IDL Syntax

1
IDL Syntax

• Declarative - no programming statements, a
  language independent way of describing interfaces
• Used to generate Stubs and Skeletons
• Based on C syntax
• Concise (OMG specification in 36 pages)
• C preprocessor directives (-fno-cpp)
• Multiple Inheritance

2
IDL Syntax (II)

• Constants
• Data type declarations
• Basic types (char, float etc)
• Constructed types (array, struct etc)
• Attributes - get and set a particular value
• Operations - methods
• Exceptions
• Interfaces
• Modules - name space scoping

3
IDL Basic Types
4
IDL Constructed Types

• Structures
• struct structeg
• string colour
• long age
• Enumerations
• enum enumeg blue, yellow, green
• Exceptions
• exception NumberTooBigException
• string reason
• long id

5
Other IDL types

• Sequences
• 1-D array with max size (fixed at compile time)
  and length (fixed at run time)
• typedef sequence ltfloatgt floatseq
• typedef sequence ltfloat, 42gt boundedfloatseq
• typedef sequence ltfloatseqgt floatfloatseq
• Arrays
• Multidimensional fixed size array
• typedef float42 floatvector
• typedef float422 floatmatrix

6

• Typedefs and Operations
• interface examplebase_example
• const short consteg 42
• typedef stringconsteg stringarrayeg
• exception exceptioneg
• enum enumeg hi, med, lo
• void opeg1(in long longname)
• char opeg2(in stringarrayeg saname) raises
  execptioneg
• void opeg3(in float p1, inout float p2, out
  float p3)
• oneway opeg4(in enumeg enname)
• attribute double deg1
• readonly attribute octet oceg1
• double get_deg1() // get method
• void set_deg1(in double value) // set
  method
• octet get_oceg1() // get method

7
PIDL

• Define ORB interfaces using Pseudo-IDL
• PIDL references cannot be passed as parameters to
  real CORBA objects
• module CORBA //PIDL
• typedef string ORBid
• typedef sequence ltstringgt arg_list
• ORB ORB_init(inout arg_list argv,
• in ORBid orb_identifier)
• interface ORB
• string object_to_string(in Object obj)
• Object string_to_object(in string obj)

8
Any

• Can express any IDL type
• Logically contains a TypeCode and a value
  described by that TypeCode
• TypeCode (PIDL) used to identify contents
• API defined in PIDL to insert/extract values
• typedef sequence ltanygt anyseq
• any opeg()