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CMSV_WRAW

CMSV_WRAW

Name


  CMSV_WRAW

Author


  Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
  craigm@lheamail.gsfc.nasa.gov

Purpose


  Write raw SAVE data to output block

Calling Sequence


  CMSV_WRAW, BLOCK, POINTER, DATA, UNIT=UNIT, $
              STRING=STRING, LONG=LONG, BYTE=BYTE, TYPE=TYPE, $
              OFFSET=OFFSET, STATUS=STATUS, ERRMSG=ERRMSG
 

Description



  This procedure writes raw integer or string data to an IDL SAVE
  block in memory. This is the lowest level writing function in the
  library, intended for developers who are investigating new and
  existing SAVE file formats.
  The data to be written is specified by the DATA parameter. The
  data must be of type BYTE, LONG or STRING, and the type is
  determined automatically from the data itself. [ The mnemonic
  STRING LONG and BYTE keywords are accepted for programming clarity
  but ignored. ]
  This procedure accepts but currently ignores the UNIT keyword. It
  is the caller's responsibility to write the BLOCK data to disk
  when appropriate.
  ==================================================================
  Research Systems, Inc. has issued a separate license intended
  to resolve any potential conflict between this software and the
  IDL End User License Agreement. The text of that license
  can be found in the file LICENSE.RSI, included with this
  software library.
  ==================================================================
  BLOCK, POINTER, OFFSET
  This procedure writes data to a byte array only. The intent is
  for users to accumulate a significant amount of data in a BLOCK
  and then write it out with a single call to WRITEU. Users should
  be aware that the block can be larger than the buffered data, so
  they should use something like the following:
          WRITEU, UNIT, BLOCK(0:POINTER-1)
  When library routines do indeed write buffered BLOCK data to disk,
  they will appropriately reset the BLOCK and POINTER. Namely,
  BLOCK will be reset to empty, and POINTER will be reset to zero.
  OFFSET will be advanced the according number of bytes.
  The terminology is as follows: BLOCK is a byte array which
  represents a portion of, or an entire, IDL SAVE file. The block
  may be a cached portion of an on-disk file, or an entire in-memory
  SAVE file. POINTER is the current file pointer within BLOCK
  (i.e., the next byte to be written is BLOCK[POINTER]). Hence, a
  POINTER value of 0 refers to the start of the block. OFFSET is
  the file offset of the 0th byte of BLOCK; thus "POINT_LUN,
  OFFSET+POINTER" should point to the same byte as BLOCK[POINTER].
  The following diagram shows the meanings for BLOCK, POINTER and
  OFFSET schematically:
                0 <- OFFSET -> |
  FILE |----------------|------*--------|--------->
  BLOCK |------*--------|
                                  0 ^ POINTER
   
  This procedure is part of the CMSVLIB SAVE library for IDL by
  Craig Markwardt. You must have the full CMSVLIB core package
  installed in order for this procedure to function properly.

Inputs



  BLOCK - a byte array, a cache of the SAVE file. Users will
          usually not access this array directly. Users are advised
          to clear BLOCK after calling POINT_LUN or writing the
          block to disk.
  POINTER - a long integer, a pointer to the next byte to be written
            from BLOCK. CMSVLIB routines will automatically advance
            the pointer.
  DATA - the data to be written. Must of type STRING, BYTE or LONG.

Keywords



  LONG - ignored (to be used for clarity)
  BYTE - ignored (to be used for clarity)
  STRING - ignored (to be used for clarity)
  UNIT - a file unit. Currently ignored.
  OFFSET - the file offset of byte zero of BLOCK.
            Upon output, if the file pointer is advanced, OFFSET will
            also be changed.
            (OFFSET is not currently used by this routine)
            Default: 0
  STATUS - upon return, this keyword will contain 1 for success and
            0 for failure.
  ERRMSG - upon return with a failure, this keyword will contain the
            error condition as a string.

Example


See Also



  CMRESTORE, SAVE, RESTORE, CMSVLIB

Modification History


  Written, 2000
  Documented, 24 Jan 2001
  Added notification about RSI License, 13 May 2002, CM
  Fixed bug in writing of empty strings, 28 Mar 2006, CM
  Fixed bug when writing strings >128 characters, 2012-04-05, CM
  NOTE: remember to modify CMSVLIB.PRO when changing library!
  $Id: cmsv_wraw.pro,v 1.9 2012/04/05 20:43:09 cmarkwar Exp $



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