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Hoffset
int32 Hoffset(int32
file_id
, uint16
tag
, uint16
ref
)
file_id
IN:
File identifier returned by
Hopen
tag
IN:
Tag of the data element
ref
IN:
Reference number of the data element
Purpose
Returns the offset of a data element in the file.
Return value
Returns the offset of the data element if the data element exists and FAIL (or -1) otherwise.
Description
Hoffset
calls
Hstartread
,
HQueryoffset
, and
Hendaccess
to determine the length of a data element.
Hoffset
uses
Hstartread
to obtain an access identifier for the specified data object.
Hoffset
will return the correct offset for a linked-block element, however it is important to remember that the data in linked-block elements is not stored contiguously. The offset returned by
Hoffset
only reflects the position of the first data block.
Hoffset
should not be used to determine the offset of an external element. In this case,
Hoffset
returns zero, an invalid offset for HDF files.
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hdfhelp@ncsa.uiuc.edu
HDF User's Reference Manual, Draft 06/09/97, NCSA HDF Development Group.