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IDLType

Description

The IDLType property is used to further specify a RemoteProcCall connector. It is typically used to specify an instantiation of such a connector, but it can also be used to specify a definition.When left out of the definition, the connector is more general and can be parameterized at instantiation time with this property.

A RemoteProcCall connector governs the interaction between SchedProcess or Process components performing remote procedure calls. The realization of this connector in the system at run-time is usually some message passing mechanism.

UniCon supports two different models of communication for RPC connections: the Mach InterProcess Communication (IPC) facility and the RPCGen remote procedure call facility. Both models use message passing as the underlying mechanism for transmitting data between processes.

Both of these models of communication are nearly identical. Both have a specification language in which the services exported by a server process are specified. Both have a compiler for the specification language that compiles the specifications of the services into "glue code." The glue code gets compiled and linked into both client and server processes; it facilitates the creation, passing, and decoding of messages using the arguments and return values of the routine calls. Lastly, both models make use of a "name server" in the run-time environment. The name server is an independent process running on the target machine that facilitates the message passing between clients and servers. Servers register their services with the name server, and clients use the name server to "look up" the services they need.

The system designer uses the IDLType property to specify the underlying model of communication for each RPC connection. For the Mach IPC facility, the system designer specifies "mach" as the value in the IDLType property. For the RPCGen facility, the designer specifies "rpcl":

mach

Mach IPC facility

rpcl

RPCGen RPC facility

The Mach IPC facility should only be chosen if the Process or SchedProcess components involved in the remote procedure call are targetted for a Mach or Real-Time Mach environment, respectively. The RPCGen facility can be used when the components are targetted for an operating system that supports RPCGen, such as SunOS.

Property Lists

The IDLType property can legally be specified in the property list in the following UniCon language elements:

<establish>
<instantiation> of a connector
<protocol>

Value Syntax

The syntax of the value part of an IDLType property is one of the two keywords rpcl or mach, optionally enclosed in double-quotes, surrounded by parentheses. The case of the letters can be upper, lower, or mixed.

Required Rule

Optional

The default value for the IDLType property is rpcl.

Merge Rule

ERROR

Subsequent specifications of the IDLType property in a single property list are reported as errors. The UniCon compiler uses the first of the duplicate IDLType properties it encounters.

Semantic Checks

The value of the IDLType property must be one of the following two values: rpcl or mach.

Example

The following is an example of an IDLType property. It is embedded in an <establish> of a RemoteProcCall connector:

  ESTABLISH RTM-RemoteProc-Call WITH
    client.timeget AS caller
    server.timeget AS definer
    IDLTYPE (mach)
  END RTM-RemoteProc-Call