关于asn1标准的描述文档：
The purpose of the ASN.1 compiler is to convert the specifications in ASN.1 notation
into some other language. At this moment, only C and C++ target languages are
supported, the latter is in upward compatibility mode.
The compiler reads the specification and emits a series of target language structures
(C’s structs, unions, enums) describing the corresponding ASN.1 types. The compiler
also creates the code which allows automatic serialization and deserialization of these
structures using several standardized encoding rules (BER, DER, XER).
For example, suppose the following ASN.1 module is given1:
