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  CLASS: Extent     --JD
  PUBLIC METHODS:
    Extent()      - Default constructor: len=0. (inline)
    print()       - Prints extent to supplied FILE *. (inline)
 
  USAGE NOTES:
   User notes go here.
  
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  METHOD:  Archive::getICBExtentList
       
     Attempts to provide the caller an extent list for use in writing ICB's.
 
     The need for this arises when writing extended attributes before the 
     fe itself is written. The archive object must get a set of appropriate
     addresses to use in writing a non-embedded EA. This may or may not
     be contiguous, hence the extent "list". This is also used by
     writeNextICB() to get locations for overflow sectors.
 
     There is really no allocation going on here. Sectors are taken from
     the icb table.
 
  ARGS:
     UINT32 offset,         IN     See explanation for "forEA".
     ExtentList &elist,     OUT    Where to write.
     UINT32 nBytes,         OUT    Total number of bytes required .
     Boolean forEA          IN     If getting an extent list for an EA,
                                   use icb table addresses offset by 
                                   "offset". The current icb table address
                                   must be preserved for writing the ICB.
 
  RETURNS:
  
  PRE-CONDS: 
       icbTable must be valid.
  
  POST-CONDS:
       icbTable        If not getting space for an EA, the icbTable will
                       get bumped.
       endICBTable     Set to True if reach end of icb table.
  
  ERRORS:
   error_End_of_ICB_table
  
  NOTES: export
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