EXTERNAL Type

---

The ASN.1 EXTERNAL type is a useful type used to include non-ASN.1 or other data within an ASN.1 encoded message. This type is described using the following ASN.1 SEQUENCE:

EXTERNAL  ::=  [UNIVERSAL 8] IMPLICIT SEQUENCE {
 
   direct-reference  OBJECT IDENTIFIER OPTIONAL,
 
   indirect-reference  INTEGER OPTIONAL,
 
   data-value-descriptor  ObjectDescriptor  OPTIONAL,
 
   encoding  CHOICE {
 
      single-ASN1-type  [0] ANY,
 
      octet-aligned     [1] IMPLICIT OCTET STRING,
 
      arbitrary         [2] IMPLICIT BIT STRING
 
   }
 
}
 

The ASN.1 compiler is used to create a meta-definition for this structure. This code will be always generated in the Asn1External.h and Asn1External.c/cpp files. The code will only be generated if the given ASN.1 source specification requires this definition. The resulting C structure is populated just like any other compiler-generated structure for working with ASN.1 data.

NOTE: It is recommended that if a specification contains multiple ASN.1 source files that reference EXTERNAL, all of these source files be compiled with a single ASN1C call in order to ensure that only a singled copy of the Asn1External source files are generated.