PySMI documentationΒΆ

PySMI library is highly modular. The top-level component is called compiler and it acts as main user-facing object. Most of other components are plugged into the compiler object prior to its use.

Normally, user asks compiler to perform certain transformation of named MIB module. Compiler will:

  • Search its data sources for given MIB module (identified by name) noting their last modification times.
  • Search compiler-managed repositories of already converted MIB modules for modules that are more recent than corresponding source MIB module.
  • If freshly transformed MIB module is found, processing stops here.
  • Otherwise compiler passes ASN.1 MIB module content to the lexer component.
  • Lexer returns a sequence of tokenized ASN.1 MIB contents. Compiler then passes that sequence of tokens to the parser component.
  • Parser runs LR algorithm on tokenized MIB thus transforming MIB contents into Abstract Syntax Tree (AST) and also noting what other MIB modules are referred to from the MIB being parsed.
  • In case of parser failure, what is usually an indication of broken ASN.1 MIB syntax, compiler may attempt to fetch pre-transformed MIB contents from configured source. This process is called borrowing in PySMI.
  • In case of successful parser completion, compiler will pass produced AST to code generator component.
  • Code generator walks its input AST and performs actual data transformation.
  • The above steps may be repeated for each of the MIB modules referred to as parser figures out. Once no more unresolved dependencies remain, compiler will call its writer component to store all transformed MIB modules.

The location of ASN.1 MIB modules and flavor of their syntax, as well as desired transformation format, is determined by respective components chosen and configured to compiler.