OSI/AS Programming Manual

APS_DATA_GETPARAM_
APS Procedure Calls
056783 Tandem Computers Incorporated 3–65
If the buffer contains multiple data elements, it has the following structure:
ZAPS-DDL-DATA-ELEMENT-HDR
data
data
ZAPS-DDL-DATA-ELEMENT-HDR
data
ZAPS-DDL-DATA-HDR
ZAPS-DDL-DATA-ELEMENT-HDR
• • •
090
For further information about user data buffers, see “Defining User Data Buffers”
in Section 2.
For a normal-mode presentation or ACSE connection, you must decode the user
data. For details, see “Encoding ACSE and Presentation User Data” in Section 2.
A nonzero value returned in more-data indicates that the buffer size you gave
for your user data buffer is too small to receive all available data in one call. To
obtain the remaining data, call APS_DATA_GETPARAM_ repeatedly until
more-data is zero. In each call after the first, specify in start-position the
point in the API internal buffer from which the data retrieval should start. This
starting point is defined as a byte offset into the user data, excluding all headers.
Use one of the following methods to determine the value of start-position:
EITHER: Calculate the appropriate byte offset.
OR: Use the next-position from one call as the start-position of
the next call.
When calculating the minimum value for the data-buffer-size parameter,
consider the following guidelines:
The buffer must always have sufficient space to hold the headers ZAPS-DDL-
DATA-HDR and ZAPS-DDL-DATA-ELEMENT-HDR.
If you specify a valid nonzero value for data-buffer-size and no user
data is available, the API returns the ZAPS-DDL-DATA-HDR (with ZNUM-
ELEMENTS set to 0) and returns the error ZAPS-ERR-NO-DATA.
If you specify a valid nonzero value for data-buffer-size and user data is
available, the API returns a minimum of ZAPS-DDL-DATA-HDR, ZAPS-
DDL-DATA-ELEMENT-HDR, and one byte of data.