graPHIGS Programming Interface: Subroutine Reference

The graPHIGS Programming Interface : Subroutine Reference

GPQEHD - Inquire List of Element Headers

GPQEHD (number, errind, actnum, header)

Note:

This subroutine is a Structure State List (SSL) inquiry. For an overview, see "SSL Inquiries"

Purpose

Use GPQEHD to inquire a list of element headers from the current open structure. This subroutine returns the list in the sequential order starting from the current element pointer. If the requested number is larger than the number of elements between the current element and the end of the open structure, only information about the existing elements is returned and the actual number parameter is set to the number of actually returned element codes.

This subroutine does not move the element pointer.

If the inquired information is available, the error indicator is returned as zero, and the values are returned in the output parameters. If the inquired information is unavailable, the error indicator contains an error number indicating the reason, and the values returned in the output parameters are unpredictable.

Note:

The format of the element headers that is returned by this subroutine is different from the information that is returned by the older Inquire Element Type and Size (GPQETS) subroutine.

Parameters

number -- specified by user, fullword integer

Number of entries requested (>=1)

errind -- returned by the graPHIGS API, fullword integer

Error indicator. If the error indicator is zero, the request has been completed. Otherwise, one of the following errors exists:

4: FUNCTION REQUIRES STATE STOP
535: CURRENT ELEMENT POINTER IS ZERO
540: REQUESTED NUMBER < ONE

actnum -- returned by the graPHIGS API, fullword integer

Number of entries actually returned.

header -- returned by the graPHIGS API, array of 2 halfword integers

List of element headers. The first and second halfword integer of each element header indicates the length and code of the structure element, respectively.

The information that corresponds to each element and length and the list of element codes used by the graPHIGS API can be found in The graPHIGS Programming Interface: Technical Reference

Error Codes

None

Related Subroutines

GPQE: Inquire Element Content
GPQED: Inquire List of Element Data
GPQETS: Inquire Element Type and Size

RCP code

201337101 (X'0C00290D')