AbstractSyntaxNotation1Element.characterString

Decodes a $(MONO CHARACTER STRING), which is a constructed data type, defined in the https://www.itu.int, International Telecommunications Union's https://www.itu.int/rec/T-REC-X.680/en, X.680.

The specification defines $(MONO CHARACTER STRING) as:

CHARACTER STRING ::= [UNIVERSAL 29] SEQUENCE {
                identification CHOICE {
                    syntaxes SEQUENCE {
                        abstract OBJECT IDENTIFIER,
                        transfer OBJECT IDENTIFIER },
                    syntax OBJECT IDENTIFIER,
                    presentation-context-id INTEGER,
                    context-negotiation SEQUENCE {
                        presentation-context-id INTEGER,
                        transfer-syntax OBJECT IDENTIFIER },
                    transfer-syntax OBJECT IDENTIFIER,
                    fixed NULL },
                string-value OCTET STRING }

This assumes AUTOMATIC TAGS, so all of the identification choices will be context-specific and numbered from 0 to 5.