OBJECT IDENTIFIER

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The ASN.1 OBJECT IDENTIFIER type is converted into a C or C++ structured type to hold the subidentifier values that make up the object identifier.

	ASN.1 production:   <name> ::= OBJECT IDENTIFIER
 

 
	Generated C code:    typedef ASN1OBJID <name>;
 

 
	Generated C++ code:  typedef ASN1TObjId ASN1T_<name>;
 

In this case, different base types are used for C and C++. The difference between the two is the C++ version includes constructors and assignment operators that make setting the value a bit easier.

The ASN1OBJID type (i.e., the type used in the C mapping) is defined in asn1type.h to be the following:

typedef struct {
 
   ASN1UINT numids;		  	/* number of subidentifiers */
 
   ASN1UINT subid[ASN_K_MAXSUBIDS];	/* subidentifier values */
 
} ASN1OBJID;
 

The constant "ASN_K_MAXSUBIDS" specifies the maximum number of sub-identifiers that can be assigned to a value of the type. This constant is set to 128 as per the ASN.1 standard. The value of this constant can be changed to a lower number for applications with restricted memory requirements.

The ASN1TObjId type used in the C++ mapping is defined in Asn1CppTypes.h as follows:

struct EXTERNRT ASN1TObjId : public ASN1OBJID {
 
   ASN1TObjId () { numids = 0; }
 
   ASN1TObjId (ASN1OCTET _numids, const ASN1UINT* _subids);
 
   ASN1TObjId (const ASN1OBJID& oid);
 
   ASN1TObjId (const ASN1TObjId& oid);
 
   void operator= (const ASN1OBJID& rhs);
 
   void operator= (const ASN1TObjId& rhs);
 
} ;
 

The definition is the same as the C type with the addition of the constructors and assignment operators. Note that a constructor and assignment operator are overloaded to use the C ASN1OBJID type. That is because value assignments are generated using the ASN1OBJID type so these methods allow direct assignment of these generated values to an object of this type.