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- Description:
The routine returns information describing the position in an HDS
container file at which the data associated with a primitive
object are stored.
- Invocation:
CALL DAT_WHERE( LOC, BLOCK, OFFSET, STATUS )
- Arguments:
-
LOC = CHARACTER * ( DAT__SZLOC ) (Given)
-
Primitive object locator.
-
BLOCK = INTEGER (Returned)
-
Number of the file block in which the object's data start. HDS
file blocks are 512 bytes long and are numbered from the
beginning of the file, starting at block 1.
-
OFFSET = INTEGER (Returned)
-
Byte offset (zero based) of the start of data within the file
block.
-
STATUS = INTEGER (Given and Returned)
-
The global status.
- Notes:
-
The use of this routine is not recommended. It is provided
solely for use by experienced programmers who are familiar with
the internal structure of HDS container files and who wish to
access the file contents directly. Note, however, that changes to
the format of an HDS file may occur in future.
-
The start of the data associated with a cell or a slice of a
primitive object may be located with this routine, but the data
associated with a slice will not, in general, be stored at
contiguous locations within the file.
-
Care must be taken that no changes are made to adjacent bytes
within the file which are not part of the requested object's
data.
-
Note that the data associated with primitive objects may not
necessarily be stored contiguously in future versions of HDS.
Next: HDS_COPY - Copy an object to a new container file
Up: ROUTINE DESCRIPTIONS
Previous: DAT_VEC - Vectorise object
HDS Hierarchical Data System
Starlink User Note 92
R.F. Warren-Smith & M.D. Lawden
23rd February 1999
E-mail:rfws@star.rl.ac.uk
Copyright (C) 1999 Central Laboratory of the Research Councils