OSF DCE Application Development Guide--Core Components

Topics in RPC Application Development
to as different buffering styles. The different buffering styles are:
• Incremental encoding
The incremental encoding style requires that you provide an allocate routine which
creates an empty buffer into which IDL encoding services can place encoded data,
and a write routine which IDL encoding services will call when the buffer is full or
all the parameters of the operation have been encoded. The IDL encoding services
call the allocate and write routines repeatedly until the encoding of all of the
parameters has been delivered to the user code. See the
idl_es_encode_incremental(3rpc) reference page for a description of the required
parameters for the allocate and write routines.
• Fixed buffer encoding
The fixed buffer encoding style requires that the application supply a single buffer
into which all the encoded data is to be placed. The buffer must have an address that
is 8-byte aligned and must be a multiple of 8 bytes in size. It must also be large
enough to hold an encoding of all the data, together with an encoding header for each
operation whose parameters are being encoded; 56 bytes should be allowed for each
encoding header.
• Dynamic buffer encoding
With the dynamic buffer encoding style, the IDL encoding services build a single
buffer containing all the encoded data and deliver the buffer to application code. The
buffer is allocated by whatever client memory management mechanism has been put
in place by the application code. The default for this is malloc(). When the
application code no longer needs the buffer, it should release the memory resource.
The dynamic buffer encoding style has performance implications. The IDL encoding
services will usually allocate a number of intermediate buffers, then allocate the
buffer to be delivered to the application code, copy data into it from the intermediate
buffers, and release the intermediate buffers.
• Incremental decoding
The incremental decoding buffering style requires that you provide a read routine
which, when called, delivers to the IDL encoding services a buffer that contains the
next part of the data to be decoded. The IDL encoding services will call the read
routine repeatedly until all of the required data has been decoded. See the idl_es_-
encode_incremental(3rpc) reference page for a description of the required
parameters for the read routine.
• Buffer decoding
The buffer decoding style requires that you supply a single buffer containing all the
encoded data. Where application performance is important, note that, if the supplied
buffer is not 8-byte aligned, the IDL encoding services allocate a temporary aligned
buffer of comparable size and copy data from the user-supplied buffer into it before
performing the requested decoding.
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