CORBA23 — TypeCode comparison proposal (01)

Summary: Points 1 through 9 need to be considered as one unit. Point 10 can be
voted on independently, but does provide a useful capability for
controlling the size and content of TypeCodes.

Proposal:

1. Make RepositoryIds mandatory for all TypeCodes that have them. [This
was done by the previous core RTF. I am just reiterating it here for
completeness.]

2. All TypeCode constants generated by the IDL compiler, as well as all
TypeCodes returned by the Interface Repository must include alias
TypeCodes wherever a typedef declaration appears in the original IDL
source.

3. Each IDL programming language mapping must provide a mechanism for
the programmer to ensure that values of the IDL any type contain the
exact typecode desired by the programmer.

4. The name() and member_name() fields of the TypeCode are for
documentary purposes only, and are never considered significant when
comparing TypeCodes.

5. Define a new equivalent operation for TypeCodes:

pseudo interface TypeCode

;

with the following semantics:

a) If the two TypeCodes are the same primitive type (null, void, short,
long, ushort, ulong, float, double, boolean, char, octet, any, TypeCode,
longlong, ulonglong, longdouble, wchar) then equivalent() returns true.

b) If the two TypeCodes are string, wstring or fixed with the same
parameters (bounds, digits or scale) then equivalent() returns true.

c) If the two TypeCodes are both arrays or both sequences, with the
same bounds and their component types are equivalent(), then
equivalent() returns true.

d) If the two TypeCodes are both object references, return true if the
their RepositoryIds are the same.

e) If the two TypeCodes are both structs, exceptions, unions, enums or
aliases, and they have the same RepositoryId, then equivalent() returns
true. Note in this case that member TypeCodes are not compared.

f) If either or both of the TypeCodes have an empty RepositoryId, then
equivalent() falls back to a structural comparison, and returns true if
all members of the two TypeCodes also are equivalent(). This case will
only occur when interoperating with an older ORB that does not yet
require RepositoryIds as mandatory for these TypeCodes. Note that the
name() and member_name() fields are not used in this comparison.

g) Otherwise, equivalent() returns false.

6. The ORB uses TypeCode::equivalent for all internal TypeCode
comparisons, such as for supporting any (and thus DII and DSI) and
DynAny.

7. If the programmer needs to distinguish between a type and/or
different aliases of that type, he can call TypeCode::id() and compare
the RepositoryIds.

8. All DynAny insert & get operations do not consider aliases as
significant. The type() operation however, will return the TypeCode
with all of the aliases intact, including type() from any DynAny member
components. DynAny::assign() and DynAny::from_any compare the internal
TypeCode of the DynAny with the TypeCode of its argument using
TypeCode::equivalent() and raise Invalid if equivalent() returns false.

9. The TypeCode::equal() operation is not used internally by the ORB
and is deprecated.

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