified, the extra methods are not generated.

   ASN.1

   C++

   Personal ::= SEQUENCE { married BOOLEAN, age INTEGER, ... }

   C++ (generated with the -relaySafe compiler option) class OSS_PUBLIC Personal /* SEQUENCE */ { public: void * operator new(size_t size); void operator delete(void *ptr); typedef ossBoolean married; typedef OSS_INT32 age; Personal(); Personal(const Personal &); Personal(married, age); ~Personal(); Personal & operator = (const Personal &); int operator == (const Personal &) const; int operator != (const Personal &) const; married & get_married(); married get_married() const; void set_married(married); age & get_age(); age get_age() const; void set_age(age); OssExtensions *get_UnknownExt(); const OssExtensions *get_UnknownExt() const; void set_UnknownExt(const OssExtensions &); int UnknownExt_is_present() const; void omit_UnknownExt(); private: married married_field; age age_field; OssExtensions *ossUnknownExt_field; };

6. A handler class is generated for each PDU type that can be used on its representation class to encode, decode, print, and so on.

   ASN.1	C++
   Personal ::= CHOICE { married BOOLEAN, age INTEGER } --<PDU>--	class OSS_PUBLIC Personal : public OssChoice /* CHOICE */ { . . . }; class OSS_PUBLIC Personal_PDU : public ConcretePDU { public: Personal_PDU(); void set_data(Personal &); Personal *get_data() const; . . . protected: OssTypeIndex get_index() const; };

7. A universal handler class is generated that can be used on any PDU type defined in the specification to encode, decode, print, and so on.

   ASN.1	C++
   ASN.1 (sample.asn) Module DEFINITIONS ::= BEGIN A ::= INTEGER B ::= IA5String END	/* Representation types */ typedef OSS_INT32 A; typedef OssString B; /* Universal PDU class */ class OSS_PUBLIC sample_PDU : public UniversalPDU { public: sample_PDU(); void set_A(A &); A *get_A() const; void set_B(B &); B *get_B() const; . . . }; /* Specific PDU classes */ class OSS_PUBLIC A_PDU : public ConcretePDU { . . . }; class OSS_PUBLIC B_PDU : public ConcretePDU { . . . };

8. A control class is generated for use with specification-defined objects in various operations. See <projectname>_Control for more details.
9. For each value reference, the ASN.1/C++ Compiler generates an initialized const reference to an initialized C++ object that contains the same value. The object that name references is initialized to "John Smith" in the compiler-generated code.

   ASN.1	C++
   NAME ::= IA5String name NAME ::= "John Smith"	typedef OssString NAME; . . . extern OSS_PUBLIC const OssString& name;

10. When the generated value is of any C++ integer or enumerated type, the constant is generated completely in the header. The generated constants can then be used as case labels in a switch statement.

    ASN.1	C++
    INT ::= INTEGER value INT ::= 777	typedef OSS_INT32 INT; . . . const OSS_INT32 value = 777;