pipe attribute
The pipe type constructor makes it possible to transmit an open-ended stream of typed data across a remote procedure call.
typedef pipe element-type pipe-declarator;
Parameters
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element-type
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Defines the size of a single element in the transfer buffer. The element-type can be a base type, predefined_type, struct, 32b enum, or type identifier. Several restrictions apply to element_types, as described in Remarks, below.
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pipe-declarator
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Specifies one or more identifiers or pointers to identifiers. Separate multiple declarators with commas.
Remarks
You can use the pipe type constructor to transmit data in both directions. An [in] pipe parameter allows the server to pull the data stream from the client during a remote procedure call. An [out] pipe parameter allows the server to push the data stream back to the client. You supply the client-side routines to push and pull the data stream and to allocate a global buffer for the data. The client and server stub routines marshal and unmarshal data and pass a reference to the buffer back to the application.
The following restrictions apply to pipes:
- A pipe element cannot be or contain a pointer, a conformant or varying array, a handle, or a context handle. Also, in the Microsoft implementation of pipes, a pipe element cannot be or contain a union, a 16b enum, or an __int3264.
- You cannot apply the [transmit_as], [represent_as], [wire_marshal], or [user_marshal] attributes to a pipe type or to the element-type.
- A pipe type cannot be a member of a structure or union, the target of a pointer, or the base type of an array.
- A data type declared to be a pipe type can only be used as a parameter of a remote call.
- You can pass a pipe parameter in either direction by value or by reference ([ref] pointer). However you cannot apply the [ptr] attribute to a pipe that is passed by reference. You cannot specify a pipe parameter with a [unique] or a full pointer, regardless of direction.
- You cannot use pipes in [object] interfaces.
- You cannot apply the [idempotent] attribute to a routine that has a pipe parameter.
- You cannot use the serialization attributes, [encode] and [decode] with pipes.
- You cannot use automatic handles, either by default, or with the [auto_handle] attribute, with pipes.
Note
The MIDL compiler supports pipes in /Oif mode only.
For more information on implementing routines with pipe parameters, see Pipes in the RPC Programmer's Guide and Reference.
Examples
typedef pipe unsigned char UCHAR_PIPE1, UCHAR_PIPE2;
//SIMPLE_STRUCT defined elsewhere
typedef pipe SIMPLE_STRUCT SIMPLE_STRUCT_PIPE;
See also