OSF DCE Application Development Guide--Core Components

Interface Definition Language
typedef struct pipe_t {
void (* pull)(
rpc_ss_pipe_state_t state,
element_t *buf,
idl_ulong_int esize,
idl_ulong_int *ecount
);
void (* push)(
rpc_ss_pipe_state_t state,
element_t *buf,
idl_ulong_int ecount
);
void (* alloc)(
rpc_ss_pipe_state_t state,
idl_ulong_int bsize,
element_t **buf,
idl_ulong_int *bcount
);
rpc_ss_pipe_state_t state;
} pipe_t;
The pipe data structure specifies pointers to three separate routines and a pipe state. The
client application has to implement these routines for the client stub to call, and the
server manager must call the associated routines generated in the server stub.
The pull routine is used for an input pipe. It pulls the next chunk of data from the client
application into the pipe. The input parameters include the pipe state, the buffer (*buf)
containing a chunk of data, and the size of the buffer (esize) in terms of the number of
pipe data elements. The output parameter is the actual count (*ecount) of the number of
pipe data elements in the buffer.
The push routine is used for an output pipe. It pushes the next chunk of data from the
pipe to the client application. The input parameters include the pipe state, the buffer
(*buf) containing a chunk of data, and a count (ecount) of the number of pipe data
elements in the buffer.
The alloc routine allocates a buffer for the pipe data. The input parameters include the
pipe state and the requested size of the buffer (bsize) in bytes. The output parameters
include a pointer to the allocated buffer (**buf), and the actual count (bcount) of the
number of bytes in the buffer. The routine allocates memory from which pipe data can
be marshalled or into which pipe data can be marshalled. If less memory is allocated than
requested, the RPC runtime uses the smaller memory and makes more callbacks to the
user. If the routine allocates more memory than requested, the excess memory is not
used.
Finally, the state is used to coordinate between these routines.
For more on how to write the code for the client and server manager, see Chapter 16.
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