Procedure Header Descriptor
The header has been extended several times over the life of the NDR engine. The current compiler still generates different headers depending on the mode of the compiler. However, more recent headers are a superset of the older ones.
The Old –Oi Header
The header has the following format:
handle_type<1>
Oi_flags<1>
[rpc_flags<4>]
proc_num<2>
stack_size<2>
[explicit_handle_description<>]
Where handle_type<1> can be one of the values shown in the following table.
| Hex | Handle |
|---|---|
| 31 | FC_BIND_GENERIC |
| 32 | FC_BIND_PRIMITIVE |
| 33 | FC_AUTO_HANDLE |
| 34 | FC_CALLBACK_HANDLE |
| 0 | (explicit handle) |
If the handle_type<1> field is nonzero, then the procedure uses an implicit handle of the indicated kind. See the Handles topic for a more information. If the handle_type<1> field is zero, the handle used for binding is one of the procedure's parameters.
Explicit handles can be primitive, generic, and context; the last one has the following FC token.
| Hex | Handle |
|---|---|
| 30 | FC_BIND_CONTEXT |
By convention, the handle type for DCOM interfaces is FC_AUTO_HANDLE.
The Oi_flags<1> field is an 8-bit mask of the following flags.
| Hex | Flag | Meaning |
|---|---|---|
| 01 | Oi_FULL_PTR_USED | Uses the full pointer package. |
| 02 | Oi_RPCSS_ALLOC_USED | Uses the RpcSs memory package. |
| 04 | Oi_OBJECT_PROC | A procedure in an object interface. |
| 08 | Oi_HAS_RPCFLAGS | The procedure has nonzero Rpc flags. |
| 10 | Oi_* | Overloaded. |
| 20 | Oi_* | Overloaded. |
| 40 | Oi_USE_NEW_INIT_ROUTINES | Uses Windows NT3.5 Beta2+ init routines. |
| 80 | Unused. |
The following flags are overloaded.
| Hex | Flag | Meaning |
|---|---|---|
| 10 | ENCODE_IS_USED | Used only in pickling. |
| 20 | DECODE_IS_USED | Used only in pickling. |
| 10 | Oi_IGNORE_OBJECT_EXCEPTION_HANDLING | Not used anymore (old OLE). |
| 20 | Oi_HAS_COMM_OR_FAULT | In raw RPC only, [comm _, fault_status]. |
| 20 | Oi_OBJ_USE_V2_INTERPRETER | In DCOM only, use –Oif interpreter. |
The rpc_flags<4> field describes how to set the RpcFlags field of the RPC_MESSAGE structure. This field is only present if the Oi_flags<1> field has Oi_HAD_RPCFLAGS set. If this field is not present, then the RPC flags for the remote procedure are zero.
Note
For performance, the async interpreters always have the rpc_flags<4> field present.
The proc_num<2> field provides the procedure's procedure number.
The stack_size<2> provides the total size of all parameters on the stack, including any this pointer and/or return value.
The explicit_handle_description<> field is described later in this document. This field is not present if the procedure uses an implicit handle.