TAO IDL Compiler: Architecture and Evolution

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TAO IDL Compiler Architecture and Evolution

• Jeff Parsons
• parsons_at_cs.wustl.edu
• Center for Distributed Object Computing
• Department of Computer Science
• Washington University, St. Louis, MO

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Early Milestones

• May 1997
• Sun implementation (no code generation)
• January 1998
• Visitor pattern
• September 1998
• Compiled marshaling
• October 1998
• Perfect hashing
• May 1999
• Partial Object By Value (OBV) support
• Recursive types

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Implied IDL

• module mod
• interface foo
• attribute long attr
• string op (
• inout float io_arg
• )

• September 1999
• Used to generate code for Asynchronous Messaging
  Invocation (AMI) implementation.
• Uses strategy pattern instead of branching
  visitor logic.
• Adds nodes to Abstract Syntax Tree (AST) implied
  by IDL declaration AMI specification.

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Implied IDL cont.
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Architecture Evolution - Modularization

• Context
• Loading Interface Repository (IFR) from IDL
  files.
• Problem
• Adding to IDL compiler is too brittle and
  complex.
• Solution - modularize the IDL compiler.
• Front end (FE) library for parsing and AST
  generation only.
• Pluggable back end (BE) libraries.
• Top-level executable.

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Pluggable BEs

• August 2000
• tao_idl BE
• January 2001
• tao_ifr BE
• No BE node classes
• No code generation
• No context states
• No visitor factory
• June 2002
• nest_idl BE - Network Embedded Software
  Technology (NEST) ORB IDL compiler
• No BE node classes
• No visitor factory

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Expanding OBV Support

• August 2001
• valuetypes in sequences
• March 2002
• abstract valuetypes
• typecodes, Any operators
• valuetype factories
• July 2002
• valuetypes in structs, unions, exceptions, arrays
• forward declared valuetypes, defined in
  non-included IDL file
• interface support list

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Latest Features and Current Work

• Asynchronous Message Handling (AMH)
• Abstract interfaces
• Forward declared structs and unions
• Enum constants
• CORBA Component Model (CCM) support - in progress
• IDL extensions
• IFR to support import
• Component Implementation Definition Language
  (CIDL) compiler

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Future Work Extensible Parser?

• Context
• NEST ORB IDL compiler uses subset of IDL 2.x.
• IDL 3.0 and Persistent State Definition Language
  (PSDL) are supersets of IDL 2.x.
• CIDL is a superset of PSDL and IDL 3.0.
• Problems
• Large grammar files
• Duplicated/unused code
• Solution
• Modular extensible parser

CIDL
IDL 3.0
IDL 2.x
NEST IDL
PSDL