DCE for the HP e3000 (B3821-90003)

52 Chapter6

Introduction to RPC

DCE-IDL Compiler for RPC 1.2.1

Out-of-Line Marshalling

Out-of-line marshalling (library-based marshalling) causes constructed

data types such as unions, pipes or large structures to be marshalled or

unmarshalled by auxiliary routines, thus reducing the stub size. The

out_of_line attribute directs the IDL compiler to place the marshalling

and unmarshalling code in IDL auxiliary stub ﬁles, rather than in the

direct ﬂow of the stub code.

In-line/Out_of_line: The in_line and out_of_line attributes affect

the stub code generated for marshaling and unmarshalling non-scalar

parameters (Non-scalar types include int, ﬂoat, char and pointers in C).

Normally IDL compiler generates marshalling and unmarshalling code

for all parameters in line. This means that if the same data type is used

repeatedly, the identical code will appear in multiple places. If

out_of_line is speciﬁed, the marshaling and unmarshalling code will

be provided as a subroutine, which is called from wherever it is needed.

Enhancing IDL Data Types

IDL support for arrays in previous version was limited to:

• Arrays with a lower bound of zero.

• Arrays with conformance or varying dimensions only in the ﬁrst

(major) dimension.

The current version of IDL will remove these restrictions by supporting

fully general arrays as described in the IDL functional speciﬁcation.

The following example includes declarations that were not supported in

previous version that, but are allowed now:

• long c1[][4];

• long c2[][0..3]; /* Same array shape as c1 */

• long c3[0..*][4]; /* Same array shape as c1 */

• long c4[0..*][0..3]; /* Same array shape as c1 */

• ﬂoat d1[1..10]; /* Equivalent to FORTRAN REAL D1(10) */

• ﬂoat d2[*..10]; /* Lower bound is determined at run time */

• ﬂoat d3[*..*]; /* Both bounds determined at run time */

The <attr_var>s are in one-to-one correspondence with the dimensions

of the array, starting at the ﬁrst. If there are fewer <attr_var>s than the

array has dimensions, the missing <attr_var>s are assumed to be null.

An <attr_var> will be non-null if and only if the lower bound of the