The goal of the ast system is provide a pure Java implementation of the Google protobuf system.

There are several reasons for creating ast.

• The existing C code generator (http://code.google.com/p/protobuf-c") IMO generates overly complicated code.

: As a rule, what is needed is code to serialize (aka encode) and deserialize (aka decode) protobuf messages. The RPC support should be entirely separate from the (de)serialize code. Even Google is deprecating the RPC output for, one presumes, the same reason.

• The Unidata ast compiler uses a more traditional compiler approach based on the use of a (mostly) read-only abstract syntax tree (AST). The key is that the AST is never (well, almost never) modified to add language specific code, which is the approach of the Google compiler. Instead, code generation is performed by repeatedly walking the bare AST to obtain information.

: The result is a much cleaner system with the AST serving as a well-defined and fixed intermediary between parsing and code generation.

• Java is a much better language that C++ for writing portable compilers.

• Finally, building the AST compiler helped the author to get a better understanding of the protobuf protocol.

A C language code generators accompanies the compiler to demonstrate its use. It also provides a good C implementation. Other code generators for, e.g. C++, Java, and Python, are possible, but the existing google generators are probably adequate for those languages.

The following documents are available:

• LICENSE.txt describes the license, which basically Apache v2.
• INSTALL.txt describes the installation procedure
• CHANGES.txt describes release changes.
• TODO.txt describes things that need to be done. Principally these items relate to recent changes to protobuf that have not yet been implemented.
• doc/astuserman.html provides a more detailed manual for using ast.
• doc/astinternals.html provides a detailed description of the internal operation of ast and how one might extend it for other languages.

Author: Dennis Heimbigner Organization: UCAR/Unidata Email: [email protected]